Rat Amnion Type IV Collagen Composition and Metabolism: DISCUSSION(3)

11 May

Our studies demonstrating differential sensitivity of kidney and amnion basement membranes to collagen breakdown by active MMP-9 and bacterial collagenase suggest that the rat amnion type IV collagen chain composition potentially favors collagenase degradation, as compared to the type IV collagen composition of adult renal tubular basement membranes. The relative abundance of cysteine-enriched type IV collagen a chains in renal basement membranes may impart greater strength to the basement membrane as a result of cross-linking through disulfide bridges. Hence, it is conceivable that type IV collagen composition determines the longevity and integrity of the basement membrane, with basement membranes that are relatively poor in the more cross-linked a chains, like amnion, being destined for turnover. However, it must be recognized that our experiments were carried out on extracted basement membrane material and that our findings may not reflect the relative susceptibilities of the collagens to degradation in situ. proventil inhaler

Degradation of the type IV collagen in amnion basement membranes may initiate the process of apoptotic cell death that we have previously described. Indeed, ultrastruc-tural studies of rat amnions documented loss of basement membrane components and delamination of amnion epithelial cells in association with features of cell death. The present studies show loss of type IV collagen by Day 20.