Cosio F G
Department of Internal Medicine, Ohio State University, Columbus 43210.
Am J Physiol. 1993 Jan;264(1 Pt 2):F106-19. doi: 10.1152/ajprenal.1993.264.1.F106.
In the present study we assessed whether the fibronectin (FN) metabolism of human mesangial cells (HMC) in culture is influenced by the contact of HMC with collagens type I and IV. HMC were grown on collagen gels or on collagen-coated surfaces (collagen films). FN concentrations were measured by enzyme-linked immunosorbent assay; FN synthesis was measured by metabolic labeling and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In addition, the structure of matrix FN was examined by immunofluorescence microscopy. Compared with cells grown on plastic, HMC on collagen gels or collagen films accumulated greater amounts of FN in the cell matrix, and in these cultures, matrix FN was organized into a complex mesh of fibers. FN fiber formation was more prominent in cells adherent to collagen IV than in cells adherent to collagen I, and these fibers were observed as early as day 1 in culture. HMC adherent to plastic deposited matrix FN as patches and only occasionally as FN fibers localized to the periphery of the cell. The accumulation of FN in the matrix of HMC on collagen was not due to an increased rate of FN synthesis. In fact, HMC on collagen gels synthesized less FN than HMC on plastic. The present results indicate that the accumulation of FN in the matrix of HMC on collagen is due to the fact that this FN is less likely to be released into the supernatant than the matrix FN produced by HMC on plastic. The decreased FN synthesis demonstrated by HMC on collagen gels was associated with an overall decrease in protein synthesis but was not associated with a decrease in FN mRNA levels. Finally, FN isolated from HMC on collagen gels contained a unique 90-kDa gelatin-binding FN fragment. In conclusion, collagens have effects on the synthesis, localization, organization, and catabolism of FN produced by HMC in culture. In particular, collagen IV, the collagen normally present in the glomerular mesangium, appears to influence uniquely the organization of mesangial matrix FN.
在本研究中，我们评估了培养的人肾小球系膜细胞（HMC）的纤连蛋白（FN）代谢是否受HMC与I型和IV型胶原接触的影响。HMC生长在胶原凝胶或胶原包被的表面（胶原膜）上。通过酶联免疫吸附测定法测量FN浓度；通过代谢标记法测量FN合成，并通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳进行分析。此外，通过免疫荧光显微镜检查基质FN的结构。与在塑料上生长的细胞相比，在胶原凝胶或胶原膜上的HMC在细胞基质中积累了更多的FN，并且在这些培养物中，基质FN被组织成复杂的纤维网。FN纤维形成在粘附于IV型胶原的细胞中比在粘附于I型胶原的细胞中更显著，并且这些纤维在培养的第1天就已观察到。粘附于塑料的HMC将基质FN沉积为斑块，仅偶尔作为定位于细胞周边的FN纤维。HMC在胶原上的基质中FN的积累并非由于FN合成速率增加。事实上，在胶原凝胶上的HMC比在塑料上的HMC合成的FN更少。目前的结果表明，HMC在胶原上的基质中FN的积累是由于与HMC在塑料上产生的基质FN相比，这种FN释放到上清液中的可能性较小。在胶原凝胶上的HMC所表现出的FN合成减少与蛋白质合成的总体减少相关，但与FN mRNA水平的降低无关。最后，从胶原凝胶上的HMC分离的FN包含一个独特的90 kDa明胶结合FN片段。总之，胶原对培养的HMC产生的FN的合成、定位、组织和分解代谢有影响。特别是，通常存在于肾小球系膜中的IV型胶原似乎独特地影响系膜基质FN的组织。
