Knockout of E2F1 enhances the polarization of M2 phenotype macrophages to accelerate the wound healing process.

Wound healing is a complex process, which is classically divided into inflammation, proliferation, and remodeling phases. Macrophages play a key role in wound healing, however, whether E2F1 mediates the M1/M2 polarization during the wound healing process is not known. Skin wounds were surgically induced in E2F1 mice and their WT littermates. At day 2 and day 7 post-surgery, the wounded skin tissues including 2 to 3 mm normal skin were obtained. The wounded skin tissues were used for the analyses of immunofluorescence staining (CD68, iNOS, CD206), western blotting (CD68, iNOS, CD206, PPAR-γ) and Co-immunoprecipitation (E2F1-PPAR-γ interactions). E2F1 mice exhibited faster wound healing process. At day 2, the M2 macrophages were remarkably increased in the E2F1 mice. Surprisingly, in the border zone of the wound, E2F1 mice had also more M2 macrophages and fewer M1 macrophages at day 7 post-surgery, suggesting a certain degree of polarization amongst the M1 and M2 phenotypes. Co-IP revealed that E2F1 indeed interacted with PPAR-γ, meanwhile western blotting and RT-PCR showed higher expression of PPAR-γ in the E2F1 mice as compared to that in the WT mice. Therefore, the findings suggest that wound healing process could be accelerated with enhanced M2 polarization through increased PPAR-γ expression in E2F1 knockout mice.