Laminin and fibronectin distribution in normal and pathological human muscle

The availability of antisera against collagen and non-collagen proteins of the extracellular matrix has opened new possibilities of studying fibrous infiltration in muscular diseases. We have examined muscle biopsies from 5 controls and 27 patients with various neuromuscular diseases by immunofluorescence and peroxidase-anti-peroxidase. We investigated the distribution of fibronectin and of laminin, a protein present in basement membranes. In normal muscle both were present around blood vessels, axons, muscle spindles and muscle fibres. In addition fibronectin filled the endomysial and perimysial space, the endoneurium and the space between the intrafusal fibres. In pathological muscle laminin distribution was similar to that in normal muscle, but some atrophic fibres appeared to have a thickened contour and irregular profiles were occasionally observed in the absence of histologically demonstrable muscle fibres. Fibronectin was increased in all the conditions with thickened endomysium and perimysium, without displaying any disease-specific character. Findings are compared with the few published observations on fibronectin and collagen types.