Effect of recombinant human endostatin on hypertrophic scar fibroblast apoptosis in a rabbit ear model

Hypertrophic scar (HS) is a dermal fibroproliferative disorder characterized by the excessive proliferation of fibroblasts and is thought to result from a cellular imbalance caused by the increased growth and reduced apoptosis of hypertrophic scar fibroblasts (HSFs). Our recent study demonstrated that recombinant human endostatin (rhEndostatin) plays a key role in the inhibition of HSF proliferation in vitro, with a resulting decrease in dermal thickness and scar hypertrophy. However, the effect of this protein on HSF apoptosis is unknown. The present study was undertaken to directly examine the effect of rhEndostatin on HSF apoptosis in the rabbit ear model. Transmission electron microscopy and flow cytometry were used to investigate HSF apoptosis in scar tissues and cultured HSFs in vitro, respectively. The expression levels of the c-jun, c-fos, NF-κB, fas, caspase-3, and bcl-2 gene products in HSFs were quantified using real-time PCR and Western blotting assays. Our data reveal that rhEndostatin (2.5 or 5 mg/ml) induces HSF apoptotic cell death in scar tissue. Additionally, HSFs treated with rhEndostatin (100 mg/L) in vitro accumulated in early and late apoptosis and displayed significantly decreased expression of c-jun, c-fos, NF-κB, fas, caspase-3 and bcl-2. In sum, these results demonstrate that rhEndostatin induces HSF apoptosis, and this phenotypeis partially due to downregulation of NF-κB and bcl-2. These findings suggest that rhEndostatin may have an inhibitory effect on scar hypertrophy in vivo via HSF apoptotic induction and therefore has potential therapeutic use for the treatment of HS.