Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang, Kyungbuk, Republic of Korea.
J Cell Physiol. 2012 Apr;227(4):1680-7. doi: 10.1002/jcp.22892.
AMP-activated protein kinase (AMPK) is an energy-sensing kinase that has recently been shown to regulate the differentiation of preadipocytes and osteoblasts. However, the role of AMPK in stem cell differentiation is largely unknown. Using in vitro culture models, the present study demonstrates that AMPK is a critical regulatory factor for osteogenic differentiation. We observed that expression and phosphorylation of AMPK were increased during osteogenesis in human adipose tissue-derived mesenchymal stem cells (hAMSC). To elucidate the role of AMPK in osteogenic differentiation, we investigated the effect of AMPK inhibition or knockdown on mineralization of hAMSC. Compound C, an AMPK inhibitor, reduced mineralized matrix deposition and suppressed the expression of osteoblast-specific genes, including alkaline phosphatase (ALP), runt-related transcription factor 2 (RUNX2), and osteocalcin (OCN). Knockdown of AMPK by shRNA-lentivirus infection also reduced osteogenesis. In addition, inhibition or knockdown of AMPK during osteogenesis inhibited ERK phosphorylation, which is required for osteogenesis. Interestingly, inhibition of AMPK induced adipogenic differentiation of hAMSC, even in osteogenic induction medium (OIM). These results provide a potential mechanism involving AMPK activation in osteogenic differentiation of hAMSC and suggest that commitment of hAMSC to osteogenic or adipogenic lineage is governed by activation or inhibition of AMPK, respectively.
AMP 激活的蛋白激酶 (AMPK) 是一种能量感应激酶，最近研究表明其可调节前脂肪细胞和成骨细胞的分化。然而，AMPK 在干细胞分化中的作用在很大程度上尚不清楚。本研究通过体外培养模型证实，AMPK 是成骨分化的关键调节因子。我们观察到，在人脂肪组织来源的间充质干细胞 (hAMSC) 成骨过程中，AMPK 的表达和磷酸化水平增加。为了阐明 AMPK 在成骨分化中的作用，我们研究了 AMPK 抑制或敲低对 hAMSC 矿化的影响。AMPK 抑制剂化合物 C 减少了矿化基质的沉积，并抑制了成骨细胞特异性基因的表达，包括碱性磷酸酶 (ALP)、 runt 相关转录因子 2 (RUNX2) 和骨钙素 (OCN)。shRNA 慢病毒感染敲低 AMPK 也减少了成骨作用。此外，成骨过程中 AMPK 的抑制或敲低抑制了 ERK 磷酸化，ERK 磷酸化是成骨所必需的。有趣的是，AMPK 的抑制诱导了 hAMSC 的脂肪分化，即使在成骨诱导培养基 (OIM) 中也是如此。这些结果提供了一个潜在的机制，涉及 AMPK 激活在 hAMSC 的成骨分化中，并且表明 hAMSC 向成骨或脂肪谱系的定向取决于 AMPK 的激活或抑制。
