Swisher J W, Rannels D E
Department of Medicine, Pennsylvania State University College of Medicine, Hershey 17033, USA.
Am J Physiol. 1997 May;272(5 Pt 1):L908-15. doi: 10.1152/ajplung.1997.272.5.L908.
Type II pulmonary epithelial cells (T2P) in primary culture assemble a biologically active extracellular matrix (ECM) from endogenously synthesized components, including fibronectin. Fibronectin is a well-recognized attachment protein that mediates cell adhesion, migration, and cytodifferentiation. In some cell types, exogenous fibronectin also is incorporated into ECM. The latter pathway of ECM assembly was thus investigated in T2P. Cells were cultured for 3-days in Dulbecco's modified Eagle's medium (DMEM) with or without 10% fetal calf serum (FCS), a source of exogenous fibronectin. Cell and matrix fractions were harvested on culture days 1, 2, and 3 to determine synthesis of cell and matrix proteins and matrix fibronectin content. During 3 days in DMEM containing 10% FCS, T2P flattened and spread to confluence more rapidly than cells in DMEM; they also produced ECM with higher fibronectin content than did cells in DMEM alone. On culture days 2 and 3, 10% FCS doubled (on average) synthesis of ECM fibronectin; in contrast, ECM fibronectin content increased nearly 10-fold. These observations suggest that cultured type II cells incorporate exogenous fibronectin into newly assembled ECM to a greater extent than the newly synthesized glycoprotein. Components of both endogenous and exogenous origin may therefore contribute to T2P assembly of a biologically active ECM.
原代培养的II型肺上皮细胞（T2P）利用内源性合成成分，包括纤连蛋白，组装生物活性细胞外基质（ECM）。纤连蛋白是一种公认的黏附蛋白，可介导细胞黏附、迁移和细胞分化。在某些细胞类型中，外源性纤连蛋白也会掺入ECM。因此，在T2P中研究了ECM组装的后一种途径。将细胞在含有或不含有10%胎牛血清（FCS，外源性纤连蛋白的来源）的杜氏改良 Eagle 培养基（DMEM）中培养3天。在培养的第1、2和3天收获细胞和基质部分，以确定细胞和基质蛋白的合成以及基质纤连蛋白含量。在含有10% FCS的DMEM中培养3天期间，T2P比在DMEM中的细胞更快地扁平并铺展至汇合；它们还产生了比单独在DMEM中的细胞具有更高纤连蛋白含量的ECM。在培养的第2天和第3天，10% FCS使ECM纤连蛋白的合成平均增加了一倍；相比之下，ECM纤连蛋白含量增加了近10倍。这些观察结果表明，培养的II型细胞将外源性纤连蛋白掺入新组装的ECM中的程度大于新合成的糖蛋白。因此，内源性和外源性来源的成分可能都有助于T2P组装生物活性ECM。
