Cyclosporin A decreases the degradation of type I collagen in rat gingivalovergrowth

Cyclosporin A (CsA) is used as an immunosuppressive agent and its prominent side effect is the induction of fibrous gingival overgrowth. The purpose o f this study was to investigate the effect of CsA on the type I collagen me tabolism in the gingiva of rats fed a powdered diet either containing or la cking CsA. Immunohistochemical analysis revealed that type I collagen was m ore prevalent in the connective tissue of CsA-treated gingiva than in these of control rats on days 15, 30, and 55 after the start of feeding. Total R NAs were isolated from mandibular molar gingiva on days 0, 3, 8, 15, 30, an d 55. Quantitative analysis of mRNA by reverse transcriptase-polymerase cha in reaction revealed that the CsA-treated groups showed a gradual decrease in expression of type I collagen and collagenase mRNAs, 0.4% and 18.0% on d ay 55 compared with those on day 0, respectively. In the control groups, ty pe I collagen and collagenase mRNAs also decreased to 19.7% and 63.0%, resp ectively, however, both mRNA expressions were significantly lower in the Cs A-treated group than in the controls. An electron microscopic analysis of f ibroblasts was performed re count the number of cells with collagen fibrils in the cytoplasm, a marker of phagocytosis of collagen by fibroblasts. The collagen fibrils were detected in 4.7% +/- 2.7% and 24.3% +/- 13.7% of fib roblasts in the overgrown gingiva treated with CsA rat for 8 days and 30 da ys, but in 57.0% +/- 5.3% and 81.3% +/- 9.2% of fibroblasts in the each con trol group gingiva, respectively. Furthermore, in vitro analysis was perfor med to measure the phagocytosis of cultured fibroblasts by flow cytometry u sing collagen-coated latex beads. Fibroblasts isolated from CsA-treated gin giva on day 8 and day 30 contained 5.7% +/- 0.6% and 9.9% +/- 1.5% phagocyt ic cells, whereas control fibroblasts contained 50.3% +/- 5.5% and 33.3% +/ - 4.9% phagocytic cells, respectively. The inhibition rate of phagocytic ac tivity was similar between in vivo and in vitro assays. These Findings sugg est that the decrease of the collagen degradation due to the lower phagocyt osis and the lower collagenase mRNA expression are closely associated with the increase of type I collagen accumulation in CsA-treated rat gingiva. (C ) 2000 Wiley-Liss, Inc.