Birth associated changes in pulmonary arterial connective tissue gene expression in the normal and hypertensive lung

Objectives: To determine the temporal and spatial expression of the connective tissue precursors, procollagen and tropoelastin mRNA in normal and pulmonary hypertensive porcine pulmonary arteries from birth onwards. Methods: Using in situ hybridisation, connective tissue gene expression for procollagen α1(I) and α1(III) and tropoelastin was studied in intrapulmonary arteries from normal piglets, 5 min-16 weeks, and from piglets made pulmonary hypertensive by exposure to hypobaric hypoxia for 3 days, from birth, 3 or 14 days of age. In addition, Type III pN-procollagen, tropoelastin and collagen I and III were studied by immunohistochemistry. Quantitative or semi-quantitative techniques were applied to both in situ and immunohistochemical studies. Results: Procollagen α1(I) and α1(III) mRNA expression increased rapidly in the media and adventitia between birth and 3 days of age (P