Diabetes is associated with increased mortality from severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Given literature suggesting a potential association between SARS-CoV-2 infection and diabetes induction, we examined pancreatic expression of angiotensin-converting enzyme 2 (ACE2), the key entry factor for SARS-CoV-2 infection. Specifically, we analyzed five public scRNA-seq pancreas datasets and performed fluorescence in situ hybridization, western blotting, and immunolocalization for ACE2 with extensive reagent validation on normal human pancreatic tissues across the lifespan, as well as those from coronavirus disease 2019 (COVID-19) cases. These in silico and ex vivo analyses demonstrated prominent expression of ACE2 in pancreatic ductal epithelium and microvasculature, but we found rare endocrine cell expression at the mRNA level. Pancreata from individuals with COVID-19 demonstrated multiple thrombotic lesions with SARS-CoV-2 nucleocapsid protein expression that was primarily limited to ducts. These results suggest SARS-CoV-2 infection of pancreatic endocrine cells, via ACE2, is an unlikely central pathogenic feature of COVID-19-related diabetes.

Reports of neural transdifferentiation of mesenchymal stem cells (MSCs) suggest the possibility that these cells may serve as a source for stem cell-based regenerative medicine to treat neurological disorders. However, some recent studies controvert previous reports of MSC neurogenecity. In the current study, we evaluate the neural differentiation potential of mouse bone marrow-derived MSCs. Surprisingly, we found that MSCs spontaneously express certain neuronal phenotype markers in culture, in the absence of specialized induction reagents. A previously published neural induction protocol that elevates cytoplasmic cyclic AMP does not upregulate neuron-specific protein expression significantly in MSCs but does significantly increase expression of the astrocyte-specific glial fibrillary acidic protein. Finally, when grafted into the lateral ventricles of neonatal mouse brain, MSCs migrate extensively and differentiate into olfactory bulb granule cells and periventricular astrocytes, without evidence of cell fusion. These results indicate that MSCs may be "primed" toward a neural fate by the constitutive expression of neuronal antigens and that they seem to respond with an appropriate neural pattern of differentiation when exposed to the environment of the developing brain.

Stromal derived factor-1 alpha (SDF-1alpha) and its receptor CXCR4 have been shown to play a role in the systematic movement of hematopoietic stem cells (HSC) in the fetal and adult stages of hematopoiesis. Under certain physiological conditions liver oval cells can participate in the regeneration of the liver. We have shown that a percentage of oval cells are of hematopoietic origin. Others have shown that bone marrow derived stem cells can participate in liver regeneration as well. In this study we examined the role of SDF-1alpha and its receptor CXCR4 as a possible mechanism for oval cell activation in oval cell aided liver regeneration. In massive liver injury models where oval cell repair is involved hepatocytes up-regulate the expression of SDF-1alpha, a potent chemoattractant for hematopoietic cells. However, when moderate liver injury occurs, proliferation of resident hepatocytes repairs the injury. Under these conditions SDF-1alpha expression is not up-regulated and oval cells are not activated in the liver. In addition, we show that oval cells express CXCR4, the only known receptor for SDF-1alpha. Lastly, in vitro chemotaxis assays demonstrated that oval cells migrate along a SDF-1alpha gradient which suggests that the SDF-1alpha/CXCR4 interaction is a mechanism by which the oval cell compartment could be activated and possibly recruit a second wave of bone marrow stem cells to the injured liver. In conclusion, these experiments begin to shed light on a possible mechanism, which may someday lead to a better understanding of the hepatic and hematopoietic interaction in oval cell aided liver regeneration.

Though osteonecrosis of the jaw (ONJ) is temporally-associated with the use of nitrogen-containing bisphosphonates (N-BPs), a cause/effect relationship has not yet been established. We hypothesize that ONJ is a two-stage process in which: a) risk factors initiate pathologic processes in the oral cavity that lead to a supranormal rate of hard tissue necrosis, and b) powerful anti-resorptives reduce the rate of removal of necrotic bone sufficiently to allow its net accumulation in the jaw. To test this hypothesis, we used the rice rat model of periodontitis. At age 28 days, rats (n=15/group) were placed on a high sucrose and casein diet to exacerbate the development of periodontitis. Animals were injected SC biweekly with vehicle or alendronate (ALN, 15μg/kg), or IV once monthly with vehicle, a low dose (LD), or a high dose (HD) of zoledronic acid (ZOL) and sacrificed after 6, 12, 18, and 24 wks. Mandibles and maxillae were analyzed to determine the effects on the: a) progression of periodontitis, b) integrity of alveolar bone, c) status of bone resorption and formation, d) vascularity, and e) osteocyte viability. We found that only HD-ZOL induced ONJ-like lesions in mandibles of rice rats after 18 and 24 wks of treatment. These lesions were characterized by areas of exposed necrotic alveolar bone, osteolysis, a honey comb-like appearance of the alveolar bone, presence of bacterial colonies, and periodontal tissue destruction. In addition, inhibition of bone formation, a paradoxical abolition of the antiresorptive effect of only HD-ZOL, increased osteocyte necrosis/apoptosis, and decreased blood vessel number were found after 18 and/or 24 wks. Our study suggests that only HD-ZOL exacerbates the inflammatory response and periodontal tissue damage in rice rats, inducing bone lesions that resemble ONJ.

Purpose We identified a discrete population of stem cell-like tumor cells expressing 5 essential transcription factors required to reprogram pluripotency in prostate tumor cell lines and primary prostate cancer tissue. Materials and Methods DU145 and PC3 human prostate cancer cell lines (ATCC®), tumor tissue from patients with prostate cancer and normal prostate tissue were evaluated for the reprogramming factors OCT3/4 (Cell Signaling Technology®), SOX2, Klf4 (Santa Cruz Biotechnology, Santa Cruz, California), Nanog (BioLegend®) and c-Myc (Cell Signaling) by semiquantitative reverse transcriptase-polymerase chain reaction, histological and immunohistochemical analysis. Stem cell-like tumor cells were enriched by flow cytometric cell sorting using E-cadherin (R&D Systems®) as a surface marker, and soft agar, spheroid and tumorigenicity assays to confirm cancer stem cell-like characteristics. Results mRNA expression of transcription factors OCT3/4 and SOX2 highly correlated in primary prostate tumor tissue samples. The number of OCT3/4 or SOX2 expressing cells was significantly increased in prostate cancer tissue compared to that in normal prostate or benign prostate hyperplasia tissue (p <0.05). When isolated from the DU145 and PC3 prostate cancer cell lines by flow cytometry, stem cell-like tumor cells expressing high OCT3/4 and SOX2 levels showed high tumorigenicity in immunodeficient mice. In vivo growth of the parental DU145 and PC3 prostate cancer cell lines was inhibited by short hairpin RNA knockdown of OCT3/4 or SOX2. Conclusions Data suggest that prostate tumor cells expressing pluripotent stem cell transcription factors are highly tumorigenic. Identifying such cells and their importance in prostate cancer growth could provide opportunities for novel targeting strategies for prostate cancer therapy.

Connective tissue growth factor (CTGF) is a matricellular protein that mediates cell-matrix interaction through various subtypes of integrin receptors. This study investigated the role of CTGF and integrin αvβ6 in hepatic progenitor/oval cell activation, which often occurs in the form of ductular reactions (DRs) when hepatocyte proliferation is inhibited during severe liver injury. CTGF and integrin αvβ6 proteins were highly expressed in DRs of human cirrhotic livers and cholangiocarcinoma. Confocal microscopy analysis of livers from Ctgf promoter driven GFP reporter mice suggested that oval cells and cholangiocytes were the main sources of CTGF and integrin αvβ6 during liver injury induced by 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC). Deletion of exon 4 of the Ctgf gene using tamoxifen inducible Cre-loxP system down-regulated integrin αvβ6 in DDC damaged livers of knockout mice. Ctgf deficiency or inhibition of integrin αvβ6 by administrating the neutralizing antibody 6.3G9 (10 mg/kg body weight) caused low levels of EpCAM and CK19 mRNAs. Also, there were smaller oval cell areas, fewer proliferating ductular epithelial cells, and lower cholestasis serum markers within two weeks after DDC treatment. Associated fibrosis was attenuated as indicated by reduced expression of fibrosis-related genes, smaller areas of α smooth muscle actin staining and low collagen production based on hydroxyproline content and the Sirius red staining. Finally, integrin αvβ6 could bind to CTGF mediating oval cell adhesion to CTGF and fibronection substrata and promoting transforming growth factor (TGF)-β1 activation in vitro. Conclusions: CTGF and integrin αvβ6 regulate oval cell activation and fibrosis, probably through interacting with their common matrix and signal partners, fibronectin and TGF-β1. CTGF and integrin αvβ6 are potential therapeutic targets to control DRs and fibrosis in related liver disease.

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