ONTOGENY OF TYPE-I PROCOLLAGEN EXPRESSION DURING HUMAN FETAL LUNG DEVELOPMENT

The cellular sites of type I procollagen (PCI) production were investi gated during fetal and early postnatal human lung development. PCI-syn thesizing cells and sites of recent collagen deposition were visualize d by immunoperoxidase staining of lung tissue with monoclonal antibodi es to human PCI. In selected cases, serial sections were also examined by in situ hybridization to establish the cellular sites of PCI gene expression and mRNA accumulation. PCI cytoplasmic immunostaining gener ally correlated with sites of mRNA accumulation and with known sites o f interstitial collagen deposition, including the adventitial and musc ular layers of large blood vessels, submesothelial and peribronchial c onnective tissue, perichondrium, and interstitial matrix. However, we also observed developmental changes in relative PCI expression for eac h of these compartments, heterogeneity in the level of PCI expression by cells within individual anatomic subcompartments, and variations in the level of PCI expression along the length of pulmonary blood vesse ls and airways. These studies emphasize the complexity of developmenta lly regulated alterations in procollagen production during lung develo pment.