Effects of human erythropoietin on transforming growth factor β1/Smad3 signal transduction pathway in acute wounds of rats

Objective To explore the effects of human erythropoietin (hEPO) on healing related transforming growth factor β₁ (TGF-β₁)/Smad3 signal transduction pathway in acute wounds of rats. Methods Seventy-two healthy Sprague Dawley rats were divided into normal saline control group, low dose group, middle dose group, and high dose group according to the random number table, with 18 rats in each group, after round acute wounds with diameter of 2.5 cm were inflicted on the back of rats. Rats in the 4 groups had debridement routinely. Wounds of rats in normal saline control group were covered by gauzes infiltrated with 1 mL normal saline, while wounds of rats in low dose group, middle dose group, and high dose group were respectively covered by gauze infiltrated with 1 mL hEPO in doses of 50, 100, and 150 U every day, and then the wounds were bandaged with 6 layers of dry gauze. Dressing change was performed once every day. On treatment day (TD) 3, 7, and 14, 6 rats from each group were taken for general observation and calculation of wound healing rate. Then the wound tissue samples were harvested after the rats were sacrificed for observation of expressions of CD31 and transforming growth factor β₁ (TGF-β₁) with immunohistochemical method. Protein expression of phosphorylated Smad3 of the wound tissue of 3 rats were detected by Western blotting. Data were processed with analysis of variance of factorial design, one-way analysis of variance, least-significant difference test, and Bonferroni correction. Results (1) On TD 3, obvious exudation and scab were observed in the wounds of rats in the 4 groups. On TD 7, the wounds of rats in low dose group, middle dose group, and high dose group were reduced compared with those in normal saline control group. On TD 14, all wounds of rats in the 4 groups were healed. On TD 7, the wound healing rates of rats in middle dose group and high dose group were significantly higher than the rate in normal saline control group (P<0.01). At the other time points, the wound healing rates of rats in the 4 groups were close (P>0.05). (2) CD31 mainly expressed in blood vessels. Except for those in low dose group on TD 3 and 7 (P>0.05), the expressions of CD31 in wound tissue of rats in low dose group on TD 14 and in middle dose group and high dose group on TD 3, 7, and 14 were significantly higher than those in normal saline control group (P<0.01). Except for those on TD 3 (P>0.05), the expressions of CD31 in wound tissue of rats in middle dose group and high dose group on TD 7 and 14 were significantly higher than those in low dose group (P<0.01). Except for that on TD 3 (P>0.05), the expressions of CD31 in wound tissue of rats in high dose group on TD 7 and 14 were significantly higher than those in middle dose group (P<0.01). (3) Except for that in low dose group on TD 3 (1.9±0.7, P>0.05), the expressions of TGF-β₁ in wound tissue of rats in low dose group on TD 7 and 14 (3.3±1.0, 3.7±0.7), and in middle dose group and high dose group on TD 3, 7, and 14 (3.3±1.0, 3.6±1.0, 3.9±0.9, 3.4±0.7, 3.8±0.8, 4.2±0.4) were significantly higher than those in normal saline control group (1.7±0.5, 2.7±1.0, 3.0±0.9, P<0.01). Except for those on TD 7 (P>0.05), the expressions of TGF-β₁ in wound tissue of rats in middle dose group and high dose group on TD 3 and 14 were significantly higher than those in low dose group (P<0.01). Except for that on TD 14 (P<0.01), the expressions of TGF-β₁ in wound tissue of rats in high dose group on TD 3 and 7 were close to those in middle dose group (P>0.05). (4) Except for those in low dose group on TD 3 and 14 and in middle dose group and high dose group on TD 14 (P>0.05), the protein expressions of phosphorylated Smad3 in wound tissue of rats in the 3 groups at the other time points were significantly higher than those in normal saline control group (P<0.01). Except for those on TD 14 (P>0.05), the protein expressions of phosphorylated Smad3 in wound tissue of rats in middle dose group and high dose group on TD 3 and 7 were significantly higher than those in low dose group (P<0.01). Except for that on TD 14 (P>0.05), the protein expressions of phosphorylated Smad3 in wound tissue of rats in high dose group on TD 3 and 7 were significantly lower than those in middle dose group (P<0.01). Conclusions Exogenous hEPO can increase the expressions of CD31, TGF-β₁, and phosphorylated Smad3 in acute wounds of rats, promote angiogenesis of wounds, and activate TGF-β₁/Smad3 signal transduction pathway to promote wound healing.