Effects of Phagocytosis of Cells Within Engineered Tissues on Macrophage Phenotype

Abstract Bioengineered allogeneic cellularized constructs (BACC) promote wound closure in deep partial thickness burns, but the mechanisms behind these effects are poorly understood. In normal wound healing, phagocytosis of cells by macrophages is a potent mechanism by which pro‐healing macrophage phenotypes form. The purpose of this study is to determine if macrophages are capable of phagocytosing BACC‐derived cells and whether this process affects macrophage phenotypes. Primary human macrophages from 21 healthy donors are cultured on BACC constructs over 6 days in vitro. Phagocytosis is analyzed by confocal imaging, timelapse imaging, multidimensional flow cytometry, and imaging flow cytometry. Macrophages phagocytosed BACC‐derived cells, although the number of macrophages that internalized BACC‐derived cells varied depending on the method of analysis. Inhibitors of efferocytosis and phagocytosis suppressed macrophage uptake of BACC cells and markers of reparative phenotypes, including CD206 and CD209, as well as the pro‐inflammatory marker CD38. These results demonstrate that macrophage phenotype changes in response to BACC are at least partially due to the phagocytosis of cells within the BACC. These findings provide important insight into how engineered tissues may influence macrophage phenotype to promote tissue repair.