Differential transmural distribution of gene expression for collagen typesI and III proximal to aortic coarctation in the rabbit

To assess the effects on the biosynthesis of collagen types I and III assoc iated with an acute increase in blood pressure, we established a mid-thorac ic aortic coarctation in the rabbit and studied gene expression and protein accumulation of these collagen types proximal to the stenosis 1, 3 and 7 d ays and 2, 4 and 8 weeks after coarctation. The mRNA level of type I collag en pro-alpha 2(I) was maximal at 3 days and returned to normal at 4 weeks, mRNA of pro-a2(I) was localized mainly in the outer media, adventitia and i ntima. Accumulation of type I collagen and its precursors was increased by 3 days, peaked at 4 weeks, and decreased toward normal by 8 weeks, correspo nding to the distribution of pro-alpha 2(1) mRNA. Gene expression for pro-a lpha 1(III) was similar to that of pro-alpha 2(I) but was distributed throu ghout the media. We conclude that the mechanical stresses associated with a n acutely induced alteration in pressure initiate rapid gene expression for collagen types I and III in the aortic wall. The response for collagen typ e I, predominantly in the outer media and adventitia, suggests that these r egions play an immediate role in the resistance to excessive dilatation of the aorta. The diffuse response for collagen type III in the media suggests participation in a more extensive remodeling response associated with the reinforcement and reorganization of the musculoelastic fascicles. Copyright (C) 2000 S. Karger AG, Basel.