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

在肾小球高血压中，肾小球系膜细胞被认为感知到增加的周期性应变，并且我们最近报道了体外周期性机械拉伸通过培养的大鼠系膜细胞中TGF-β的自分泌/旁分泌来增强ECM组分的表达。TGF-β通常作为与潜在TGF-β结合蛋白-1（LTBP-1）相关的大的潜在复合物分泌，已知LTBP-1结合细胞外基质（ECM）组分。由于LTBP-ECM相互作用已被认为在TGF-β的活化和生物学作用中起作用，因此我们检查了LTBP-1在牵张诱导的TGF-β介导的ECM表达中的作用。肾小球系膜细胞分别表达短型和长型LTBP-1、LTBP-1 S和LTBP-1 L的mRNA。在抗人LTBP-1的多克隆抗体或对应于人LTBP-1的N-末端部分的合成寡肽的存在下，使系膜细胞经历循环拉伸24-36小时，所述合成寡肽用作针对LTBP-ECM缔合的竞争性抑制剂。抗LTBP-1抗体和合成寡肽均能抑制牵张诱导的I型胶原和纤连蛋白mRNA的表达，且呈剂量依赖性，但加入重组TGF-β Ab 39可恢复其抑制作用，或不改变外源性TGF-β对水貂肺上皮细胞生长的抑制作用。这些结果表明，系膜细胞分泌TGF-β作为大的潜在复合物，LTBP-ECM相互作用可能是TGF-β作用和ECM积累的关键步骤，提供了一种新的治疗策略，以对抗肾小球硬化和其他纤维化疾病的进展。

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.