Further, sea buckthorn procyanidins (SBPC) from bark extract enhance the healing of acetic acid-induced gastric lesions by reducing ulcer size in a dose-dependent manner, increasing epidermal growth factor (EGF) levels in plasma, and up-regulating the expression of epidermal growth factor receptor (EGFR) and proliferating cell nuclear antigen (PCNA) around the ulcer site, which promotes mucosal repair and epithelial renewal (Xu et al., 2007). Here, PCNA is linked to ulcer disease.