Publications by authors named "Sunita P Ho"

52 Publications

Mineralized Peyronie's plaque has a phenotypic resemblance to bone.

Acta Biomater 2021 Nov 21. Epub 2021 Nov 21.

Division of Biomaterials and Bioengineering, Department of Preventative and Restorative Dental Sciences, School of Dentistry, University of California San Francisco, California, United States of America; Department of Urology, School of Medicine, University of California, San Francisco, California, United States of America. Electronic address:

Mineralized Peyronie's plaque (MPP) impairs penile function. The association, colocalization, and dynamic interplay between organic and inorganic constituents can provide insights into biomineralization of Peyronie's plaque. Human MPPs (n = 11) were surgically excised, and the organic and inorganic constituents were spatially mapped using multiple high-resolution imaging techniques. Multiscale image analyses resulted in spatial colocalization of elements within a highly porous material with heterogenous composition, lamellae, and osteocytic lacuna-like features with a morphological resemblance to bone. The lower (520 ±179 mg/cc) and higher (1024 ± 155 mg/cc) mineral density regions were associated with higher (11%) and lower (7%) porosities in MPP. Energy dispersive X-ray and micro-X-ray fluorescent spectroscopic maps in the higher mineral density regions of MPP revealed higher counts of calcium (Ca) and phosphorus (P), and a Ca/P ratio of 1.48 ± 0.06 similar to bone. More importantly, higher counts of zinc (Zn) were localized at the interface between softer (more organic to inorganic ratio) and harder (less organic to inorganic ratio) tissue regions of MPP and adjacent softer matrix, indicating the involvement of Zn-related proteins and/or pathways in the formation of MPP. In particular, dentin matrix protein-1 (DMP-1) was colocalized in a matrix rich in proteoglycans and collagen that contained osteocytic lacuna-like features. This combined materials science and biochemical with correlative microspectroscopic approach provided insights into the plausible cellular and biochemical pathways that incite mineralization of an existing fibrous Peyronie's plaque. STATEMENT OF SIGNIFICANCE: Aberrant human penile mineralization is known as mineralized Peyronie's plaque (MPP) and often results in a loss of form and function. This study focuses on investigating the spatial association of matrix proteins and elemental composition of MPP by colocalizing calcium, phosphorus, and trace metal zinc with dentin matrix protein 1 (DMP-1), acidic proteoglycans, and fibrillar collagen along with the cellular components using high resolution correlative microspectroscopic techniques. Spatial maps provided insights into cellular and biochemical pathways that incite mineralization of fibrous Peyronie's plaque in humans.
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http://dx.doi.org/10.1016/j.actbio.2021.11.025DOI Listing
November 2021

Corrigendum to "Physicochemical and biochemical spatiotemporal maps of a mouse penis". [J. Biomech. 101 (2020) 109637].

J Biomech 2021 Aug 25;125:110563. Epub 2021 Jun 25.

Division of Biomaterials and Bioengineering, Department of Preventive and Restorative Dental Sciences, School of Dentistry, University of California San Francisco, San Francisco, CA, United States; Department of Urology, School of Medicine, University of California San Francisco, San Francisco, CA, United States. Electronic address:

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http://dx.doi.org/10.1016/j.jbiomech.2021.110563DOI Listing
August 2021

Functional adaptation of interradicular alveolar bone to reduced chewing loads on dentoalveolar joints in rats.

Dent Mater 2021 03 12;37(3):486-495. Epub 2021 Feb 12.

Division of Preclinical Education, Biomaterials & Engineering, Department of Preventive and Restorative Dental Sciences, University of California San Francisco, CA 94143, United States; Department of Urology, University of California San Francisco, CA 94143, United States. Electronic address:

Objectives: The effects of reduced chewing loads on load bearing integrity of interradicular bone (IB) within dentoalveolar joints (DAJ) in rats were investigated.

Methods: Four-week-old Sprague Dawley rats (N = 60) were divided into two groups; rats were either fed normal food, which is hard-pellet food (HF) (N = 30), or soft-powdered chow (SF) (N = 30). Biomechanical testing of intact DAJs and mapping of the resulting mechanical strains within IBs from 8- through 24-week-old rats fed HF or SF were performed. Tension- and compression-based mechanical strain profiles were mapped by correlating digital volumes of IBs at no load with the same IBs under load. Heterogeneity within IB was identified by mapping cement lines and TRAP-positive multinucleated cells using histology, and mechanical properties using nanoindentation technique.

Results: Significantly decreased interradicular functional space, IB volume fraction, and elastic modulus of IB in the SF group compared with the HF group were observed, and these trends varied with an increase in age. The elastic modulus values illustrated significant heterogeneity within IB from HF or SF groups. Both compression- and tension-based strains were localized at the coronal portion of the IB and the variation in strain profiles complemented the observed material heterogeneity using histology and nanoindentation.

Significance: Interradicular space and IB material-related mechanoadaptations in a DAJ are optimized to meet soft food related chewing demands. Results provided insights into age-specific regulation of chewing loads as a plausible "therapeutic dose" to reverse adaptations within the periodontal complex as an attempt to regain functional competence of a dynamic DAJ.
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http://dx.doi.org/10.1016/j.dental.2020.12.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8019359PMC
March 2021

Structure and elemental composition of Ceftriaxone induced pediatric nephrolithiasis.

Urolithiasis 2021 Aug 15;49(4):309-320. Epub 2021 Feb 15.

Department of Urology, Beijing Friendship Hospital, Capital Medical University, 95 Yong An Road, Xi Cheng District, Beijing, 100050, China.

Ceftriaxone is a widely used antibiotic because to its broad-spectrum gram-negative coverage, safety, and biological half life (5-9 h) permit dose once-daily administration. It is specifically used in pediatric patients in developing countries. Ceftriaxone forms insoluble sludge/stone when combined with calcium in the urinary system. In this study, Ceftriaxone induced sludge/stones from pediatric patients were collected to identify its microstructure and composition to gather insights into the mechanism of Ceftriaxone induced sludge/stone formation. The results illustrated that Ceftriaxone induced stones formed rapidly following antibiotic administration. Ceftriaxone calcium salt crystals could easily be broken with minimal intervention. However, Ceftriaxone combined with calcium phosphate formed an insoluble stone aggregate.
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http://dx.doi.org/10.1007/s00240-020-01231-5DOI Listing
August 2021

Structural and chemical heterogeneities of primary hyperoxaluria kidney stones from pediatric patients.

J Pediatr Urol 2021 04 20;17(2):214.e1-214.e11. Epub 2020 Nov 20.

Division of Preclinical Education, Biomaterials & Engineering, School of Dentistry, University of California San Francisco, San Francisco, CA, 94143, USA; Department of Urology, School of Medicine, University of California San Francisco, San Francisco, CA, 94143, USA. Electronic address:

Objective: Calcium oxalate stones are the most common type among stone-forming patients and in some cases result from predisposed genetic conditions. In this work, we examined the differences in structure and chemical composition between oxalate stones from patients from three groups: 1) pediatric patients that were genetically predisposed (primary hyperoxaluria) to form stones (PPH); 2) control pediatric patients that did not have such genetic predisposition (PN-PH); 3) adult patients that formed oxalate stones without the genetic predisposition (A-CaOx). A variety of instrumental analyses were conducted to identify physicochemical properties of stones characteristic of predisposed pediatric (PPH), pediatric hyperoxaluria (PN-PH), and adult (A-CaOx) patient populations.

Methods: Genetic variants of 16 stone-forming patients were determined using whole-exome gene sequencing. Components of stones from PPH (n = 6), PN-PH (n = 5), and A-CaOx (n = 5) groups were identified using Fourier transform infrared (FTIR) spectroscopy. Stone morphology and density were evaluated using high resolution X-ray computed tomography (micro-XCT). Stone microstructure and elemental composition were mapped with scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy, respectively.

Results: Calcium oxalate bipyramidal crystals were found on stones from all groups. Stones from PPH patients with PH types I and II were composed of calcium oxalate monohydrate (COM) with relatively uniform mineral density (1224 ± 277 mg/cc) and distinct smooth surfaces. By contrast, micro-spherical calcium phosphate particles were found only on PN-PH stones, which also showed a broader range of mineral densities (1266 ± 342 mg/cc). Stones from the PN-PH group also contained phosphorus (P), which was absent in NP-PH stones. A-CaOx stones were of significantly lower mineral density (645 ± 237 mg/cc) than pediatric stones and were more heterogeneous in their elemental composition.

Conclusion: Unique structural and compositional characteristics were identified in stones from pediatric patients with primary hyperoxaluria. These include the absence of phosphorus, a narrower mineral density distribution, and a uniform elemental composition compared to stones from pediatric patients without the genetic predisposition. Thus, characterization of stones at the macro- and micro-scales in combination with genetic testing of patients can provide insights and accurate diagnosis to develop a treatment plan for effective patient care.
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http://dx.doi.org/10.1016/j.jpurol.2020.11.023DOI Listing
April 2021

Ectopic biomineralization in kidney stone formers compared to non-stone formers.

Transl Androl Urol 2020 Oct;9(5):2129-2137

Department of Urology, University of California San Francisco, San Francisco, CA, USA.

Background: Kidney stone formers (SFs) are at increased risk of stroke, myocardial infarction, and atherosclerosis of the carotid and coronary arteries. These cardiovascular and urologic pathologies can result from ectopic biomineral deposition. The objectives of this study are: (I) to evaluate risk factors for ectopic biomineralization, and (II) to characterize the overall burden of ectopic minerals in known SFs compared to non-stone formers (NSFs) matched for these risk factors.

Methods: Presence and quantity of biominerals at eight anatomic locations (abdominal aorta, common iliac arteries, pelvic veins, prostate or uterus, mesentery, pancreas, and spleen) were determined in a case control study by retrospective analysis of clinical non-contrast computed tomography scans obtained from 190 SFs and 190 gender- and age-matched NSFs (renal transplant donors). Predictors of biomineralization were determined using negative binomial regression. A subgroup of 140 SFs and 140 NSFs were matched for risk factors for systemic biomineralization, and mineralization was compared between these matched SFs and NSFs using ordinal logistic regression.

Results: Hypertension, hyperlipidemia, diabetes mellitus, and smoking were more common amongst SFs. Risk factors for increased systemic biomineralization included history of nephrolithiasis, male gender, older age, and history of hyperlipidemia. When controlling for these comorbidities, SFs had significantly increased biomineralization systemically and at the abdominal aorta, iliac arteries, prostate, mesentery, pancreas, and spleen compared to NSFs.

Conclusions: The current study provides evidence that SFs are at increased risk of biomineralization systemically, independent of common risk factors of atherosclerosis.
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http://dx.doi.org/10.21037/tau-19-927DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7658123PMC
October 2020

Design of drug-like hepsin inhibitors against prostate cancer and kidney stones.

Acta Pharm Sin B 2020 Jul 28;10(7):1309-1320. Epub 2019 Sep 28.

University of Edinburgh, Institute of Quantitative Biology, Biochemistry and Biotechnology, Edinburgh, Scotland, EH9 3BF, UK.

Hepsin, a transmembrane serine protease abundant in renal endothelial cells, is a promising therapeutic target against several cancers, particularly prostate cancer. It is involved in the release and polymerization of uromodulin in the urine, which plays a role in kidney stone formation. In this work, we design new potential hepsin inhibitors for high activity, improved specificity towards hepsin, and promising ADMET properties. The ligands were developed through a novel hierarchical pipeline. This pipeline explicitly accounts for off-target binding to the related serine proteases matriptase and HGFA (human hepatocyte growth factor activator). We completed the pipeline incorporating ADMET properties of the candidate inhibitors into custom multi-objective optimization functions. The ligands designed show excellent prospects for targeting hepsin the blood stream and the urine and thus enable key experimental studies. The computational pipeline proposed is remarkably cost-efficient and can be easily adapted for designing inhibitors against new drug targets.
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http://dx.doi.org/10.1016/j.apsb.2019.09.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7452031PMC
July 2020

High-Throughput Screening: today's biochemical and cell-based approaches.

Drug Discov Today 2020 Oct 12;25(10):1807-1821. Epub 2020 Aug 12.

Department of Pharmaceutical Chemistry and the Small Molecule Discovery Center, University of California, San Francisco, CA, USA. Electronic address:

High-throughput screening (HTS) provides starting chemical matter in the adventure of developing a new drug. In this review, we survey several HTS methods used today for hit identification, organized in two main flavors: biochemical and cell-based assays. Biochemical assays discussed include fluorescence polarization and anisotropy, FRET, TR-FRET, and fluorescence lifetime analysis. Binding-based methods are also surveyed, including NMR, SPR, mass spectrometry, and DSF. On the other hand, cell-based assays discussed include viability, reporter gene, second messenger, and high-throughput microscopy assays. We devote some emphasis to high-content screening, which is becoming very popular. An advisable stage after hit discovery using phenotypic screens is target deconvolution, and we provide an overview of current chemical proteomics, in silico, and chemical genetics tools. Emphasis is made on recent CRISPR/dCas-based screens. Lastly, we illustrate some of the considerations that inform the choice of HTS methods and point to some areas with potential interest for future research.
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http://dx.doi.org/10.1016/j.drudis.2020.07.024DOI Listing
October 2020

Jean Oliver: Master of the Nephron.

Urology 2020 Oct 13;144:17-20. Epub 2020 Jun 13.

University of California, San Francisco, Department of Urology, San Francisco, CA.

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http://dx.doi.org/10.1016/j.urology.2020.06.002DOI Listing
October 2020

Fatty acid-binding protein 4 downregulation drives calcification in the development of kidney stone disease.

Kidney Int 2020 05 29;97(5):1042-1056. Epub 2020 Feb 29.

Department of Urology, University of California, San Francisco, California, USA. Electronic address:

Nephrolithiasis is a significant source of morbidity, and its incidence has increased significantly over the last decades. This rise has been attributed to concurrent increasing rates of obesity, associated with a 3-time risk of developing NL. To date, the mechanism by which obesity is linked to stone formation has not been elucidated. We aimed to utilize a transcriptomics approach to discover the missing link between these two epidemic diseases. We investigated gene expression profiling of nephrolithiasis patients by two RNA-sequencing approaches: comparison between renal papilla tissue with and without the presence of calcified Randall's plaques (RP), and comparison between the papilla, medulla, and cortex regions from within a single recurrent stone forming kidney. Results were overlaid between differently expressed genes found in the patient cohort and in the severely lithogenic kidney to identify common genes. Overlay of these two RNA-sequencing datasets demonstrated there is impairment of lipid metabolism in renal papilla tissue containing RP linked to downregulation of fatty acid binding protein (FABP) 4. Immunohistochemistry of human kidney specimens and microarray analysis of renal tissue from a nephrolithiasis mouse model confirmed that FABP4 downregulation is associated with renal stone formation. In a FABP4 knockout mouse model, FABP4 deficiency resulted in development of both renal and urinary crystals. Our study revealed that FABP4 plays an important, previously unrecognized role in kidney stone formation, providing a feasible mechanism to explain the link between nephrolithiasis and metabolic syndrome.
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http://dx.doi.org/10.1016/j.kint.2020.01.042DOI Listing
May 2020

Polymicrobial periodontal disease triggers a wide radius of effect and unique virome.

NPJ Biofilms Microbiomes 2020 03 10;6(1):10. Epub 2020 Mar 10.

Department of Orofacial Sciences, School of Dentistry, University of California San Francisco, San Francisco, CA, USA.

Periodontal disease is a microbially-mediated inflammatory disease of tooth-supporting tissues that leads to bone and tissue loss around teeth. Although bacterially-mediated mechanisms of alveolar bone destruction have been widely studied, the effects of a polymicrobial infection on the periodontal ligament and microbiome/virome have not been well explored. Therefore, the current investigation introduced a new mouse model of periodontal disease to examine the effects of a polymicrobial infection on periodontal ligament (PDL) properties, changes in bone loss, the host immune response, and the microbiome/virome using shotgun sequencing. Periodontal pathogens, namely Porphyromonas gingivalis, Treponema denticola, Tannerella forsythia, and Fusobacterium nucleatum were used as the polymicrobial oral inoculum in BALB/cByJ mice. The polymicrobial infection triggered significant alveolar bone loss, a heightened antibody response, an elevated cytokine immune response, a significant shift in viral diversity and virome composition, and a widening of the PDL space; the latter two findings have not been previously reported in periodontal disease models. Changes in the PDL space were present at sites far away from the site of insult, indicating that the polymicrobial radius of effect extends beyond the bone loss areas and site of initial infection and wider than previously appreciated. Associations were found between bone loss, specific viral and bacterial species, immune genes, and PDL space changes. These findings may have significant implications for the pathogenesis of periodontal disease and biomechanical properties of the periodontium. This new polymicrobial mouse model of periodontal disease in a common mouse strain is useful for evaluating the features of periodontal disease.
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http://dx.doi.org/10.1038/s41522-020-0120-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7064479PMC
March 2020

Physicochemical and biochemical spatiotemporal maps of a mouse penis.

J Biomech 2020 03 16;101:109637. Epub 2020 Jan 16.

Division of Biomaterials and Bioengineering, Department of Preventive and Restorative Dental Sciences, School of Dentistry, University of California San Francisco, San Francisco, CA, United States; Department of Urology, School of Medicine, University of California San Francisco, San Francisco, CA, United States. Electronic address:

Spatiotemporal mechanobiology resulting in penile pathologies continues to be investigated using small scale animals models such as mice. However, species-dependent functional biomechanics of a mouse penis, is not known. In this study, spatial mapping of a mechanosensitive transcription factor, scleraxis (Scx), at ages 4, 5, 6 weeks, and 1 year were generated to identify mechanoactive regions within penile tissues. Reconstructed volumes of baculum collected using micro X-ray computed tomography illustrated significantly increased baculum length with decreased porosity, and increased mineral density (p < 0.05) with age. The bony-baculum was held centrally in the Scx positive corpus cavernosum glandis (CCG), indicating mechanoactivity within the struts in a 6 week old mouse. The struts also were stained positive for fibrillar proteins including collagen and elastin, and globular proteins including protein gene product 9.5, and α-smooth muscle actin. The corpus cavernosum penis (CCP) contained significantly (p < 0.05) more collagen than CCG within the same penis, and both regions contained blood vessels with equivalent innervation at any given age. Comparison of volumes of flaccid and erect penile forms revealed functional characteristics of the CCP. Results of this study provided insights into biomechanical function of the CCG; in that, it is a high-pressure chamber that stiffens the penis and is similar to the human corpus cavernosum.
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http://dx.doi.org/10.1016/j.jbiomech.2020.109637DOI Listing
March 2020

Biomechanical pathways of dentoalveolar fibrous joints in health and disease.

Periodontol 2000 2020 02;82(1):238-256

Division of Preclinical Education, Biomaterials & Engineering, Department of Preventive and Restorative Dental Sciences, School of Dentistry, University of California San Francisco, San Francisco, California, USA.

Spatial and temporal adaptations within periodontal tissues and their interfaces result from functional loads. Functional loads can be physiologic and/or pathologic in nature. The prolonged effect of these loads can alter the overall biomechanics of a dentoalveolar fibrous joint (dentoalveolar joint) by changing the form of the tooth root and its socket. This "sculpting" of the tooth root and alveolar bony socket is a consequence of several mechano-biological changes that occur within the periodontal complex of a load-bearing dentoalveolar joint. These include changes in biochemical expressions, structure, elemental composition, and mechanical properties of alveolar bone, the underlying tissues of the roots of teeth, and their interfaces. These physicochemical changes in tissues continue to prompt mechano-responsive biochemical activities at the attachment sites of periodontal ligament (soft) with bone (hard), and ligament with cementum (hard), which are the entheses of a load-bearing dentoalveolar joint. Forces at soft-hard tissue attachment sites between disparate materials with different stiffness values theoretically generate strain singularities or discontinuities. These discontinuities under prolonged functional loading increase the probability for failure to occur specifically at the enthesial zones. However, in a normal dentoalveolar joint, gradual stiffness gradients exist from ligament to bone, and from ligament to cementum. The gradual transitions in stiffness from softer ligament (lower stiffness) to harder bone or cementum (higher stiffness) or vice versa optimize tissue and interfacial strains. Optimization of tissue and ligament-enthesial physical and chemical properties facilitates transmission of cyclic forces of varying magnitudes and frequencies that collectively maintain the overall biomechanics of a dentoalveolar joint. The objectives of this review are 3-fold: (i) to illustrate physicochemical adaptations at the periodontal ligament entheses of a human periodontal complex affected by subgingival calculus; (ii) to demonstrate how to "program" the hallmarks of periodontitis in small-scale vertebrates in vivo to generate spatiotemporal maps of physicochemical adaptations in a diseased dentoalveolar joint; and (iii) to correlate dentoalveolar joint biomechanics in healthy and diseased states to spatiotemporal maps of physicochemical adaptations within respective periodontal tissues. This interdisciplinary approach demonstrates that physicochemical adaptations within periodontal tissues using the mechanics of materials (tissue mechanics), materials science (tissue composition), and mechano-biology (matrix molecules) can help explain the mechano-adaptation of dentoalveolar joints in normal and diseased functional states. Multiscale biomechanics and mechano-biology approaches can provide insights into the functional competence of a diseased relative to a normal dentoalveolar joint. Insights gathered from interdisciplinary and multiscale biomechanics approaches include the following: (i) physiologic loads related to chewing maintain a balance between mineral-forming and-resorbing biochemical cellular events, resulting in gradual stiffness gradients at the periodontal ligament entheses, and, in turn, sustain the overall biomechanics of a normal "healthy" dentoalveolar joint; (ii) pathologic loads resulting from tissue degradation and physical changes to the periodontal complex promote an abrupt stiffness gradient at the periodontal ligament entheses. The shift from gradual to an abrupt stiffness gradient could prompt a shift in the biochemical cascades, exacerbate mechano-responsive biochemical expressions at periodontal ligament entheses farther away from the site of insult, and culminate in joint degradation; (iii) sustained pathologic function on periodontally diseased joints exacerbates degradation of periodontal ligament entheses providing insights into "rescue therapy", such as the use of an adequate "mechanocal dose" to regain joint function; and (iv) spatiotemporal maps of changes in biochemical expressions, and physicochemical properties of strain-dominated affected sites, including the periodontal ligament entheses, can guide anatomy-specific therapeutics for tissue regeneration and/or disease control with the purpose of regaining dentoalveolar joint function. Modulation of occlusal loads could minimize disease progression and potentially assist in regaining functional attachment of ligament to bone and/or ligament to cementum of the dentoalveolar joint. Elucidating mechanisms that drive the breakdown of the functionally active periodontal complex burdened with microbes will provide the required critical insights into regenerative medicine and/or biomimetic approaches that would facilitate rescue/regain of dentoalveolar joint function.
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http://dx.doi.org/10.1111/prd.12306DOI Listing
February 2020

Microanatomical changes and biomolecular expression at the PDL-entheses during experimental tooth movement.

J Periodontal Res 2019 Jun 28;54(3):251-258. Epub 2018 Nov 28.

Division of Biomaterials and Bioengineering, Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, California.

The novel aspect of this study was to contextualize the co-localization of biomolecular expression in widened and narrowed periodontal ligament (PDL)-space within a mechanically activated periodontal complex. The PDL is unique as it is the only ligament with both innervation and vascularization. Maxillary molars in 6-week-old male C57BL/6 mice (N = 5) were experimentally translated for 2 weeks using an elastic spacer. Contralateral teeth were used as controls. Mechanical testing of the periodontal complex of a mouse in situ and imaging using X-ray micro-computed tomography (micro-XCT) illustrated deformations within blood vessels (BV) of the PDL. PDL-bone and PDL-cementum entheses at the widened and narrowed PDL-spaces following experimental tooth movement (ETM) illustrated osterix (OSX), bone sialoprotein (BSP), cluster of differentiation 146 (CD146), and protein gene product 9.5 (PGP9.5), indicating active remodeling at these sites. PGP9.5 positive nerve bundles (NBs) were co-localized with multinucleated cells (MCs), Howship's resorption lacunae, and CD146 positive BVs. Association between nerves and MC was complemented by visualizing the proximity of osmium tetroxide stained NBs with the ultrastructure of MCs by performing scanning transmission electron microscopy. Spatial association of NB with BV, and NB with MC, provided insights into the plausible co-activation of NBs to initiate osteoclastic activity. Resorption of mineral occurred as an attempt to restore PDL-space of the load-bearing complex, specifically at the PDL-entheses. Mapping of anatomy-specific structural elements and their association with regenerative molecules by correlating light and electron micrographs provided insights into the use of these extracellular matrix molecules as plausible targets for pharmacological interventions related to tooth movement. Within the realm of tissue regeneration, modulation of load can reverse naturally occurring mineral formation to experimentally induced resorption, and naturally occurring mineral resorption to experimentally induced formation at the enthesial sites to permit tooth translation.
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http://dx.doi.org/10.1111/jre.12625DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6465084PMC
June 2019

Re: Geobiology Reveals How Human Kidney Stones Dissolve In Vivo.

Eur Urol 2019 03 16;75(3):532. Epub 2018 Nov 16.

Department of Urology, School of Medicine, University of California San Francisco, San Francisco, CA, USA. Electronic address:

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http://dx.doi.org/10.1016/j.eururo.2018.11.004DOI Listing
March 2019

Architecture-Guided Fluid Flow Directs Renal Biomineralization.

Sci Rep 2018 09 21;8(1):14157. Epub 2018 Sep 21.

Department of Urology, School of Medicine, University of California San Francisco, San Francisco, CA, 94143, USA.

Nephrocalcinosis often begins on a calcium phosphate deposit, at the tip of the medullo-papillary complex (MPC) known as Randall's plaque (RP). Contextualizing proximally observed biominerals within the MPC has led us to postulate a mechanobiological switch that can trigger interstitial biomineralization at the MPC tip, remote from the intratubular biominerals. Micro X-ray computed tomography scans of human MPCs correlated with transmission and scanning electron micrographs, and X-ray energy dispersive spectrometry demonstrated novel findings about anatomically-specific biominerals. An abundance of proximal intratubular biominerals were associated with emergence of distal interstitial RP. The fundamental architecture of the MPC and mineral densities at the proximal and distal locations of the MPC differed markedly. A predominance of plate-like minerals or radially oriented plate-like crystallites within spheroidal minerals in the proximal intratubular locations, and core-shell type crystallites within spheroidal minerals in distal interstitial locations were observed. Based on the MPC anatomic location of structure-specific biominerals, a biological switch within the mineral-free zone occurring between the proximal and distal locations is postulated. The "on" and "off" switch is dependent on changes in the pressure differential resulting from changes in tubule diameters; the "Venturi effect" changes the "circumferential strain" and culminates in interstitial crystal deposits in the distal tubule wall in response to proximal tubular obstruction. These distal interstitial mineralizations can emerge into the collecting system of the kidney linking nephrocalcinosis with nephrolithiasis.
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http://dx.doi.org/10.1038/s41598-018-30717-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6155006PMC
September 2018

Novel insights into renal mineralization and stone formation through advanced imaging modalities.

Connect Tissue Res 2018 12;59(sup1):102-110

a Department of Urology , University of California San Francisco , San Francisco , California , USA.

Purpose/Aim: The most common kidney stone composed of calcium oxalate forms on interstitial calcium phosphate mineral known as a Randall's plaque (RP). Due to limited information about events leading to the initial deposition of nanometer size interstitial calcium phosphate pre-clusters, there continues to be a debate on the initial site of calcium phosphate deposition and factors leading to stone formation.

Materials And Methods: High-resolution X-ray micro-computed tomography (CT), and light and electron microscopy techniques were used to characterize human renal pyramids and five representative kidney stones with identifiable stems. Mineral densities of mineralized aggregates within these specimens were correlated with micro- and ultra-structures as seen using light and electron microscopy techniques.

Results: The earliest detectable biominerals in the human renal papilla were proximal intratubular plate-like calcium phosphate deposits. Unoccluded tubules in stems connected to calcium phosphate stones were observed by electron microscope and X-ray micro-CT. These tubules were similar in diameter (30-100 μm) and shape to those observed in the distal regions of the renal papilla.

Conclusions: Observations were patterned through a novel and unified theory of stepwise-architecture guided biomineralization (a combination of smaller structures leading to a larger but similar structural framework). A plausible stepwise progression in renal biomineralization is proposed; proximal intratubular calcium phosphate deposits can lead to interstitial yet calcium phosphate rich RP and mature into a stem on which a calcium oxalate stone grows within the collecting system of a kidney.
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http://dx.doi.org/10.1080/03008207.2017.1409219DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6120852PMC
December 2018

Beginnings of nephrolithiasis: insights into the past, present and future of Randall's plaque formation research.

Curr Opin Nephrol Hypertens 2018 07;27(4):236-242

Department of Urology, School of Medicine.

Purpose Of Review: Kidney stones form as a result of heterogeneous nucleation on a calcium phosphate lesion in the renal papilla known as Randall's plaque. Stone disease has plagued humans for millennia with relatively little progress made in the realm of prevention. An understanding of the historical aspects of research into Randall's plaque is necessary to interpret novel correlative imaging discoveries. Focus for the past several decades has been on the distal papillary tip, and the overlooked Anderson-Carr-Randall progression is revitalized with novel supporting evidence.

Recent Findings: Novel correlative techniques of three-dimensional micro-XCT imaging combined with electron and light microscopy techniques have revealed that the earliest mineralization event in the papilla is a distinct event that occurs proximal to the region where Randall's plaque has traditionally been identified.

Summary: The history of Randall's plaque research and the Anderson-Carr-Randall progression is reviewed. Proximal intratubular mineral deposits in normal and Randall's plaque affected papillae may be a target for future therapeutic interventions for nephrolithiasis. Further collaboration between nephrologists and urologists is necessary to cure this debilitating disease.
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http://dx.doi.org/10.1097/MNH.0000000000000414DOI Listing
July 2018

A continuum of mineralization from human renal pyramid to stones on stems.

Acta Biomater 2018 04 9;71:72-85. Epub 2018 Feb 9.

Department of Urology, University of California San Francisco, San Francisco, CA 94143, United States; Division of Biomaterials and Bioengineering, Department of Preventive and Restorative Dental Sciences, University of California San Francisco, San Francisco, CA 94143, United States. Electronic address:

The development of new modalities for kidney stone prevention rests upon understanding the progression of mineralization within the renal pyramid. The progression from small foci of mineralized volumes within the renal pyramid to larger interstitial plaques that ultimately lead into clinically detectable calcium-based stones on calcium phosphate stems will be presented through correlative microscopy approach. High resolution X-ray computed tomography (micro-XCT), electron microscopy, and energy dispersive X-ray (EDX) compositional analyses of interstitial plaques, stems, and attached stones were performed. Increase in mineral density progressed with mineralization severity, with the highest mineral densities detected within mature Randall's plaque and stems to which kidney stones were attached. EDX analyses revealed variable elemental composition within interstitial plaque, stems, and stones. Micro-XCT reconstructions of stones with stems enabled visualization of unoccluded tubules within stems, with average tubule diameters corresponding to thin limbs of Henle, blood vessels, and collecting ducts. Correlative microscopy confirmed that the progression of mineralization leading to calcium-based nephrolithiasis occurs through a continuum involving four anatomically and structurally distinct biomineralization regions: 1) proximal intratubular mineralization within the renal pyramid; 2) interstitial Randall's plaque near the tip of the papilla; 3) emerging plaque (stems); and, 4) the body of heterogeneous stones.

Statement Of Significance: Nephrolithiasis is a common condition affecting nearly 1 in 11 Americans. The most common type of stone, calcium oxalate is known to form on a calcium phosphate deposit on the renal papilla known as Randall's plaque. Novel imaging techniques have identified distinct regions of biomineralization not just at the tip, but throughout the renal papilla. The classic understanding of Randall's plaque formation is reformulated using correlative imaging techniques. This study establishes a stepwise progression of anatomically-specific biomineralization events including, 1) proximal intratubular mineralization within the renal pyramid; 2) interstitial Randall's plaque near the tip of the papilla; 3) emerging plaque (stems); and, 4) the body of heterogeneous stones, and provides insights into the need for plausible site-specific therapeutic intervention.
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http://dx.doi.org/10.1016/j.actbio.2018.01.040DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5899955PMC
April 2018

Anatomically-specific intratubular and interstitial biominerals in the human renal medullo-papillary complex.

PLoS One 2017 16;12(11):e0187103. Epub 2017 Nov 16.

Division of Biomaterials and Bioengineering, Department of Preventive and Restorative Dental Sciences, School of Dentistry, University of California San Francisco, San Francisco, California, United States of America.

Limited information exists on the anatomically-specific early stage events leading to clinically detectable mineral aggregates in the renal papilla. In this study, quantitative multiscale correlative maps of structural, elemental and biochemical properties of whole medullo-papillary complexes from human kidneys were developed. Correlative maps of properties specific to the uriniferous and vascular tubules using high-resolution X-ray computed tomography, scanning and transmission electron microscopy, energy dispersive X-ray spectroscopy, and immunolocalization of noncollagenous proteins (NCPs) along with their association with anatomy specific biominerals were obtained. Results illustrated that intratubular spherical aggregates primarily form at the proximal regions distant from the papillary tip while interstitial spherical and fibrillar aggregates are distally located near the papillary tip. Biominerals at the papillary tip were closely localized with 10 to 50 μm diameter vasa recta immunolocalized for CD31 inside the medullo-papillary complex. Abundant NCPs known to regulate bone mineralization were localized within nanoparticles, forming early pathologic mineralized regions of the complex. Based on the physical association between vascular and urothelial tubules, results from light and electron microscopy techniques suggested that these NCPs could be delivered from vasculature to prompt calcification of the interstitial regions or they might be synthesized from local vascular smooth muscle cells after transdifferentiation into osteoblast-like phenotypes. In addition, results provided insights into the plausible temporal events that link the anatomically specific intratubular mineral aggregates with the interstitial biomineralization processes within the functional unit of the kidney.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0187103PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5690653PMC
December 2017

Periodontal ligament entheses and their adaptive role in the context of dentoalveolar joint function.

Dent Mater 2017 06 2;33(6):650-666. Epub 2017 May 2.

Division of Biomaterials and Bioengineering, Department of Preventive and Restorative Dental Sciences, University of California San Francisco, San Francisco, CA 94143, United States. Electronic address:

Objective: The dynamic bone-periodontal ligament (PDL)-tooth fibrous joint consists of two adaptive functionally graded interfaces (FGI), the PDL-bone and PDL-cementum that respond to mechanical strain transmitted during mastication. In general, from a materials and mechanics perspective, FGI prevent catastrophic failure during prolonged cyclic loading. This review is a discourse of results gathered from literature to illustrate the dynamic adaptive nature of the fibrous joint in response to physiologic and pathologic simulated functions, and experimental tooth movement.

Methods: Historically, studies have investigated soft to hard tissue transitions through analytical techniques that provided insights into structural, biochemical, and mechanical characterization methods. Experimental approaches included two dimensional to three dimensional advanced in situ imaging and analytical techniques. These techniques allowed mapping and correlation of deformations to physicochemical and mechanobiological changes within volumes of the complex subjected to concentric and eccentric loading regimes respectively.

Results: Tooth movement is facilitated by mechanobiological activity at the interfaces of the fibrous joint and generates elastic discontinuities at these interfaces in response to eccentric loading. Both concentric and eccentric loads mediated cellular responses to strains, and prompted self-regulating mineral forming and resorbing zones that in turn altered the functional space of the joint.

Significance: A multiscale biomechanics and mechanobiology approach is important for correlating joint function to tissue-level strain-adaptive properties with overall effects on joint form as related to physiologic and pathologic functions. Elucidating the shift in localization of biomolecules specifically at interfaces during development, function, and therapeutic loading of the joint is critical for developing "functional regeneration and adaptation" strategies with an emphasis on restoring physiologic joint function.
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http://dx.doi.org/10.1016/j.dental.2017.03.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5495547PMC
June 2017

A Critical Role of TRPM7 As an Ion Channel Protein in Mediating the Mineralization of the Craniofacial Hard Tissues.

Front Physiol 2016 6;7:258. Epub 2016 Jul 6.

Department of Orofacial Sciences, University of California, San FranciscoSan Francisco, CA, USA; Center for Children's Oral Health Research, University of California, San FranciscoSan Francisco, CA, USA.

Magnesium ion (Mg(2+)) is the fourth most common cation in the human body, and has a crucial role in many physiological functions. Mg(2+) homeostasis is an important contributor to bone development, however, its roles in the development of dental mineralized tissues have not yet been well known. We identified that transient receptor potential cation channel, subfamily M, member 7 (TRPM7), was significantly upregulated in the mature ameloblasts as compared to other ameloblasts through our whole transcript microarray analyses of the ameloblasts. TRPM7, an ion channel for divalent metal cations with an intrinsic serine/threonine protein kinase activity, has been characterized as a key regulator of whole body Mg(2+) homeostasis. Semi-quantitative PCR and immunostaining for TRMP7 confirmed its upregulation during the maturation stage of enamel formation, at which ameloblasts direct rapid mineralization of the enamel matrix. The significantly hypomineralized craniofacial structures, including incisors, molars, and cranial bones were demonstrated by microCT analysis, von Kossa and trichrome staining in Trpm7 (Δkinase∕+) mice. A previously generated heterozygous mouse model with the deletion of the TRPM7 kinase domain. Interestingly, the skeletal phenotype of Trpm7 (Δkinase∕+) mice resembled those found in the tissue-nonspecific alkaline phosphatase (Alpl) KO mice, thus we further examined whether ALPL protein content and alkaline phosphatase (ALPase) activity in ameloblasts, odontoblasts and osteoblasts were affected in those mice. While ALPL protein in Trpm7 (Δkinase∕+) mice remained at the similar level as that in wt mice, ALPase activities in the Trpm7 (Δkinase∕+) mice were almost nonexistent. Supplemented magnesium successfully rescued the activities of ALPase in ameloblasts, odontoblasts and osteoblasts of Trpm7 (Δkinase∕+) mice. These results suggested that TRPM7 is essential for mineralization of enamel as well as dentin and bone by providing sufficient Mg(2+) for the ALPL activity, underlining the key importance of ALPL for biomineralization.
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http://dx.doi.org/10.3389/fphys.2016.00258DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4934143PMC
July 2016

Strain mapping and correlative microscopy of the alveolar bone in a bone-periodontal ligament-tooth fibrous joint.

Proc Inst Mech Eng H 2016 Sep 3;230(9):847-857. Epub 2016 Aug 3.

1 Division of Biomaterials and Bioengineering, Department of Preventive and Restorative Dental Sciences, University of California-San Francisco, San Francisco, CA, USA.

This study details a method to calculate strains within interradicular alveolar bone using digital volume correlation on X-ray tomograms of intact bone-periodontal ligament-tooth fibrous joints. The effects of loading schemes (concentric and eccentric) and optical magnification on the resulting strain in alveolar bone will be investigated with an intent to correlate deformation gradients with data sets from other complementary techniques. Strain maps will be correlated with structural and site-specific mechanical properties obtained on the same specimen using atomic force microscopy and atomic force microscopy-based nanoindentation technique. Specimens include polydimethylsiloxane as a standard material and intact hemi-mandibles harvested from rats. X-ray tomograms were taken at no-load and loaded conditions using an in situ load cell coupled to a micro X-ray computed tomography unit. Digital volume correlation was used to calculate deformations within alveolar bone. Comparison of strain maps was made as a result of different loading schemes (concentric vs eccentric) and at different magnifications (4× vs 10×). Virtual sections and strain maps from digital volume correlation solutions were aligned with structure and reduced elastic modulus to correlate datasets of the same region within a specimen. Strain distribution between concentrically and eccentrically loaded complexes was different but illustrated a similar range. Strain maps of homogeneous materials (polydimethylsiloxane) resulting from digital volume correlation at different magnifications were similar. However, strain maps of heterogeneous materials at lower and higher magnification differed. The digital volume correlation technique illustrated a dependence on optical magnification specifically for heterogeneous materials such as bone. The results at a higher optical magnification highlight the potential for extracting deformation at higher resolutions. Correlation of data spaces from different complementary techniques is plausible and could provide insights into biological and physicochemical processes that lead to functional adaptation of tissues and joints.
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http://dx.doi.org/10.1177/0954411916655183DOI Listing
September 2016

The origins of urinary stone disease: upstream mineral formations initiate downstream Randall's plaque.

BJU Int 2017 Jan 14;119(1):177-184. Epub 2016 Jul 14.

Department of Urology, School of Dentistry, University of California San Francisco, San Francisco, CA, USA.

Objectives: To describe a new hypothesis for the initial events leading to urinary stones. A biomechanical perspective on Randall's plaque formation through form and function relationships is applied to functional units within the kidney, we have termed the 'medullo-papillary complex' - a dynamic relationship between intratubular and interstitial mineral aggregates.

Methods: A complete MEDLINE search was performed to examine the existing literature on the anatomical and physiological relationships in the renal medulla and papilla. Sectioned human renal medulla with papilla from radical nephrectomy specimens were imaged using a high resolution micro X-ray computed tomography. The location, distribution, and density of mineral aggregates within the medullo-papillary complex were identified.

Results: Mineral aggregates were seen proximally in all specimens within the outer medulla of the medullary complex and were intratubular. Distal interstitial mineralisation at the papillary tip corresponding to Randall's plaque was not seen until a threshold of proximal mineralisation was observed. Mineral density measurements suggest varied chemical compositions between the proximal intratubular (330 mg/cm ) and distal interstitial (270 mg/cm ) deposits. A review of the literature revealed distinct anatomical compartments and gradients across the medullo-papillary complex that supports the empirical observations that proximal mineralisation triggers distal Randall's plaque formation.

Conclusion: The early stone event is initiated by intratubular mineralisation of the renal medullary tissue leading to the interstitial mineralisation that is observed as Randall's plaque. We base this novel hypothesis on a multiscale biomechanics perspective involving form and function relationships, and empirical observations. Additional studies are needed to validate this hypothesis.
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http://dx.doi.org/10.1111/bju.13555DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5161725PMC
January 2017

Effect of proteoglycans at interfaces as related to location, architecture, and mechanical cues.

Arch Oral Biol 2016 Mar 3;63:82-92. Epub 2015 Dec 3.

Division of Biomaterials and Bioengineering, Department of Preventive and Restorative Dental Sciences, School of Dentistry, University of California, San Francisco, San Francisco, CA 94143, United States. Electronic address:

Introduction: Covalently bound functional GAGs orchestrate tissue mechanics through time-dependent characteristics.

Objective: The role of specific glycosaminoglycans (GAGs) at the ligament-cementum and cementum-dentin interfaces within a human periodontal complex were examined. Matrix swelling and resistance to compression under health and modeled diseased states was investigated.

Materials And Methods: The presence of keratin sulfate (KS) and chondroitin sulfate (CS) GAGs at the ligament-cementum and cementum-dentin interfaces in human molars (N=5) was illustrated by using enzymes, atomic force microscopy (AFM), and AFM-based nanoindentation. The change in physical characteristics of modeled diseased states through sequential digestion of keratin sulfate (KS) and chondroitin sulfate (CS) GAGs was investigated. One-way ANOVA tests with P<0.05 were performed to determine significant differences between groups. Additionally, the presence of mineral within the seemingly hygroscopic interfaces was investigated using transmission electron microscopy.

Results: Immunohistochemistry (N=3) indicated presence of biglycan and fibromodulin small leucine rich proteoglycans at the interfaces. Digestion of matrices with enzymes confirmed the presence of KS and CS GAGs at the interfaces by illustrating a change in tissue architecture and mechanics. A significant increase in height (nm), decrease in elastic modulus (GPa), and tissue deformation rate (nm/s) of the PDL-C attachment site (215±63-424±94nm; 1.5±0.7-0.4±0.2GPa; 21±7-48±22nm/s), and cementum-dentin interface (122±69-360±159nm; 2.9±1.3-0.7±0.3GPa; 18±4-30±6nm/s) was observed.

Conclusions: The sequential removal of GAGs indicated loss in intricate structural hierarchy of hygroscopic interfaces. From a mechanics perspective, GAGs provide tissue recovery/resilience. The results of this study provide insights into the role of GAGs toward conserved tooth movement in the socket in response to mechanical loads, and modulation of potentially deleterious strain at tissue interfaces.
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http://dx.doi.org/10.1016/j.archoralbio.2015.11.021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4761423PMC
March 2016

Biomechanics and strain mapping in bone as related to immediately-loaded dental implants.

J Biomech 2015 Sep 19;48(12):3486-94. Epub 2015 Jun 19.

Division of Biomaterials and Bioengineering, Department of Preventive and Restorative Dental Sciences, School of Dentistry, University of California San Francisco, San Francisco, CA, USA. Electronic address:

The effects of alveolar bone socket geometry and bone-implant contact on implant biomechanics, and resulting strain distributions in bone were investigated. Following extraction of lateral incisors on a cadaver mandible, implants were placed immediately and bone-implant contact area, stability implant biomechanics and bone strain were measured. In situ biomechanical testing coupled with micro X-ray microscopy (µ-XRM) illustrated less stiff bone-implant complexes (701-822 N/mm) compared with bone-periodontal ligament (PDL)-tooth complexes (791-913 N/mm). X-ray tomograms illustrated that the cause of reduced stiffness was due to limited bone-implant contact. Heterogeneous elemental composition of bone was identified by using energy dispersive X-ray spectroscopy (EDS). The novel aspect of this study was the application of a new experimental mechanics method, that is, digital volume correlation, which allowed mapping of strains in volumes of alveolar bone in contact with a loaded implant. The identified surface and subsurface strain concentrations were a manifestation of load transferred to bone through bone-implant contact based on bone-implant geometry, quality of bone, implant placement, and implant design. 3D strain mapping indicated that strain concentrations are not exclusive to the bone-implant contact regions, but also extend into bone not directly in contact with the implant. The implications of the observed strain concentrations are discussed in the context of mechanobiology. Although a plausible explanation of surgical complications for immediate implant treatment is provided, extrapolation of results is only warranted by future systematic studies on more cadaver specimens and/or in vivo models.
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http://dx.doi.org/10.1016/j.jbiomech.2015.05.014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4663100PMC
September 2015

Multiscale biomechanical responses of adapted bone-periodontal ligament-tooth fibrous joints.

Bone 2015 Dec 4;81:196-207. Epub 2015 Jul 4.

Division of Biomaterials and Bioengineering, Department of Preventive and Restorative Dental Sciences, University of California San Francisco, CA 94143, United States. Electronic address:

Reduced functional loads cause adaptations in organs. In this study, temporal adaptations of bone-ligament-tooth fibrous joints to reduced functional loads were mapped using a holistic approach. Systematic studies were performed to evaluate organ-level and tissue-level adaptations in specimens harvested periodically from rats (N=60) given powder food for 6 months over 8,12,16,20, and 24 weeks. Bone-periodontal ligament (PDL)-tooth fibrous joint adaptation was evaluated by comparing changes in joint stiffness with changes in functional space between the tooth and alveolar bony socket. Adaptations in tissues included mapping changes in the PDL and bone architecture as observed from collagen birefringence, bone hardness and volume fraction in rats fed soft foods (soft diet, SD) compared to those fed hard pellets as a routine diet (hard diet, HD). In situ biomechanical testing on harvested fibrous joints revealed increased stiffness in SD groups (SD:239-605 N/mm) (p<0.05) at 8 and 12 weeks. Increased joint stiffness in early development phase was due to decreased functional space (at 8 weeks change in functional space was -33 μm, at 12 weeks change in functional space was -30 μm) and shifts in tissue quality as highlighted by birefringence, architecture and hardness. These physical changes were not observed in joints that were well into function, that is, in rodents older than 12 weeks of age. Significant adaptations in older groups were highlighted by shifts in bone growth (bone volume fraction 24 weeks: Δ-0.06) and bone hardness (8 weeks: Δ-0.04 GPa, 16 weeks: Δ-0.07 GPa, 24 weeks: Δ-0.06 GPa). The response rate (N/s) of joints to mechanical loads decreased in SD groups. Results from the study showed that joint adaptation depended on age. The initial form-related adaptation (observed change in functional space) can challenge strain-adaptive nature of tissues to meet functional demands with increasing age into adulthood. The coupled effect between functional space in the bone-PDL-tooth complex and strain-adaptive nature of tissues is necessary to accommodate functional demands, and is temporally sensitive despite joint malfunction. From an applied science perspective, we propose that adaptations are registered as functional history in tissues and joints.
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http://dx.doi.org/10.1016/j.bone.2015.07.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4663099PMC
December 2015

Mineral density volume gradients in normal and diseased human tissues.

PLoS One 2015 9;10(4):e0121611. Epub 2015 Apr 9.

Division of Biomaterials and Bioengineering, Department of Preventive and Restorative Dental Sciences, University of San Francisco, San Francisco, California, United States of America.

Clinical computed tomography provides a single mineral density (MD) value for heterogeneous calcified tissues containing early and late stage pathologic formations. The novel aspect of this study is that, it extends current quantitative methods of mapping mineral density gradients to three dimensions, discretizes early and late mineralized stages, identifies elemental distribution in discretized volumes, and correlates measured MD with respective calcium (Ca) to phosphorus (P) and Ca to zinc (Zn) elemental ratios. To accomplish this, MD variations identified using polychromatic radiation from a high resolution micro-computed tomography (micro-CT) benchtop unit were correlated with elemental mapping obtained from a microprobe X-ray fluorescence (XRF) using synchrotron monochromatic radiation. Digital segmentation of tomograms from normal and diseased tissues (N=5 per group; 40-60 year old males) contained significant mineral density variations (enamel: 2820-3095 mg/cc, bone: 570-1415 mg/cc, cementum: 1240-1340 mg/cc, dentin: 1480-1590 mg/cc, cementum affected by periodontitis: 1100-1220 mg/cc, hypomineralized carious dentin: 345-1450 mg/cc, hypermineralized carious dentin: 1815-2740 mg/cc, and dental calculus: 1290-1770 mg/cc). A plausible linear correlation between segmented MD volumes and elemental ratios within these volumes was established, and Ca/P ratios for dentin (1.49), hypomineralized dentin (0.32-0.46), cementum (1.51), and bone (1.68) were observed. Furthermore, varying Ca/Zn ratios were distinguished in adapted compared to normal tissues, such as in bone (855-2765) and in cementum (595-990), highlighting Zn as an influential element in prompting observed adaptive properties. Hence, results provide insights on mineral density gradients with elemental concentrations and elemental footprints that in turn could aid in elucidating mechanistic processes for pathologic formations.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0121611PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4391782PMC
April 2016

Removal of SOST or blocking its product sclerostin rescues defects in the periodontitis mouse model.

FASEB J 2015 Jul 10;29(7):2702-11. Epub 2015 Mar 10.

*Department of Biomedical Sciences, Texas A&M University Baylor College of Dentistry, Dallas, Texas, USA; State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Sichuan, China; Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, San Francisco, California, USA; Department of Periodontics, University of Texas Health Science Center, San Antonio, San Antonio, Texas, USA; The State Key Laboratory Breeding Base of Basic Science of Stomatology & Key Laboratory of Oral Biomedicine, School & Hospital of Stomatology, Wuhan University, Wuhan, China; Regeneron Pharmaceuticals, Tarrytown, New York, USA; and Department of Metabolic Disorders, Amgen Incorporated, Thousand Oaks, California, USA

Understanding periodontal ligament (PDL) biology and developing an effective treatment for bone and PDL damage due to periodontitis have been long-standing aims in dental medicine. Here, we first demonstrated by cell lineage tracing and mineral double-labeling approaches that murine PDL progenitor cells display a 2- and 3-fold higher mineral deposition rate than the periosteum and endosteum at the age of 4 weeks, respectively. We next proved that the pathologic changes in osteocytes (Ocys; changes from a spindle shape to round shape with a >50% reduction in the dendrite number/length, and an increase in SOST) are the key pathologic factors responsible for bone and PDL damage in periostin-null mice (a periodontitis animal model) using a newly developed 3-dimensional FITC-Imaris technique. Importantly, we proved that deleting the Sost gene (a potent inhibitor of WNT signaling) or blocking sclerostin function by using the mAb in this periodontitis model significantly restores bone and PDL defects (n = 4-5; P < 0.05). Together, identification of the key contribution of the PDL in normal alveolar bone formation, the pathologic changes of the Ocys in periodontitis bone loss, and the novel link between sclerostin and Wnt signaling in the PDL will aid future drug development in the treatment of patients with periodontitis.
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http://dx.doi.org/10.1096/fj.14-265496DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4478802PMC
July 2015

Essential role of osterix for tooth root but not crown dentin formation.

J Bone Miner Res 2015 Apr;30(4):742-6

Biomedical Sciences, Texas A&M Baylor College of Dentistry, Dallas, TX, USA.

Tooth is made of crown and root. It is widely believed that dentin formation in crown and root uses the same regulatory mechanism. However, identification of nuclear factor 1 C (NFIC)'s unique function in determining root but not crown dentin formation challenges the old thinking. In searching for the target molecules downstream of NFIC, we unexpectedly found a sharp reduction of osterix (OSX), the key transcription factor in skeleton formation, in the Nfic knockout (Nfic-KO) tooth root. We then demonstrated a dose-dependent increase of Osx in the odontoblast cell line due to a transient transfection of Nfic expression plasmid. Studies of global and conditional Osx-KO mice revealed no apparent changes in the crown dentin tubules and dentin matrix. However, the OSX conditional KO (cKO) mice (crossed to the 2.3-kb collagen type 1 [Col1]-Cre) displayed an increase in cell proliferation but great decreases in expressions of root dentin matrix proteins (dentin matrix protein 1 [DMP1] and dentin sialophosphoprotein [DSPP]), leading to an inhibition in odontoblast differentiation, and short, thin root dentin with few dentin tubules. Compared to the Nfic-KO tooth, which contains essentially no dentin tubules and remains in a "root-less" status at adult stages, the Osx-cKO root phenotype had partially improved at the late stage, indicating that other factors can compensate for OSX function. Thus, we conclude that OSX, one of the key downstream molecules of NFIC, plays a critical role in root, but not crown, formation.
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http://dx.doi.org/10.1002/jbmr.2391DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4617775PMC
April 2015
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