Carol A. Tozzi

ISOLATION OF DIFFERENTIALLY EXPRESSED GENES IN HYPERTENSIVE PULMONARY ARTERY OF RATS

Pulmonary artery remodeling is a complex biological process, and a key molecular mechanism regulating this process is selective up- and downregulation of genes. We used reverse transcriptase-polymerase chain reaction (RT-PCR) differential display in a rat model of hypoxic pulmonary hypertension to identify selectively expressed genes relevant to pulmonary artery remodeling. We characterized the pattern of gene expression in hypertensive and normal arteries. Eight differentially expressed cDNAs were selected, isolated, and characterized. Homology searches identified 4 previously identified genes and 4 novel genes that were not further characterized. The known genes were beta-glucoronidase, hemeoxygenase-2 (HO-2), glycerol-3-phosphate dehydrogenase, and cytoplasmic gamma-actin. Each of the 4 known genes was relevant to processes involved in pulmonary artery remodeling. We conclude that mRNA differential display was informative in identifying genes coding for products directly involved in pulmonary artery remodeling.

Remodeling of Rat Neonatal Pulmonary Artery: Role of Matrix Metalloproteinases

We studied whether rapid thinning of large pulmonary arteries of neonatal rats is associated with breakdown of collagen. Pulmonary artery extracts from fetal to 21 days of age were assayed for collagen content and matrix metalloproteinases. Within 3 days postpartum, no changes in collagen content, collagenolytic activity, or levels of stromelysin-l or gelatinase A were observed. After day 3, collagen content and total proteolytic activity increased with little change in matrix metalloproteinase expression. Thus, collagen was not degraded, and the late increases in collagen and total proteolytic activity were probably growth related. Unlike adult rats in which collagen is broken down after reversal of hypoxic pulmonary artery remodeling, collagen is not broken down in neonatal pulmonary arteries during adaptation to extrauterine life.