Buch S, Jones C, Liu J, Han R N, Tanswell A K, Post M
Medical Research Council Group in Lung Development, Hospital for Sick Children Research Institute, Toronto, Ontario, Canada.
Exp Cell Res. 1994 Mar;211(1):142-9. doi: 10.1006/excr.1994.1070.
There is increasing evidence to suggest that platelet-derived growth factor (PDGF), or PDGF-like molecules, play a role in fetal lung morphogenesis. The cellular sources of PDGF and its target cells within the fetal lung remain to be defined. In the present study, we investigated the developmental expression of PDGF and its cognate receptor genes in fetal rat lung fibroblasts. Northern analysis revealed that fetal lung fibroblasts express the PDGF A-chain, B-chain, and beta-receptor genes. The cells actively translated these mRNAs into protein as demonstrated by immunocytochemistry and by metabolic labeling with [35S]methionine, followed by immunoprecipitation with specific PDGF-AA and -BB antibodies. Affinity cross-linking with 125I-labeled PDGF-BB demonstrated the presence of PDGF beta-receptors on fetal lung fibroblasts. The development expression of the PDGF genes was examined in fibroblasts derived from the early canalicular (Day 19) to the early saccular stage (Day 21) of lung development (term = 22 days). PDGF A-chain gene expression was at a low but constant level during late gestation. No change in either the transcription rate or stability of the message for this gene was observed with advancing gestation. Despite these mRNA observations, PDGF-AA is the major secreted form in the medium of the fibroblasts. Expression of PDGF B-chain gene was greatest during the early canalicular stage (Day 19) and declined sharply thereafter. The greater expression of PDGF B-chain during the canalicular stage was due to a greater rate of transcription and a greater PDGF B-chain mRNA stability. The PDGF beta-receptor gene was expressed at a lower but constant level in these cells during late gestation. The constant level of PDGF beta-receptor mRNA could be attributed to a balanced increased synthesis of the message coupled to an increased breakdown of the transcript. These data indicate that fetal lung fibroblasts synthesize PDGF-AA, PDGF-BB, and PDGF beta-receptor and that they regulate the developmental expression of these PDGF genes differently.
越来越多的证据表明，血小板衍生生长因子（PDGF）或类PDGF分子在胎儿肺形态发生中发挥作用。PDGF在胎儿肺内的细胞来源及其靶细胞仍有待确定。在本研究中，我们调查了PDGF及其同源受体基因在胎鼠肺成纤维细胞中的发育表达情况。Northern分析显示，胎鼠肺成纤维细胞表达PDGF A链、B链和β受体基因。免疫细胞化学以及用[35S]甲硫氨酸进行代谢标记，随后用特异性PDGF-AA和-BB抗体进行免疫沉淀，结果表明这些细胞能将这些mRNA积极翻译成蛋白质。用125I标记的PDGF-BB进行亲和交联，证明胎鼠肺成纤维细胞上存在PDGFβ受体。在肺发育从早期小管期（第19天）到早期囊状期（第21天）（足月为22天）的成纤维细胞中检测了PDGF基因的发育表达。PDGF A链基因在妊娠后期表达水平较低但保持恒定。随着妊娠进展，未观察到该基因的转录速率或信息稳定性发生变化。尽管有这些mRNA观察结果，但PDGF-AA是成纤维细胞培养基中的主要分泌形式。PDGF B链基因在早期小管期（第19天）表达最高，此后急剧下降。小管期PDGF B链表达较高是由于转录速率较高以及PDGF B链mRNA稳定性较高。PDGFβ受体基因在妊娠后期这些细胞中的表达水平较低但保持恒定。PDGFβ受体mRNA的恒定水平可归因于信息合成增加与转录本降解增加之间的平衡。这些数据表明，胎鼠肺成纤维细胞合成PDGF-AA、PDGF-BB和PDGFβ受体，并且它们对这些PDGF基因的发育表达调控方式不同。
