Difference in M2 Macrophage Infiltration Between Cell-Assisted Fat Graft and Biomaterial-Encapsulated Stem Cell-Assisted Fat Graft: An Experimental Animal Study

Background and Objectives: Autologous fat transplantation using fat alone can lead to postoperative complications. Laminin–alginate beads have been investigated as carriers for adipose mesenchymal stem cells (ASCs), with the potential to modulate cell release kinetics, influence macrophage responses, and thereby affect the maintenance of graft volume. We hypothesized that encapsulating ASCs in laminin–alginate beads would allow gradual ASC release into the transplantation site and influence the macrophage-related microenvironment during fat graft maturation. Materials and Methods: ASCs were isolated from two female enhanced green fluorescent protein (eGFP) transgenic rats. For SC (ASC + fat) grafts, ASCs were freely mixed with 1 mL of mature adipose tissue. For bead-encapsulated cell (BEC) (laminin–alginate + ASC + fat) grafts, ASCs were first encapsulated in laminin–alginate beads and subsequently mixed with 1 mL of fat tissue. The fat graft was subcutaneously injected into the backs of the rats, which were subsequently euthanized at weeks 4, 6, and 8. The grafts were then harvested for histological and immunofluorescence analyses. Results: The histological analysis indicated that the number of eGFP-ASCs in the BEC grafts gradually increased between weeks 4 and 8, whereas that in the SC grafts decreased over the same period. The BEC grafts also exhibited a numerically higher degree of M2 macrophage infiltration. Conclusions: Laminin–alginate bead encapsulation was associated with prolonged persistence of eGFP-ASCs within the graft area. Although the macrophage-related findings were not statistically significant, they suggest a potential interaction between gradual ASC release and the local graft microenvironment.