Local Delivery of Adipose Stem Cell Promotes Allograft Survival in A Rat Hind Limb Model of Vascularized Composite Allotransplantation.

BACKGROUND: Adipose stem cells (ASCs) are a promising cell-based immunotherapy due to their minimally invasive harvest, high yield, and immunomodulatory capacity. In this study, we investigated the effects of local vs. systemic ASC delivery on VCA survival and alloimmune regulation.

METHODS: Lewis rats received hindlimb transplants from Brown Norway rats and were administered donor-derived ASCs (passage 3-4, 1x10 6 cells/rat) locally in the allograft, or contralateral limb, or systemically at postoperative day (POD) 1. Recipients were treated intraperitoneal with rabbit anti-rat lymphocyte serum on POD -4 and 1, and daily tacrolimus for 21 days. Limb allografts were monitored for clinical signs of rejection. Donor cell chimerism, immune cell differentiation, and cytokine expression in recipient lymphoid organs were measured by flow cytometric analysis. The immunomodulation function of ASCs was tested by mixed lymphocyte reaction (MLR) assay and ASC stimulation studies.

RESULTS: Local-ASC treated recipients achieved significant prolonged allograft survival (85.7% survived >130 days, n=6) compared to systemic- and contralateral-ASC groups. Secondary donor skin allografts transplanted to the local-ASC long-term surviving recipients accepted permanently without additional immunosuppression. The increases in donor cell chimerism and regulatory T-cells were evident in blood and draining lymph nodes of the local-ASC group. Moreover, MLR showed that ASCs inhibited donor-specific T cell proliferation independently of direct ASC-T-cell contact. ASCs upregulated anti-inflammatory molecules in response to cytokines stimulation in vitro.

CONCLUSIONS: Local delivery of ASCs promoted long-term survival and modulated alloimmune responses in a full MHC-mismatched VCA model and was more effective than systemic administration.