Defective extracellular matrix reorganization by chronic wound fibroblastsis associated with alterations in TIMP-1, TIMP-2, and MMP-2 activity

Chronic leg wounds are characterized by defective remodeling of the extrace llular matrix, failure of reepithelialization, and prolonged inflammation. The hypothesis that this defective extracellular matrix remodeling is assoc iated with phenotypic differences in the activity of the matrix metalloprot einases and tissue inhibitors of metalloproteinases was studied in chronic wound and patient-matched normal fibroblasts in three-dimensional collagen lattice systems. Chronic wound fibroblasts exhibited no differences in morp hology or proliferation (p > 0.1) compared with patient-matched uninvolved dermal fibroblasts. The ability of chronic wound fibroblasts to reorganize extracellular matrix was significantly impaired, however, in comparison to the uninvolved dermal fibroblasts (p < 0.01). This difference in extracellu lar matrix reorganization was not related to differences in proliferation w ithin the collagen lattices (p > 0.05) or attachment to type I collagen (p > 0.1). Marked differences were evident in matrix metalloproteinase-2 activ ity between chronic wound and patient-matched normal fibroblasts. Whereas l evels of pro-matrix metalloproteinase-2 were similar between the two fibrob last populations (p > 0.1), the chronic wound fibroblasts exhibited signifi cantly decreased levels of the 62 kDa active form of matrix metalloproteina se-2 (p < 0.01). Reverse zymography and enzyme-linked immunosorbent assay d emonstrated that the decreased matrix metalloproteinase-2 activity was asso ciated with increased production of tissue inhibitors of metalloproteinase- 1 and -2 by the chronic wound fibroblasts (p < 0.05). Increased production of tissue inhibitors of metalloproteinases in chronic wound fibroblasts was also reflected in decreased levels of matrix metalloproteinase-1 (p < 0.00 5). These data suggest that the impaired ability of chronic wound fibroblas ts to reorganize extracellular matrix in vitro is related to decreased leve ls of active matrix metalloproteinase-2 and matrix metalloproteinase-1 resu lting from increased production of tissue inhibitors of metalloproteinase-1 and -2 by chronic wound fibroblasts. These findings provide a mechanism to explain the impaired cellular responses and extracellular matrix reorganiz ation observed in chronic leg wounds in vivo.