Activated CD4+ T Cells impact adipose-serived stromal cell function through CD40-dependant activation

Abstract

Background & Aim Although native bone marrow-derived mesenchymal stromal cells (BM-MSC) have been described to express CD40, how CD40 is regulated on MSC, and whether CD40 signaling affects MSC activation and function remain unknown. We recently demonstrated that adipose-derived stromal cells (ASC) exhibit a stronger capacity to inhibit immune response than BM-MSC, supporting their use for clinical applications to treat inflammatory diseases and degenerative disorders. Moreover, obesity is associated with adipose tissue inflammation and recruitment of immune cells that could in turn affect the phenotype of native ASC in situ. We thus decided to explore CD40 regulation, signalization, and function on native and in vitro-expanded ASC. Methods, Results & Conclusion Adipose Tissue Stromal Vascular Fractions (ATSVF) were obtained from obese and non-obese donors during lipectomy. Comparison of gene expression was carried out by using RNA sequencing. Some gene expression levels were assessed by QPCR on the total cells or on the CD146− CD34+ Lin− purified ASC. Next, ASC isolated by adhesion in culture were submitted to various stimuli or co-culture with activated CD4+ T cells. Changes in gene expression and secretion profiles were studied by Q-PCR and ELISA. Neutrophil migration was measured through Transwell and involvement of the candidate pathways was assessed by using specific siRNAs. We first revealed through gene expression profiling that the inflammatory signature found in adipose tissue stromal vascular fractions from obese patients included an upregulation of CD40L and was associated with a simultaneous induction of CD40 expression on native ASC. We further confirmed that inflammatory cytokines and direct contact with activated CD4+ T cells upregulated membrane CD40 expression on in vitro-expanded ASC. Stimulation of ASC by CD40L induced a modification of their gene expression profile evaluated by RNAseq reflecting an activation of NF-kB pathway. In agreement, we confirmed by DNA-binding ELISA, the activation of NF-kB pathways by CD40L stimulation. More specifically we focused on the strong induction of inflammatory chemokines, in particular IL-8, triggered on ASC by CD4+ T cells in a CD40/CD40L-dependant manner. Accordingly, CD40L-stimulated ASC recruited more efficiently neutrophils. Overall, these data strongly suggest an interaction between CD4+ T cells, ASC, and neutrophils within inflammatory sites. This observation must be kept in mind when using ASC to treat inflammatory diseases.