Fig. 3

Canine ASCs and PMSCs inhibit lymphocyte proliferation in a contact-dependent manner. Canine adipose-derived MSCs (ASCs) and placenta-derived MSCs (PMSCs) possess immune-suppressive functions. a Canine ASCs and PMSCs co-incubated with stimulated peripheral blood mononuclear cells (PBMCs) suppress lymphocyte proliferation. PMSCs significantly decrease lymphocyte proliferation more potently as compared to ASCs. Transwells were added to remove physical contact between MSCs and mitogen (ConA) stimulated PBMCs. Lymphocyte proliferation increased when ASCs and PMSCs were not in direct contact with activated PBMCs. b To determine the role of indoleamine 2,3 dioxygenase (IDO) and prostaglandin E₂ (PGE₂) in MSC-mediated immunosuppression 1-methyl-DL-tryptophan (1-MT) and indomethacin was added to co-cultures to block each respective mediator. Blocking of IDO activity using 1-MT resulted in no alterations in MSC-mediated suppression of PBMC proliferation. Blocking PGE₂ using indomethacin resulted in a loss of lymphocyte inhibition by ASCs but no effects were observed by PMSCs. PBMC stimulation is normalized and data is presented as a reduction to each respective donor. Representative photomicrographs of ConA stimulated PBMCs and PMSC LSA conditions (c). Data presented as mean and standard error. *p < 0.05, **p < 0.01, ***p < 0.001. 1-MT, 1-methyl-DL-tryptophan; ConA, concanavalin A; IDO, indoleamine 2,3 dioxygenase; LSA, leukocyte suppression assay; MSC, mesenchymal stem cell; PBMCs, peripheral blood mononuclear cells; PGE₂, prostaglandin E₂