骨形态发生蛋白9通过JNKs激酶途径调控间充质干细胞成骨分化

前期研究发现骨形态发生蛋白9(bone morphogenetic protein 9，BMP9)除了通过经典Smad途径外，也可通过丝裂原活化蛋白激酶(mitogen activated protein kinases，MAPKs)中的p38激酶途径调控间充质干细胞成骨分化．本研究继续探讨MAPKs的重要成员c-Jun氨基末端激酶(c-Jun N-terminal kinases，JNKs)对于BMP9诱导间充质干细胞成骨分化的调控作用．利用BMP9重组腺病毒感染间充质干细胞，通过体外细胞实验和体内动物实验，初步分析BMP9是否可通过JNKs激酶途径调控间充质干细胞成骨分化．结果表明：BMP9可通过促进JNKs激酶磷酸化而导致其活化；JNKs抑制剂SP600125可抑制由BMP9诱导的间充质干细胞的碱性磷酸酶(alkaline phosphatase，ALP)活性、骨桥蛋白(osteocpontin，OPN)和骨钙素(osteocalcin，OCN)表达以及钙盐沉积；利用抑制剂SP600125抑制JNKs激酶活性后，BMP9诱导Runx2的表达和转录活性，以及Smad经典途径的激活也相应受到抑制；RNA干扰导致JNKs基因沉默同样也可抑制BMP9诱导的间充质干细胞成骨分化以及裸鼠皮下异位成骨．因此，BMP9可通过活化JNKs激酶途径，从而调控间充质干细胞成骨分化．

BMP9 Regulates Osteogenic Differentiation of Mesenchymal Stem Cells Through JNKs Kinase Pathway

In addition to Smad pathway, our previous study has shown that BMP9 can induce osteogenic differentiation of mesenchymal stem cells (MSCs) through p38 MAPKs pathway. In this study, we explore the possible involvement and detail role of JNKs (c-Jun N-terminal kinases) in BMP9-indcued osteogenic differentiation of MSCs. BMP9 was introduced into MSCs by recombinant adenoviruses protocol, then, in vitro and in vivo assays were conducted to detect whether BMP9 can induce osteogenic differentiation of MSCs through JNKs kinase pathway. The results showed that BMP9 can activate JNKs kinase through increase the phosphorylated form of JNKs kinase. JNKs kinase inhibitor SP600125 can inhibit ALP activity, OPN and OCN expression, as well as calcium deposition induced by BMP9 in MSCs. Furthermore, SP600125 also led to a decrease in BMP9-induced Runx2 activity and canonical Smad signaling. Moreover, when JNKs kinase was silenced by RNA interference in MSCs, BMP9-induced osteogenic differentiation in vitro and ectopic bone formation in vivo were accordingly inhibited along with knockdown of JNKs. Taken together, those results intensively suggested that BMP9 can induce and regulate osteogenic differentiation of MSCs through activating JNKs kinase pathway.