PCNA and keloid: Real-time PCR, immunofluorescence, and Western blot demonstrated that PCNA expression was higher in keloid fibroblasts than that in normal skin fibroblasts (P < 0.01), which was significantly suppressed by NaHS pretreatment (P < 0.01) (Figure 4), further indicating that exogenous H2S supplementation inhibited keloid fibroblast proliferation.