Study on vitreous fibrosis induced by blood cells

In order to examine the individual role of each blood cell type in causing vitreous fibrosis, monocytes and/or lymphocytes, or erythrocytes were separated from rabbit blood and injected into rabbit vitreous bodies. Vitreous fibrosis was induced by intravitreal injections of the mixture of monocytes and lymphocytes, monocytes alone, lymphocytes alone, and erythrocytes. Cell density-dependent vitreous fibrosis was observed in eyes injected with monocytes and/or lymphocytes. Lymphocytes were more potent than monocytes in inducing fibrosis. Glycosaminoglycans (GAGs) synthesized by fibrotic vitreous bodies induced by the mixture of monocytes and lymphocytes, and erythrocytes were characterized. The results indicated that 91% of total GAGs synthesized by normal vitreous was hyaluronic acid (HA). In contrast, in fibrotic vitreous, the synthesis of HA was decreased to about 30% whereas that of chondroitin sulfate (CS) was increased to 47-59% of total newly synthesized GAGs. The ratio of CS against total newly synthesized GAGs in fibrotic vitreous corresponded to the grade of fibrosis. Control vitreous bodies injected with freeze-thawed monocytes and lymphocytes synthesized 70% of HA and 12% of CS although no vitreous fibrosis was observed. These results suggest that intravitreal injection of monocytes and/or lymphocytes or erythrocytes may cause the infiltration of fibroblasts or fibroblast-like cells or the transformation of hyalocytes into fibroblasts, and that these fibroblasts may be responsible for the synthesis of CS.