Shiratori M, Michalopoulos G, Shinozuka H, Singh G, Ogasawara H, Katyal S L
Department of Pathology, University of Pittsburgh School of Medicine, Pennsylvania 15261.
Am J Respir Cell Mol Biol. 1995 Feb;12(2):171-80. doi: 10.1165/ajrcmb.12.2.7532419.
Hepatocyte growth factor (HGF) and its receptor, the product of c-MET proto-oncogene, are highly expressed in both fetal and adult lung, though their physiologic functions in the lung are largely unknown. In the present study, we examined whether alveolar type II cells in the lung are the target of HGF and whether HGF has any effects on growth of these cells. The alveolar epithelial type II cells were isolated from the lungs of adult male Sprague-Dawley rats by elastase digestion, and the cells were used to determine whether they express HGF and c-MET mRNAs and whether recombinant HGF has any effect on their DNA synthesis in primary culture. The effects were further compared with those induced by epidermal growth factor (EGF), acidic fibroblast growth factor (aFGF), transforming growth factor-alpha (TGF-alpha), and transforming growth factor-beta 1 (TGF-beta 1). Northern blot analysis and in situ hybridization revealed that type II cells express c-MET mRNA but not HGF mRNA. HGF stimulated [3H]thymidine incorporation into type II cells in primary cultures. An increase was also seen in labeling index as determined by nuclear immunostaining of bromodeoxyuridine-incorporated DNA. While aFGF (200 ng/ml) exerted an effect comparable to HGF (25 ng/ml) on DNA synthesis in type II cells, EGF (20 ng/ml) and TGF-alpha (100 ng/ml) had lesser effects. TGF-beta 1, a potent inhibitor of epithelial cell proliferation, at 0.25 to 2 ng/ml, did not inhibit HGF-induced [3H]thymidine incorporation into type II cells. The results indicate that HGF exerts its effects on type II cells as a potent mitogen by a paracrine mode of action.
肝细胞生长因子（HGF）及其受体（c-MET原癌基因的产物）在胎儿和成人肺组织中均高表达，但其在肺中的生理功能仍 largely未知。在本研究中，我们检测了肺中的II型肺泡细胞是否为HGF的靶细胞，以及HGF对这些细胞的生长是否有任何影响。通过弹性蛋白酶消化从成年雄性Sprague-Dawley大鼠的肺中分离出II型肺泡上皮细胞，并将这些细胞用于确定它们是否表达HGF和c-MET mRNA，以及重组HGF对其原代培养中的DNA合成是否有任何影响。将这些效应与表皮生长因子（EGF）、酸性成纤维细胞生长因子（aFGF）、转化生长因子-α（TGF-α）和转化生长因子-β1（TGF-β1）诱导的效应进行进一步比较。Northern印迹分析和原位杂交显示II型细胞表达c-MET mRNA但不表达HGF mRNA。HGF刺激原代培养的II型细胞中[3H]胸苷掺入。通过对掺入溴脱氧尿苷的DNA进行核免疫染色确定的标记指数也有所增加。虽然aFGF（200 ng/ml）对II型细胞中DNA合成的作用与HGF（25 ng/ml）相当，但EGF（20 ng/ml）和TGF-α（100 ng/ml）的作用较小。TGF-β1是上皮细胞增殖的强效抑制剂，在0.25至2 ng/ml时，不抑制HGF诱导的[3H]胸苷掺入II型细胞。结果表明，HGF通过旁分泌作用方式作为一种强效有丝分裂原对II型细胞发挥作用。
