Epidermis promotion of collagenase in hypertrophic scar organ culture.

The pathophysiological biology of human hypertrophic scar was examined in a long-term organ culture system. Fresh full-thickness, thin slices of scar were placed in petri dishes. Tissue was successfully maintained for 2 weeks in an environment made up of CMRL-1066 medium, fetal bovine serum, insulin, and hydrocortisone under an environment of 40% O2, 5% CO2, and 55% N2 at 37 degrees C on a rocking platform. Histologically the explants were viable and remained differentiated. The omission of hydrocortisone caused localized destruction of the connective tissue matrix under the epidermal layer. Transplanting the epidermis to the adipose surface of an explant before culturing in hydrocortisone-free medium, produced localized connective tissue matrix destruction only within the deep dermal layer. Removal of the epidermis before culturing in hydrocortisone-free medium produced no localized connective tissue matrix destruction. Culture medium from intact explants maintained in hydrocortisone-free media had higher levels of latent collagenase activity compared to epidermal free explants and intact explants in hydrocortisone-containing medium. This hypertrophic scar latent collagenase had a molecular weight estimated to be 33,000 by molecular-sieve chromatography. The active form of the enzyme had a molecular weight estimated to be 26,000. When examined by gel electrophoresis, activated collagenase cleaved types I and III native collagens, producing TC-A peptide fragments of alpha chains. Type V collagen was not cleaved by this enzyme. Metal chelators such as 1,10-phenanthroline blocked enzymatic activity. Serine and sulfhydryl proteolytic inhibitors showed no effects. Intact hypertrophic scar has the capacity to produce collagenase which appears responsible for the destruction of the connective tissue matrix of the scar. The production of hypertrophic scar collagenase is somehow controlled by the epidermis.