Microvescicles Derived from Mesenchymal Stromal Cells Are Not as Effective as Their Cellular Counterpart in the Ability to Modulate Immune Responses In Vitro

Abstract

Mesenchymal stromal cells (MSCs) are multipotent cells that possess broad immunomodulatory properties; the mechanisms underlying these properties have not been completely clarified. Aim of this study was to compare in vitro immunomodulatory effects of MSCs with those of microvesicles (MVs) released in supernatants from the same MSCs. MSCs were generated from bone marrow of 12 healthy donors (HDs) and MVs were isolated from their supernatant by serial ultracentrifugation according to two different procedures. Both MSCs and MVs were characterized by flow cytometry and incubated in vitro with peripheral blood mononuclear cells (PBMCs) of 12 HDs after stimulation with PHA and CpG. Growth factors and cytokines were quantified by ELISA. MVs were identified as 0.1-1 μm particles positive for CMFDA, CD107, and CD13. MSCs were significantly more capable to inhibit in vitro PHA-induced T-cell proliferation as compared with the corresponding MVs (P<0.01 and P<0.05 for MSC:PBMC ratio 1:2 and 1:10, respectively). While MVs displayed similar inhibitory activity on B-cell proliferation (P=0.43 as compared with PBMCs/CpG/MSCs; MSC:PBMC ratio 1:10) they induced lower inhibitory effect on plasmacell differentiation and antibody secretion (P<0.05 as compared with PBMCs/CpG/MSCs). For both T and B cells, MSC co-colture induced a statistically significant increase in IL-10 and TGFβ and decrease of GM-CSF and IFNγ, as compared with MV incubation. Our data indicate a lower in vitro immunomodulatory effect of MVs on T-cell proliferation and antibody formation, as compared with their cellular counterpart. The relative clinical benefit of either MSCs or MVs needs to be compared in proper prospective studies.

The secretome of mesenchymal stromal cells: Role of extracellular vesicles in immunomodulation

“…Moreover, EV-MSCs express some specific exosomal markers, such as CD107 [50,51], CD63, CD9 and CD81 [52,53].…”

“…A comparison between the immune-modulatory effect of bone marrow MSCs and derived EVs has been recently performed [51]. MSCs and MSC-EVs display a similar inhibitory effect on B-cell proliferation, but EV-MSCs show a lower inhibitory activity on B cell differentiation and antibody secretion, with respect to MSCs.…”

“…Moreover, MSCs are more efficient than MSC-EVs in the inhibition of T-cell proliferation in vitro. For both T and B cells, incubation with MSC-EVs induces a minor IL-10 and TGF-␤ increase and a minor GM-CSF and IFN-␥ decrease, with respect to MSCs [51]. However, it should be considered the limitations inherent to a comparison between EVs and MSCs for the difficulty in counting EVs and defining the EVs/target cells ratio.…”

Recent Developments in Cellular Immunotherapy for HSCT-Associated Complications

“…Furthermore, considerations regarding the immunomodulatory potency of the vesicles in relation to their cellular counterparts need to be taken into account. A recent report on the immunosuppressive effect of BM-MSCs and their derived EVs has shown the latter were considerably less potent in suppressing T cell proliferation and preventing B cell differentiation (115). EVs were also seen to be not as effective in modulating DC maturation as their parent cells (101).…”

Bone Marrow Mesenchymal Stem Cells Enhance the Differentiation of Human Switched Memory B Lymphocytes into Plasma Cells in Serum-Free Medium

“…However, their role on human B-cell maturation is still controversial [39]. MSC from human bone marrow were shown to inhibit proliferation [40, 41] and B-lymphocyte Ig secretion following polyclonal activation with CpG [42]. In contrast, MSC have been shown to promote LPS-activated B-lymphocyte IgG secretion [43].…”