Background: Autologous fat transplantation using fat alone can lead to postoperative complications, such as fat reabsorption or necrosis. Our previous research revealed that encapsulating adipose mesenchymal stem cells (ASCs) in laminin–alginate beads helps to preserve fat grafts volume after fat transplantation.
We hypothesized slower ASCs release rate into the transplantation site along with the presence of laminin-alginate degradation increases M2 macrophage Infiltration and enhanced fat graft survival.

Methods: ASCs were isolated from two female enhanced green fluorescent protein (eGFP)-transgenic rats and either freely mixed (~1.6 x 10^6 cells)with 1 milliliter of mature adipose tissue obtained from donor rat’s groin region, as the SC (ASC + fat) graft (n=9, three in each subgroup), or (~1.6 x 10^6 cells) encapsulated in laminin–alginate beads before mixing also with 1 milliliter of fat tissue obtained from donor rat’s groin region, as the bead-encapsulated cell (BEC) (laminin–alginate + ASC + fat) graft (n=9, three in each subgroup). After subcutaneous fat graft was injected to rats back, The rats are than sacrificed at 4th, 6th and 8th week and the grafts are harvested for histological and Immunofluorescence analysis.

Results: Histological analysis demonstrated that the eGFP-ASCs in the BEC grafts gradually increased between weeks 4 and 8 (weeks 4, 1.99%; weeks 8, 2.87%), whereas the eGFP-ASCs in the SC graft decreased over the same period. The BEC grafts were also noted with significantly more M2 macrophages infiltration.

Conclusions: Laminin–alginate bead-encapsulated ASCs may improved sustainability of fat grafts compares to the use of ASCs alone. The benefits of laminin–alginate beads may be due to a slower ASCs release rate into the transplantation site and the resultant increase M2 macrophage infiltration in the graft. However, outcomes are obtained in a experimental rat model and further validation in more translationally relevant models is needed.