Borok Z, Lubman R L, Danto S I, Zhang X L, Zabski S M, King L S, Lee D M, Agre P, Crandall E D
Will Rogers Institute Pulmonary Research Center, Division of Pulmonary and Critical Care Medicine, University of Southern California, Los Angeles, California 90033, USA.
Am J Respir Cell Mol Biol. 1998 Apr;18(4):554-61. doi: 10.1165/ajrcmb.18.4.2838.
We investigated the role of keratinocyte growth factor (KGF) in regulation of alveolar epithelial cell (AEC) phenotype in vitro. Effects of KGF on cell morphology, expression of surfactant apoproteins A, B, and C (SP-A, -B, and -C), and expression of aquaporin 5 (AQP5), a water channel present in situ on the apical surface of alveolar type I (AT1) cells but not expressed in alveolar type II (AT2) cells, were evaluated in AECs grown in primary culture. Observations were made on AEC monolayers grown in serum-free medium without KGF (control) or grown continuously in the presence of KGF (10 ng/ml) from either Day 0 (i.e., the time of plating) or Day 4 or 6 through Day 8 in culture. AECs monolayers express AQP5 only on their apical surfaces as determined by cell surface biotinylation studies. Control AECs grown in the absence of KGF through Day 8 express increasing levels of AQP5, consistent with transition toward the AT1 cell phenotype. Exposure of AECs to KGF from Day 0 results in decreased AQP5 expression, retention of a cuboidal morphology, and greater numbers of lamellar bodies relative to control on Day 8 in culture. AECs treated with KGF from Day 4 or 6 exhibit a decrease in AQP5 expression through subsequent days in culture, as well as an increase in expression of surfactant apoproteins. These data, showing that KGF both prevents and reverses the increase in AQP5 (and decrease in surfactant apoprotein) expression that accompanies progression of the AT2 toward the AT1 cell phenotype, support the concepts that transdifferentiation between AT2 and AT1 cell phenotypes is at least partially reversible and that KGF may play a major role in modulating AEC phenotype.
我们在体外研究了角质形成细胞生长因子（KGF）在调节肺泡上皮细胞（AEC）表型中的作用。评估了KGF对原代培养的AEC细胞形态、表面活性物质载脂蛋白A、B和C（SP-A、-B和-C）表达以及水通道蛋白5（AQP5）表达的影响，AQP5是一种位于I型肺泡（AT1）细胞顶端表面原位存在但在II型肺泡（AT2）细胞中不表达的水通道。观察了在无KGF的无血清培养基中生长的AEC单层细胞（对照），或从培养第0天（即接种时间）或第4天或第6天至第8天在KGF（10 ng/ml）存在下连续生长的AEC单层细胞。通过细胞表面生物素化研究确定，AEC单层细胞仅在其顶端表面表达AQP5。在无KGF的情况下培养至第8天的对照AEC细胞表达的AQP5水平不断增加，这与向AT1细胞表型的转变一致。从第0天开始将AEC细胞暴露于KGF会导致AQP5表达降低、保持立方形态以及在培养第8天时相对于对照有更多的板层小体。从第4天或第6天开始用KGF处理的AEC细胞在随后的培养天数中表现出AQP5表达降低，以及表面活性物质载脂蛋白表达增加。这些数据表明，KGF既能阻止又能逆转随着AT2细胞向AT1细胞表型进展而伴随出现的AQP5表达增加（以及表面活性物质载脂蛋白表达降低），支持了AT2和AT1细胞表型之间的转分化至少部分可逆以及KGF可能在调节AEC表型中起主要作用的观点。
