Accumulation of glycosaminoglycans in radiation-induced muscular fibrosis

The content and biosynthesis of glycosaminoglycans (GAGs) were studied in the pig thigh muscle after acute local gamma-irradiation. Seven months following irradiation, the muscular tissue next to the irradiation cone was replaced by severe mutilating fibrosis delimited by an intermediary perifbrotic zone. Fibrosis, perifibrotic tissue and normal muscle, were sampled and incubated with [3H]glucosamine and [35S]sulphate, and GAGs were isolated following pronase digestion. Results showed a parallel increase of collagen and GAG content in perifibrotic and fibrotic tissues. Sulphated GAGs, heparan sulphate and dermatan sulphate were preferentially accumulated in fibrotic tissue, while the hyaluronic acid content increased only slightly. Synthesis of sulphated GAGs was more elevated in fibrotic tissue than in perifibrotic zone as compared with normal muscle. Seven months after irradiation well-developed fibrotic tissue continued to synthesize and to accumulate extracellular matrix macromolecules, indicating the invasive aspect of post-irradiation fibrosis.