Myeloid-derived suppressor cells as biomarkers of the effectiveness of therapy with new biological agents in axial spondyloarthritis

Innate immune cells, including myeloid cells — myeloid derived suppressor cells (MDSCs) — are supposed to play an important role in the pathogenesis of axial spondyloarthritis (AxSp). Myeloid derived suppressor cells represent a heterogeneous population of immature cells capable of suppressing innate and adaptive immune responses with the most pronounced suppressor activity against T cells. Biological disease-modifying antirheumatic drugs (bDMARDs) can reduce the clinical and laboratory disease activity, but their effectiveness varies widely in different patients with AxSp. The present study is aimed at studying MDSCs subpopulations and their suppressive function depending on the response to bDMARD therapy in AxSp. The study included AxSp patients with a disease duration of 16.5 years (median); HLA-B27 (+) status was detected in 79% of cases. All patients received bDMARDs at least the past 12 weeks, including TNF inhibitors (etanercept, certolizumab pegol, adalimumab, or golimumab) or IL-17 inhibitors (secukinumab, ixekizumab, or netakimab). Percentage of granulocytic MDSCs (G-MDSCs, Lin-HLA-DR-CD33+CD66b+), monocytic MDSCs (M-MDSCs, HLA-DRlow/-CD14+), MDSCs of early stage differentiation (E-MDSCs, Lin-HLA-DR- CD33+CD66b-), as well as intracellular expression of arginase-1 was assessed by flow cytometry. Frequency of circulating MDSC subpopulations of patients with a stable response to bDMARDs (responders) did not differ significantly compared to healthy donors. Patients not responding to bDMARDs therapy showed increased relative and absolute number of E-MDSCs compared to healthy donors (pU = 0.01 and pU = 0.02, respectively) and the responders (pU = 0.03 and pU = 0.07, respectively). Increased percentage of E-MDSCs was positively correlated to disease activity — ESR (Rs = 0.821; p = 0.023), CRP (Rs = 0.714; p = 0.07) and ASDASCRP (Rs = 0.829; p = 0.042) in the non-responder group. Responder patients exhibited no correlation between disease activity and circulating MDSCs. The suppressor potential of MDSCs was analyzed by the intracellular expression of arginase-1 molecule which is involved in the inhibition of T cell response. Patients with the stable response were characterized by increased expression of arginase-1 in E-MDSCs compared to donors (pU = 0.02). Non-responders did not demonstrate significant changes in Arg-1 expression, however, the percentage of arginase-1-expressing G-MDSCs was positively correlated to indexes ASDASESR (Rs = 0.857; p = 0.014) and BASDAI (Rs = 0.785; p = 0.036). Thus, E-MDSCs as well as arginase-1 expression in MDSCs may serve as biomarkers of effectiveness bDMARD therapy, and act as potential candidate predictors of response to therapy in AxSp

Expansion of myeloid-derived suppressor cells in the peripheral blood of patients with ankylosing spondylitis

Expansion of myeloid-derived suppressor cells (MDSCs) due to impaired differentiation of myeloid progenitor cells under conditions of inflammation was described in a number of autoimmune diseases, including rheumatoid arthritis, systemic lupus erythematosus, and type 1 diabetes mellitus. Studying the role of MDSCs in ankylosing spondylitis is an important issue, given that increased concentration of proinflammatory mediators in this pathology can also cause myelopoiesis disorders. The aim of present work was to study the quantitative content of MDSC subpopulations in patients with different clinical phenotypes and activity of AS. 37 patients, including 10 patients without peripheral skeletal lesions (axial form) and 27 patients with simultaneous lesions of spine and peripheral joints (peripheral form) were recruited into the study. The control group consisted of 32 age/sex-related healthy donors. Evaluation of granulocytic (LinHLA-DRCD33+CD66b+; G-MDSC), monocytic (CD14+HLA-DRlow/-; M-MDSC) and early-stage MDSCs (LinHLA-DRCD33+CD66b- ; E-MDSC) was performed using corresponding antibodies (BD Biosciences, USA) in the population of peripheral blood mononuclear cells by flow cytometry. In general, the AS patients were characterized by an increased relative and absolute amount of M-MDSC (p = 0.00002 and p = 0.00003, respectively) and G-MDSC (p = 0.0002 and p = 0.0006, respectively). Patient gender, age, and HLA-B27 expression did not significantly affect the content of these cells in peripheral blood. An increase in the median values of M-MDSC was detected both in patients with axial (Ме 5.0 (3.2-6.3) versus 2.4 (1.7-3.5) %; p = 0.001) and peripheral form (Ме 5.0 (3.0-7.0) versus 2.4 (1.7-3.5) %; p = 0.0002) AS. At the same time, the G-MDSC expansion was observed only in patients with involvement of peripheral joints (Ме 0.16 (0.07-0.3) % versus 0.05 (0.04-0.09) %; p = 0.0001). The relative contents of E-MDSC, M-MDSC and G-MDSC in the axial form of AS was in direct correlation with the activity of the disease (R = 0.58, p = 0.02; R = 0.73, p = 0.08 and R = 0.65 p = 0.04, respectively). This relationship was not observed in peripheral form of AS. The data obtained suggest a potential involvement of MDSCs in pathogenesis and phenotypic heterogeneity of AS. Simultaneously, the revealed direct correlation between the MDSC contents and the disease activity suggests a decrease in suppressive activity and/or appearance of pro-inflammatory activity in MDSC, thus requiring further research in the field

IN VITRO ACTIVATION OF EARLY-STAGE APOPTOSIS OF T LYMPHOCYTES BY TRANSFERRING APOPTOTIC AUTOLOGOUS CELL CULTURE COMPONENTS IN PATIENTS WITH RHEUMATOID ARTHRITIS

Defects in programmed death of peripheral blood lymphocytes may result into autotolerance and chronic persistence of inflammatory reaction in rheumatoid arthritis. According to recent data, apoptosis is not an autonomous process, i.e., an excessive accumulation of cells in conjunction with a depleted medium leads to cellular excess, thus causing effect of cells already committed to apoptosis upon surrounding cells, by morphogenetic damage due to mechanical forces. Such effects are called compensatory proliferation or apoptosis-induced proliferation. Extracellular vesicles (ectosomes and apoptotic bodies) also have a negative effect on cultured cells, triggering their programmed apoptotic death. In turn, apoptosis can also be controlled by neighboring cells in non-autonomous manner.We conducted studies that allowed us to optimize methods aimed at the initiation of apoptotic cell death and to investigate the effects of apoptotic environment upon autologous cells under physiological conditions. The selected conditions in combination with a fluorescent labeling of lymphocytes and subsequent separate flow cytometric analysis allowed us to evaluate parameters of early apoptosis in subpopulations of peripheral blood T-lymphocytes in rheumatoid arthritis. In vitro studies of cells from the patients with rheumatoid arthritis allowed us to reveal a pronounced readiness of primary (CFSE) and secondary (CFSE+)-induced T lymphocytes for early apoptosis after stimulation with anti-CD3 antibodies. It was observed both against initial level of apoptosis, and when compared to cells induced for apoptosis. The obtained data suggest that stimulation of T lymphocytes with antibodies against CD3, and, as a result, an in vitro rise in cell proliferation rate leading to increased levels of early apoptosis not only among the cells directly receiving a proliferative stimulus, but also to increased effect of cellular and humoral components from anti-CD3-stimulated cultures upon normally proliferating lymphocytes.The transfer of an autologous apoptotic “aCD3” and dexamethasone-stimulated cultures, which were initially induced under conditions of cell overcrowding and medium exhaustion, was shown to activate the process of early apoptosis among normally proliferating cells. Glucocorticoids are known to serve as agents of cell death induced by activation. At pharmacological concentrations, glucocorticoids and their synthetic analogues stimulate endonucleases in activated lymphocytes. These enzymes destroy DNA in the internucleosomal regions thus resulting into cell apoptosis. The results obtained in present study suggest an opportunity of an in vitro early-stage apoptosis induction in T lymphocytes from the patients with rheumatoid arthritis, by means of cells subjected to activation-induced apoptosis

Induction of lymphocyte apoptosis in healthy individuals and patients with rheumatoid arthritis under “cellular neighborhood” in vitro

The aim of the study was to investigate the features of T-lymphocyte apoptosis induced by components of autologous apoptotic cultures in vitro in norm and rheumatoid arthritis in the context of «cellular neighborhood».Materials and methods. Subjects of the study were blood samples of patients with rheumatoid arthritis (RA) and healthy women of comparable age. Developed protocol allowed to differentially evaluate the parameters of proliferation, early and late stages of apoptosis in the «primary» (CFSE-) and «secondary» (CFSE+) induced apoptotic T-lymphocyte cultures. It was estimated the effect of cellular and humoral components of unstimulated, anti-CD3- and dexamethasone-stimulated cells under the conditions of overcrowding and depleted culture media on autologous lymphocytes, cultured under physiological conditions, in norm and RA.Results. Comparative qualitative analysis revealed the features of the processes of T-lymphocyte apoptosis in norm and pathology. Also, the parameters of early and late stages of apoptosis of a «primary» induced culture and «secondary» induced cells after transferring the cellular and humoral components of apoptotic cultures did not differ significantly either initially or during culturing in both investigated groups. But it was a significant increase in the amount of living T-cells in «primary»-induced unstimulated and dexamethasone-stimulated RA patients’ cultures compared to similar donors’ cultures.Conclusion. There was no difference between stimulated with anti-CD3 antibodies cells and the «secondary» induced cultures. Taking into account the absence of significant differences in the parameters of activation apoptosis, the increased number of living cells in RA patients’ cultures relative to donors’ is evidence of contribution of non-autonomous apoptosis effects to cellular homeostasis in RA