| Summary: | 碩士 === 臺北醫學大學 === 醫學科學研究所 === 102 === Stem cell niche is known to regulate stem cells self-renew and differentiation. Our previous studies have demonstrated that the niche hypoxia maintains the Oct-4 level through HIF-2α-IGF-1R signal loop in mouse germline stem cells. However, how the niche extracellular matrix cooperates with hypoxia-derived signals still remains largely unknown. For this purpose, the CD49f positive alkaline phosphatase positive GSCs (CD49f+AP+GSCs) were purified with magnetic-activated cell sorting assay (MACS) and cultivated in serum free culture medium. We found the CD49f+AP+GSCs showed significant AP activity and expressed stemness-related genes when cultivated on laminin-coated plates. We have previously demonstrated a HIF-2α-IGF-1R signal loop in maintaining Oct-4 in mGSCs. In this study, we found laminin dose-dependently increase the expression levels of HIF-2α and Oct-4 protein in CD49f+AP+GSCs. Furthermore, IGF-1 synergistically increased the HIF-2α and Oct-4 levels of CD49f+AP+GSCs cultivated on laminin-coating plates. IGF-1 dose-dependently increased the CD49f levels and knockdown of endogenous IGF-1R using siRNA effectively suppressed the expressions of CD49f, suggesting the role of IGF-1R in CD49f expression. Further experiments knockdown the CD49f significantly suppressed the expression of HIF-2α and Oct-4, but not the IGF-1R. In conclusion, our data demonstrated that IGF-1R signal stimulates the expressions of HIF-2α and Oct-4 requiring integrin α6. Findings in this study would provide insights into nich and endocrinology underlying the early pluripotent germ line development.
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