Fibroblast-specific focal adhesion kinase links mechanical force to fibrosis via chemokine-mediated inflammatory pathways

Hypertrophic scar (HTS) formation is characterized by exuberant fibroproliferation for reasons that remain poorly understood1. One important but often overlooked component of wound repair is mechanical force, which regulates reciprocal cell-matrix interactions through focal adhesion components including focal adhesion kinase (FAK)1,2. Here we report that FAK is activated following cutaneous injury and that this activation is potentiated by mechanical loading. Transgenic mice lacking fibroblast-specific FAK exhibit significantly less fibrosis in a preclinical model of HTS formation. Inflammatory pathways involving monocyte chemoattractant protein-1 (MCP-1), a chemokine highly implicated in human skin fibrosis3, are triggered following FAK activation, mechanistically linking physical force to fibrosis. Further, small molecule inhibition of FAK effectively abrogates fibroproliferative mechanisms in human cells and significantly reduces scar formation in vivo. Collectively, these findings establish a molecular basis for HTS formation based on the mechanical activation of fibroblast-specific FAK and demonstrate the therapeutic potential of targeted mechanomodulatory strategies. Wildtype murine tissue was harvested at either day 6 or 14 post-injury following 48 hours or 10 days of mechanical loading, respectively (n=4 mice per group per time point). Murine RNA was isolated, labeled, and hybridized to the GeneChip microarray according to the manufacturer’s protocols (Affymetrix, Santa Clara, CA, USA). Each gene in the microarray was represented by 20 oligonucleotide pairs, with each pair consisting of an oligonucleotide perfectly matched to the cDNA sequence, and a second oligonucleotide containing a single base mismatch. Raw microarray data (sample intensity files) were processed using GeneSpring GX 11.0 (Agilent Technologies Inc., Santa Clara, CA, USA).

肥厚性瘢痕（Hypertrophic scar, HTS）的形成以过度成纤维细胞增殖为特征，但其具体发病机制目前仍未完全阐明¹。伤口修复过程中一个重要却常被忽视的因素是机械力，其可通过黏着斑相关组分（包括黏着斑激酶，focal adhesion kinase, FAK）¹,²调控细胞与细胞外基质的双向相互作用。
本研究证实，皮肤损伤后黏着斑激酶会被激活，且该激活过程可因机械负荷而增强。成纤维细胞特异性敲除黏着斑激酶的转基因小鼠，在肥厚性瘢痕形成的临床前模型中，纤维化程度显著降低。黏着斑激酶激活后会触发涉及单核细胞趋化蛋白-1（monocyte chemoattractant protein-1, MCP-1）的炎症通路——该趋化因子与人类皮肤纤维化密切相关³，从而在机制上将物理力与纤维化过程联系起来。此外，小分子抑制剂靶向黏着斑激酶，可有效抑制人类细胞中的成纤维细胞增殖机制，并在体内显著减少瘢痕形成。综上，本研究确立了基于成纤维细胞特异性黏着斑激酶机械激活的肥厚性瘢痕形成分子机制，并证实了靶向机械调节策略的治疗潜力。
野生型小鼠组织分别于损伤后第6天或第14天采集，对应施加48小时或10天机械负荷（每组每个时间点n=4只小鼠）。按照制造商实验方案（Affymetrix，美国加利福尼亚州圣克拉拉市），对小鼠RNA进行提取、标记，并与GeneChip基因芯片进行杂交。该基因芯片中每个基因由20个寡核苷酸对代表，每对包含一条与cDNA序列完全匹配的寡核苷酸，以及一条携带单个碱基错配的寡核苷酸。原始基因芯片数据（样本强度文件）使用GeneSpring GX 11.0（Agilent Technologies Inc.，美国加利福尼亚州圣克拉拉市）进行处理。