Cartilage injuries caused by arthritis or trauma pose formidable challenges for effective clinical management due to the limited intrinsic proliferative capability of chondrocytes.Autologous stem cell-based therapies ...Cartilage injuries caused by arthritis or trauma pose formidable challenges for effective clinical management due to the limited intrinsic proliferative capability of chondrocytes.Autologous stem cell-based therapies and transgene-enhanced cartilage tissue engineering may open new avenues for the treatment of cartilage injuries.Bone morphogenetic protein 2(BMP2)induces effective chondrogenesis of mesenchymal stem cells(MSCs)and can thus be explored as a potential therapeutic agent for cartilage defect repair.However,BMP2 also induces robust endochondral ossification.Although the precise mechanisms through which BMP2 governs the divergence of chondrogenesis and osteogenesis remain to be fully understood,blocking endochondral ossification during BMP2-induced cartilage formation may have practical significance for cartilage tissue engineering.Here,we investigate the role of Sox9-donwregulated Smad7 in BMP2-induced chondrogenic differentiation of MSCs.We find that overexpression of Sox9 leads to a decrease in BMP2-induced Smad7 expression in MSCs.Sox9 inhibits BMP2-induced expression of osteopontin while enhancing the expression of chondrogenic marker Col2a1 in MSCs.Forced expression of Sox9 in MSCs promotes BMP2-induced chondrogenesis and suppresses BMP2-induced endochondral ossification.Constitutive Smad7 expression inhibits BMP2-induced chondrogenesis in stem cell implantation assay.Mouse limb explant assay reveals that Sox9 expands BMP2-stimulated chondrocyte proliferating zone while Smad7 promotes BMP2-intitated hypertrophic zone of the growth plate.Cell cycle analysis indicates that Smad7 induces significant early apoptosis in BMP2-stimulated MSCs.Taken together,our results strongly suggest that Sox9 may facilitate BMP2-induced chondrogenesis by downregulating Smad7,which can be exploited for effective cartilage tissue engineering.展开更多
基金The reported work was supported in part by research grants from the Natural Sciences Foundation of China(#81572142 and#81371972 to WH)the National Institutes of Health(AT004418 to TCH)+4 种基金the U.S.Department of Defense(OR130096 to JMW)the Scoliosis Research Society(TCH and MJL)the 973 Program of the Ministry of Science and Technology of China(#2011CB707906 to TCH)The reported work was also supported in part by The University of Chicago Cancer Center Support Grant(P30CA014599)the National Center for Advancing Translational Sciences of the National Institutes of Health through Grant Number UL1 TR000430.
文摘Cartilage injuries caused by arthritis or trauma pose formidable challenges for effective clinical management due to the limited intrinsic proliferative capability of chondrocytes.Autologous stem cell-based therapies and transgene-enhanced cartilage tissue engineering may open new avenues for the treatment of cartilage injuries.Bone morphogenetic protein 2(BMP2)induces effective chondrogenesis of mesenchymal stem cells(MSCs)and can thus be explored as a potential therapeutic agent for cartilage defect repair.However,BMP2 also induces robust endochondral ossification.Although the precise mechanisms through which BMP2 governs the divergence of chondrogenesis and osteogenesis remain to be fully understood,blocking endochondral ossification during BMP2-induced cartilage formation may have practical significance for cartilage tissue engineering.Here,we investigate the role of Sox9-donwregulated Smad7 in BMP2-induced chondrogenic differentiation of MSCs.We find that overexpression of Sox9 leads to a decrease in BMP2-induced Smad7 expression in MSCs.Sox9 inhibits BMP2-induced expression of osteopontin while enhancing the expression of chondrogenic marker Col2a1 in MSCs.Forced expression of Sox9 in MSCs promotes BMP2-induced chondrogenesis and suppresses BMP2-induced endochondral ossification.Constitutive Smad7 expression inhibits BMP2-induced chondrogenesis in stem cell implantation assay.Mouse limb explant assay reveals that Sox9 expands BMP2-stimulated chondrocyte proliferating zone while Smad7 promotes BMP2-intitated hypertrophic zone of the growth plate.Cell cycle analysis indicates that Smad7 induces significant early apoptosis in BMP2-stimulated MSCs.Taken together,our results strongly suggest that Sox9 may facilitate BMP2-induced chondrogenesis by downregulating Smad7,which can be exploited for effective cartilage tissue engineering.
