Kurpakus M A, Stock E L, Jones J C
Department of Cell, Molecular and Structural Biology, Northwestern University Medical School, Chicago, Illinois.
Dev Biol. 1992 Apr;150(2):243-55. doi: 10.1016/0012-1606(92)90239-d.
Extracellular matrix is considered to play an important role in determining the phenotype of cells with which it interacts. Here we have investigated the possibility that extracellular matrix is involved in specifying the pattern of keratin expression in epithelial cells. For these studies, we have developed an explant system in which epithelial cells from one type of stratified epithelial tissue, namely conjunctiva, are maintained on an extracellular matrix substrate derived from a different tissue, namely cornea. These ocular tissues are ideal for such analyses since they express distinct sets of keratins. For example, bovine conjunctival epithelium processed for immunofluorescence is not recognized by antibody preparations against keratin K3 or K12. In contrast, K3 and K12 antibodies generate intense staining in bovine corneal epithelium. At the immunochemical level, conjunctival cells in situ appear to possess no K12 and only trace amounts of K3, whereas corneal epithelial cells in situ possess both K3 and K12. When conjunctival cells are maintained on a corneal substrate with an intact basement membrane for 10 days in vitro they begin to express keratin K12 as determined by immunofluorescence. On the other hand, conjunctival cells that are maintained on a corneal substrate lacking a basement membrane fail to show staining with K12 antibodies. Conjunctival cells begin to show intense staining using K3 antibodies within about 10 days of being placed in culture regardless of their substrate. These results indicate that basement membrane can play a positive role in determining cell-specific expression of certain keratins such as K12. However, other keratins such as K3 may be "unmasked" and/or their expression may be upregulated simply by placing conjunctival epithelial cells in culture. We speculate that in conjunctiva K3 expression is influenced by certain negative exogenous factors. We discuss the possible means of regulation of keratin expression in our model system.
细胞外基质被认为在决定与其相互作用的细胞表型方面发挥着重要作用。在此，我们研究了细胞外基质参与确定上皮细胞中角蛋白表达模式的可能性。对于这些研究，我们开发了一种外植体系统，其中来自一种复层上皮组织（即结膜）的上皮细胞被维持在源自另一种组织（即角膜）的细胞外基质底物上。这些眼组织非常适合此类分析，因为它们表达不同的角蛋白组。例如，经免疫荧光处理的牛结膜上皮不被抗角蛋白K3或K12的抗体制剂识别。相反，K3和K12抗体在牛角膜上皮中产生强烈染色。在免疫化学水平上，原位结膜细胞似乎不具有K12，仅含有微量的K3，而原位角膜上皮细胞同时具有K3和K12。当结膜细胞在体外完整基底膜的角膜底物上维持10天时，通过免疫荧光测定，它们开始表达角蛋白K12。另一方面，维持在缺乏基底膜的角膜底物上的结膜细胞未能显示出K12抗体染色。无论底物如何，结膜细胞在培养约10天内开始使用K3抗体显示强烈染色。这些结果表明基底膜在决定某些角蛋白（如K12）的细胞特异性表达方面可以发挥积极作用。然而，其他角蛋白（如K3）可能只是被“暴露”，和/或它们的表达可能仅仅通过将结膜上皮细胞置于培养中而被上调。我们推测在结膜中K3的表达受某些负性外源性因素影响。我们讨论了我们模型系统中角蛋白表达的可能调节方式。
