RECRUITMENT OF PERIPHERAL MONONUCLEAR-CELLS BY MAMMALIAN COLLAGENASE DIGESTS OF TYPE-I COLLAGEN

Type I collagen is highly susceptible to proteolytic cleavage by neutral mammalian collagenase. Following an initial site specific cleavage of the substrate, two characteristic products are generated, TC(A) and TC(B). These two products then spontaneously denature and are degraded into multiple smaller molecular weight peptides. We prepared TC(A) and TC(B) from native type I collagen by the action of rat uterine fibroblast neutral collagenase. In addition we prepared denatured type I alpha-chains and exposed them to the action of collagenase under controlled conditions in order to generate small molecular weight peptides. We then examined intact type I collagen, TC(A) and TC(B) and type I gelatin peptides for chemotactic activity in a Boyden chamber assay using both human peripheral monocytes and polymorphonuclear leucocytes as target cells. Intact type I collagen, while chemotactic for neutrophils, failed to elicit any chemotactic response in mononuclear cells. In addition, the results demonstrate an absence of any detectable chemotactic activity for either TC(A) or TC(B) when human peripheral monocytes were used as the target cells. However, type I collagen peptides demonstrated chemotactic activity for peripheral monocytes. Maximum cell migration was found with digests which had been exposed to neutral mammalian collagenase for three to four hours. No chemotactic activity was found using the same peptides, when neutrophils were used as the target cells. The data strongly suggest that chemotactic activity for mononuclear cells, normally suppressed in intact type I collagen, is revealed and/or activated by neutral collagenase digestion. Conversely, chemotactic activity for neutrophils is lost when intact type I collagen is digested into smaller molecular weight fragments. To further examine the mechanism(s) of the directed migratory response to collagen peptides, we used the ubiquitous extracellular matrix tripeptide, ARG-GLY-ASP, present in type I collagen, to probe the chemotactic response to type I gelatin peptides. Arg-Gly-Asp had no intrinsic agonist activity. Co-incubation of peripheral mononuclear cells with Arg-Gly-Asp did not block the cell migration response to collagen peptides. These latter observations demonstrate that RGD is not critical for monocyte migration to type I collagen peptides.