Defense mechanism of glomerular visceral epithelial cells against stress

哺乳动物肾小球内脏上皮细胞（vec）与小管上皮细胞相比含有丰富的中间纤维（if）。对从两栖动物到哺乳动物的广泛研究表明，这一特征在低等脊椎动物中是普遍的，这表明IF在VECs中起着重要作用。大鼠VECs表达desmin。在Masugi肾炎中，desmin的染色强度与注射抗gbm抗血清和蛋白尿的剂量平行。在嘌呤霉素氨基核苷肾病中，Western blotting和免疫染色显示VECs中desmin数量的增加和减少与蛋白尿平行。这些结果表明，内皮细胞中desmin的表达受到应激条件（如肾病）的影响。Plectin是一种IFs相关蛋白，被认为是IFs的细胞质交联元件。根据细胞类型的不同，粘附素主要通过细胞质、细胞周围或两者同时存在。VECs独特地显示粘附素主要附着在核周区域。嘌呤霉素氨基核苷肾病的细胞质染色变得强烈。我们假设VECs中丰富的IFs和独特分布的plectin能够抵抗来自狭缝隔膜和脉冲毛细血管壁的超滤液产生的机械应力。

Glomerular visceral epithelial cells (VECs) in mammals contain abundant intermediate filaments (IFs) in comparison with tubular epithelial cells. An extensive investigation of various species from amphibia to mammals showed that the characteristic was common to lower vertebrate, suggesting an important role of IF in VECs. Rat VECs express desmin. In Masugi nephritis, the staining intensity of desmin was parallel with the amount of injected dose of anti-GBM antisera and proteinuria. In puromycin aminonucleoside nephrosis, increase and decrease of the amount of desmin in VECs was shown to be parallel to proteinuria by Western blotting and immunostaining. These findings indicated that desmin expression in VECs was influenced by the condition under stress such as nephrosis. Plectin is an IF-associated protein which is postulated to function as a general cytoplasmic cross-linking element of IFs. Depending on cell types, plectin was found primarily either through the cytoplasm, at the cell periphery, or in the both location. VECs uniquely showed plectin attached predominantly to the perinuclear region. The cytoplasmic staining became intense in puromycine aminonucleoside nephrosis. We hypothesize that abundant IFs and uniquely distributed plectin in VECs function to resist mechanical stress produced by ultrafiltrate from slit diaphragm and pulsing capillary walls.