Effects of thymosin β4 and dimethyloxalylglycine on the wound healing of rat oral mucosa

Abstract

Introduction: Thymosin β4 (Tβ4), with 43 amino acids, is a major G-actin sequestering protein, which was originally isolated from bovine thymus. In previous studies, exogenous Tβ4 was demonstrated to have multifunctional activities such as angiogenesis, anti-apoptosis, anti-oxidative stress and anti-inflammation. Dimethyloxalylglycine (DMOG) was reported to inhibit oxygen-dependent degradation of hypoxia inducible factor-1 alpha (HIF-1α). The stabilization of HIF-1α can lead to up-regulation of angiogenesis markers, which favor wound healing. Previous study demonstrated that DMOG could enhance the production of vascular endothelial growth factor (VEGF) in periodontal fibroblasts. However, there is no information yet about the effects of Tβ4 and DMOG on wound healing in the oral mucosa. To investigate the feasibility Tβ4 and DMOG as oral wound healing agents, in this study, the effects of the molecules on cell motility, mRNA expression of matrix metalloproteinases (MMPs), mRNA and protein expression of angiogenesis marker genes and wound closure of rat palatal were observed. Materials and Methods: Rat palatal (RP) cells obtained from Sprague-Dawley (SD) rats were established in primary culture. Migration assay was performed by using a culture-insert. Matrix metalloproteinase 2 (MMP2) and VEGF were chosen to demonstrate whether the mRNA and protein expression of both markers were influenced by treatment with Tβ4 at various concentrations (0, 1, 10, 100, 1000 ng/ml) and at different time courses (6 hours and 24 hours). Additionally, the mRNA and protein expressions of VEGF of RP cells treated with DMOG at different concentrations (0, 0.1, 0.5, 1, 2 mM) were evaluated. To confirm the stabilization effect of DMOG on HIF-1α, the protein expression of HIF-1α was detected by western blotting. For the in vivo assay, excisional wounds, 3 mm in diameter, were made at the center part of the palate of the SD rats. Tβ4 and DMOG with vehicles were topically applied 3 times during one week. The wound areas were measured photographically and histologically at 1 week after preparation of wounds. Results: Tβ4 stimulated RP cell migration at the higher concentrations (100 and 1000 ng/ml) in 0% FBS level while there was no effect of DMOG on the migration of RP cells. Tβ4 increased the mRNA expression and protein level of both the MMP2 and VEGF significantly. Tβ4 enhanced the VEGF mRNA expression time-dependently. Tβ4 stimulated the MMP2 mRNA level at 6 hours significantly but it decreased the expression of MMP2 mRNA at 24 hours. In addition, the mRNA and protein expressions of VEGF were significantly stimulated by the treatment of DMOG at higher concentrations. HIF-1α was stabilized in protein level by the treatment with DMOG. In animal study, it was found that 1 mg/ml Tβ4-treated and DMOG-treated groups increased the rat palatal wound contracture significantly. Conclusions: According to the present study, both Tβ4 and DMOG enhanced the wound healing of rat palatal mucosa. Therefore, Tβ4 and DMOG can be considered as the candidates for agents promoting wound healing of oral mucosa.