In Vitro and In Vivo Immunomodulatory Effects of Mesenchymal Stem Cells from Adipose Tissue.

Previous studies have shown the immunomodulatory properties of bone marrow mesenchymal stem cells (BM-MSCs), opening the possibility of using these cells for the treatment of graft-versus-host disease (GVHD) in patients transplanted with allogeneic hematopoietic grafts. Additionally, Phase I studies in patients with Crohn’s disease suggested the efficacy of adipose tissue-derived mesenchymal stem cells (Ad-MSCs) for the healing of Crohn’s fistulas. In the present study we have investigated in vitro and in vivo, the immunomodulatory effects of Ad-MSCs, compared to BM-MSCs. We observed that both BM-MSCs and Ad-MSCs were negative for CD34, CD45, CD14, CD31 and MHC class I expression, while positive for CD29, CD44, CD90 and CD105. When studying the immunomodulatory effects of these cells in vitro, we found that - as happened with BM-MSCs - Ad-MSCs did not induce proliferation of allogeneic lymphocytes and were not lysed by cytotoxic T cells or alloreactive natural killer cells, indicating that Ad-MSCs are non-immunogenic. Additionally, the presence of Ad-MSCs inhibited in a dose-dependent fashion, both the mixed lymphocyte reaction (MLR) and the T cell proliferation induced by mitogens. To determine whether cell-to-cell contact between Ad-MSCs and PBMNCs was required for immunosuppression, transwell experiments were conducted. Phytohaemagglutinin (PHA)-stimulated lymphocytes were cultured in the upper chamber of a transwell, while irradiated Ad-MSCs remained in the lower chamber. As observed with BM-MSCs, Ad-MSCs were also capable of suppressing the lymphocytes proliferation in this transwell assay. When conditioned medium from Ad-MSCs was added to the MLR, the immuno-suppressive effect persisted, although at a lower level than that observed in a cell-to-cell contact system. Next we studied whether our in vitro findings were of significance in an in vivo mouse model of haploidentical transplantation. In these experiments irradiated F1(C57Bl/Balbc) recipient mice received 1x10⁷ bone marrow cells from C57Bl mice, together with 2x10⁷ splenocytes from the donor, to induce GVHD. One cohort of recipient mice received additional i.v. infusions of 5x10⁵ mouse Ad-MSCs, administered at periodic intervals for up to 28 days post-transplant. When compared to the control group, the severity of the GVHD was significantly reduced in mice receiving Ad-MSCs. Our results suggest that Ad-MSCs obtained from adipose tissue may constitute a new and readily available source of immunomodulatory cells for the prophylaxis and/or treatment of GVHD in patients transplanted with allogeneic grafts.