No abstract

Recent studies have shown that adult tissues contain stem/ progenitor cells capable of not only generating mature cells of their tissue of origin but also transdifferentiating themselves into other tissue cells. Murine skin-derived precursor cells, for example, have been described as unique, nonmesenchymal-like stem cells capable of mesodermal and ectodermal neurogenic differentiation. Human-derived skin precursors are less well characterized.In this study, the isolation and characterization of adherent, mesenchymal stem cell-like cells from human scalp tissue (hSCPs) are described. hSCPs initially isolated by both medium-selection (ms-hSCPs) and single-cell (c-hSCPs) methods were cultured in medium containing epidermal growth factor and fibroblast growth factor-β. Cultured mshSCPs and c-hSCPs demonstrated a consistent growth rate, continuously replicated in cell culture, and displayed a stable phenotype indistinguishable from each other. Both hSCPs expressed surface antigen profile (CDw90, SH2, SH4, CD105, CD166, CD44, CD49d-e, and HLA class I) similar to that of bone marrow mesenchymal stem cells (BM-MSCs). The growth kinetics, surface epitopes, and differentiation potential of c-hSCP cells were characterized and compared with BM-MSCs. In addition to differentiation along the osteogenic, chondrogenic, and adipogenic lineages, hSCPs can effectively differentiate into neuronal precursors evident by neurogenic gene expression of glial fibrillary acid protein, NCAM, neuron filament-M, and microtubule-associated protein 2 transcripts. Therefore, hSCPs may potentially be a better alternative of BM-MSCs for neural repairing, in addition to their other mesenchymal regenerative capacity. Our study suggests that hSCPs may provide an alternative adult stem cell resource that may be useful for regenerative tissue repair and autotransplantations. Stem Cells 2005;23:1012-1020

MicroRNAs (miRNAs) can regulate cell survival and death by targeting apoptosis-related gene expression. miR-210 is one of the most hypoxia-sensitive miRNAs. In this study, we evaluated the roles of miR-210 in hypoxia-induced insults to neural cells. Treatment of neuro-2a cells with oxygen/glucose deprivation (OGD) induced cell apoptosis in a time-dependent manner. In parallel, OGD time-dependently increased cellular miR-210 levels. Knocking down miR-210 expression using specific antisenses significantly attenuated OGD-induced neural apoptosis. Concurrently, OGD increased hypoxia-inducible factor (HIF)-1α mRNA and protein syntheses. Pretreatment with YC-1, an inhibitor of HIF-1α, reduced OGD-caused cell death. Sequentially, OGD specifically decreased antiapoptotic Bcl-2 mRNA and protein levels in neuro-2a cells. A search by a bioinformatic approach revealed that miR-210-specific binding elements exist in the 3'-untranslated region of Bcl-2 mRNA. Application of miR-210 antisenses simultaneously alleviated OGD-involved inhibition of Bcl-2 mRNA expression. In comparison, overexpression of miR-210 synergistically diminished OGD-caused inhibition of Bcl-2 mRNA expression and consequently induced greater cellular insults. Taken together, this study shows that OGD can induce miR-210 expression through activating HIF-1α. And miR-210 can mediate hypoxia-induced neural apoptosis by targeting Bcl-2.

Nitric oxide (NO) can regulate osteoblast activities. Our previous study showed that NO induced osteoblast apoptosis [Chen RM, Liu HC, Lin YL, Jean WC, Chen JS, Wang JH. Nitric oxide induces osteoblast apoptosis through the de novo synthesis of Bax protein. J Orthop Res 2002;20:295-3021. This study was further aimed to evaluate the mechanism of NO-induced osteoblast apoptosis from the viewpoints of mitochondrial functions, intracellular oxidative stress, and the anti-apoptotic Bcl-2 protein using neonatal rat calvarial osteoblasts as the experimental model. Exposure of osteoblasts to sodium nitroprusside (SNP), an NO donor, significantly increased amounts of lactate dehydrogenase in the culture medium, and decreased cell viability in concentration-and time-dependent manners. Administration of SNP in osteoblasts time-dependently led to DNA fragmentation. The mitochondrial membrane potential was significantly reduced following SNP administration. SNP decreased complex I NADH dehydrogenase activity in a time-dependent manner. Levels of cellular adenosine triphosphate (ATP) were suppressed by SNP. In parallel with the mitochondrial dysfunction, SNP time-dependently increased levels of intracellular reactive oxygen species. Immunoblotting analysis revealed that SNP reduced Bcl-2 protein levels. Exposure to lipopolysaccharide (LPS) and IFN-y significant increased endogenous nitrite production. In parallel with the increase in endogenous NO, administration of LPS and IFN-y suppressed cell viability, mitochondrial membrane potential, and ATP synthesis. Results of this study show that NO released from SNP can induce osteoblast insults and apoptosis, and the mechanism may involve the modulation of mitochondrial functions, intracellular reactive oxygen species, and Bcl-2 protein.