Oleanolic acid inhibits hypertrophic scarring in the rabbit ear model

Summary Background. Hypertrophic scarring, a common proliferative disorder of dermal fibroblasts, results from an overproduction of collagen and excessive deposition of extracellular matrix. Although treatment with surgical excision or steroid hormones can modify the symptoms, numerous treatment‐related complications have been described. Aim. To investigate the effects of oleanolic acid (OA), a naturally occurring triterpenoid, on hypertrophic scarring in a rabbit ear model. Methods. A rabbit ear model of hypertrophic scarring was used, with wounds produced with a biopsy punch. Oleanolic acid (2.5%, 5% and 10%) was applied once daily to the scars for 22 days. On postoperative day 28, the scars were excised, and the tissue used for histological examination and assays of the levels of collagens I and III, matrix metalloproteinase (MMP)‐1 and transforming growth factor (TGF)‐β1. The scar elevation index (SEI) was also determined. Results. Treatment with different concentrations of oleanolic acid (OA) for 22 days significantly inhibited hypertrophic scarring in rabbit ear tissue. Levels of TGF‐β1, collagen I and collagen III were significantly decreased and levels of MMP‐1 significantly increased in the scar tissue. SEI was also significantly reduced. Histological findings showed significant amelioration of the scar tissue. Conclusions. OA suppresses hypertrophic scarring in the rabbit ear model and may be an effective cure for human hypertrophic scarring.