Sox9 augments BMP2-induced chondrogenic differentiation by downregulating Smad7 in mesenchymal stem cells (MSCs)

Abstract

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.

Carrageenan enhances chondrogenesis and osteogenesis in human bone marrow stem cell culture

“…www.ecmjournal.org Also, in the present study, the longest time point was day 14, whilst previous studies have shown formation of cartilage-like tissue from BMSCs (with or without a scaffold) after 4 weeks in culture (Meinel et al, 2004;Xue et al, 2012). Sox-9 expression is also of particular importance, as it has been shown to inhibit bone morphogenetic protein 2 (BMP-2)-induced expression of osteopontin, to enhance collagen type II expression in mesenchymal stem cells (Zhao et al, 2017) and chondrocytes (Bell et al, 1997;Zhao et al, 1997) and to play a pivotal role in chondrogenesis and chondrocyte differentiation (Akiyama et al, 2002;Bi et al, 1999;Ikegami et al, 2011). Further, forced ectopic Sox-9 expression in vitro (in mouse hypertrophic chondrocytes) and in vivo (in mice) results in downregulation of collagen type X (Leung et al, 2011), which, although its deposition was enhanced in the presence of MMC, was detected in smaller amounts than collagen type I and II.…”

Osteocyte TGFβ1‑Smad2/3 is positively associated with bone turnover parameters in subchondral bone of advanced osteoarthritis

“…Standard surgical procedures were performed during knee arthroplasty and specimen collection did not involve any clinical intervention. The collection of human specimens and animal experiments in the present study were approved by the Ethics Committee of the First Affiliated Hospital of chongqing Medical University (Permit number: 2015-316), under which the effect of Smad7 on chondrogenesis and endochondral ossification (25), osteocyte TGFβ-Smad4 on osteoblastic and osteoclastic differentiation (26) had been previously have identified. Written informed consent was obtained from participants.…”

A simplified system for the effective expression and delivery of functional mature microRNAs in mammalian cells

“…The qPCR reactions were done in triplicate. All expression values were normalized to the reference gene GAPDH expression by using the 2 -ΔΔCt method [50][51][52][53]. The sequences of the qPCR primers are listed in Supplemental Table 1.…”