Abnormalities in fibrillin 1-containing microfibrils in dermal fibroblast cultures from patients with systemic sclerosis (scleroderma)

Objective. To determine if there are abnormalities in fibrillin 1-containin g microfibrils in the extracellular matrix (ECM) of primary dermal fibrobla sts explanted from patients with systemic sclerosis (SSc). Methods. Explanted fibroblasts from unaffected skin of 12 SSc patients were used to examine fibrillin 1-containing microfibrils by immunofluorescence (IF) using a monoclonal antibody (mAb) to fibrillin 1. Metabolic labeling o f the fibroblast cultures was used to study the synthesis, secretion, and p rocessing of fibrillin 1, as well as to observe microfibril formation and s tability. Microfibrils elaborated by the SSc cells were analyzed by electro n microscopy for ultrastructural abnormalities, and the results were confir med by immunoblotting. Results. Control and SSc fibroblasts displayed a prominent meshwork of fibr illin 1-containing microfibrils when visualized by IF using a fibrillin 1 m Ab. Paradoxically, metabolic studies indicated a paucity of fibrillin I in the ECM in the majority of the SSc fibroblast strains. Subsequent rotary-sh adowed electron microscopy revealed reduced amounts of and ultrastructural abnormalities in the microfibrils elaborated by all strains of SSc cells. I mmunoblots confirmed the lack of the high molecular weight form of fibrilli n 1 in the SSc fibroblasts of Choctaw American Indians. Finally, in vitro s tudies indicated that the amount of fibrillin 1 in the ECM of SSc cells dim inished at a faster rate than the amount of fibrillin 1 in the ECM of contr ol cells with time. Conclusion. Although SSc fibroblasts assemble microfibrils, these microfibr ils are unstable, suggesting that an inherent defect of fibrillin 1-contain ing microfibrils may play a role in the pathogenesis of SSc.