L. Barnes1,2, M. S. Hu1, A. T. Cheung1, A. L. Moore1,3, C. D. Marshall1, T. Leavitt1, A. Dubnika1, M. Ahmed1, G. C. Gurtner1, H. Lorenz1, J. Rajadas1, M. T. Longaker1 1Stanford University,Palo Alto, CA, USA 2Howard Hughes Medical Institute,Chevy Chase, MD, USA 3Brigham And Women’s Hospital,Boston, MA, USA
Introduction:
Skin defects resulting from trauma, tumor resections, and congenital anomalies pose a significant reconstructive challenge. Thus, it is necessary to develop novel approaches in regenerative medicine to improve tissue repair. Macrophages can be polarized to two phenotypes (M1 and M2) that have been shown to have different functions: M1 phenotype macrophages are pro-inflammatory, while M2 phenotype macrophages are pro-regenerative. Using an established humanized splinted excisional wound model in mice, we now demonstrate the ability of supraphysiologic levels of murine M2-polarized macrophage subpopulations to further promote skin regeneration in vivo.
Methods:
In this study, monocytes were isolated from the bone marrow of mice expressing green fluorescent protein (GFP) constitutively in the cytoplasm of all cells (FVB-Tg(CAG-luc,-GFP)L2G85Chco/J mice (JAX, Bar Harbor, Maine)). They were subsequently differentiated into macrophages using macrophage colony-stimulating factor (M-CSF), seeded onto biomimetic scaffolds containing recombinant interleukin-10 (IL-10) to polarize them, and transplanted onto splinted excisional wounds on the dorsa of wild-type (FVB/NJ) mice. Gross wound progression and size was assessed from digital photographs. Wound tissue was harvested for histologic, immunohistochemical, gene expression, and cellular analysis.
Results:
Gene expression analysis confirmed that macrophages seeded onto the biomimetic scaffold containing IL-10 were polarized to the M2-phenotype in vivo within 48 hours. Digital image and histologic analysis demonstrated that supraphysiologic levels of M2-polarized macrophages significantly accelerated wound healing without adverse effects on scar size and quality when compared to controls (*p<0.05).
Conclusion:
We have shown that polarizing M2-macrophages on a biomimetic scaffold in vivo accelerates wound healing. This method minimizes the time cells spend in culture and has been shown to be optimal for cell delivery. Given that monocytes can be readily isolated from peripheral blood, this technique could allow for the rapid delivery of a patient’s own cells to enhance cutaneous wound healing.