Production of Collagenase and Tissue Inhibitor of Metalloproteinases by Fibroblasts Derived from Normal and Fibrotic Human Lungs· Annie Pardo, Ph,D.; Moises Selnwn, M.D., F.C.C.~; Remedios Ralnirez, B.S.; Carlos Ranws, Al.Sc; Martha Montano, M.Sc.; George Stricklin, Ph.D; and Ganesh Raghu, M.D.

Several experiments have demonstrated low collagenolytic activity during the development of pulmonary fibrosis. In order to determine if fibroblasts playa role in this alteration, procollagenase and tissue inhibitor of metalloproteinases (TIMP) were quantified in fibroblasts derived from 12 human lung specimens (normal = 6, idiopathic pulmonary fibrosis [IPF] = 6). Under basal conditions, three cell strains from normal and three from fibrotic lung specimens did not synthesize collagenase and a similar number of normal and IPF-derived fibroblast strains produced the enzyme. However, the rate of enzyme synthesis among normal and fibrotic collagenase producing fibroblasts exhibited significant differences. Thus, whereas normal fibroblasts produced more than 300 ng/ml, fibrotic lung fibroblasts secreted approximately half of this amount (lIS ± 67 ng/ml). Phorbol myristate acetate (PMA) enhanced collagenase production in all of the 12 lung fibroblast lines tested. In four IPF fibroblasts, PMA increased collagenase secretion close to

those of normal stimulated lung fibroblasts; however, a lower induction was observed in cell strains from two fibrotic lung specimens. There was a wide variation in TIMP production both in normal and fibrotic lung fibroblasts, and no statistically significant difference was observed. Under basal conditions, TIMP levels ranged from 329 to 16,911 ng/ml in normal lung cells, and from 377 to 17,557 in fibrotic lung fibroblasts. PMA induced a severalfold increase in all cell lines. These results suggest that there are subpopulations of lung fibroblasts with different potential to produce collagenase and TIMP in vitro, and that the predominance of low collagenase-producing subsets may contribute to the development of fibrosis. (Chest 1992; 102:1085-89)

pulmonary fibrosis (I PF) is a disorder of I diopathic unkno\\'ll etiology, characterized by diffuse inter-

advanced phases of experimental and hunlan pulnlonary fibrosis, a noteworthy decrease in collagenolytic activity takes place. "H.9 This supports the contention that an alteration in collagen catabolism plays a nlajor role in lung fibrogenesis. Moreover, we have documented that decreased collagenolytic activity appears to occur during inflamnlation prior to the developlnent of fibrosis. 10 In contrast, increased collagen synthesis seems to be a transient and reversible feature of the collagen turnover abnormalities occurring in the darnaged tissue. 10 In addition, we have found an increased collagenase inhibitory activity in supernatants obtained from fibrotic lung homogenates compared with normal lung specimens. 11 The decrease in collagenolysis may depend on a complex series of mechanisms, including, among others, the production ofprocollagenase, the activation of this enzyme precursor, the action of collagenase inhibitors, and the substrate susceptibility in the lung microenvironment. 12-14 In normal lung parenchyma, the cells responsible for interstitial collagen breakdown are mainly fibroblasts and macrophages. Under culture conditions, both cells produce procollagenase and tissue inhibitor of metalloproteinases (TIMP) and therefore actively participate in collagen tissue remodeling. 15,16

stitial inflammation and exaggerated collagen accumulation, leading to progressive destruction of the alveolo-capillary units. I Despite numerous studies performed both in human and experimental pulmonary fibrosis,2-6 the sequence of cellular and molecular events involved in the development of IPF is still unclear. A common feature in the pathogenesis of fibrosis is probably an imbalance in the norlnal hOlneostasis of collagen. Collagen synthesis exceeds breakdown, either by an increase of the former and/or a decrease in the latter, resulting in an excessive deposition of this protein in the lung parenchyma. 7 We have demonstrated that in

*Fronl the Facultad de Ciendas, Universidad Nadonal Aul

Production of collagenase and tissue inhibitor of metalloproteinases by fibroblasts derived from normal and fibrotic human lungs.

Several experiments have demonstrated low collagenolytic activity during the development of pulmonary fibrosis. In order to determine if fibroblasts p...
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