Obliterative arteriopathy is one of the major obstacles to long-term survival of human renal allografts. However, the cellular composition of obliterative arteriopathy has been incompletely characterized. We have performed immunocytochemical investigations of cellular components of obliterative arteriopathy and also investigated immunophenotypic features of proliferating smooth muscle cells in these lesions.
Three renal allografts that had been removed due to rejection were available for this study. Time lapse between transplantation and removal of the renal allograft in these patients was 2 months, 5 months, and 4 years and 9 months, respectively. Tissue blocks cut from these renal allografts were fixed in methanol-Carnoy's fixative, and embedded in paraffin. Serial sections from each block were cut and used for histopathological and immunocytochemical studies. Monoclonal antibodies used for this study were as follows: anti-muscle actin antibody, HHF35; anti-smooth muscle actin antibody, CGA7; anti-vimentin antibody; anti-desmin antibody; anti-macrophage antibody, HAM56; and anti-Factor VIII-related antigen antibody.
In all the allografts, obliterative arteriopathy was observed in the interlobular and arcuate arteries. In an early stage of proliferative lesions (2 months), the hyperplastic intima consisted largely of macrophages, intermixed with smooth muscle cells. At this stage, smooth muscle cells at the luminal site stained positive with HHF35, but negative with CGA7. In older lesions (5 months, 4 years and 9 months), however, the thickened intima consisted almost entirely of smooth muscle cells. At this stage, smooth muscle cells stained positive with both HHF35 and CGA7.
These findings suggest that 1) macrophage may play an important role in an early stage of obliterative arteriopathy and 2) an immunophenotypic expression of intimal smooth muscle cells in obliterative arteriopathy may be different between young and older lesions.