Section of Plastic Surgery, Department of Surgery.
Epigenomics Core, and.
J Clin Invest. 2020 Oct 1;130(10):5444-5460. doi: 10.1172/JCI136142.
Cells sense the extracellular environment and mechanical stimuli and translate these signals into intracellular responses through mechanotransduction, which alters cell maintenance, proliferation, and differentiation. Here we use a mouse model of trauma-induced heterotopic ossification (HO) to examine how cell-extrinsic forces impact mesenchymal progenitor cell (MPC) fate. After injury, single-cell (sc) RNA sequencing of the injury site reveals an early increase in MPC genes associated with pathways of cell adhesion and ECM-receptor interactions, and MPC trajectories to cartilage and bone. Immunostaining uncovers active mechanotransduction after injury with increased focal adhesion kinase signaling and nuclear translocation of transcriptional coactivator TAZ, inhibition of which mitigates HO. Similarly, joint immobilization decreases mechanotransductive signaling, and completely inhibits HO. Joint immobilization decreases collagen alignment and increases adipogenesis. Further, scRNA sequencing of the HO site after injury with or without immobilization identifies gene signatures in mobile MPCs correlating with osteogenesis, and signatures from immobile MPCs with adipogenesis. scATAC-seq in these same MPCs confirm that in mobile MPCs, chromatin regions around osteogenic genes are open, whereas in immobile MPCs, regions around adipogenic genes are open. Together these data suggest that joint immobilization after injury results in decreased ECM alignment, altered MPC mechanotransduction, and changes in genomic architecture favoring adipogenesis over osteogenesis, resulting in decreased formation of HO.
细胞感知细胞外环境和机械刺激，并通过机械转导将这些信号转化为细胞内反应，从而改变细胞的维持、增殖和分化。在这里，我们使用创伤诱导异位骨化 (HO) 的小鼠模型来研究细胞外力如何影响间充质祖细胞 (MPC) 的命运。在损伤后，损伤部位的单细胞 (sc) RNA 测序揭示了与细胞黏附和细胞外基质-受体相互作用途径相关的 MPC 基因的早期增加，以及 MPC 向软骨和骨的轨迹。免疫染色揭示了损伤后活跃的机械转导，焦点黏附激酶信号增加，转录共激活因子 TAZ 的核易位，抑制该信号可减轻 HO。同样，关节固定可减少机械转导信号，并完全抑制 HO。关节固定减少胶原排列并增加脂肪生成。此外，损伤后固定或不固定的 HO 部位的 scRNA 测序确定了与成骨相关的移动 MPC 中的基因特征，以及来自不可移动 MPC 的与脂肪生成相关的特征。这些相同 MPC 中的 scATAC-seq 证实，在移动 MPC 中，骨生成基因周围的染色质区域开放，而在不可移动 MPC 中，脂肪生成基因周围的染色质区域开放。这些数据表明，损伤后关节固定会导致细胞外基质排列减少、MPC 机械转导改变以及基因组结构发生变化，有利于脂肪生成而不是成骨，从而减少 HO 的形成。
