Bone morphogenetic protein 9 (BMP9) has been validated as one of the most potent osteoinduction factors, but its underlying mechanism remains unclear. As a member of the matrix metalloproteinase (MMP) family, MMP13 may be involved in regulating the lineage-specific differentiation of mouse embryonic fibroblasts (MEFs). The goal of this study was to determine whether MMP13 regulates the osteoinduction potential of BMP9 in MEFs, which are multipotent progenitor cells widely used for stem cell biology research. In vitro and in vivo experiments showed that BMP9-induced osteogenic markers and/or bone were enhanced by exogenous MMP13 in MEFs, but were reduced by MMP13 knockdown or inhibition. The expression of hypoxia inducible factor 1 alpha (HIF-1α) was induced by BMP9, which was enhanced by MMP13. The protein expression of β-catenin and phosphorylation level of glycogen synthase kinase-3 beta (GSK-3β) were increased by BMP9 in MEFs, as was the translocation of β-catenin from the cytoplasm to the nucleus; all these effects of BMP9 were enhanced by MMP13. Furthermore, the MMP13 effects of increasing BMP9-induced β-catenin protein expression and GSK-3β phosphorylation level were partially reversed by HIF-1α knockdown. These results suggest that MMP13 can enhance the osteoinduction potential of BMP9, which may be mediated, at least in part, through the HIF-1α/β-catenin axis. Our findings demonstrate a novel role of MMP13 in the lineage decision of progenitor cells and provide a promising strategy to speed up bone regeneration.

骨形态发生蛋白9 (BMP9) 已被证实是最有效的骨诱导因子之一，但其潜在机制仍不清楚。作为基质金属蛋白酶 (MMP) 家族的成员，MMP13 可能参与调节小鼠胚胎成纤维细胞 (MEF) 的谱系特异性分化。本研究的目的是确定 MMP13 是否调节 MEF 中 BMP9 的骨诱导潜力，MEF 是广泛用于干细胞生物学研究的多能祖细胞。体外和体内实验表明，MEF 中外源 MMP13 增强了 BMP9 诱导的成骨标志物和/或骨，但敲低或抑制 MMP13 则降低了 BMP9 诱导的成骨标志物和/或骨。缺氧诱导因子 1 α (HIF-1α) 的表达由 BMP9 诱导，并由 MMP13 增强。BMP9 增加了 MEF 中 β-catenin 的蛋白表达和糖原合成酶激酶 3 beta (GSK-3β) 的磷酸化水平，β-catenin 从细胞质易位到细胞核；BMP9 的所有这些作用均被 MMP13 增强。此外，MMP13 增加 BMP9 诱导的 β-catenin 蛋白表达和 GSK-3β 磷酸化水平的作用可通过 HIF-1α 敲低部分逆转。这些结果表明 MMP13 可以增强 BMP9 的骨诱导潜力，这可能至少部分通过 HIF-1α/β-连环蛋白轴介导。我们的研究结果证明了 MMP13 在祖细胞谱系决定中的新作用，并为加速骨再生提供了一种有前途的策略。