FIBRONECTIN IS THE MAJOR FIBROBLAST CHEMOATTRACTANT IN RABBIT ANTIGLOMERULAR BASEMENT-MEMBRANE DISEASE

Tbe mechanism for fibroblast recruitment in renal fibrosis due to anti -glomerular basement membrane (anti-GBM) disease is unknown. Since fib roblast recruitment can occur via chemotaxis, assessment of the possib le production of fibroblast chemotactic activity by affected renal tis sue and its identification could provide important clues. Anti-GBM dis ease was induced by injection of guinea pig anti-rabbit GEM immunoglob ulin G into rabbits previously, sensitized to guinea Pig immunoglobuli n G. On days 4, 7, and 14 after induction, renal tissue was harvested and glomeruli isolated. Overnight serum-free conditioned media from wh ole cortex and glomeruli were prepared and assayed for fibroblast chem otactic activity Tbe results show low level activity in both condition ed media from control animals In contrast, conditioned media from anti -GBM-treated animals at all time points showed significantly elevated fibroblast chemotactic activity peaking on day 4 with subsequent reduc tion thereafter The magnitude of increase in cortical conditioned medi a was significantly higher than that for glomerular conditioned media, suggesting that most of the activity was derived om extraglomerular s ources Gelfiltration analysis revealed the activity to be heterogeneou s, consisting of at least four major species with estimated molecular weights ranging from 10 to >100 kd Acidification of conditioned media failed to increase chemotactic activity significantly, whereas proteas e digestion abolished it. Treatment of conditioned media with antifibr onectin inhibited >85% of the chemotactic activity, whereas antibodies to platelet-derived growth factor and transforming growth factor-beta did not have a significant effect. These findings taken together sugg est that fibronectin-derived peptides represent the predominant fibrob last chemoattractant produced fry renal cortex in anti-GEM disease.