Role of HIF-1α and VEGF in human mesenchymal stem cell proliferation by 17β-estradiol: involvement of PKC, PI3K/Akt, and MAPKs

Yun SP, Lee MY, Ryu JM, Song CH, Han HJ. Role of HIF-1 alpha and VEGF in human mesenchymal stem cell proliferation by 17 beta-estradiol: involvement of PKC, PI3K/Akt, and MAPKs. Am J Physiol Cell Physiol 296: C317-C326, 2009. First published November 5, 2008; doi:10.1152/ajpcell.00415.2008.-17 beta-Estradiol (E-2) is a steroid hormone well known for its roles in the regulation of various cell functions. However, the precise role that E-2 plays in the proliferation of human mesenchymal stem cells (hMSCs) has not been completely elucidated. In the present study, we examined the effects of E-2 on cell proliferation and the related signaling pathways using hMSCs. We showed that E-2, at >= 10(-9) M, significantly increased [H-3] thymidine incorporation after 24 h of incubation, and E-2 also increased [H-3] thymidine incorporation at >6 h. Also, E-2 significantly increased the percentage of the cell population in the S phase based on FACS analysis. Moreover, E-2 increased estrogen receptor (ER), PKC, phosphatidylinositol 3-kinase (PI3K)/Akt, and MAPK phosphorylation. Subsequently, these signaling molecules were involved in an E-2-induced increase of [H-3] thymidine incorporation. E-2 also increased hypoxia-inducible factor (HIF)-1 alpha and VEGF protein levels. These levels of protein expression were inhibited by ICI-182,780 (10(-6) M, an ER antagonist), staurosporine and bisindolylmaleimide I (10(-6) M, a PKC inhibitor), LY-294002 (10(-6) M, a PI3K inhibitor), Akt inhibitor (10(-5) M), SP-600125 (10(-6) M, a SAPK/JNK inhibitor), and PD-98059 (10(-5) M, a p44/42 MAPKs inhibitor). In addition, HIF-1 alpha small interfering (si) RNA and ICI-182,780 inhibited E-2-induced VEGF expression and cell proliferation. VEGF siRNA also significantly inhibited E-2-induced cell proliferation. In conclusion, E-2 partially stimulated hMSC proliferation via HIF-1 alpha activation and VEGF expression through PKC, PI3K/Akt, and MAPK pathways.