Regulatory B Cells Contribute to the Clinical Response After Bone Marrow-Derived Mesenchymal Stromal Cell Infusion in Patients With Systemic Sclerosis

Abstract

Mesenchymal stromal cells (MSCs) have recently emerged as an interesting therapeutic approach for patients with progressive systemic sclerosis (SSc), a rare and life-threatening orphan autoimmune disease. Whereas MSC immunomodulatory potential is considered as a central mechanism for their clinical benefit, very few data are available on the impact of MSCs on immune cell subsets in vivo. In the current extended study of a phase I/II clinical trial exploring the injection of a single dose of allogeneic bone marrow-MSCs (alloBM-MSCs) in patients with severe SSc (NCT02213705), we performed a longitudinal in-depth characterization of circulating immune cells in 19 MSC-treated patients, including 14 responders and 5 non-responders. By a combination of flow cytometry and transcriptomic analyses, we highlighted an increase in circulating CD24hiCD27posCD38lo/neg memory B cells, the main IL-10-producing regulatory B cell (Breg) subset, and an upregulation of IL10 expression in ex-vivo purified B cells, specifically in responder patients, early after the alloBM-MSC infusion. In addition, a deeper alteration of the B-cell compartment before alloBM-MSC treatment, including a higher expression of profibrotic cytokines IL6 and TGFβ by sorted B cells was associated with a non-responder clinical status. Finally, BM-MSCs were able to directly upregulate IL-10 production in activated B cells in vitro. These data suggest that cytokine-producing B cells, in particular Breg, are pivotal effectors of BM-MSC therapeutic activity in SSc. Their quantification as activity biomarkers in MSC potency assays and patient selection criteria may be considered to reach optimal clinical benefit when designing MSC-based clinical trials.

Biomarkers in Systemic Sclerosis: An Overview

“…The SSc vascular damage is characterized by the presence of a characteristic processes with a vasomotor instability with an imbalance of vasoactive factors: overproduction of vasoconstrictors (ET-1) and underproduction of vasodilators (NO and prostacyclin) [6][7][8][9][10][11][12][13][22][23][24][25][106][107][108][109]. The free radical nitric oxide (NO) is a potent vasodilator and is synthesized from L-arginine by NO synthase (NOS) [10][11][12][13][14][15][16][17][18][19][22][23][24][25][40][41][42][43][44][45][46][47][48][106][107][108][109][110][111][112][113]. Endothelial isoforms of NOS (eNOS or NOS 3) has been identified with a constitutive expression, other isoforms are shown...…”

“…Endothelial isoforms of NOS (eNOS or NOS 3) has been identified with a constitutive expression, other isoforms are shown in other cell types. Furthermore, an inducible expression (iNOS or NOS 2) in response to a variety of stimuli is possible, with NO-mediated signalling apparent in the skin [10][11][12][13][14][15][16][17][18][19][40][41][42][43][44][45][46][47][48][106][107][108][109][110][111][112][113]. Several studies reported that NO have a biphasic effect in physiological and pathological conditions, being both beneficial and detrimental depending on the concentration and local environment [10][11][12][13][14][15][16][17][18][19][40][41][42][43][44][45][46][47][48].…”

“…Furthermore, an inducible expression (iNOS or NOS 2) in response to a variety of stimuli is possible, with NO-mediated signalling apparent in the skin [10][11][12][13][14][15][16][17][18][19][40][41][42][43][44][45][46][47][48][106][107][108][109][110][111][112][113]. Several studies reported that NO have a biphasic effect in physiological and pathological conditions, being both beneficial and detrimental depending on the concentration and local environment [10][11][12][13][14][15][16][17][18][19][40][41][42][43][44][45][46][47][48]. Recently observation proposed the regulation of NO by endogenous levels of the NOS inhibitor asymmetric dimethylarginine (ADMA) [10]…”

“…Several studies reported that NO have a biphasic effect in physiological and pathological conditions, being both beneficial and detrimental depending on the concentration and local environment [10][11][12][13][14][15][16][17][18][19][40][41][42][43][44][45][46][47][48]. Recently observation proposed the regulation of NO by endogenous levels of the NOS inhibitor asymmetric dimethylarginine (ADMA) [10][11][12][13][14][15][16][17][18][19][22][23][24][25][40][41][42][43][44][45][46][47][48][106][107][108][109][110][111][112]…”

“…Antinuclear antibodies (ANA) are present in more than 90% of SSc patients, along with anticentromere, anti-Th/To, and anti-topoisomerase I antibodies, which are considered the classic biomarkers present in 60% of SSc patients and help to define precise clinical classifications [4,7,[29][30][31][32][33][34][35][36][37]. Other autoantibodies, such as those directed against the endothelium or fibroblasts, against angiotensin II type 1 receptor, endothelin-1 type A receptor, platelet-derived growth factor receptor (anti-PDGFR), and extracellular matrix (ECM) proteins [16][17][18][19][20][38][39][40][41][42][43][44][45] are also found in SSc patients. More complex autoantibody systems against G-protein-coupled receptors, growth factors, and respective receptors have also been described in SSc [21,[45][46][47][48][49].…”