Comparison of the effects of human recombinant epidermal growth factor and platelet-rich plasma on healing of rabbit patellar tendon

Objectives: This study aims to compare the histological healing process and gene expression profile in tendon after the administration of human recombinant epidermal growth factor (hrEGF) and plateletrich plasma (PRP). Materials and methods: A total of 24 mature New Zealand white rabbits (6-month-old; weight 2.5-3.0 kg) were used in the study. Patellar tendons of rabbits were tenotomized and then repaired. Rabbits were separated into three groups and repair areas were injected with 1 mL hrEGF in group 1 (n=9) and 1 mL PRP in group 2 (n=9). No injection was performed in group 3 (controls, n= 6). Tissue samples were obtained from the repaired patellar tendons of three rabbits each from groups 1 and 2 and of two rabbits from group 3 at the end of the first, second, and fourth weeks, and these tissues were histologically and genetically assessed. Expression levels of tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-6, IL-8, and chemokine receptors (CXCR1, CXCR2) were examined. Results: The frequency of neovascularization was detected to be higher in group 1 compared to group 3 at the end of the second and fourth weeks (p=0.018 and p=0.009, respectively). Group 1 was detected to show more increase in terms of the prevalence of tenocytes (p=0.014 and p=0.009, respectively) at the end of the second week, and in terms of collagen intensity at the end of the fourth week (p=0.0018 and p=0.034, respectively) compared to groups 2 and 3. Highest levels of TNF-alpha, IL-6, and IL-8 were detected in group 1, followed by groups 2 and 3 at all time points. Highest CXCR2 gene expression was detected in group 1. Conclusion: Compared to PRP, hrEGF caused more increase in healing tissue at neovascularization, tenocyte, fibroblast, collagen, and tissue macrophage levels; and higher levels of TNF-alpha, IL-6, IL8, and CXCR2. Intralesional hrEGF administration can effectively accelerate tendon healing.