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-containing microfibrils in the extracellular matrix (ECM) of primary dermal fibroblasts 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 of the fibroblast cultures was used to study the synthesis, secretion, and processing of fibrillin 1, as well as to observe microfibril formation and stability. Microfibrils elaborated by the SSc cells were analyzed by electron microscopy for ultrastructural abnormalities, and the results were confirmed by immunoblotting.
RESULTS: Control and SSc fibroblasts displayed a prominent meshwork of fibrillin 1-containing microfibrils when visualized by IF using a fibrillin 1 mAb. Paradoxically, metabolic studies indicated a paucity of fibrillin 1 in the ECM in the majority of the SSc fibroblast strains. Subsequent rotary-shadowed electron microscopy revealed reduced amounts of and ultrastructural abnormalities in the microfibrils elaborated by all strains of SSc cells. Immunoblots confirmed the lack of the high molecular weight form of fibrillin 1 in the SSc fibroblasts of Choctaw American Indians. Finally, in vitro studies indicated that the amount of fibrillin 1 in the ECM of SSc cells diminished at a faster rate than the amount of fibrillin 1 in the ECM of control cells with time.
CONCLUSION: Although SSc fibroblasts assemble microfibrils, these microfibrils are unstable, suggesting that an inherent defect of fibrillin 1-containing microfibrils may play a role in the pathogenesis of SSc.