Inhibitory effect of recombinant human endostatin on the proliferation of hypertrophic scar fibroblasts in a rabbit ear model

Hypertrophic scar (HS) is a pathological scar that particularly occurs after traumatic injuries, surgical procedures and burning. Abnormal activation of hypertrophic scar fibroblasts (HSFs) intensifies fibrosis during wound healing. Our previous studies demonstrated that recombinant human endostatin (rhEndostatin) prevented synovial thickening in adjuvant arthritis (AA) rats via inhibition of proliferation and enhancement of apoptosis in synovial fibroblasts. However, the effect of this protein on HSF proliferation is not known. This study investigated the inhibitory effect of rhEndostatin on the proliferation of cultured HSFs in a rabbit ear model. MTT assay and flow cytometric detection were performed to investigate HSF proliferation and cell cycle progression, respectively. The expression levels of p53, p21, cyclinD1, cyclin-dependent kinase 4 (CDK4) and proliferating cell nuclear antigen (PCNA) in HSFs were detected using real-time PCR and Western blotting. Our data revealed that HSFs treated with rhEndostatin were significantly inhibited in a concentration-dependent manner with an IC50 value of 100 mg/L. Also, rhEndostatin (100 mg/L) primarily induced G(0)/G(1) and partially G(2)/M cell cycle arrest of HSFs. There were significant decreases in the expression levels of p53, p27, CDK4, cyclinD(1) and PCNA in HSFs treated with rhEndostatin. In conclusion, rhEndostatin inhibited HSF proliferation via G(0)/G(1) and/or G(2)/M phase arrest of the cell cycle, which was partially due to the down-regulation of cyclinD(1), CDK4 and PCNA. These findings suggest that rhEndostatin may reduce scar hypertrophy in vivo via inhibition of HSF proliferation and may be a novel agent for HS treatment.