The molecular mechanism of the effect of mechanical stretch on various factors in glomerular cells.

在肾小球高血压中，系膜细胞被认为感知到循环张力的增加，我们最近报道了体外循环机械拉伸通过培养大鼠系膜细胞自分泌/旁分泌TGF-β来增强ECM成分的表达。TGF-β通常作为与潜伏TGF-β结合蛋白-1 （LTBP-1）相关的大潜伏复合物分泌，已知其与细胞外基质（ECM）成分结合。由于LTBP-ECM相互作用已被认为在TGF-β的激活和生物学作用中发挥作用，我们研究了LTBP-1在拉伸诱导的TGF-β介导的ECM表达中的作用。系膜细胞分别表达LTBP-1、LTBP-1S和LTBP-1L的短链和长链mRNA。在针对人LTBP-1的多克隆抗体或与人LTBP-1 n端部分对应的合成寡肽存在的情况下，系膜细胞被循环拉伸24-36小时，该抗体可作为LTBP-ECM结合的竞争性抑制剂。抗ltbp -1抗体和合成寡肽均能抑制拉伸诱导的I型胶原和纤维连接蛋白mRNA表达，且呈剂量依赖性，但通过添加重组TGF-β Ab39可恢复Ab39和寡肽的抑制作用，或者寡肽不改变外源添加TGF-β对水貂肺上皮细胞的生长抑制作用。这些结果表明，系膜细胞分泌TGF-β作为大潜伏复合物，LTBP-ECM相互作用可能是TGF-β作用和ECM积累的关键步骤，为治疗肾小球硬化和其他纤维化疾病的进展提供了新的治疗策略。

In glomerular hypertension mesangial cells are believed to perceive the increased cyclic strain and we have recently reported that cyclic mechanical stretch in vitro enhances the expression of ECM components via an autocrine/paracrine secretion of TGF-β in cultured rat mesangial cells. TGF-β is usually secreted as a large latent complex associated with latent TGF-β binding protein-1 (LTBP-1), which is known to bind to extracellular matrix (ECM) components. Because the LTBP-ECM interaction has been suggested to play a role in the activation and biological action of TGF-β, we examined the role of LTBP-1 in the stretch-induced, TGF-β mediated ECM expression. Mesangial cells expressed mRNA for short and long forms of LTBP-1, LTBP-1S and LTBP-1L, respectively. Mesangial cells were subjected to cyclic stretch for 24-36 h in the presence of polyclonal antibody raised against human LTBP-1 or synthetic oligopeptides corresponding to N-terminal portions of human LTBP-1, which is to work as competitive inhibitors against the LTBP-ECM association. Both anti-LTBP-1 antibody and synthetic oligopeptides inhibited the stretch-induced mRNA expression of type I collagen and fibronectin in a dose-dependent manner, but the inhibition by Ab39 and the oligopeptides was recovered by adding recombinant TGF-β Ab39 or the oligopeptides did not change the effect of exogenously added TGF-β such as growth inhibition in mink lung epithelial cells. These results suggest that mesangial cells secrete TGF-β as large latent complex and the LTBP-ECM interaction may be a pivotal step in TGF-β action and ECM accumulation, providing a new therapeutic strategy against progression of glomerulosclerosis and other fibrotic diseases.