Histomorphometric analysis of the phenotypical differentiation of recruited macrophages following subcutaneous implantation of an allogenous acellular dermal matrix

This study aimed to clarify the phenotypical differentiation of recruited macrophages following subdermal implantation of an allogenous, acellular dermal matrix (aADM). In 20 male Wistar rats, one leg was randomly chosen for subcutaneous implantation of an aADM, while the other side received an autogenous dermis graft for control purposes. After 7 and 14 postoperative days, 10 animals were killed. Biopsies were obtained from the healing area and subjected to immunohistochemical staining (targets: pan macrophage marker CD68, M1 macrophage marker CD197, M2 macrophage marker CD163), histomorphometric analysis and reverse transcriptase polymerase chain reaction (targets: iNOS, arginase). No differences were detected in the total number of recruited macrophages between the groups. Allogenous ADMs significantly stimulated proinflammatory M1 differentiation, while autogenous dermis induced the regeneration promoting M2 phenotype. Proinflammatory M1 differentiation of macrophages might provide a potential explanation for profibrotic tissue deposition at the aADM interface following subcutaneous implantation, which has been observed previously.