Participance of fibronectin and various collagen types in the formation of fibrous extracellular matrix in cardiosclerosis.

Investigation of the extracellular matrix composition of the left heart ventricle was carried out on autopsy material of subjects, aged from 60 to 70 years, in a number of cases, including: (1) tissue without cardiosclerosis; (2) granulation tissue formed 2 weeks after infarction; (3) post-infarctial fibrous scars; (4) diffuse cardiosclerosis in consequence of stenotic coronary atherosclerosis. Cryostat sections treated with highly specific antibodies to fibronectin and types I, III, IV and V collagens were examined by the indirect immunofluorescence technique. Fibronectin and the mentioned collagenous proteins were detected in the extracellular matrix of granulation tissue. In contrast, fibronectin and collagen type IV were not revealed in post-infarctial fibrous scars. Collagen types III and V were diffusely distributed in fibrous tissue, whereas collagen type I was demonstrated to accumulate preferentially in the deeper regions of post-infarctial scars. Fibronectin and collagen types I, III, V, but never type IV, were also found in the connective tissue in diffuse cardiosclerosis. The significance of type V collagen in the extracellular matrix is discussed.