Publications by authors named "Ramaswamy Sharma"

38 Publications

Part-time cancers and role of melatonin in determining their metabolic phenotype.

Life Sci 2021 May 8;278:119597. Epub 2021 May 8.

Departamento de Biologia Estrutural e Funcional, Instituto de Biociencias, Botucatu, Sao Poalo 18618-689, Brazil.

This brief review describes the association of the endogenous pineal melatonin rhythm with the metabolic flux of solid tumors, particularly breast cancer. It also summarizes new information on the potential mechanisms by which endogenously-produced or exogenously-administered melatonin impacts the metabolic phenotype of cancer cells. The evidence indicates that solid tumors may redirect their metabolic phenotype from the pathological Warburg-type metabolism during the day to the healthier mitochondrial oxidative phosphorylation on a nightly basis. Thus, they function as cancer cells only during the day and as healthier cells at night, that is, they are only part-time cancerous. This switch to oxidative phosphorylation at night causes cancer cells to exhibit a reduced tumor phenotype and less likely to rapidly proliferate or to become invasive or metastatic. Also discussed is the likelihood that some solid tumors are especially aggressive during the day and much less so at night due to the nocturnal rise in melatonin which determines their metabolic state. We further propose that when melatonin is used/tested in clinical trials, a specific treatment paradigm be used that is consistent with the temporal metabolic changes in tumor metabolism. Finally, it seems likely that the concurrent use of melatonin in combination with conventional chemotherapies also would improve cancer treatment outcomes.
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http://dx.doi.org/10.1016/j.lfs.2021.119597DOI Listing
May 2021

Medical Histopathology Laboratories: Remote Teaching in Response to COVID-19 Pandemic.

Acad Pathol 2021 Jan-Dec;8:2374289521998049. Epub 2021 Mar 8.

Department of Pathology, Joe R. and Teresa Lozano Long School of Medicine, University of Texas Health San Antonio, San Antonio, TX, USA.

The COVID-19 pandemic required the rapid conversion of medical school curricula to virtual instruction. Prior to the crisis, histopathology teaching laboratories at UT Health San Antonio included completion of an Individual Laboratory Quiz before the laboratory session, a Team Application Exercise released and completed during the laboratory session with guidance from faculty, and a graded Team Laboratory Quiz at the end of the laboratory session. Adaptation of this interactive, in-person activity to a fully online platform included releasing the Team Application Exercise earlier to provide ample time for students to work virtually with their teams, conducting laboratory sessions using Microsoft Teams, with 5 to 6 teams led by a single instructor, and requiring the Team Laboratory Quiz to be taken individually for ensuring quiz security and test integrity. For incentivizing collaboration while completing the Team Application Exercise, the final score was either the student's individual score on the Team Laboratory Quiz or their team's average, whichever was higher. Comparison of student scores on the modified Team Laboratory Quiz to Team Laboratory Quiz scores using the earlier laboratory format prior to COVID-19 showed a significant decline; however, scores on other weekly quizzes or examinations were unaffected. Students welcomed the early release of Team Application Exercise and easier access to faculty but indicated that the modified Team Laboratory Quiz decreased peer-teaching and learning experience and increased anxiety. Faculty indicated the loss of personal interaction with students as a major theme. These data suggest that novel pedagogical approaches are required for online histopathology instruction to accommodate differences in learning styles while maintaining the benefits of team collaboration.
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http://dx.doi.org/10.1177/2374289521998049DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7944527PMC
March 2021

Anti-Warburg Effect of Melatonin: A Proposed Mechanism to Explain its Inhibition of Multiple Diseases.

Int J Mol Sci 2021 Jan 14;22(2). Epub 2021 Jan 14.

Centro de Investigacion Biomedica de Occidente, Instituto Mexicano del Seguro Social, Guadalajara, Jalisco CP45150, Mexico.

Glucose is an essential nutrient for every cell but its metabolic fate depends on cellular phenotype. Normally, the product of cytosolic glycolysis, pyruvate, is transported into mitochondria and irreversibly converted to acetyl coenzyme A by pyruvate dehydrogenase complex (PDC). In some pathological cells, however, pyruvate transport into the mitochondria is blocked due to the inhibition of PDC by pyruvate dehydrogenase kinase. This altered metabolism is referred to as aerobic glycolysis (Warburg effect) and is common in solid tumors and in other pathological cells. Switching from mitochondrial oxidative phosphorylation to aerobic glycolysis provides diseased cells with advantages because of the rapid production of ATP and the activation of pentose phosphate pathway (PPP) which provides nucleotides required for elevated cellular metabolism. Molecules, called glycolytics, inhibit aerobic glycolysis and convert cells to a healthier phenotype. Glycolytics often function by inhibiting hypoxia-inducible factor-1α leading to PDC disinhibition allowing for intramitochondrial conversion of pyruvate into acetyl coenzyme A. Melatonin is a glycolytic which converts diseased cells to the healthier phenotype. Herein we propose that melatonin's function as a glycolytic explains its actions in inhibiting a variety of diseases. Thus, the common denominator is melatonin's action in switching the metabolic phenotype of cells.
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http://dx.doi.org/10.3390/ijms22020764DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7828708PMC
January 2021

Role of Melatonin on Virus-Induced Neuropathogenesis-A Concomitant Therapeutic Strategy to Understand SARS-CoV-2 Infection.

Antioxidants (Basel) 2021 Jan 2;10(1). Epub 2021 Jan 2.

Department of Cell Systems & Anatomy, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA.

Viral infections may cause neurological disorders by directly inducing oxidative stress and interrupting immune system function, both of which contribute to neuronal death. Several reports have described the neurological manifestations in Covid-19 patients where, in severe cases of the infection, brain inflammation and encephalitis are common. Recently, extensive research-based studies have revealed and acknowledged the clinical and preventive roles of melatonin in some viral diseases. Melatonin has been shown to have antiviral properties against several viral infections which are accompanied by neurological symptoms. The beneficial properties of melatonin relate to its properties as a potent antioxidant, anti-inflammatory, and immunoregulatory molecule and its neuroprotective effects. In this review, what is known about the therapeutic role of melatonin in virus-induced neuropathogenesis is summarized and discussed.
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http://dx.doi.org/10.3390/antiox10010047DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7823793PMC
January 2021

Melatonin synthesis in and uptake by mitochondria: implications for diseased cells with dysfunctional mitochondria.

Future Med Chem 2021 Feb 5;13(4):335-339. Epub 2021 Jan 5.

Departamento de Morfología y Biología Celular, Facultad de Medicina, c/JulianClaveria, 6, Oviedo 33006, Spain.

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http://dx.doi.org/10.4155/fmc-2020-0326DOI Listing
February 2021

Sirtuins and the circadian clock interplay in cardioprotection: focus on sirtuin 1.

Cell Mol Life Sci 2021 Mar 3;78(6):2503-2515. Epub 2021 Jan 3.

Department of Cell Systems and Anatomy, UT Health San Antonio, San Antonio, TX, USA.

Chronic disruption of circadian rhythms which include intricate molecular transcription-translation feedback loops of evolutionarily conserved clock genes has serious health consequences and negatively affects cardiovascular physiology. Sirtuins (SIRTs) are nuclear, cytoplasmic and mitochondrial histone deacetylases that influence the circadian clock with clock-controlled oscillatory protein, NAMPT, and its metabolite NAD. Sirtuins are linked to the multi-organ protective role of melatonin, particularly in acute kidney injury and in cardiovascular diseases, where melatonin, via upregulation of SIRT1 expression, inhibits the apoptotic pathway. This review focuses on SIRT1, an NAD-dependent class III histone deacetylase which counterbalances the intrinsic histone acetyltransferase activity of one of the clock genes, CLOCK. SIRT1 is involved in the development of cardiomyocytes, regulation of voltage-gated cardiac sodium ion channels via deacetylation, prevention of atherosclerotic plaque formation in the cardiovascular system, protection against oxidative damage and anti-thrombotic actions. Overall, SIRT1 has a see-saw effect on cardioprotection, with low levels being cardioprotective and higher levels leading to cardiac hypertrophy.
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http://dx.doi.org/10.1007/s00018-020-03713-6DOI Listing
March 2021

Central and peripheral actions of melatonin on reproduction in seasonal and continuous breeding mammals.

Gen Comp Endocrinol 2021 01 18;300:113620. Epub 2020 Sep 18.

Department of Cell Systems and Anatomy, UT Health San Antonio, San Antonio, TX, United States.

Under field conditions, especially for mammals that inhabit high latitudes, the regulation of seasonal breeding activity to ensure delivery of the young at the time most conducive to their survival is essential. This is most frequently accomplished by the annual reproductive cycle being linked to seasonal photoperiod changes which determine the nocturnal duration of the pineal melatonin signal. Mating can occur during any season that ensures spring/early summer delivery of the offspring. Thus, the season of mating is determined by the duration of pregnancy. The precise hormonal control of the annual cycle of reproduction by melatonin is accomplished at the level of the hypothalamo-pituitary axis which, in turn, determines the physiological state of the gonad and adnexa due to the regulation of pituitary gonadotrophin release. Many species are continuous rather than seasonal breeders. In these species, melatonin has a minor hormonal influence on the central regulation of reproduction but, nevertheless, its antioxidant functions at the level of the gonads support optimal reproductive physiology. Possibly like all cells, those in the ovary, e.g., granulosa cells and oocytes (less is known about melatonin synthesis by the testes or spermatogenic cells), synthesize melatonin which is used locally to combat free radicals and reactive nitrogen species which would otherwise cause oxidative/nitrosative stress to these critically important cells. Oxidative damage to the oocyte, zygote, blastocyst, etc., results in an abnormal fetus which is either sloughed or gives rise to an unhealthy offspring. The importance of the protection of the gametes (both oocytes and sperm) from oxidative molecular mutilation cannot be overstated. Fortunately, as a highly effective free radical scavenger and indirect antioxidant (by upregulating antioxidant enzyme), locally-produced melatonin is in the optimal location to protect the reproductive system from such damage.
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http://dx.doi.org/10.1016/j.ygcen.2020.113620DOI Listing
January 2021

Circadian disruption, melatonin rhythm perturbations and their contributions to chaotic physiology.

Adv Med Sci 2020 Sep 4;65(2):394-402. Epub 2020 Aug 4.

Department of Cell Systems and Anatomy, UT Health, San Antonio, TX, USA.

The aim of this report is to summarize the data documenting the vital nature of well-regulated cellular and organismal circadian rhythms, which are also reflected in a stable melatonin cycle, in supporting optimal health. Cellular fluctuations in physiology exist in most cells of multicellular organisms with their stability relying on the prevailing light:dark cycle, since it regulates, via specialized intrinsically-photoreceptive retinal ganglion cells (ipRGC) and the retinohypothalamic tract, the master circadian oscillator, i.e., the suprachiasmatic nuclei (SCN). The output message of the SCN, as determined by the light:dark cycle, is transferred to peripheral oscillators, so-called slave cellular oscillators, directly via the autonomic nervous system with its limited distribution. and indirectly via the pineal-derived circulating melatonin rhythm, which contacts every cell. Via its regulatory effects on the neuroendocrine system, particularly the hypothalamo-pituitary-adrenal axis, the SCN also has a major influence on the adrenal glucocorticoid rhythm which impacts neurological diseases and psychological behaviors. Moreover, the SCN regulates the circadian production and secretion of melatonin. When the central circadian oscillator is disturbed, such as by light at night, it passes misinformation to all organs in the body. When this occurs the physiology of cells becomes altered and normal cellular functions are compromised. This physiological upheaval is a precursor to pathologies. The deterioration of the SCN/pineal network is often a normal consequence of aging and its related diseases, but in today's societies where manufactured light is becoming progressively more common worldwide, the associated pathologies may also be occurring at an earlier age.
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http://dx.doi.org/10.1016/j.advms.2020.07.001DOI Listing
September 2020

CSF-1 in Osteocytes Inhibits Nox4-mediated Oxidative Stress and Promotes Normal Bone Homeostasis.

JBMR Plus 2020 Jul 13;4(7):e10080. Epub 2019 Jun 13.

Department of Biochemistry and Structural Biology University of Texas Health Science Center at San Antonio TX USA.

CSF-1 is a key factor in regulating bone remodeling; osteocytes express CSF-1 and its receptor. Viable osteocytes are essential for bone remodeling through cell-cell contact and secretion of factors that regulate osteoblasts and osteoclasts. Increased oxidative stress contributes to osteocyte death and correlates with bone loss during aging. The NADPH oxidase Nox4 is a major source of ROS in bone. CSF-1 decreases Nox4, suggesting that CSF-1 protects against oxidative stress. Here, we show that osteocyte apoptosis previously reported in our global CSF-1KO mice is associated with increased Nox4, as well as 4-HNE expression in osteocytes. Osteocytes isolated from CSF-1KO mice were less viable and showed increased intracellular ROS, elevated NADPH oxidase activity/Nox4 protein, activation of mTOR/S6K, and downstream apoptosis signals compared with WT osteocytes. Nox4 expression was also increased in CSF-1KO osteocytes and colocalized with MitoTracker Red in mitochondria. Notably, CSF-1 inhibited Nox4 expression and apoptosis cascade signals. In additional studies, shNox4 decreased these signals in CSF-1KO osteocytes, whereas overexpression of Nox4 in WT osteocytes activated the apoptosis pathway. To determine the role of CSF-1 in osteocytes, DMP1Cre-CSF-1cKO (CSF-1cKO) mice that lack CSF-1 in osteocytes/late osteoblasts were developed. Osteocyte defects in CSF-1cKO mice overlapped with those in CSF-1KO mice, including increased apoptosis, Nox4, and 4-HNE-expressing osteocytes. CSF-1cKO mice showed unbalanced cancellous bone remodeling with decreased bone formation and resorption. Continued exposure to high Nox4/ROS levels may further compromise bone formation and predispose to bone loss and skeletal fragility. Taken together, our findings suggest a novel link between CSF-1, Nox4-derived ROS, and osteocyte survival/function that is crucial for osteocyte-mediated bone remodeling. Results reveal new mechanisms by which CSF-1/oxidative stress regulate osteocyte homeostasis, which may lead to therapeutic strategies to improve skeletal health in aging. © 2018 American Society for Bone and Mineral Research.
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http://dx.doi.org/10.1002/jbm4.10080DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7340444PMC
July 2020

Switching diseased cells from cytosolic aerobic glycolysis to mitochondrial oxidative phosphorylation: A metabolic rhythm regulated by melatonin?

J Pineal Res 2021 Jan 24;70(1):e12677. Epub 2020 Oct 24.

Department of Cell Systems and Anatomy, UT Health Science Center at San Antonio, San Antonio, TX, USA.

This commentary reviews the concept of the circadian melatonin rhythm playing an essential role in reducing the development of diseases such as solid tumors which adopt cytosolic aerobic glycolysis (Warburg effect) to support their enhanced metabolism. Experimental data show that solid mammary tumors depend on aerobic glycolysis during the day but likely revert to mitochondrial oxidative phosphorylation at night for ATP production. This conversion of diseased cells during the day to a healthier phenotype at night occurs under control of the circulating melatonin rhythm. When the nocturnal melatonin rise is inhibited by light exposure at night, cancer cells function in the diseased state 24/7. The ability of melatonin to switch cancer cells as well as other diseased cells, for example, Alzheimer disease, fibrosis, hyperactivation of macrophages, etc, from aerobic glycolysis to mitochondrial oxidative phosphorylation may be a basic protective mechanism to reduce pathologies.
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http://dx.doi.org/10.1111/jpi.12677DOI Listing
January 2021

Collateral circulation of the femoral and genicular systems in human lower limbs is highly uncommon.

J Anat 2020 10 11;237(4):791-797. Epub 2020 Jun 11.

Department of Cell Systems and Anatomy, UT Health San Antonio, San Antonio, TX, USA.

The descending branch of the lateral circumflex artery is a septocutaneous vessel that is vital for free and pedicle thigh flap transfer surgeries when repairing tissue defects. It also forms an anastomosis with the superior lateral genicular artery to create a collateral pathway for circumventing occlusions in the superficial femoral artery (SFA). Many anatomical texts and atlases imply the persistence of this anastomosis. However, previous studies indicate variability in the source of the arteries that form the anastomosis, and have reported cases where an anastomosis does not exist. We hypothesized that variations from the conventional accepted pattern can be predicted by comparisons of arterial diameters, and that unconventional anastomoses may be present to facilitate collateral circulation to the limb. Fifty-one limbs were dissected and analyzed to establish the source of the descending branch of the lateral circumflex artery, classify the types of anastomoses, and compare the diameters of the descending branch of the lateral circumflex artery, the SFA and the profunda femoris artery to the common femoral artery (CFA). Vessel diameters were normalized to the diameter of the CFA to allow comparison of limbs from both sexes and to minimize the effects of cadaver size on correlating vessel size to the presence or absence of collateral circuits. We report that 62.7% of limbs (32/51) had typical branching patterns; however, only 27.4% of limbs (14/51) had any anastomosis to connect the proximal and distal regions of the thigh. Importantly, the SFA had a wider relative diameter in limbs without anastomoses than in limbs that had normal anastomoses, perhaps precluding the formation of a collateral pathway. Overall, collateral circulation of the lower limb was highly uncommon, in contrast to information inferred from anatomical texts. This study suggests the need for more thorough procedures for determining viable anastomoses prior to thigh flap surgeries to ensure flap survival.
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http://dx.doi.org/10.1111/joa.13226DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7495286PMC
October 2020

Correlation of Medical College Admission Test Scores and Self-assessment Materials with the United States Medical Licensing Examination Step 1 Performance.

Cureus 2020 Apr 2;12(4):e7519. Epub 2020 Apr 2.

Cell Systems and Anatomy, University of Texas Health Science Center at San Antonio, San Antonio, USA.

Purpose Candidates' performance on the United States Medical Licensing Examination (USMLE) Step 1 examination had been correlated with the Medical College Admission Test (MCAT). However, in 2015, a new MCAT format was released and its correlation with Step 1 remains to be fully analyzed. Preparation for Step 1 typically involves purchasing and perusing practice tests from the National Board of Medical Examiners (NBME) and UWorld; however, their predictive value to performance on Step 1 remains to be ascertained, especially with the release of five new NBME practice tests. Additionally, there is a need for accurately predicting Step 1 scores to self-evaluate study progress and reduce student anxiety. Rationale Program directors rank USMLE Step 1 scores as the number one criterion in selecting interviewees for residency. Step 1 scores are more important than Step 2 scores, Dean's letter, or other letters of recommendation in determining the overall ranking of a candidate after interviews. Hypotheses The authors hypothesized that the new MCAT scores correlated positively with Step 1 scores and that the new NBME practice tests were more predictive of performance on Step 1 as compared to old NBME tests.  Methods Linear regression analysis followed by either analysis of variance (ANOVA) or Student's t-tests were used to analyze 399 responses. Data obtained was used to update an existing Step 1 score predictor, which was then validated. Results A positive correlation between the MCAT (average score: 510.1 ± 6.3) and Step 1 scores (average score: 246.1 ± 14.2) was observed. While new NBME practice tests were more predictive of Step 1 scores than old NBME tests, UWorld test scores were the most predictive. Students who practiced with the new NBME practice tests scored significantly higher than students who did not use them. However, students using any of the UWorld practice tests did significantly better than students who practiced using only NBME practice tests but not UWorld practice tests. Ironically, NBME16,the second-most correlativetest to Step 1 performance, is no longer available for purchase. Overall, taking six or more practice tests significantly enhanced Step 1 scores; the optimal number of tests was found to be between six and nine. The predicted score by an updated Step 1 score predictor was within 3.8 points or 1.6% of the actual Step 1 score. Conclusions We believe this study will aid in the selection and purchase of appropriate self-assessment tests as preparatory material for the USMLE Step 1 examination. It will also introduce them to an existing Step 1 score predictor that will help determine their readiness for Step 1.
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http://dx.doi.org/10.7759/cureus.7519DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7198101PMC
April 2020

Melatonin in Mitochondria: Mitigating Clear and Present Dangers.

Physiology (Bethesda) 2020 03;35(2):86-95

Department of Cell Systems and Anatomy, University of Texas Health San Antonio, San Antonio, Texas.

In cancer cells, glucose is primarily metabolized to pyruvate and then to lactate in the cytosol. By allowing the conversion of pyruvate to acetyl-CoA in mitochondria, melatonin reprograms glucose metabolism in cancer cells to a normal cell phenotype. Acetyl-CoA in the mitochondria also serves as a necessary co-factor for the rate-limiting enzyme in melatonin synthesis, thus ensuring melatonin production in mitochondria of normal cells.
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http://dx.doi.org/10.1152/physiol.00034.2019DOI Listing
March 2020

Melatonin inhibits Warburg-dependent cancer by redirecting glucose oxidation to the mitochondria: a mechanistic hypothesis.

Cell Mol Life Sci 2020 Jul 22;77(13):2527-2542. Epub 2020 Jan 22.

Department of Anatomy, Institute of Bioscience, Sao Paulo State University, Botucatu, Brazil.

Melatonin has the ability to intervene in the initiation, progression and metastasis of some experimental cancers. A large variety of potential mechanisms have been advanced to describe the metabolic and molecular events associated with melatonin's interactions with cancer cells. There is one metabolic perturbation that is common to a large number of solid tumors and accounts for the ability of cancer cells to actively proliferate, avoid apoptosis, and readily metastasize, i.e., they use cytosolic aerobic glycolysis (the Warburg effect) to rapidly generate the necessary ATP required for the high metabolic demands of the cancer cells. There are several drugs, referred to as glycolytic agents, that cause cancer cells to abandon aerobic glycolysis and shift to the more conventional mitochondrial oxidative phosphorylation for ATP synthesis as in normal cells. In doing so, glycolytic agents also inhibit cancer growth. Herein, we hypothesize that melatonin also functions as an inhibitor of cytosolic glycolysis in cancer cells using mechanisms, i.e., downregulation of the enzyme (pyruvate dehydrogenase kinase) that interferes with the conversion of pyruvate to acetyl CoA in the mitochondria, as do other glycolytic drugs. In doing so, melatonin halts the proliferative activity of cancer cells, reduces their metastatic potential and causes them to more readily undergo apoptosis. This hypothesis is discussed in relation to the previously published reports. Whereas melatonin is synthesized in the mitochondria of normal cells, we hypothesize that this synthetic capability is not present in cancer cell mitochondria because of the depressed acetyl CoA; acetyl CoA is necessary for the rate limiting enzyme in melatonin synthesis, arylalkylamine-N-acetyltransferase. Finally, the ability of melatonin to switch glucose oxidation from the cytosol to the mitochondria also explains how tumors that become resistant to conventional chemotherapies are re-sensitized to the same treatment when melatonin is applied.
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http://dx.doi.org/10.1007/s00018-019-03438-1DOI Listing
July 2020

A Three-Dimensional Print Model of the Pterygopalatine Fossa Significantly Enhances the Learning Experience.

Anat Sci Educ 2020 Sep 27;13(5):568-580. Epub 2020 Jan 27.

Department of Cell Systems and Anatomy, Long School of Medicine, UT Health, San Antonio, Texas.

The pterygopalatine fossa (PPF) is a bilateral space deep within the skull that serves as a major neurovascular junction. However, its small volume and poor accessibility make it a difficult space to comprehend using two-dimensional illustrations and cadaveric dissections. A three-dimensional (3D) printed model of the PPF was developed as a visual and kinesthetic learning tool for completely visualizing the fossa, its boundaries, its communicating channels, and its neurovascular structures. The model was evaluated by analyzing student performance on pre- and post-quizzes and a student satisfaction survey based on the five-point Likert scale. The first cohort comprised of 88 students who had never before studied the PPF. The second cohort consisted of 30 students who were previously taught the PPF. Each cohort was randomly divided into a control group who were provided with a half skull and an intervention group that were provided with the 3D printed model. The intervention group performed significantly better on the post-quiz as compared to the control group in cohort I (P = 0.001); while not significant, it also improved learning in cohort II students (P = 0.124). Satisfaction surveys indicated that the intervention group found the 3D printed model to be significantly more useful (P < 0.05) as compared to the half skull used by the control group. Importantly, the effect sizes for cohorts I and II (0.504 and 0.581, respectively) validated the statistical results. Together, this study highlights the importance of 3D printed models as teaching tools in anatomy education.
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http://dx.doi.org/10.1002/ase.1942DOI Listing
September 2020

Neurotensin receptor 1 deletion decreases methamphetamine self-administration and the associated reduction in dopamine cell firing.

Addict Biol 2021 01 19;26(1):e12854. Epub 2019 Nov 19.

Aging & Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA.

We previously reported that a non-selective pharmacological blockade of neurotensin receptors in the ventral tegmental area (VTA) decreases methamphetamine (METH) self-administration in mice. Here, we explored the consequences of genetic deletion of neurotensin receptor 1 (NtsR1) on METH self-administration and VTA dopamine neuron firing activity. We implanted mice with an indwelling jugular catheter and trained them to nose-poke for intravenous infusions of METH. Mice with NtsR1 deletion (KO) acquired self-administration similar to wildtype (WT) and heterozygous (HET) littermates. However, in NtsR1 KO and HET mice, METH intake and motivated METH seeking decreased when the response requirement was increased to a fixed ratio 3 and when mice were tested on a progressive ratio protocol. After completion of METH self-administration, single cell in vivo extracellular recordings of dopamine firing activity in the VTA were obtained in anesthetized mice. Non-bursting dopamine neurons from KO mice fired at slower rates than those from WT mice, supporting an excitatory role for NtsR1 on VTA dopamine neuronal activity. In WT mice, a history of METH self-administration decreased dopamine cell firing frequency compared with cells from drug-naïve controls. NtsR1 KO and HET mice did not exhibit this decline in dopamine cell firing activity after METH experience. We also observed an increase in population activity following METH self-administration that was strongest in the WT group. Our results suggest a role for NtsR1 in METH-seeking behavior and indicate that ablation of NtsR1 prevents the detrimental effects of prolonged METH self-administration on VTA dopamine cell firing frequency.
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http://dx.doi.org/10.1111/adb.12854DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8011996PMC
January 2021

Case report of unique anastomosis between facial and inferior alveolar arteries.

Surg Radiol Anat 2020 May 9;42(5):603-606. Epub 2019 Nov 9.

Department of Cell Systems and Anatomy, Long School of Medicine, UT Health San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA.

Purpose: Understanding anatomical variations of the facial artery and its branches is important for dental and medical practitioners.

Methods: Routine cadaveric dissection of the head and neck was performed to demonstrate the origin and branches of the facial artery.

Results: Facial artery emerged from a common linguofacial trunk off the external carotid artery. On the face, the facial artery first gave off a pre-masseteric branch. Immediately after, an aberrant artery emerged from the facial artery that coursed along the ramus of the mandible, which upon further dissection and examination was found to anastomose with inferior alveolar artery within the ramus of the mandible.

Conclusions: We report a unique anastomosis between facial and inferior alveolar arteries, vessels that have not been previously shown to communicate. This case report may provide useful information for oral and maxillofacial surgeons as well as dentists performing inferior alveolar nerve blocks.
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http://dx.doi.org/10.1007/s00276-019-02375-9DOI Listing
May 2020

Melatonin: A hypothesis regarding its use to treat Wilson disease.

Med Hypotheses 2019 Dec 24;133:109408. Epub 2019 Sep 24.

Department of Cell Systems and Anatomy, UT Health San Antonio, San Antonio, TX 78229, USA.

Wilson disease is associated with excessive copper accumulation in cells, primarily in the liver and brain. The subcellular lesions caused by an excess of this essential metal accounts for many of the signs of Wilson disease. The drugs used to treat this disease are not always effective, and depending on dose, they may have collateral toxicity. Melatonin is an endogenously-produced molecule that functions as a copper chelator, a potent antioxidant, and as a suppressor of endoplasmic reticulum stress and the unfolded protein response in both the liver and the brain, while also reducing fibrosis/cirrhosis in the liver. Melatonin is inexpensive, non-toxic and can be administered via any route. Melatonin should be tested for its potential utility in experimental models of Wilson disease with extension to the human if melatonin proves to be effective in the animal studies.
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http://dx.doi.org/10.1016/j.mehy.2019.109408DOI Listing
December 2019

Melatonin Synthesis and Function: Evolutionary History in Animals and Plants.

Front Endocrinol (Lausanne) 2019 17;10:249. Epub 2019 Apr 17.

Department of Cell Systems and Anatomy, The University of Texas Health Science Center at San Antonio (UT Health), San Antonio, TX, United States.

Melatonin is an ancient molecule that can be traced back to the origin of life. Melatonin's initial function was likely that as a free radical scavenger. Melatonin presumably evolved in bacteria; it has been measured in both α-proteobacteria and in photosynthetic cyanobacteria. In early evolution, bacteria were phagocytosed by primitive eukaryotes for their nutrient value. According to the endosymbiotic theory, the ingested bacteria eventually developed a symbiotic association with their host eukaryotes. The ingested α-proteobacteria evolved into mitochondria while cyanobacteria became chloroplasts and both organelles retained their ability to produce melatonin. Since these organelles have persisted to the present day, all species that ever existed or currently exist may have or may continue to synthesize melatonin in their mitochondria (animals and plants) and chloroplasts (plants) where it functions as an antioxidant. Melatonin's other functions, including its multiple receptors, developed later in evolution. In present day animals, via receptor-mediated means, melatonin functions in the regulation of sleep, modulation of circadian rhythms, enhancement of immunity, as a multifunctional oncostatic agent, etc., while retaining its ability to reduce oxidative stress by processes that are, in part, receptor-independent. In plants, melatonin continues to function in reducing oxidative stress as well as in promoting seed germination and growth, improving stress resistance, stimulating the immune system and modulating circadian rhythms; a single melatonin receptor has been identified in land plants where it controls stomatal closure on leaves. The melatonin synthetic pathway varies somewhat between plants and animals. The amino acid, tryptophan, is the necessary precursor of melatonin in all taxa. In animals, tryptophan is initially hydroxylated to 5-hydroxytryptophan which is then decarboxylated with the formation of serotonin. Serotonin is either acetylated to -acetylserotonin or it is methylated to form 5-methoxytryptamine; these products are either methylated or acetylated, respectively, to produce melatonin. In plants, tryptophan is first decarboxylated to tryptamine which is then hydroxylated to form serotonin.
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http://dx.doi.org/10.3389/fendo.2019.00249DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6481276PMC
April 2019

Clinical Case-Based Image Portfolios in Medical Histopathology.

Anat Sci Educ 2019 Mar 17;12(2):200-209. Epub 2018 Aug 17.

Department of Pathology, Long School of Medicine, UT-Health, San Antonio, Texas.

This descriptive article describes the use of clinical case-based portfolios in histopathology teaching laboratories in conjunction with virtual microscopy not only to integrate histology and pathology disciplines for first and second year medical students but also to stimulate student engagement, promote self-directed and group-based learning and enhance student-to-student interaction in a structured manner. Portfolios consisted of PowerPoint files encompassing four to five clinical case studies relevant to the topics covered that week. Portfolios integrated study materials provided in the module-specific lectures, clinical skill lectures, and online interactive content. Two sets of portfolios, Individual and Group, were used. Individual Portfolios were completed by each student and uploaded prior to the laboratory session. Group Portfolios were completed by students working together in small groups during the laboratory session with minimal faculty assistance. The functional utility and acceptance of Individual and Group Portfolios among first- and second-year medical students was evaluated using electronic surveys and examination performances. Both first- and second-year students agreed that the use of portfolios in conjunction with virtual microscopy promoted understanding and encouraged discussion of the topics covered during the week and that group members worked well together and contributed to the completion of the portfolios. Performances on the Histology and Cell Biology and Pathology sections on the United States Medical Licensing Examination (USMLE ) remained consistent and in line with national averages. Overall, use of portfolios promoted peer teaching and contributed towards successful transition to the new system-based integrated curriculum with continued strong performance on the USMLE.
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http://dx.doi.org/10.1002/ase.1794DOI Listing
March 2019

Caspase-2 modulates osteoclastogenesis through down-regulating oxidative stress.

Bone 2016 12 10;93:233-234. Epub 2016 Jun 10.

Department of Biochemistry, University of Texas Health Science Center, San Antonio, TX 78229-3900, USA. Electronic address:

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http://dx.doi.org/10.1016/j.bone.2016.06.004DOI Listing
December 2016

Dopaminergic Neurons Exhibit an Age-Dependent Decline in Electrophysiological Parameters in the MitoPark Mouse Model of Parkinson's Disease.

J Neurosci 2016 Apr;36(14):4026-37

Departments of Physiology, Center for Biomedical Neuroscience, University of Texas Health Science Center, San Antonio, Texas 78229

Unlabelled: Dopaminergic neurons of the substantia nigra (SN) play a vital role in everyday tasks, such as reward-related behavior and voluntary movement, and excessive loss of these neurons is a primary hallmark of Parkinson's disease (PD). Mitochondrial dysfunction has long been implicated in PD and many animal models induce parkinsonian features by disrupting mitochondrial function. MitoPark mice are a recently developed genetic model of PD that lacks the gene for mitochondrial transcription factor A specifically in dopaminergic neurons. This model mimics many distinct characteristics of PD including progressive and selective loss of SN dopamine neurons, motor deficits that are improved byl-DOPA, and development of inclusion bodies. Here, we used brain slice electrophysiology to construct a timeline of functional decline in SN dopaminergic neurons from MitoPark mice. Dopaminergic neurons from MitoPark mice exhibited decreased cell capacitance and increased input resistance that became more severe with age. Pacemaker firing regularity was disrupted in MitoPark mice and ion channel conductances associated with firing were decreased. Additionally, dopaminergic neurons from MitoPark mice showed a progressive decrease of endogenous dopamine levels, decreased dopamine release, and smaller D2 dopamine receptor-mediated outward currents. Interestingly, expression of ion channel subunits associated with impulse activity (Cav1.2, Cav1.3, HCN1, Nav1.2, and NavB3) was upregulated in older MitoPark mice. The results describe alterations in intrinsic and synaptic properties of dopaminergic neurons in MitoPark mice occurring at ages both before and concurrent with motor impairment. These findings may help inform future investigations into treatment targets for prodromal PD.

Significance Statement: Parkinson's disease (PD) is the second most diagnosed neurodegenerative disorder, and the classic motor symptoms of the disease are attributed to selective loss of dopaminergic neurons of the substantia nigra. The MitoPark mouse is a genetic model of PD that mimics many of the key characteristics of the disease and enables the study of progressive neurodegeneration in parkinsonism. Here we have identified functional deficits in the ion channel physiology of dopaminergic neurons from MitoPark mice that both precede and are concurrent with the time course of behavioral symptomatology. Because PD is a progressive disease with a long asymptomatic phase, identification of early functional adaptations could lay the groundwork to test therapeutic interventions that halt or reverse disease progression.
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http://dx.doi.org/10.1523/JNEUROSCI.1395-15.2016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4821912PMC
April 2016

The Role of the Carboxyl Terminus Helix C-D Linker in Regulating KCNQ3 K+ Current Amplitudes by Controlling Channel Trafficking.

PLoS One 2015 21;10(12):e0145367. Epub 2015 Dec 21.

Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America.

In the central and peripheral nervous system, the assembly of KCNQ3 with KCNQ2 as mostly heteromers, but also homomers, underlies "M-type" currents, a slowly-activating voltage-gated K+ current that plays a dominant role in neuronal excitability. KCNQ3 homomers yield much smaller currents compared to KCNQ2 or KCNQ4 homomers and KCNQ2/3 heteromers. This smaller current has been suggested to result either from divergent channel surface expression or from a pore that is more unstable in KCNQ3. Channel surface expression has been shown to be governed by the distal part of the C-terminus in which helices C and D are critical for channel trafficking and assembly. A sequence alignment of this region in KCNQ channels shows that KCNQ3 possesses a longer linker between helix C and D compared to the other KCNQ subunits. Here, we investigate the role of the extra residues of this linker on KCNQ channel expression. Deletion of these residues increased KCNQ3 current amplitudes. Total internal reflection fluorescence imaging and plasma membrane protein assays suggest that the increase in current is due to a higher surface expression of the channels. Conversely, introduction of the extra residues into the linker between helices C and D of KCNQ4 reduced current amplitudes by decreasing the number of KCNQ4 channels at the plasma membrane. Confocal imaging suggests a higher fraction of channels, which possess the extra residues of helix C-D linker, were retained within the endoplasmic reticulum. Such retention does not appear to lead to protein accumulation and activation of the unfolded protein response that regulates protein folding and maintains endoplasmic reticulum homeostasis. Taken together, we conclude that extra helix C-D linker residues play a role in KCNQ3 current amplitudes by controlling the exit of the channel from the endoplasmic reticulum.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0145367PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4687061PMC
July 2016

A dominant-negative F-box deleted mutant of E3 ubiquitin ligase, β-TrCP1/FWD1, markedly reduces myeloma cell growth and survival in mice.

Oncotarget 2015 Aug;6(25):21589-602

Department of Cellular and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.

Treatment of multiple myeloma with bortezomib can result in severe adverse effects, necessitating the development of targeted inhibitors of the proteasome. We show that stable expression of a dominant-negative F-box deleted (∆F) mutant of the E3 ubiquitin ligase, SCFβ-TrCP/FWD1, in murine 5TGM1 myeloma cells dramatically attenuated their skeletal engraftment and survival when inoculated into immunocompetent C57BL/KaLwRij mice. Similar results were obtained in immunodeficient bg-nu-xid mice, suggesting that the observed effects were independent of host recipient immune status. Bone marrow stroma offered no protection for 5TGM1-∆F cells in cocultures treated with tumor necrosis factor (TNF), indicating a cell-autonomous anti-myeloma effect. Levels of p100, IκBα, Mcl-1, ATF4, total and cleaved caspase-3, and phospho-β-catenin were elevated in 5TGM1-∆F cells whereas cIAP was down-regulated. TNF also activated caspase-3 and downregulated Bcl-2, correlating with the enhanced susceptibility of 5TGM1-∆F cells to apoptosis. Treatment of 5TGM1 tumor-bearing mice with a β-TrCP1/FWD1 inhibitor, pyrrolidine dithiocarbamate (PDTC), significantly reduced tumor burden in bone. PDTC also increased levels of cleaved Mcl-1 and caspase-3 in U266 human myeloma cells, correlating with our murine data and validating the development of specific β-TrCP inhibitors as an alternative therapy to nonspecific proteasome inhibitors for myeloma patients.
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http://dx.doi.org/10.18632/oncotarget.4120DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4673288PMC
August 2015

Caspase-2 modulates osteoclastogenesis through down-regulating oxidative stress.

Bone 2015 Jul 19;76:40-8. Epub 2015 Mar 19.

Department of Biochemistry, University of Texas Health Science Center, San Antonio, TX 78229-3900, USA. Electronic address:

The loss of caspase-2 (Casp-2) in mice results in an osteopenic phenotype associated with increased numbers of osteoclasts in vivo. In this study, we show that Casp-2 is involved in osteoclastogenesis. Protein levels of Casp-2 decrease during the differentiation of macrophages to osteoclasts. Furthermore, siRNA-mediated Casp-2 knockdown in osteoclast precursors or differentiation of bone marrow macrophage (BMM) precursors from Casp2(-/-) mice results in increased osteoclast numbers and tartrate-resistant acid phosphatase (TRAP) activity. Casp2(-/-) osteoclasts are larger in size compared to wild-type osteoclasts and exhibited increased numbers of nuclei, perhaps due to increased precursor fusion. The loss of Casp-2 did not alter earlier stages of differentiation, but had a greater consequence on later stages involving NFATc1 auto-amplification and pre-osteoclast fusion. We have previously shown that the loss of Casp-2 results in increased oxidative stress in the bone. Reactive oxygen species (ROS) is known to play a critical role in late osteoclast differentiation and we show that total ROS and specifically, mitochondrial ROS, significantly increased in Casp2(-/-) BMM precursors after RANKL administration, with a concomitant reduction in FoxO3a and its target antioxidant enzymes, catalase and superoxide 2 (SOD2). Because mitochondrial ROS has been identified as a putative regulator of the later stages of differentiation, the heightened ROS levels in Casp2(-/-) cells likely promote precursor fusion and increased osteoclast numbers. In conclusion, our results indicate a novel role of Casp-2 in the osteoclast as a modulator of total and mitochondrial ROS and osteoclast differentiation.
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http://dx.doi.org/10.1016/j.bone.2015.03.006DOI Listing
July 2015

Aging decreases L-type calcium channel currents and pacemaker firing fidelity in substantia nigra dopamine neurons.

J Neurosci 2014 Jul;34(28):9310-8

Department of Physiology, Center for Biomedical Neuroscience, University of Texas Health Science Center, San Antonio, Texas 78229

Substantia nigra dopamine neurons are involved in behavioral processes that include cognition, reward learning, and voluntary movement. Selective deterioration of these neurons is responsible for the motor deficits associated with Parkinson's disease (PD). Aging is the leading risk factor for PD, suggesting that adaptations occurring in dopamine neurons during normal aging may predispose individuals to the development of PD. Previous studies suggest that the unique set of ion conductances that drive spontaneous, rhythmic firing of action potentials could predispose substantia nigra dopamine neurons to selective neurodegeneration. Here we show, using patch-clamp electrophysiological recordings in brain slices, that substantia nigra dopamine neurons from mice 25-30 months of age (old) have comparable membrane capacitance and input resistance to neurons from mice 2-7 months of age (young). However, neurons from old mice exhibit slower firing rates, narrower spike widths, and more variable interspike intervals compared with neurons from young mice. Dopamine neurons from old mice also exhibit smaller L-type calcium channel currents, providing a plausible mechanism that likely contributes to the changes in impulse activity. Age-related decrements in the physiological function of dopamine neurons could contribute to the decrease in voluntary movement and other dopamine-mediated behaviors observed in aging populations. Furthermore, as pharmacological antagonism of L-type calcium channels has been proposed as a potential treatment for the early stages of PD, our results could point to a limited temporal window of opportunity for this therapeutic intervention.
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http://dx.doi.org/10.1523/JNEUROSCI.4228-13.2014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4087208PMC
July 2014

Differentiated adipose-derived stem cell cocultures for bone regeneration in polymer scaffolds in vivo.

J Craniofac Surg 2014 Jul;25(4):1504-9

From the *Division of Plastic and Reconstructive Surgery, University of Texas Health Science Center at San Antonio, †Department of Biomedical Engineering, University of Texas at San Antonio, and ‡Cellular and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, Texas.

Critical-sized bone defects can lead to significant morbidity, and interventions are limited by the availability and donor-site morbidity of bone grafts. Polymer scaffolds seeded with cells have been explored to replace bone grafts. Adipose-derived stem cells have shown great promise for vascularization and osteogenesis of these constructs, and cocultures of differentiated stem cells are being explored to augment vessel and bone formation. Adipose-derived stem cells were differentiated into endothelial cells and osteoblasts, and in vitro studies showed increased proliferation of cocultured cells compared with undifferentiated adipose-derived stem cells and monocultures of endothelial cells and osteoblasts. The cells were seeded into polylactic acid gas-plasma-treated scaffolds as cocultures and monocultures and then implanted into critical-sized rat calvarial defects. The cocultures were in a 1:1 osteoblast to endothelial cell ratio. The increase in proliferation seen by the cocultured cells in vitro did not translate to increased vascularization and osteogenesis in vivo. In vivo, there were trends of increased vascularization in the endothelial cell group and increased osteogenesis in the osteoblast and endothelial monoculture groups, but no increase was seen in the coculture group compared with the undifferentiated adipose-derived stem cells. Endothelial cells enhance vascularization and osteoblast and endothelial cell monocultures enhance bone formation in the polymer scaffold. Predifferentiation of adipose-derived stem cells is promising for improving vascularization and osteogenesis in polymer scaffolds but requires future evaluation of coculture ratios to fully characterize this response.
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http://dx.doi.org/10.1097/SCS.0000000000000755DOI Listing
July 2014

Caspase-2 maintains bone homeostasis by inducing apoptosis of oxidatively-damaged osteoclasts.

PLoS One 2014 1;9(4):e93696. Epub 2014 Apr 1.

Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio, Texas, United States of America.

Osteoporosis is a silent disease, characterized by a porous bone micro-structure that enhances risk for fractures and associated disabilities. Senile, or age-related osteoporosis (SO), affects both men and women, resulting in increased morbidity and mortality. However, cellular and molecular mechanisms underlying senile osteoporosis are not fully known. Recent studies implicate the accumulation of reactive oxygen species (ROS) and increased oxidative stress as key factors in SO. Herein, we show that loss of caspase-2, a cysteine aspartate protease involved in oxidative stress-induced apoptosis, results in total body and femoral bone loss in aged mice (20% decrease in bone mineral density), and an increase in bone fragility (30% decrease in fracture strength). Importantly, we demonstrate that genetic ablation or selective inhibition of caspase-2 using zVDVAD-fmk results in increased numbers of bone-resorbing osteoclasts and enhanced tartrate-resistant acid phosphatase (TRAP) activity. Conversely, transfection of osteoclast precursors with wild type caspase-2 but not an enzymatic mutant, results in a decrease in TRAP activity. We demonstrate that caspase-2 expression is induced in osteoclasts treated with oxidants such as hydrogen peroxide and that loss of caspase-2 enhances resistance to oxidants, as measured by TRAP activity, and decreases oxidative stress-induced apoptosis of osteoclasts. Moreover, oxidative stress, quantified by assessment of the lipid peroxidation marker, 4-HNE, is increased in Casp2-/- bone, perhaps due to a decrease in antioxidant enzymes such as SOD2. Taken together, our data point to a critical and novel role for caspase-2 in maintaining bone homeostasis by modulating ROS levels and osteoclast apoptosis during conditions of enhanced oxidative stress that occur during aging.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0093696PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3972236PMC
June 2015

Effect of adipose tissue-derived osteogenic and endothelial cells on bone allograft osteogenesis and vascularization in critical-sized calvarial defects.

Tissue Eng Part A 2012 Aug 10;18(15-16):1552-61. Epub 2012 May 10.

Division of Plastic and Reconstructive Surgery, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229-3900, USA.

The use of processed bone allograft to repair large osseous defects of the skull has been limited, given that it lacks the osteogenic cellularity and intrinsic vascular supply which are essential elements for successful graft healing and, at the same time, the areas to be targeted through tissue-engineering applications. In this study, we investigated the effect of predifferentiated rat adipose tissue-derived osteoblastic cells (OBs) and endothelial cells (ECs) on calvarial bone allograft healing and vascularization using an orthotopic critical-sized calvarial defect model. For this purpose, thirty-seven 8 mm critical calvarial defects in Lewis rats were treated with bone allografts seeded with no cells, undifferentiated adipose tissue-derived stem cells (ASC), OBs, ECs, and OBs and ECs simultaneously. After 8 weeks, the bone volume and mineral density were calculated using microcomputed tomography and the microvessel formation using immunohistochemical staining and imaging software. The amount of bone within the 8 mm defect was significantly higher for the allografts treated with ECs compared with the allografts treated with OBs (p=0.05) and simultaneously with the two cell lineages (p=0.02). There were no significant differences in bone formation between the latter two groups and the control groups (allografts treated with no cells and undifferentiated ASC). There were no significant differences in bone mineral density among the groups. The amount of microvessels was significantly higher in the group treated with ECs relative to all groups (p=< 0.05). Our results show that the implantation of ASC-derived ECs improves the vascularization of calvarial bone allografts at 8 weeks after treatment. This cell-based vascularization strategy can be used to improve the paucity of perfusion in allogenic bone implants. However, in this study, the treatment of allografts with OBs alone or in combination with ECs did not support bone formation or vascularization.
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http://dx.doi.org/10.1089/ten.tea.2011.0515DOI Listing
August 2012