Publications by authors named "Antonio Nanci"

83 Publications

A hydride transfer complex reprograms NAD metabolism and bypasses senescence.

Mol Cell 2021 09;81(18):3848-3865.e19

CRCHUM, 900 Saint-Denis St, Montréal, QC H2X 0A9, Canada; Département de Biochimie et Médecine Moléculaire, Université de Montréal, Montréal, QC H3C 3J7, Canada. Electronic address:

Metabolic rewiring and redox balance play pivotal roles in cancer. Cellular senescence is a barrier for tumorigenesis circumvented in cancer cells by poorly understood mechanisms. We report a multi-enzymatic complex that reprograms NAD metabolism by transferring reducing equivalents from NADH to NADP. This hydride transfer complex (HTC) is assembled by malate dehydrogenase 1, malic enzyme 1, and cytosolic pyruvate carboxylase. HTC is found in phase-separated bodies in the cytosol of cancer or hypoxic cells and can be assembled in vitro with recombinant proteins. HTC is repressed in senescent cells but induced by p53 inactivation. HTC enzymes are highly expressed in mouse and human prostate cancer models, and their inactivation triggers senescence. Exogenous expression of HTC is sufficient to bypass senescence, rescue cells from complex I inhibitors, and cooperate with oncogenic RAS to transform primary cells. Altogether, we provide evidence for a new multi-enzymatic complex that reprograms metabolism and overcomes cellular senescence.
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http://dx.doi.org/10.1016/j.molcel.2021.08.028DOI Listing
September 2021

An Unusual Maxillary Tumor with Tubuloductal Epithelial Structures, Solid Epithelial Nests and Stromal Odontogenic Ameloblast-Associated Protein Deposits. Tubuloductal/Syringoid Variant of Central Odontogenic Fibroma with Amyloid?

Head Neck Pathol 2021 Aug 2. Epub 2021 Aug 2.

Faculty of Dental Medicine, Université de Montréal, Montréal, Québec, H3T 1J4, Canada.

Glandular tumors of jaw bones present, most often, histopathologic features of salivary gland and, rarely, of cutaneous glandular neoplasms. They are thought to originate from odontogenic epithelium. An unusual maxillary tumor presenting as a radiolucency in the periapical area of the right permanent lateral incisor of a 74-year-old male is presented causing root resorption. Preparations revealed occasionally branching tubular cords and ductal structures characterized, mostly, by a bilayer composed of luminal cuboidal to low columnar cytokeratin (CK) 7, Ber-EP4 and occasionally CK8/18 positive cells, and abluminal, CK5/6 positive, basal/basaloid cells revealing nuclear reactivity for p63/p40. Smooth muscle actin and calponin were negative, save for a single focus of calponin positive cells, confirming absence of myoepithelial support or epithelial mesenchymal transition. CK19 exhibited staining of both layers, the luminal being more intense. Eosinophilic secretory material and, occasionally, a luminal pellicle were decorated with CK8/18 and polyclonal carcinoembryonic antigen (CEA). CD1a identified only rare Langerhans' cells and Ki67 decorated 1-2% of abluminal cell nuclei. Small solid nests of epithelial cells were also present. Infrequently, an apparent transition of a nest into a tubular structure was appreciated. The partially inflamed stroma featured multiple hyalinized acellular deposits consistent with amyloid, as confirmed by bright orange Congo red reactivity with apple-green birefringence, which reacted with odontogenic ameloblast-associated (ODAM) protein antibody but not with antibodies for amelotin and secretory calcium-binding phosphoprotein proline-glutamine rich 1. Based on the above, the diagnosis of tubuloductal/syringoid variant of central odontogenic fibroma with ODAM amyloid is favored.
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http://dx.doi.org/10.1007/s12105-021-01369-7DOI Listing
August 2021

Dopaminergic neurons establish a distinctive axonal arbor with a majority of non-synaptic terminals.

FASEB J 2021 08;35(8):e21791

Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montréal, QC, Canada.

Chemical neurotransmission typically occurs through synapses. Previous ultrastructural examinations of monoamine neuron axon terminals often failed to identify a pre- and postsynaptic coupling, leading to the concept of "volume" transmission. Whether this results from intrinsic properties of these neurons remains undefined. We find that dopaminergic neurons in vitro establish a distinctive axonal arbor compared to glutamatergic or GABAergic neurons in both size and propensity of terminals to avoid direct contact with target neurons. While most dopaminergic varicosities are active and contain exocytosis proteins like synaptotagmin 1, only ~20% of these are synaptic. The active zone protein bassoon was found to be enriched in dopaminergic terminals that are in proximity to a target cell. Finally, we found that the proteins neurexin-1α and neuroligin-1 play a critical role in the formation of synapses by dopamine (DA) neurons. Our findings suggest that DA neurons are endowed with a distinctive developmental connectivity program.
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http://dx.doi.org/10.1096/fj.202100201RRDOI Listing
August 2021

A proline rich protein from the gingival seal around teeth exhibits antimicrobial properties against Porphyromonas gingivalis.

Sci Rep 2021 01 27;11(1):2353. Epub 2021 Jan 27.

Laboratory for the Study of Calcified Tissues and Biomaterials, Faculty of Dental Medicine, Université de Montréal, Montreal, QC, Canada.

The gingival seal around teeth prevents bacteria from destroying the tooth-supporting tissues and disseminating throughout the body. Porphyromonas gingivalis, a major periodontopathogen, degrades components of the specialized extracellular matrix that mediates attachment of the gingiva to the tooth. Of these, secretory calcium-binding phosphoprotein proline-glutamine rich 1 (SCPPPQ1) protein has a distinctive resistance to degradation, suggesting that it may offer resistance to bacterial attack. In silico analysis of its amino acid sequence was used to explore its molecular characteristics and to predict its two- and three-dimensional structure. SCPPPQ1 exhibits similarities with both proline-rich and cationic antimicrobial proteins, suggesting a putative antimicrobial potential. A combination of imaging approaches showed that incubation with 20 μM of purified SCPPPQ1 decrease bacterial number (p < 0.01). Fluorescence intensity decreased by 70% following a 2 h incubation of Porphyromonas gingivalis with the protein. Electron microscopy analyses revealed that SCPPPQ1 induced bacterial membrane disruption and breaches. While SCPPPQ1 has no effect on mammalian cells, our results suggest that it is bactericidal to Porphyromonas gingivalis, and that this protein, normally present in the gingival seal, may be exploited to maintain a healthy seal and prevent systemic dissemination of bacteria.
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http://dx.doi.org/10.1038/s41598-021-81791-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7840901PMC
January 2021

No endospore formation confirmed in members of the phylum Proteobacteria.

Appl Environ Microbiol 2020 Dec 18. Epub 2020 Dec 18.

Department of Microbiology & Immunology, The University of British Columbia, Vancouver, BC, Canada.

Endospore formation is used by members of the phylum Firmicutes to withstand extreme environmental conditions. Several recent studies have proposed endospore formation in species outside of Firmicutes, particularly in and , members of the phylum Proteobacteria. Here, we aimed to investigate endospore formation in these two species by using advanced imaging and analytical approaches. Examination of the phase-bright structures observed in and using cryo-electron tomography failed to identify endospores or stages of endospore formation. We determined that the phase-bright objects in cells were triacylglycerol storage granules and those in were aggregates of cellular debris. In addition, and containing phase-bright objects do not possess phenotypic and genetic features of endospores, including enhanced resistance to heat, presence of dipicolinic acid, or the presence of many of the genes associated with endospore formation. Our results support the hypothesis that endospore formation is restricted to the phylum Firmicutes. Bacterial endospore formation is an important process that allows the formation of dormant life forms called spores. As such, organisms able to sporulate can survive harsh environmental conditions for hundreds of years. Here, we follow up on previous claims that two members of Proteobacteria, and , are able to form spores. We conclude that those claims were incorrect and show that the putative spores in and are storage granules and cellular debris, respectively. This study concludes that endospore formation is still unique to the phylum Firmicutes.
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http://dx.doi.org/10.1128/AEM.02312-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8090866PMC
December 2020

Influence of Nanotopography on Early Bone Healing during Controlled Implant Loading.

Nanomaterials (Basel) 2020 Nov 3;10(11). Epub 2020 Nov 3.

Laboratory for the Study of Calcified Tissues and Biomaterials, Department of Stomatology, Faculty of Dental Medicine, Université de Montréal, Montréal, QC H3C3J7, Canada.

Nanoscale surface modifications influence peri-implant cell fate decisions and implant loading generates local tissue deformation, both of which will invariably impact bone healing. The objective of this study is to determine how loading affects healing around implants with nanotopography. Implants with a nanoporous surface were placed in over-sized osteotomies in rat tibiae and held stable by a system that permits controlled loading. Three regimens were applied: (a) no loading, (b) one daily loading session with a force of 1.5N, and (c) two such daily sessions. At 7 days post implantation, animals were sacrificed for histomorphometric and DNA microarray analyses. Implants subjected to no loading or only one daily loading session achieved high bone implant contact (BIC), bone implant distance (BID) and bone formation area near the implant (BFAt) values, while those subjected to two daily loading sessions showed less BFAt and BIC and more BID. Gene expression profiles differed between all groups mainly in unidentified genes, and no modulation of genes associated with inflammatory pathways was detected. These results indicate that implants with nanotopography can achieve a high level of bone formation even under micromotion and limit the inflammatory response to the implant surface.
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http://dx.doi.org/10.3390/nano10112191DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7693286PMC
November 2020

New Insights Into Sulfur Metabolism Through Coupled Gene Expression, Solution Chemistry, Microscopy, and Spectroscopy Analyses.

Front Microbiol 2020 13;11:411. Epub 2020 Mar 13.

School of Geography and Earth Science, Faculty of Science, McMaster University, Hamilton, ON, Canada.

Here, we experimentally expand understanding of the reactions and enzymes involved in ATCC 19377 S and metabolism by developing models that integrate gene expression analyzed by RNA-Seq, solution sulfur speciation, electron microscopy and spectroscopy. The metabolism model involves the conversion of to , S and mediated by the sulfur oxidase complex (Sox), tetrathionate hydrolase (TetH), sulfide quinone reductase (Sqr), and heterodisulfate reductase (Hdr) proteins. These same proteins, with the addition of rhodanese (Rhd), were identified to convert S to , and polythionates in the S metabolism model. Our combined results shed light onto the important role specifically of TetH in metabolism. Also, we show that activity of Hdr proteins rather than Sdo are likely associated with S oxidation. Finally, our data suggest that formation of intracellular is a critical step in S metabolism, and that recycling of internally generated occurs, through comproportionating reactions that result in . Electron microscopy and spectroscopy confirmed intracellular production and storage of S during growth on both S and substrates.
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http://dx.doi.org/10.3389/fmicb.2020.00411DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7082400PMC
March 2020

Nanoporosity Stimulates Cell Spreading and Focal Adhesion Formation in Cells with Mutated Paxillin.

ACS Appl Mater Interfaces 2020 Apr 19;12(13):14924-14932. Epub 2020 Mar 19.

Laboratory for the Study of Calcified Tissues and Biomaterials, Department of Stomatology, Faculty of Dentistry, Université de Montréal, Montréal, Québec H3C3J7, Canada.

We have evaluated the response to nanotopography of CHO-K1 cells that express wild-type paxillin or paxillin with mutations at serine 273 that inhibit phosphorylation. Cells were grown on nanoporous and polished titanium surfaces. With all cell types, immunofluorescence showed that adhesion and spreading were minimally affected on the treated surface and that the actin filaments were more abundant and well-aligned. Scanning electron microscopy revealed changes in cell shape and abundant filopodia with lateral nanoprotrusions in response to nanoporosity. Gene expression of proteins associated with cellular adhesion and protrusions was significantly increased on the nanoporous surface regardless of the cell type. In particular, α-actinin, Rac1, Cdc42, and ITGα1 were upregulated in S273 cells with alanine substitutions, whereas FAK, Pxn, and Src were downregulated, leading to improved focal adhesion formation. These findings suggest that the surface nanoporosity can "compensate for" the genetic mutations that affect the biomechanical relationship of cells to surfaces.
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http://dx.doi.org/10.1021/acsami.0c01172DOI Listing
April 2020

System for application of controlled forces on dental implants in rat maxillae: Influence of the number of load cycles on bone healing.

J Biomed Mater Res B Appl Biomater 2020 04 31;108(3):965-975. Epub 2019 Jul 31.

Laboratory for the Study of Calcified Tissues and Biomaterials, Faculty of Dental Medicine, Université de Montréal, Montreal, QC, Canada.

Experimental studies on the effect of micromotion on bone healing around implants are frequently conducted in long bones. In order to more closely reflect the anatomical and clinical environments around dental implants, and eventually be able to experimentally address load-management issues, we have developed a system that allows initial stabilization, protection from external forces, and controlled axial loading of implants. Screw-shaped implants were placed on the edentulous ridge in rat maxillae. Three loading regimens were applied to validate the system; case A no loading (unloaded implant) for 14 days, case B no loading in the first 7 days followed by 7 days of a single, daily loading session (60 cycles of an axial force of 1.5 N/cycle), and case C no loading in the first 7 days followed by 7 days of two such daily loading sessions. Finite element modeling of the peri-implant compressive and tensile strains plus histological and immunohistochemical analyses revealed that in case B any tissue damage resulting from the applied force (and related interfacial strains) did not per se disturb bone healing, however, in case C, the accumulation of damage resulting from the doubling of loading sessions severely disrupted the process. These proof-of-principle results validate the applicability of our system for controlled loading, and provide new evidence on the importance of the number of load cycles applied on healing of maxillary bone.
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http://dx.doi.org/10.1002/jbm.b.34449DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7078813PMC
April 2020

Cross-Linked Elastin-like Polypeptide Membranes as a Model for Medial Arterial Calcification.

Biomacromolecules 2019 07 21;20(7):2625-2636. Epub 2019 Jun 21.

Department of Mining and Materials Engineering , McGill University , Montreal , Quebec H3A 0C5 , Canada.

Calcium phosphate minerals deposit on the elastin-rich medial layers of arteries in the majority of seniors, diabetic, and chronic kidney disease patients, causing severe cardiovascular complications. There is no cure for medial calcification, and the mechanism of mineral formation on elastin layers is unknown. Here we propose cross-linked elastin-like polypeptide membranes as models to study medial calcification. Calcium phosphates deposit first on fibers and filaments and then spread to globular structures present in the membranes. Mineral phase evolution analyzed by near-edge X-ray spectroscopy matches that previously observed in a mouse model of medial calcification, showing that this simple system captures some of the key in vivo findings. This work shows how minerals form and evolve upon nucleation on elastin and provides an in vitro model that can be tuned to study hypotheses related to arterial calcification mechanisms and test drugs to stop or revert mineralization.
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http://dx.doi.org/10.1021/acs.biomac.9b00417DOI Listing
July 2019

Selective bacterial degradation of the extracellular matrix attaching the gingiva to the tooth.

Eur J Oral Sci 2019 08 22;127(4):313-322. Epub 2019 Jun 22.

Laboratory for the Study of Calcified Tissues and Biomaterials, Université de Montréal, Montréal, QC, Canada.

The junctional epithelium (JE) is a specialized portion of the gingiva that seals off the tooth-supporting tissues from the oral environment. This relationship is achieved via a unique adhesive extracellular matrix that is, in fact, a specialized basal lamina (sBL). Three unique proteins - amelotin (AMTN), odontogenic ameloblast-associated (ODAM), and secretory calcium-binding phosphoprotein proline-glutamine rich 1 (SCPPPQ1) - together with laminin-332 structure the supramolecular organization of this sBL and determine its adhesive capacity. Despite the constant challenge of the JE by the oral microbiome, little is known of the susceptibility of the sBL to bacterial degradation. Assays with trypsin-like proteases, as well as incubation with Porphyromonas gingivalis, Prevotella intermedia, and Treponema denticola, revealed that all constituents, except SCPPPQ1, were rapidly degraded. Porphyromonas gingivalis was also shown to alter the supramolecular network of reconstituted and native sBLs. These results provide evidence that proteolytic enzymes and selected gram-negative periodontopathogenic bacteria can attack this adhesive extracellular matrix, intimating that its degradation could contribute to progression of periodontal diseases.
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http://dx.doi.org/10.1111/eos.12623DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6771947PMC
August 2019

Surface nanocavitation of titanium modulates macrophage activity.

Int J Nanomedicine 2018 5;13:8297-8308. Epub 2018 Dec 5.

Laboratory for the Study of Calcified Tissues and Biomaterials, Department of Stomatology, Faculty of Dental Medicine, Université de Montréal, Montreal, QC, Canada,

Background: Nanoscale surface modifications are widely touted to improve the biocompatibility of medically relevant materials. Immune cells, such as macrophages, play a critical role in the initial healing events following implantation.

Methods: To understand the response of macrophages to nanotopography better, we exposed U937-derived macrophages to a distinctive mesoporous titanium surface (TiNano) produced by a process of simple chemical nanocavitation, and to mechanically polished titanium (TiPolished) and glass coverslip (Glass) surfaces as controls. Cell numbers and morphology were evaluated. Osteopontin expression and that of the proinflammatory SPARC protein and its stabilin 1 receptor were analyzed. Release of inflammation-associated cytokines and chemokines was also measured.

Results: Compared to the two control surfaces, there were fewer U937 cells on TiNano, and these exhibited a more rounded morphology with long filopodia. The cells showed areas of punctate actin distribution, indicating formation of podosomes. Of the three proteins examined, only osteopontin's immunofluorescence signal was clearly reduced. Irrespective of the substrate, the cytokine assay revealed important variations in expression levels of the multiple molecules analyzed and downregulation in a number of chemokines by the TiNano surface.

Conclusion: These results indicate that macrophages sense and respond to the physicochemical cueing generated by the nanocavitated surface, triggering cellular and molecular changes consistent with lesser inflammatory propensity. Given the previously reported beneficial outcome of this mesoporous surface on osteogenic activity, it could be presumed that modulation of the macrophagic response it elicits may also contribute to initial bone-integration events.
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http://dx.doi.org/10.2147/IJN.S185436DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6287524PMC
February 2019

High-yield production of human Dicer by transfection of human HEK293-EBNA1 cells grown in suspension.

BMC Biotechnol 2018 12 6;18(1):76. Epub 2018 Dec 6.

Département de Biochimie et Médecine Moléculaire, Université de Montréal, C.P. 6128, Succursale Centre-Ville, Montréal, H3C 3J7, QC, Canada.

Background: Dicer is a 219-kDa protein that plays key roles in gene regulation, particularly as the ribonuclease III enzyme responsible for cleaving precursor miRNA substrates. Its enzymatic activity is highly regulated by protein factors, and this regulation can impact on the levels of miRNAs and modulate the behavior of a cell. To better understand the underlying mechanisms of regulation, detailed enzymatic and structural characterization of Dicer are needed. However, these types of studies generally require several milligrams of recombinant protein, and efficient preparation of such quantities of pure human Dicer remains a challenge. To prepare large quantities of human Dicer, we have optimized transfection in HEK293-6E cells grown in suspension and streamlined a purification procedure.

Results: Transfection conditions were first optimized to achieve expression levels between 10 and 18 mg of recombinant Dicer per liter of culture. A three-step purification protocol was then developed that yields 4-9 mg of purified Dicer per liter of culture in a single day. From SEC-MALS/RI analysis and negative stain TEM, we confirmed that the purified protein is monomerically pure ( ≥ 98%) and folds with the characteristic L-shape geometry. Using an electrophoretic mobility shift assay, a dissociation constant (K) of 5 nM was measured for Dicer binding to pre-let-7a-1, in agreement with previous reports. However, when probing the cleavage activity of Dicer for pre-let-7a-1, we measured k (7.2 ± 0.5 min) and K (1.2 ± 0.3 μM) values that are much higher than previously reported due to experimental conditions that better respect the steady-state assumption.

Conclusions: The expression and purification protocols described here provide high yields of monomerically pure and active human Dicer. Cleavage studies of a pre-let-7 substrate with this purified Dicer reveal higher k and K values than previously reported and support the current view that conformational changes are associated with substrate binding. Large quantities of highly pure Dicer will be valuable for future biochemical, biophysical and structural investigations of this key protein of the miRNA pathway.
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http://dx.doi.org/10.1186/s12896-018-0485-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6282390PMC
December 2018

Axons morphometry in the human spinal cord.

Neuroimage 2019 01 13;185:119-128. Epub 2018 Oct 13.

NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, QC, Canada; Functional Neuroimaging Unit, CRIUGM, Université de Montréal, Montréal, QC, Canada. Electronic address:

Due to the technical challenges of large-scale microscopy and analysis, to date only limited knowledge has been made available about axon morphometry (diameter, shape, myelin thickness, volume fraction), thereby limiting our understanding of neuronal microstructure and slowing down research on neurodegenerative pathologies. This study addresses this knowledge gap by establishing a state-of-the-art acquisition and analysis framework for mapping axon morphometry, and providing the first comprehensive mapping of axon morphometry in the human spinal cord. We dissected, fixed and stained a human spinal cord with osmium tetroxide, and used a scanning electron microscope to image the entirety of 23 axial slices, covering C1 to L5 spinal levels. An automatic method based on deep learning was then used to segment each axon and myelin sheath to produce maps of axon morphometry. These maps were then registered to a standard spinal cord magnetic resonance imaging (MRI) template. Between 500,000 (lumbar) and 1 million (cervical) myelinated axons were segmented at each level of this human spinal cord. Morphometric features show a large disparity between tracts, but high right-left symmetry. Our results suggest a modality-based organization of the dorsal column in the human, as it has been observed in the rat. The generated axon morphometry template is publicly available at https://osf.io/8k7jr/ and could be used as a reference for quantitative MRI studies. The proposed framework for axon morphometry mapping could be extended to other parts of the central or peripheral nervous system that exhibit coherently-oriented axons.
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http://dx.doi.org/10.1016/j.neuroimage.2018.10.033DOI Listing
January 2019

Interaction via the N terminus of the type IV secretion system (T4SS) protein VirB6 with VirB10 is required for VirB2 and VirB5 incorporation into T-pili and for T4SS function.

J Biol Chem 2018 08 5;293(35):13415-13426. Epub 2018 Jul 5.

From the Department of Biochemistry and Molecular Medicine, Faculty of Medicine, Université de Montréal, Montréal, Quebec H3C 3J7, Canada and

Many bacterial pathogens employ multicomponent protein complexes such as type IV secretion systems (T4SSs) to transfer virulence factors into host cells. Here we studied the interaction between two essential T4SS components: the very hydrophobic inner membrane protein VirB6, which may be a component of the translocation channel, and VirB10, which links the inner and outer bacterial membranes. To map the interaction site between these two T4SS components, we conducted alanine scanning and deleted six-amino acid stretches from the N-terminal periplasmic domain of VirB6 from Using the bacterial two-hybrid system to analyze the effects of these alterations on the VirB6-VirB10 interaction, we identified the amino acid regions 16-21 and 28-33 and Leu-18 in VirB6 as being required for this interaction. SDS-PAGE coupled with Western blotting of cell lysates and native PAGE of detergent-extracted membrane proteins revealed that the corresponding VirB6 residues in (Phe-20 and amino acids 18-23 and 30-35) modulate the stability of both VirB6 and VirB5. However, the results from immuno-EM and super-resolution microscopy suggested that these regions and residues are not required for membrane association or for polar localization of VirB6. The six-amino acid deletions in the N terminus of VirB6 abolished pilus formation and virulence of , and the corresponding deletions in the VirB6 homolog TraD from the plasmid pKM101-T4SS abrogated plasmid transfer. Our results indicate that specific residues of the VirB6 N-terminal domain are required for VirB6 stabilization, its interaction with VirB10, and the incorporation of VirB2 and VirB5 into T-pili.
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http://dx.doi.org/10.1074/jbc.RA118.002751DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6120205PMC
August 2018

Bone healing response in cyclically loaded implants: Comparing zero, one, and two loading sessions per day.

J Mech Behav Biomed Mater 2018 09 31;85:152-161. Epub 2018 May 31.

Laboratory for the Study of Calcified Tissues and Biomaterials, Faculty of Dentistry, Université de Montréal, Montreal, QC, Canada. Electronic address:

When bone implants are loaded, they are inevitably subjected to displacement relative to bone. Such micromotion generates stress/strain states at the interface that can cause beneficial or detrimental sequels. The objective of this study is to better understand the mechanobiology of bone healing at the tissue-implant interface during repeated loading. Machined screw shaped Ti implants were placed in rat tibiae in a hole slightly bigger than the implant diameter. Implants were held stable by a specially-designed bone plate that permits controlled loading. Three loading regimens were applied, (a) zero loading, (b) one daily loading session of 60 cycles with an axial force of 1.5 N/cycle for 7 days, and (c) two such daily sessions with the same axial force also for 7 days. Finite element analysis was used to characterize the mechanobiological conditions produced by the loading sessions. After 7 days, the implants with surrounding interfacial tissue were harvested and processed for histological, histomorphometric and DNA microarray analyses. Histomorphometric analyses revealed that the group subjected to repeated loading sessions exhibited a significant decrease in bone-implant contact and increase in bone-implant distance, as compared to unloaded implants and those subjected to only one loading session. Gene expression profiles differed during osseointegration between all groups mainly with respect to inflammatory and unidentified gene categories. The results indicate that increasing the daily cyclic loading of implants induces deleterious changes in the bone healing response, most likely due to the accumulation of tissue damage and associated inflammatory reaction at the bone-implant interface.
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http://dx.doi.org/10.1016/j.jmbbm.2018.05.044DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6035061PMC
September 2018

VirB8 homolog TraE from plasmid pKM101 forms a hexameric ring structure and interacts with the VirB6 homolog TraD.

Proc Natl Acad Sci U S A 2018 06 21;115(23):5950-5955. Epub 2018 May 21.

Department of Biochemistry and Molecular Medicine, Faculty of Medicine, Université de Montréal, Montréal, QC, Canada H3C 3J7;

Type IV secretion systems (T4SSs) are multiprotein assemblies that translocate macromolecules across the cell envelope of bacteria. X-ray crystallographic and electron microscopy (EM) analyses have increasingly provided structural information on individual T4SS components and on the entire complex. As of now, relatively little information has been available on the exact localization of the inner membrane-bound T4SS components, notably the mostly periplasmic VirB8 protein and the very hydrophobic VirB6 protein. We show here that the membrane-bound, full-length version of the VirB8 homolog TraE from the plasmid pKM101 secretion system forms a high-molecular-mass complex that is distinct from the previously characterized periplasmic portion of the protein that forms dimers. Full-length TraE was extracted from the membranes with detergents, and analysis by size-exclusion chromatography, cross-linking, and size exclusion chromatography (SEC) multiangle light scattering (MALS) shows that it forms a high-molecular-mass complex. EM and small-angle X-ray scattering (SAXS) analysis demonstrate that full-length TraE forms a hexameric complex with a central pore. We also overproduced and purified the VirB6 homolog TraD and show by cross-linking, SEC, and EM that it binds to TraE. Our results suggest that TraE and TraD interact at the substrate translocation pore of the secretion system.
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http://dx.doi.org/10.1073/pnas.1802501115DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6003364PMC
June 2018

Three-dimensional printed PLA scaffold and human gingival stem cell-derived extracellular vesicles: a new tool for bone defect repair.

Stem Cell Res Ther 2018 04 13;9(1):104. Epub 2018 Apr 13.

Department of Medical, Oral and Biotechnological Sciences, University "G. d'Annunzio", Via dei Vestini, 66100, Chieti, Italy.

Background: The role of bone tissue engineering in the field of regenerative medicine has been a main research topic over the past few years. There has been much interest in the use of three-dimensional (3D) engineered scaffolds (PLA) complexed with human gingival mesenchymal stem cells (hGMSCs) as a new therapeutic strategy to improve bone tissue regeneration. These devices can mimic a more favorable endogenous microenvironment for cells in vivo by providing 3D substrates which are able to support cell survival, proliferation and differentiation. The present study evaluated the in vitro and in vivo capability of bone defect regeneration of 3D PLA, hGMSCs, extracellular vesicles (EVs), or polyethyleneimine (PEI)-engineered EVs (PEI-EVs) in the following experimental groups: 3D-PLA, 3D-PLA + hGMSCs, 3D-PLA + EVs, 3D-PLA + EVs + hGMSCs, 3D-PLA + PEI-EVs, 3D-PLA + PEI-EVs + hGMSCs.

Methods: The structural parameters of the scaffold were evaluated using both scanning electron microscopy and nondestructive microcomputed tomography. Nanotopographic surface features were investigated by means of atomic force microscopy. Scaffolds showed a statistically significant mass loss along the 112-day evaluation.

Results: Our in vitro results revealed that both 3D-PLA + EVs + hGMSCs and 3D-PLA + PEI-EVs + hGMSCs showed no cytotoxicity. However, 3D-PLA + PEI-EVs + hGMSCs exhibited greater osteogenic inductivity as revealed by morphological evaluation and transcriptomic analysis performed by next-generation sequencing (NGS). In addition, in vivo results showed that 3D-PLA + PEI-EVs + hGMSCs and 3D-PLA + PEI-EVs scaffolds implanted in rats subjected to cortical calvaria bone tissue damage were able to improve bone healing by showing better osteogenic properties. These results were supported also by computed tomography evaluation that revealed the repair of bone calvaria damage.

Conclusion: The re-establishing of the integrity of the bone lesions could be a promising strategy in the treatment of accidental or surgery trauma, especially for cranial bones.
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http://dx.doi.org/10.1186/s13287-018-0850-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5899396PMC
April 2018

TDP-43 regulates the alternative splicing of hnRNP A1 to yield an aggregation-prone variant in amyotrophic lateral sclerosis.

Brain 2018 05;141(5):1320-1333

Department of Neurosciences, Université de Montréal, Montréal, QC, Canada.

See Fratta and Isaacs (doi:10.1093/brain/awy091) for a scientific commentary on this article.The RNA binding proteins TDP-43 (encoded by TARDBP) and hnRNP A1 (HNRNPA1) are each mutated in certain amyotrophic lateral sclerosis cases and are often mislocalized in cytoplasmic aggregates within motor neurons of affected patients. Cytoplasmic inclusions of TDP-43, which are accompanied by a depletion of nuclear TDP-43, are observed in most amyotrophic lateral sclerosis cases and nearly half of frontotemporal dementia cases. Here, we report that TDP-43 binds HNRNPA1 pre-mRNA and modulates its splicing, and that depletion of nuclear TDP-43 results in increased inclusion of a cassette exon in the HNRNPA1 transcript, and consequently elevated protein levels of an isoform containing an elongated prion-like domain, referred to as hnRNP A1B. Combined in vivo and in vitro approaches demonstrated greater fibrillization propensity for hnRNP A1B, which drives protein aggregation and is toxic to cells. Moreover, amyotrophic lateral sclerosis patients with documented TDP-43 pathology showed neuronal hnRNP A1B cytoplasmic accumulation, indicating that TDP-43 mislocalization may contribute to neuronal vulnerability and loss via altered HNRNPA1 pre-mRNA splicing and function. Given that TDP-43 and hnRNP A1 each bind, and thus modulate, a third of the transcriptome, our data suggest a much broader disruption in RNA metabolism than previously considered.
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http://dx.doi.org/10.1093/brain/awy062DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5917749PMC
May 2018

Chemical nanocavitation of surfaces to enhance the utility of stainless steel as a medical material.

Colloids Surf B Biointerfaces 2018 Jan 22;161:677-687. Epub 2017 Nov 22.

Laboratory for the Study of Calcified Tissues & Biomaterials, Faculté de Médecine Dentaire, Université de Montréal, Montréal, Québec H3T 1J4 Canada; Département de Biochimie et Médecine Moléculaire, Université de Montréal, Montréal, Québec H3C 3J7, Canada. Electronic address:

While stainless steel is a broadly used alloy with interesting mechanical properties, its applications in medicine suffers from inherent biocompatibility limitations. An attractive opportunity to improve its performance is to alter its surface, but this has proven challenging. We now show how high range anodization conditions using HSO/HO as an atypical electrolyte can efficiently nanocavitate the surface of both stainless steel SS304 and SS316 and create a topography with advantageous biomedical characteristics. We describe the structural and chemical features of the resulting surfaces, and propose a nanocorrosion/transpassivation/repassivation mechanism for its creation. Our approach creates a thin mesoporous layer of crystalline oxide that selectively promotes mammalian cell activity and limits bacterial adhesion. The modified surfaces favor the formation and maturation of focal adhesion plaques and environment-sensing filopodia with abundant extra small lateral membrane protrusions, suggesting an increase in membrane fluidity. These protrusions represent a yet undescribed cellular response. Such surfaces promise to facilitate the integration of implantable SS devices, in general. In addition, our strategy simultaneously provides a simple, commercially attractive way to control the adhesion of microorganisms, making nanostructured stainless steel broadly useful in hospital environments, in manufacturing medical devices, as well as offering possibilities for non-medical applications.
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http://dx.doi.org/10.1016/j.colsurfb.2017.11.051DOI Listing
January 2018

A nanoporous titanium surface promotes the maturation of focal adhesions and formation of filopodia with distinctive nanoscale protrusions by osteogenic cells.

Acta Biomater 2017 09 17;60:339-349. Epub 2017 Jul 17.

Laboratory for the Study of Calcified Tissues and Biomaterials, Department of Stomatology, Faculty of Dentistry, Université de Montréal, C.P 6128 succursale Centre-Ville, Montréal, Québec H3C3J7, Canada; Department of Biochemistry and Molecular Medicine, Faculty of Medicine, Université de Montréal, C.P 6128 succursale Centre-Ville, Montréal, Québec H3C3J7, Canada. Electronic address:

While topography is a key determinant of the cellular response to biomaterials, the mechanisms implicated in the cell-surface interactions are complex and still not fully elucidated. In this context, we have examined the effect of nanoscale topography on the formation of filopodia, focal adhesions, and gene expression of proteins associated with cell adhesion and sensing. Commercially pure titanium discs were treated by oxidative nanopatterning with a solution of HSO/HO 50:50 (v/v). Scanning electron microscopy and atomic force microscopy characterizations showed that this facile chemical treatment efficiently creates a unique nanoporous surface with a root-mean-square roughness of 11.5nm and pore diameter of 20±5nm. Osteogenic cells were cultured on polished (control) and nanotextured discs for periods of 6, 24, and 72h. Immunofluorescence analysis revealed increases in the adhesion formation per cell area, focal adhesion length, and maturity on the nanoporous surface. Gene expression for various focal adhesion markers, including paxillin and talin, and different integrins (e.g. α1, β1, and α5) was also significantly increased. Scanning electron microscopy revealed the presence of more filopodia on cells grown on the nanoporous surface. These cell extensions displayed abundant and distinctive nanoscale lateral protrusions of 10-15nm diameter that molded the nanopore walls. Together the increase in the focal adhesions and abundance of filopodia and associated protrusions could contribute to strengthening the adhesive interaction of cells with the surface, and thereby, alter the nanoscale biomechanical relationships that trigger cellular cascades that regulate cell behavior.

Statement Of Significance: Oxidative patterning was exploited to create a unique three-dimensional network of nanopores on titanium surfaces. Our study illustrates how a facile chemical treatment can be advantageously used to modulate cellular behavior. The nanoscale lateral protrusions on filopodia elicited by this surface are novel adhesive structures. Altogether, the increases in focal adhesion, length, maturity, and filopodia with distinctive lateral protrusions could substantially increase the contact area and adhesion strength of cells, thereby promoting the activation of cellular signaling cascades that may explain the positive osteogenic outcomes previously achieved with this surface. Such physicochemical cueing offers a simple attractive alternative to the use of bioactive agents for guiding tissue repair/regeneration around implantable metals.
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http://dx.doi.org/10.1016/j.actbio.2017.07.022DOI Listing
September 2017

Interactions of AMTN, ODAM and SCPPPQ1 proteins of a specialized basal lamina that attaches epithelial cells to tooth mineral.

Sci Rep 2017 04 24;7:46683. Epub 2017 Apr 24.

Laboratory for the Study of Calcified Tissues and Biomaterials, Department of Stomatology, Faculty of Dental medicine Université de Montréal, Montréal, Québec, Canada.

A specialized basal lamina (sBL) mediates adhesion of certain epithelial cells to the tooth. It is distinct because it does not contain collagens type IV and VII, is enriched in laminin-332, and includes three novel constituents called amelotin (AMTN), odontogenic ameloblast-associated (ODAM), and secretory calcium-binding phosphoprotein proline-glutamine rich 1 (SCPPPQ1). The objective of this study was to clarify the structural organization of the sBL. Fluorescence and immunogold labeling showed that the three proteins co-localize. Quantitative analysis of the relative position of gold particles on the sBL demonstrates that the distribution of ODAM is skewed towards the cell while that of AMTN and SCPPPQ1 tends towards the tooth surface. Bacterial two-hybrid analysis and co-immunoprecipitation, gel filtration of purified proteins and transmission electron and atomic force microscopies highlight the propensity of AMTN, ODAM, and SCPPPQ1 to interact with and among themselves and form supramolecular aggregates. These data suggest that AMTN, ODAM and SCPPPQ1 participate in structuring an extracellular matrix with the distinctive capacity of attaching epithelial cells to mineralized surfaces. This unique feature is particularly relevant for the adhesion of gingival epithelial cells to the tooth surface, which forms a protective seal that is the first line of defense against bacterial invasion.
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http://dx.doi.org/10.1038/srep46683DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5402393PMC
April 2017

Absence of the dermatan sulfate chain of decorin does not affect mouse development.

J Negat Results Biomed 2017 Apr 17;16(1). Epub 2017 Apr 17.

Research Center, Shriners Hospitals for Children - Canada, 1003 Boulevard Décarie, Montréal, H4A 0A9, QC, Canada.

Background: In vitro studies suggest that the multiple functions of decorin are related to both its core protein and its dermatan sulfate chain. To determine the contribution of the dermatan sulfate chain to the functional properties of decorin in vivo, a mutant mouse whose decorin lacked a dermatan sulfate chain was generated.

Results: Homozygous mice expressing only the decorin core protein developed and grew in a similar manner to wild type mice. In both embryonic and postnatal mice, all connective tissues studied, including cartilage, skin and cornea, appeared to be normal upon histological examination, and their collagen fibrils were of normal diameter and organization. In addition, abdominal skin wounds healed in an identical manner in the mutant and wild type mice.

Conclusions: The absence of a dermatan sulfate chain on decorin does not appear to overtly influence its functional properties in vivo.
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http://dx.doi.org/10.1186/s12952-017-0074-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5393030PMC
April 2017

Cag-delta (Cag3) protein from the Helicobacter pylori 26695 cag type IV secretion system forms ring-like supramolecular assemblies.

FEMS Microbiol Lett 2017 01 15;364(1). Epub 2016 Dec 15.

Department of Biochemistry and Molecular Medicine, Faculty of Medicine, Université de Montréal, Montreal, QC H3C 3J7, Canada

Helicobacter pylori is an important cause of gastric pathologies and persistent infection can lead to stomach cancer. Virulent H. pylori strains encode a type IV secretion system responsible for translocation of the oncogenic CagA protein into cells of the gastric mucosa. Gene HP0522 encodes the essential component Cagδ (Cag3), and we show by gel filtration and cross-linking that purified Cagδ forms high molecular mass complexes. In contrast, its interaction partner CagT is mostly monomeric, but co-fractionates after gel filtration. Analysis by transmission electron microscopy revealed that purified Cagδ complexes can self-assemble ring-like structures. Cagδ-overexpressing Escherichia coli exhibits membrane-associated circular profiles in regions of the cell envelope with intense immunogold labelling with a Cagδ-specific antiserum. Our results suggest that Cagδ has the capacity to form macromolecular structures contributing to the assembly of the type IV secretion system.
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http://dx.doi.org/10.1093/femsle/fnw280DOI Listing
January 2017

Laminin γ2 knockout mice rescued with the human protein exhibit enamel maturation defects.

Matrix Biol 2016 May-Jul;52-54:207-218. Epub 2016 Mar 5.

Laboratory for the Study of Calcified Tissues and Biomaterials, Department of Stomatology, Faculty of Dentistry, Université de Montréal, Montréal, Québec, Canada; Department of Biochemistry and Molecular Medicine, Université de Montréal, Montréal, Québec, Canada. Electronic address:

The epithelial ameloblasts are separated from the maturing enamel by an atypical basement membrane (BM) that is enriched in laminin 332 (LM-332). This heterotrimeric protein (α3, ß3 and γ2 chains) provides structural integrity to BMs and influences various epithelial cell processes including cell adhesion and differentiation. Mouse models that lack expression of individual LM-332 chains die shortly after birth. The lethal phenotype of laminin γ2 knockout mice can be rescued by human laminin γ2 (LAMC2) expressed using a doxycycline-inducible (Tet-on) cytokeratin 14 promoter-rtTA. These otherwise normal-looking rescued mice exhibit white spot lesions on incisors. We therefore investigated the effect of rescue with human LAMC2 on enamel maturation and structuring of the atypical BM. The maturation stage enamel organ in transgenic mice was severely altered as compared to wild type controls, a structured BM was no longer discernible, dystrophic matrix appeared in the maturing enamel layer, and there was residual enamel matrix late into the maturation stage. Microtomographic scans revealed excessive wear of occlusal surfaces on molars, chipping of enamel on incisor tips, and hypomineralization of the enamel layer. No structural alterations were observed at other epithelial sites, such as skin, palate and tongue. These results indicate that while this humanized mouse model is capable of rescue in various epithelial tissues, it is unable to sustain structuring of a proper BM at the interface between ameloblasts and maturing enamel. This failure may be related to the atypical composition of the BM in the maturation stage and reaffirms that the atypical BM is essential for enamel maturation.
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http://dx.doi.org/10.1016/j.matbio.2016.03.002DOI Listing
December 2017

Histomorphometric analysis of overloading on palatal tooth movement into the maxillary sinus.

Am J Orthod Dentofacial Orthop 2015 Sep;148(3):423-30

Professor and chair, Department of Orthodontics and Dentofacial Orthopedics, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan; distinguished adjunct professor, King Abdulaziz University, Jeddah, Saudi Arabia.

Introduction: Our objective was to evaluate the effect of overloading on the palatal movement of the maxillary molar.

Methods: The maxillary first molars of male C57Bl/6 mice were moved palatally with loads of 10 or 30 g for 14 days, and the amount of tooth movement was longitudinally measured on microcomputed tomography images. Bone remodeling around the molar root with the 30-g load was evaluated at days 3, 5, 7, and 14 after the start of tooth movement using histomorphometry and immunodetection of bone-restricted interferon inducible transmembrane-like protein, a novel marker of active bone formation.

Results: In the 10-g load group, the amount of tooth movement increased dramatically between days 5 and 7 and increased gradually thereafter. Tooth movement at days 5 and 7 was significantly lower in the 30-g-load group than in the 10-g load group; however, the total tooth movement at 14 days was similar in the 2 groups. An orthodontic load of 30 g stimulated bone formation on the sinus wall, but bone resorption on the periodontal ligament side was delayed because of hyalinization, which means that strong force application did not accelerate tooth movement. Moreover, some root resorption was induced by the excessive force.

Conclusions: Root penetration into the sinus and bone height reduction do not occur because new bone formation on the maxillary sinus is induced before bone resorption on the periodontal side, even though an excessive orthodontic force is applied. However, an excessive force can induce root resorption.
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http://dx.doi.org/10.1016/j.ajodo.2015.04.032DOI Listing
September 2015

Influence of periodontal tissue thickness on buccal plate remodelling on immediate implants with xenograft.

J Clin Periodontol 2015 Jun 4;42(6):590-8. Epub 2015 May 4.

Department of Bucco-Maxilo-Facial Surgery and Traumatology and Periodontology, School of Dentistry of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil.

Aim: To evaluate the influence of gingival thickness and bone grafting on buccal bone plate remodelling after immediate implant placement in sockets with thin buccal bone, using a flapless approach.

Materials And Methods: The gingiva of eight dogs was thinned at one side of the mandible, mandibular premolars were extracted without flaps, and four implants were installed on each side at 1.5 mm from the buccal bone. The sites were randomly assigned into: TG (test group) = thin gingiva; TG + GM (TG with grafting material); CG (control group) = normal gingiva; and CG + GM (CG with grafting material). After 12 weeks the dogs were sacrificed and the samples were processed for histological analysis.

Results: All animals exhibited a thin buccal bone initially. In all the experimental groups the buccal gap was filled with newly formed bone and the buccal bone level was slightly apical to the implant shoulder. There were no statistically significant differences among the groups for the histomorphometric parameters.

Conclusions: The thickness of the buccal bone was a fundamental factor in buccal bone plate resorption, even with flapless implantation. The gingival thickness or the addition of a biomaterial in the gap did not influence the results.
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http://dx.doi.org/10.1111/jcpe.12405DOI Listing
June 2015

Characterisation of secretory calcium-binding phosphoprotein-proline-glutamine-rich 1: a novel basal lamina component expressed at cell-tooth interfaces.

Cell Tissue Res 2014 Dec 6;358(3):843-55. Epub 2014 Sep 6.

Shriners Hospital for Children, Montréal, Québec, Canada.

Functional genomic screening of the rat enamel organ (EO) has led to the identification of a number of secreted proteins expressed during the maturation stage of amelogenesis, including amelotin (AMTN) and odontogenic ameloblast-associated (ODAM). In this study, we characterise the gene, protein and pattern of expression of a related protein called secretory calcium-binding phosphoprotein-proline-glutamine-rich 1 (SCPPPQ1). The Scpppq1 gene resides within the secretory calcium-binding phosphoprotein (Scpp) cluster. SCPPPQ1 is a highly conserved, 75-residue, secreted protein rich in proline, leucine, glutamine and phenylalanine. In silico data mining has revealed no correlation to any known sequences. Northern blotting of various rat tissues suggests that the expression of Scpppq1 is restricted to tooth and associated tissues. Immunohistochemical analyses show that the protein is expressed during the late maturation stage of amelogenesis and in the junctional epithelium where it localises to an atypical basal lamina at the cell-tooth interface. This discrete localisation suggests that SCPPPQ1, together with AMTN and ODAM, participates in structuring the basal lamina and in mediating attachment of epithelia cells to mineralised tooth surfaces.
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http://dx.doi.org/10.1007/s00441-014-1989-3DOI Listing
December 2014

Osteogenic cell cultures cannot utilize exogenous sources of synthetic polyphosphate for mineralization.

J Cell Biochem 2014 Dec;115(12):2089-102

Department of Stomatology, Faculty of Dentistry, Université de Montréal, P.O. Box 6128 Station Centre-Ville, Montréal Québec, Canada, H3C 3J7.

Phosphate is critical for mineralization and deficiencies in the regulation of free phosphate lead to disease. Inorganic polyphosphates (polyPs) may represent a physiological source of phosphate because they can be hydrolyzed by biological phosphatases. To investigate whether exogenous polyP could be utilized for mineral formation, mineralization was evaluated in two osteogenic cell lines, Saos-2 and MC3T3, expressing different levels of tissue non-specific alkaline phosphatase (tnALP). The role of tnALP was further explored by lentiviral-mediated overexpression in MC3T3 cells. When cells were cultured in the presence of three different phosphate sources, there was a strong mineralization response with β-glycerophosphate (βGP) and orthophosphate (Pi) but none of the cultures sustained mineralization in the presence of polyP (neither chain length 17-Pi nor 42-Pi). Even in the presence of mineralizing levels of phosphate, low concentrations of polyP (50 μM) were sufficient to inhibit mineral formation. Energy-dispersive X-ray spectroscopy confirmed the presence of apatite-like mineral deposits in MC3T3 cultures supplemented with βGP, but not in those with polyP. While von Kossa staining was consistent with the presence or absence of mineral, an unusual Alizarin staining was obtained in polyP-treated MC3T3 cultures. This staining pattern combined with low Ca:P ratios suggests the persistence of Ca-polyP complexes, even with high residual ALP activity. In conclusion, under standard culture conditions, exogenous polyP does not promote mineral deposition. This is not due to a lack of active ALP, and unless conditions that favor significant processing of polyP are achieved, its mineral inhibitory capacity predominates.
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http://dx.doi.org/10.1002/jcb.24886DOI Listing
December 2014

Oxidative nanopatterning of titanium generates mesoporous surfaces with antimicrobial properties.

Int J Nanomedicine 2014 13;9:2319-25. Epub 2014 May 13.

Faculty of Dental Medicine, Université de Montréal, Montreal, QC, Canada.

Mesoporous surfaces generated by oxidative nanopatterning have the capacity to selectively regulate cell behavior, but their impact on microorganisms has not yet been explored. The main objective of this study was to test the effects of such surfaces on the adherence of two common bacteria and one yeast strain that are responsible for nosocomial infections in clinical settings and biomedical applications. In addition, because surface characteristics are known to affect bacterial adhesion, we further characterized the physicochemical properties of the mesoporous surfaces. Focused ion beam (FIB) was used to generate ultrathin sections for elemental analysis by energy-dispersive X-ray spectroscopy (EDS), nanobeam electron diffraction (NBED), and high-angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) imaging. The adherence of Staphylococcus aureus, Escherichia coli and Candida albicans onto titanium disks with mesoporous and polished surfaces was compared. Disks with the two surfaces side-by-side were also used for direct visual comparison. Qualitative and quantitative results from this study indicate that bacterial adhesion is significantly hindered by the mesoporous surface. In addition, we provide evidence that it alters structural parameters of C. albicans that determine its invasiveness potential, suggesting that microorganisms can sense and respond to the mesoporous surface. Our findings demonstrate the efficiency of a simple chemical oxidative treatment in generating nanotextured surfaces with antimicrobial capacity with potential applications in the implant manufacturing industry and hospital setting.
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http://dx.doi.org/10.2147/IJN.S61333DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4026557PMC
December 2014
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