Abstract
Background
Bone mesenchymal stem cells (BMSCs)-derived exosomes (B-exos) are attractive for applications in enabling alloantigen tolerance. An in-depth mechanistic understanding of the interaction between B-exos and dendritic cells (DCs) could lead to novel cell-based therapies for allogeneic transplantation. Herein, the potential of a B-exos-based application combined with DCs was explored for inducing allogeneic transplant tolerance.
Methods
After mixed culture of BMSCs and DCs for 48 hours, DCs from the upper layer were collected to analyze the expression levels of surface markers and mRNAs of inflammation-related cytokines. Then the DCs were co-cultured with B-exo before being collected to detect the mRNA and protein expression levels of indoleamine 2,3-dioxygenase (IDO). The treated DCs from different groups were co-cultured with naïve CD4 + T cells from the mouse spleen. The proliferation of CD4 + T cells and the proportion of CD4 + CD25 + Foxp3 + T cells were analyzed. Finally, the skins of BALB/c mice were transplanted to the back of C57 mice to establish a mouse allogeneic skin transplantation model.
Results
The coculture of DCs with BMSCs in a trans-well system downregulated the expression of the major histocompatibility complex class II (MHC-II) and CD80/86 costimulatory molecules on DCs, as well as the mRNA expression of interleukin-10 (IL-10), IL-12, and transforming growth factor-β (TGF-β). However, these findings were abolished when treated with GW4869. Moreover, B-exos (5 µg/mL) increased the expression of indoleamine 2,3-dioxygenase (IDO) in DCs treated with lipopolysaccharide (LPS) compared to the control cells. CD4 + CD25 + Foxp3 + T cells increased when cultured with B-exos-exposed DCs, which was attenuated by 1-methyl tryptophan (1MT). Mice recipients injected with B-exos-treated DCs significantly prolonged the skin allograft survival. The allografts showed slight cell infiltration and significantly preserved graft structure. Also, the level of CD4 + CD25 + Foxp3 + T cells was significantly higher in B-exos-exposed DCs recipient animals than that in other groups.
Conclusions
Taken together, these data suggested that the B-exos suppress the maturation of DCs and increase the expression of IDO, which might shed light on the role of B-exos in inducing alloantigen tolerance.
“Pruning” of Alloreactive CD4+T Cells Using 5- (and 6-)Carboxyfluorescein Diacetate Succinimidyl Ester Prolongs Skin Allograft Survival
