A comparative analysis of collagen III, IV, laminin and fibronectin in Duchenne muscular dystrophy biopsies and cell cultures

The role of collagen type III and IV (Coll III, IV) in Duchenne muscular dystrophy (DMD) was investigated by the indirect immunofluorescence technique (IIF) both in muscle biopsies and derived cell cultures. Ten dystrophic cases were studied and compared with twelve suitable control cases, extending the IIF analysis to two other representative non-collagenous proteins of the extracellular matrix (ECM), namely fibronectin (FN) and laminin (LM). DMD biopsies generally displayed a thickening of endomysial and/or perimysial connective, as compared to control specimens. All the markers analyzed were found to contribute to this connective proliferation, although from a quantitative point of view the relative involvement decreases progressively from FN through Coll III and IV to LM. However, due to Coll IV selective endomysial localization, Coll IV alteration can be considered a specific indicator of a muscle cell defect. Results from DMD muscle cultures revealed no significant changes in comparison to control cultures, except for Coll IV. A well-organized, Coll IV-containing pericellular matrix was noted in a fraction of DMD cultures as a unique feature seen in no control culture. This alteration was again considered significant since Coll IV is the only marker clearly associated with the myotube component still expressed in vitro. The negative results obtained on the other marker proteins should not however be considered definitive, due to the lack in the simplified in vitro system used of humoral and/or neuronal factors which may be needed to express gene defect(s) in differentiated cells.