Human Adipose Tissue-Derived Mesenchymal Stromal Cells Inhibit CD4+ T Cell Proliferation and Induce Regulatory T Cells as Well as CD127 Expression on CD4+CD25+ T Cells.

Agnese Fiori,Stefanie Uhlig,Harald Klüter,Karen Bieback

doi:10.3390/cells10010058

Abstract

Mesenchymal stromal cells (MSC) exert their immunomodulatory potential on several cell types of the immune system, affecting and influencing the immune response. MSC efficiently inhibit T cell proliferation, reduce the secretion of pro-inflammatory cytokines, limit the differentiation of pro-inflammatory Th subtypes and promote the induction of regulatory T cells (Treg). In this study, we analyzed the immunomodulatory potential of human adipose tissue-derived MSC (ASC), on CD4+ T cells, addressing potential cell-contact dependency in relation to T cell receptor stimulation of whole human peripheral blood mononuclear cells (PBMC). ASC were cultured with not stimulated or anti-CD3/CD28-stimulated PBMC in direct and transwell cocultures; PBMC alone were used as controls. After 7 days, cocultures were harvested and we analyzed: (1) the inhibitory potential of ASC on CD4+ cell proliferation and (2) phenotypic changes in CD4+ cells in respect of Treg marker (CD25, CD127 and FoxP3) expression. We confirmed the inhibitory potential of ASC on CD4+ cell proliferation, which occurs upon PBMC stimulation and is mediated by indoleamine 2,3-dioxygenase. Importantly, ASC reduce both pro- and anti-inflammatory cytokine secretion, without indications on specific Th differentiation. We found that stimulation induces CD25 expression on CD4+ cells and that, despite inhibiting overall CD4+ cell proliferation, ASC can specifically induce the proliferation of CD4+CD25+ cells. We observed that ASC induce Treg (CD4+CD25+CD127−FoxP3+) only in not stimulated cocultures and that ASC increase the ratio of CD4+CD25+CD127+FoxP3− cells at the expense of CD4+CD25+CD127−FoxP3− cells. Our study provides new insights on the interplay between ASC and CD4+ T cells, proposing that ASC-dependent induction of Treg depends on PBMC activation which affects the balance between the different subpopulations of CD4+CD25+ cells expressing CD127 and/or FoxP3.

Highlights

The inhibitory potential of adipose tissue-derived MSC (ASC) was corroborated by calculating the division index (DI) of CD4+ cells within the peripheral blood mononuclear cells (PBMC) live population based on VPD450 dye dilution (Figure 2A)
We observed that (1) upon PBMC stimulation, CD25 expression is increased and the CD4+CD25+ population is further expanded by ASC, (2) ASC promote a selective increase in the proportion of CD4+CD25+CD127+FoxP3- cells independently of PBMC stimulation and (3) in not stimulated conditions, ASC increase the percentage of Suppression of T-lymphocyte proliferation induced by cellular/non-specific stimuli was one of the first identified mechanisms of Mesenchymal stromal cells (MSC)-mediated immunomodulation [4]
This ASC-mediated induction of Treg in not stimulated cocultures is in line with findings in the literature, despite different MSC sources, culture conditions and timing of the coculture [2,19,20]. This is in line with the high TGF-β concentrations measured in the conditioned media of cocultures. Our study proposes another point of view on ASCmediated Treg induction: both ASC and anti-CD3/anti-CD28 stimulation affect the balance between the CD127±FoxP3± subpopulations, which inevitably affects the amount of Treg

Summary

Introduction

Mesenchymal stromal cells (MSC) have gained broad interest in regenerative medicine for their ability to modulate tissue repair and inflammation by secreting trophic and immunomodulatory factors. Their immunomodulatory activities have been reported to favor the skewing of the immune response towards a pro-regenerative and antiinflammatory milieu [1,2]. MSC can modulate both innate and adaptive immune responses acting on several cell types of immune cells. Molecular mechanisms regulating MSC/T cell interplay rely on both cell-to-cell contact and secretion of soluble factors [6]. The interaction with antigen-presenting cells (APC) was found to be dependent on cell contact [8]

Methods

Results

Discussion

Conclusion