Inhibition of type I procollagen production in photodamage: correlation between presence of high molecular weight collagen fragments and reduced procollagen synthesis.

Three-dimensional lattices of reconstituted, polymerized type I collagen were subjected to partial hydrolysis by organ culture fluid from human skin or by various matrix metalloproteinases, including matrix metalloproteinase-1 (interstitial collagenase), -2 (72 kDa gelatinase A), -8 (neutrophil collagenase), -9 (92 kDa gelatinase B), or -13 (collagenase 3). Following partial digestion, human dermal fibroblasts were incubated on the enzyme-treated or control lattices and examined for ability to contract the collagen lattice and synthesize type I procollagen. Collagen lattices partially degraded by organ culture fluid were contracted by fibroblasts under conditions in which control collagen lattices were not. On the partially degraded collagen, fibroblasts synthesized reduced amounts of type I procollagen (approximately 70% reduction). Purified matrix metalloproteinases with collagenolytic activity duplicated the effects of the human skin organ culture fluid, although matrix metalloproteinases 8 and 13 were less efficient than matrix metalloproteinase-1 (65% vs 40% and 18% reduction in type I procollagen production for matrix metalloproteinases 1, 8, and 13, respectively). Matrix metalloproteinases 2 and 9 were without effect on intact collagen; however, when collagen lattices were subjected to digestion by a combination of matrix metalloproteinases 1 and 9, fragments produced by matrix metalloproteinase-1 were further degraded by the gelatinase. Collagen contraction and inhibition of procollagen synthesis were both reduced. Matrix metalloproteinase-2 was less effective than matrix metalloproteinase-9 in clearing matrix metalloproteinase-1-generated fragments. Matrix metalloproteinase-2 was also less effective in preventing contraction and inhibiting the downregulation of type I procollagen synthesis. These observations suggest that in the presence of high molecular weight fragments of type I collagen, type I procollagen synthesis is inhibited. As these fragments are processed further, there is less inhibition of type I procollagen production.