The Immunostimulatory Potential of Mesenchymal Stem Cells for formation of Tertiary Lymphoid Structures in Lupus Nephritis

Abstract

Formation of tertiary lymphoid structures (TLS) occurs in tissues targeted by chronic inflammatory processes, such as infection and autoimmunity. In systemic lupus erythematosus (SLE), TLS have been observed in the kidneys of lupus-prone mice and in kidney biopsies of SLE patients with Lupus Nephritis (LN). Here the role of tissue-specific mesenchymal stem cells (MSCs) as lymphoid tissue organizer cells on the activation of CD4+ T cells from three groups of donors; Healthy, SLE patients and LN patients were investigated. Human MSCs were stimulated with the pro-inflammatory cytokines TNF-α and IL-1β to resemble an inflammatory condition. CD4+ T cells isolated from PBMC were co-cultured with stimulated and non-stimulated MSCs at 1:1 and 1:100 ratios (MSCs:CD4+ T cells) or seeded alone as a control. The AlamarBlue® proliferation assay was performed on CD4+ T cells at day zero and at day 5, 7 and 10 after co-culture. Flow cytometric analyses were conducted on CD4+ T cells at day zero and day 10 to analyse the Th1, Th2, Th9, Th17, Th22, and Th1/17 subsets before and after co-culturing with MSCs. To detect MSCs within TLS in kidneys of lupus-prone (NZBxNZW) F1 mice confocal imaging was used. After stimulation a significant increase in the expression of CCL19, VCAM1, ICAM1, TNF-α, and IL-1β were observed in MSCs. For all groups CD4+ T cells co-cultured with stimulated MSCs and non-stimulated MSCs at 1:100 ratio proliferated significantly more at day 10 compared to day zero and CD4+ T cells cultured. CD4+ T cells co-cultured with stimulated MSCs at 1:100 ratio proliferated significantly more than co-cultured with non-stimulated MSCs at day 10 in healthy and SLE groups, but not in the LN group. No difference in cell proliferation at 1:1 ratio was detected. An increase in Th2 and Th17 subsets were observed in the healthy group at day 10 when co-cultured with stimulated MSCs at 1:100 ratio compared to day zero and CD4+ T cells alone at day 10. MSC-like cells were detected within the pelvic wall of the kidneys and within the developed TLS. Our data suggest that tissue-specific MSCs could have pivotal roles in accelerating early inflammatory processes and initiating the formation of TLS in chronic inflammatory condition.