The LIM domain-containing proteins Pinch1/2 regulate integrin activation and cell–extracellular matrix interaction and adhesion. Here, we report that deleting Pinch1 in limb mesenchymal stem cells (MSCs) and Pinch2 globally (double knockout; dKO) in mice causes severe chondrodysplasia, while single mutant mice do not display marked defects. Pinch deletion decreases chondrocyte proliferation, accelerates cell differentiation and disrupts column formation. Pinch loss drastically reduces Smad2/3 protein expression in proliferative zone (PZ) chondrocytes and increases Runx2 and Col10a1 expression in both PZ and hypertrophic zone (HZ) chondrocytes. Pinch loss increases sclerostin and Rankl expression in HZ chondrocytes, reduces bone formation, and increases bone resorption, leading to low bone mass. In vitro studies revealed that Pinch1 and Smad2/3 colocalize in the nuclei of chondrocytes. Through its C-terminal region, Pinch1 interacts with Smad2/3 proteins. Pinch loss increases Smad2/3 ubiquitination and degradation in primary bone marrow stromal cells (BMSCs). Pinch loss reduces TGF-β-induced Smad2/3 phosphorylation and nuclear localization in primary BMSCs. Interestingly, compared to those from single mutant mice, BMSCs from dKO mice express dramatically lower protein levels of β-catenin and Yap1/Taz and display reduced osteogenic but increased adipogenic differentiation capacity. Finally, ablating Pinch1 in chondrocytes and Pinch2 globally causes severe osteopenia with subtle limb shortening. Collectively, our findings demonstrate critical roles for Pinch1/2 and a functional redundancy of both factors in the control of chondrogenesis and bone mass through distinct mechanisms.

包含LIM域的蛋白Pinch1 / 2调节整联蛋白的活化以及细胞与细胞外基质的相互作用和粘附。在这里，我们报告说，删除小鼠肢体间充质干细胞（MSCs）中的Pinch1和全局删除Pinch2（双敲除； dKO）会导致严重的软骨发育不良，而单个突变小鼠没有显示出明显的缺陷。捏缺失会减少软骨细胞增殖，加速细胞分化并破坏柱的形成。少量收缩会急剧减少增生区（PZ）软骨细胞中Smad2 / 3蛋白的表达，并增加PZ和肥大区（HZ）软骨细胞中Runx2和Col10a1的表达。少量收缩会增加HZ软骨细胞中的硬化素和Rankl表达，减少骨形成，并增加骨吸收，从而导致骨量低。体外研究表明，Pinch1和Smad2 / 3在软骨细胞核中共定位。通过其C端区域，Pinch1与Smad2 / 3蛋白相互作用。收缩损失增加了原代骨髓基质细胞（BMSC）中的Smad2 / 3泛素化和降解。收缩损失减少了原代BMSCs中TGF-β诱导的Smad2 / 3磷酸化和核定位。有趣的是，与单突变小鼠相比，dKO小鼠的骨髓间充质干细胞表达的β-catenin和Yap1 / Taz蛋白水平显着降低，并且成骨能力降低但成脂分化能力增强。最后，在软骨细胞中消融Pinch1和整体消融Pinch2会导致严重的骨质减少，肢体细微缩短。总的来说，