Thy-1 expression, a possible marker of early myofibroblast development, in renal tubulointerstitial fibrosis induced in rats by cisplatin.

Interstitial fibrosis is regarded as the common final pathway in chronic renal failure. Myofibroblasts play an important role in the renal fibrosis through producing extracellular matrices. In addition to expressions of cytoskeletons such as vimentin, desmin and α-smooth muscle actin (α-SMA), Thy-1 expression was investigated in cisplatin-induced rat renal interstitial fibrosis, to clarify the characteristics of myofibroblasts. Immunohistochemically, myofibroblasts in the renal fibrotic lesions reacted to vimentin, desmin and α-SMA in varying degrees, and the expression degrees were increased with advancing fibrosis. Vimentin expression was the greatest and the increased expression retained even in scar at end stages, whereas desmin and α-SMA expressions were almost completely decreased in scar. In double immunofluorescence, there were myofibroblasts reacting to both vimentin/desmin, desmin/α-SMA or α-SMA/vimentin, indicating that renal myofibroblasts can simultaneously express different cytoskeletons. Thy-1 expression in renal myofibroblasts was increased according to progressing fibrosis; however, the increased expression was decreased in scar, similar to desmin and α-SMA expressions. Some myofibroblasts expressing Thy-1 reacted simultaneously to vimentin or desmin, but there were no cells reacting to both Thy-1 and α-SMA. Because well-differentiated myofibroblasts are characterized mainly by α-SMA expression and the pericytes (immature stromal stem cells) showed a positive reaction to Thy-1, renal myofibroblasts might be originated from immature mesenchymal cells through loosing Thy-1 expression. This study for the first time shows that renal myofibroblasts can variously exhibit such mesenchymal markers as vimentin, desmin, α-SMA and Thy-1; particularly, Thy-1 immunohistochemistry would be used to detect myofibroblasts at early stages in analyzing chemically induced renal lesions.