Extracellular matrix structure after heart transplantation

Following heart transplantation remodeling of the donor heart causes changes in the extracellular myocardial matrix. We investigated 20 right ventricular endomyocardial biopsies taken 17±4 days (group I, n=9) and 63±13 days (group II, n=11) after heart transplantation from 16 patients transplanted for end-stage cardiomyopathy (15 dilated/1 ischemic). Immunohistochemical staining for collagen I, collagen III, collagen IV, and fibronectin was used. Evaluation was performed at a magnification of 400× using a computer-assisted image analyzing system measuring the relative area stained by the immunoperoxidase method, the number of cells in the given area, and the total area. Collagen I per cell was 13.9±5.9 μm2 in group I and increased significantly 66±13 days after heart transplantation in the perimysium around the myocardial cells as well as in the endocardium to 49.9±15.1 μm2 (P<0.05). No quantitative change in collagen III was noted (75.7±12.4 versus 75.5±16.0 μm2 n.s.). Collagen IV was found in the perimysial, in the capillary bed and in the vascular network. Significant quantitative change in the amount of collagen IV was not found (64.1±12.6 versus 61.0±8.9 μm2). Fibronectin was found in the entire perimysial extracellular matrix and in the endocardium in relationship with collagen I and III. An increased amount of fibronectin from 87.09±9.9 μm2 (group I) to 140.8±17.9 μm2 (group II, P<0.05) was found. The cell area and cell diameters were not significantly different (group I; cell area 772±227 μm2, diameter 31.3 μm; group II; cell area 776±224 μm2, diameter 31.4 μm).y It is concluded that remodeling of the donor heart after transplantation is characterized by a specific increase in collagen I and fibronectin, whereas a change in other collagen subtypes was not observed.