Fibrosis of the peritoneal cavity remains a serious, life-threatening problem in the treatment
of kidney failure with peritoneal dialysis. The mechanism of fibrosis remains unclear partly
because the fibrogenic cells have not been identified with certainty. Recent studies have
proposed mesothelial cells to be an important source of myofibroblasts through the epithelial–
mesenchymal transition; however, confirmatory studies in vivo are lacking. Here, we show
by inducible genetic fate mapping that type I collagen–producing submesothelial fibroblasts …