Synthesis of proteoglycans is augmented in dystrophic mdx mouse skeletal muscle

Mdx mice uniquely recover from degenerative dystrophic lesions through an i ntense myoproliferative response. The onset and progression of this process are controlled by a complex set of interactions between myoblasts and thei r environment. The presence of the extracellular matrix is essential for no rmal myogenesis. Proteoglycans are abundant components of the extracellular matrix. The synthesis of proteoglycans in mdx mice during skeletal muscle regeneration was evaluated. Incorporation of radioactive sulfate demonstrat ed a significant increase in the synthesis of several types of proteoglycan s in mdx animals compared to age-matched controls. The size and charge of p roteoglycans synthesized by the mdx mice remained unchanged. In particular, one of the up-regulated proteoglycans, the small chondroitin/dermatan sulf ate proteoglycan decorin which is known to bind and to sequester transformi ng growth factor-beta, was investigated. Immunocytolocalization and in situ hybridization studies showed that decorin mainly accumulated in the endomy sium, i.e. around individual skeletal muscle fibers from M. titialis anteri or and diaphragm.