Heparin-like glycosaminoglycans are normal components of the blood vessel wall and may play an important role in the regulation of smooth muscle cell growth, migration, and differentiation. We have recently shown that heparin and related molecules can regulate the secretory phenotype of rat aortic smooth muscle cells (SMC) in vitro. In these cells, heparin induces the synthesis of a previously undescribed, low molecular weight (Mr = 60,000) collagenous protein. The research described in this application is directed toward the development of specific molecular probes to the 60Kd collagen and the utilization of these probes to study the production, distribution, structure, and regulation of this molecule. Specifically, we intend to develop monoclonal antibodies to the 45Kd pepsin-resistant form of the 60Kd collagen following its isolation from heparin-treated SMC cell layers. These antibodies will be used to study the distribution of this collagen in vivo in a spectrum of normal rat tissues. In addition, the distribution of the 60Kd collagen will be analyzed in the aorta at various time points after injury by balloon catheterization. This approach will allow us to sample SMC in different functional states (quiescent, migratory, proliferative, post-proliferative, and involved in connective tissue synthesis). Using a differential hybridization selection technique, we will clone in plasmid vectors gene sequences complementary to the 60Kd collagen mRNA. These cDNAs will be sequenced to generate structural data on the 60Kd collagen. Finally, we will study the molecular basis of regulation of the 60Kd collagen by heparin, using a cDNA as a specific probe for 60Kd collagen mRNA levels. It is hoped that a detailed investigation of this new vascular wall collagen and its regulation by heparin will contribute to our understanding of SMC function in both normal and atherosclerotic conditions.
