Assessment of immunomodulatory impact of multipotential stromal cells (MSCs) on monocytes in healthy controls and in patients with rheumatoid arthritis.


Priyanka Dutta1, Chi Wong1, Maya H Buch1,2, Graham P Cook3, Elena Jones1, Michael F. McDermott1


1Leeds Institute of Rheumatic and Musculoskeletal Medicine, University of Leeds, LeedsUK;2NIHR-Leeds Musculoskeletal Biomedical Research Unit (NIHR-LMBRU), Chapel Allerton Hospital, Leeds, UK; 3Leeds Institute of Cancer Studies and Pathology, University of Leeds, Leeds, UK


Multipotential stromal cells (MSCs) possess the capacity for multilineage differentiation and are used for their applications in bone and cartilage regeneration. MSCs have been shown to possess immunoregulatory properties, acting on both adaptive and innate immune cells, including monocytes. Consequently, MSCs have has been proposed as a therapy for autoimmune diseases, including rheumatoid arthritis (RA).


To study the immunomodulatory effects of MSCs, and their conditioned media, on RA monocytes using a whole blood co-culture assay, thereby approaching a physiologically relevant setting.


All experiments were performed using the IP006 clonal MSC cell line, conforming to ISCT phenotypic criteria for MSCs. For detection of intracellular TNF and IL-6 pro-inflammatory cytokine release by activated monocytes, whole blood from healthy control (HC) donors, early RA and established RA patients was stimulated with 1ng/ml lipopolysaccharide (LPS) and treated with Brefeldin A for 6 hours at 37oC. Subsequently, intracellular staining, using antibodies against TNF and IL-6 was carried out and analysed by flow cytometry. For the co-culture experiments 8x106 MSCs or 1.6 ml of MSC conditioned media (MSC-CM) were added to 0.2ml of the whole blood. The early RA patient cohort was treatment naïve, whereas the established RA cohort was multidrug resistant (failed to respond to 2 DMARDs and 2 Biologics).


In HC blood, the addition of MSCs inhibited intracellular TNF and IL-6 expression in LPS-activated monocytes, by 1.6-fold and 2.1-fold, respectively. Greater inhibition of both TNF and IL-6 was observed, when MSC-CM was used instead of MSCs (TNF- 2.1-fold, n=13 and IL-6- 3.2-fold, n=19). Thus, for treatment of cytokine production by patients with early RA, bloods were treated with MSC-CM. This resulted in statistically significant inhibition of TNF (p<0.001) and IL-6 (p<0.0001) levels in activated monocytes (n=17), by 1.4-fold and 2.5-fold, respectively. The most potent immunosuppressive effects of IP006 MSC-CM were found in bloods from patients with established multidrug resistant disease. IP006 MSC-CM treatment inhibited production of TNF, by 3-fold (p<0.0001), and IL-6, by 2-fold (p< 0.01).


Both MSCs and MSC-CM displayed potent immunosuppressive effects on monocytes in health and RA, thereby providing evidence for a non-cell contact mechanism and supporting MSC-based therapies for RA.