Evidence for Increased Collagenase as a Genetic Characterist ic in Cell Culture * BY EUGENE

Recessive dystrophic epidermolysis bullosa (RDEB) ~ is a debilitating and often fatal disease characterized by repeated blistering after minor trauma. The morphologic finding of collagen degeneration (1) coupled with increased collagenase activity in explant cultures of skin from RDEB patients (2, 3) suggested that excessive collagenase might be repsonsible for the blistering phenomenon. This postulate was further substantiated by the demonstration of increased tissue levels of immunoreactive eollagenase (iHSC) in both the unaffected and blistered skin of RDEB patients (4). Evidence that some abnormality in the regulation of collagenase synthesis or activity was important in the pathogenesis of the disease was obtained when collagenases derived from skin fibroblast cultures of two patients with RDEB were shown to be structurally altered (5). The enzymes, which appeared to be overproduced in cell culture, demonstrated increased thermolability and reduced affinity for Ca 2+, a cofactor required both for enzyme activity and thermal stability (6). In addition, there was decreased activity per unit immunoreactive protein, raising the question of the relationship of the altered enzymes to the blistering phenomenon. If a primary defect in the regulation of synthesis and/or degradation of collagenase were basic to the etiology of RDEB, k might be expected that increased levels of iHSC would be seen in fibroblast cultures. Thus, it seemed essential to determine (a) whether a quantitative increase in iHSC and/or collagenase activity could be found in RDEB fibroblast cultures, (b) whether such a phenotypie trait persists through many cell passages, (c) whether this trait might be utilized to distinguish RDEB from other genetic forms of the disease, and (d) the extent to which heterogeneity is manifested within the fibroblast cultures of various RDEB patients.