Recruitment of mesenchymal stem cells and macrophages by dual release of stromal cell-derived factor-1 and a macrophage recruitment agent enhances wound closure.

In this study, the wound closure of mouse skin defects was examined in terms of recruitment of mesenchymal stem cells (MSC) and macrophages. For the cells recruitment, stromal derived factor-1 (SDF-1) of a MSC recruitment agent and sphingosine-1 phosphate agonist (SEW2871) of a macrophages recruitment agent were incorporated into gelatin hydrogels, and then released in a controlled fashion. When applied to a skin wound defect of mice, gelatin hydrogels incorporating mixed 500 ng SDF-1 and 0.4, 0.8, or 1.6 mg SEW2871-micelles recruited a higher number of both MSC and macrophages than those incorporating SDF-1 or phosphate buffered saline. However, the number of M1 phenotype macrophages for the hydrogel incorporating mixed SDF-1 and SEW2871-micelles recruited was remarkably low to a significant extent compared with that for those hydrogel incorporating 0.4, 0.8, or 1.6 mg SEW2871-micelles. On the other hand, the number of M2 macrophages 3 days after the implantation of the hydrogels incorporating SDF-1 and 0.4 mg SEW2871-micelles significantly increased compared with that for other hydrogels. In vivo experiments revealed the hydrogels incorporating SDF-1 and 0.4 mg SEW2871-micelles promoted the wound closure of skin defect to a significant stronger extent than those incorporating SEW2871-micelles, SDF-1, and a mixture of SDF-1 and higher doses of SEW2871-micelles. It is concluded that the in vivo recruitment of MSC and macrophages to the defects may contribute to the tissue regeneration of skin wound.