Ultrastructural features of proliferating fibroblasts in inflammatory granulomas.

Proliferating fibroblasts in subcutaneous connective tissue of rats after injection of peanut oil or implantation of an almost insoluble synthetic material (silicap) were characterized electron microscopically. In tissue samples of both the foreign body granulomas typical fibroblasts with abundant rough endoplasmic reticulum and a peculiar cellular modulation resembling histiocytes concerning their organelle composition were found. The morphological picture of the latter cells does not allow the conclusion that their function must be a merely phagocytic one. True myofibroblasts as detected in other stages of connective tissue proliferation are not present. The capillary vessels show a clear proliferation of their vascular cells and migration of these cells with assumption of fibroblastic features is suggested basing on morphological observations.