Figure 3: Sirius red staining of penis under a light microscope. There were fewer smooth muscle cells in the TGF-β1 group than in the control group; there were more collagen fibers in the TGF-β1 group than in the control group. (a) TGF-β1 group; (b) control group. Arrow: smooth muscle cells; circle: collagen fibers. Images were obtained from rabbits euthanized at 20 days after TGF-β1 injection. TGF-β1: transforming growth factor β1.