Down-regulation of CD105 is associated with multi-lineage differentiation in human umbilical cord blood-derived mesenchymal stem cells.

Umbilical cord blood-derived mesenchymal stem cells (UCB-MSCs) have multi-lineage differentiation potential, thus highlighting the feasibility of using UCB-MSCs as a valuable source of stem-cells for cell-based therapy. However, there are no well-defined markers for assessment of the multi-potency of UCB-MSCs. Thus, we focused on the identification of suitable markers by examining cell surface protein expressions of UCB-MSCs as their multi-lineage differentiations progressed. The expression of CD105, one of the cell surface proteins, was significantly decreased in differentiated osteoblasts, chondrocytes, adipocytes, and respiratory epithelium, and the portion of CD105-positive cells from 99.4+/-0.1% to 3.5+/-1.4%, 3.5+/-2.3%, 16.7+/-3.6%, and 2.1+/-1.5%, respectively. As to such indicators as alkaline phosphatase (ALP), glycosaminoglycan (GAG), oil Red O, and surfactant protein C (SPC), they showed increases, confirming differentiation of UCB-MSCs into osteoblasts, chondrocytes, adipocytes, and respiratory epithelium. This is the first study to demonstrate a negative correlation between expression of CD105 over the time course of multi-lineage differentiation and the degree of differentiation of UCB-MSCs. We propose that CD105 is a useful novel marker to characterize differentiation status of isolated human UCB-MSCs, which will be useful to facilitate the application of such cells in stem-cell therapy.

Autophagic death of adult hippocampal neural stem cells following insulin withdrawal.

Novel therapeutic approaches using stem cell transplantation to treat neurodegenerative diseases have yielded promising results. However, survival of stem cells after transplantation has been very poor in animal models, and considerable efforts have been directed at increasing the viability of engrafted stem cells. Therefore, understanding the mechanisms that regulate survival and death of neural stem cells is critical to the development of stem cell-based therapies. Hippocampal neural (HCN) stem cells derived from the adult rat brain undergo cell death following insulin withdrawal, which is associated with downregulation of antiapoptotic Bcl-2 family members. To understand the type of cell death in HCN cells following insulin withdrawal, apoptosis markers were assessed. Of note, DNA fragmentation or caspase-3 activation was not observed, but rather dying cells displayed features of autophagy, including increased expression of Beclin 1 and the type II form of light chain 3. Electron micrographs showed the dramatically increased formation of autophagic vacuoles with cytoplasmic contents. Staurosporine induced robust activation of caspase-3 and nucleosomal DNA fragmentation, suggesting that the machinery of apoptosis is intact in HCN cells despite the apparent absence of apoptosis following insulin withdrawal. Autophagic cell death was suppressed by knockdown of autophagy-related gene 7, whereas promotion of autophagy by rapamycin increased cell death. Taken together, these data demonstrate that HCN cells undergo a caspase-independent, autophagic cell death following insulin withdrawal. Understanding the mechanisms governing autophagy of adult neural stem cells may provide novel strategies to improve the survival rate of transplanted stem cells for treatment of neurodegenerative diseases. Disclosure of potential conflicts of interest is found at the end of this article.