Human Adipose Tissue-Derived Mesenchymal Stem Cells in Parkinson's Disease: Inhibition of T Helper 17 Cell Differentiation and Regulation of Immune Balance Towards a Regulatory T Cell Phenotype.

BACKGROUND

Parkinson's disease (PD) is a neurodegenerative disorder displaying a typical neuroinflammation pathology that may result from an imbalance between regulatory T cells (Treg) and T helper 17 (Th17) cells. Human adipose tissue-derived mesenchymal stem cells (Ad-MSCs) exert immunomodulatory effects by inhibiting effector T cell responses and have been used to treat diverse immune disorders. We aimed to investigate the modulating effect of human Ad-MSCs on peripheral blood mononuclear cells (PBMCs) of patients with PD, focusing on differentiation into Th17 and Treg cells.

METHODS

We isolated human peripheral blood CD4+T cells and co-cultured them with Ad-MSCs at a ratio of 4:1 under either Th17 or Treg cell polarizing conditions for 4 days to detect the proportions of IL-17-producing CD4+T (Th17) and CD4+CD25+Foxp3+regulatory T (Treg) cells by flow cytometry. We also determined the mRNA expression levels of the retinoid-related orphan nuclear receptor (RORγt) transcription factor and those of interleukin-6 receptor (IL-6R), interleukin-23 receptor (IL-23R), leukemia inhibitory factor (LIF), and LIF receptor (LIFR) by quantitative reverse transcription PCR. We detected levels of cytokines in the supernatant (including LIF, IL-6, IL-23, IL-10, and TGF-β) using ELISA.

RESULTS

Our results showed that Ad-MSCs specifically inhibited the differentiation of PBMCs of patients with PD into IL-17-producing CD4+T cells by decreasing expressions of IL-6R, IL-23R, and RORγt (the key transcription factor for Th17 cells). Moreover, Ad-MSCs induced a functional CD4+CD25+Foxp3+T regulatory cell phenotype as evidenced by the secretion of IL-10. The levels of IL-6, IL-23, and TGF-β remained constant after co-culture under either the Th17 or the Treg cell polarizing condition. In addition, levels of LIF protein and its receptor mRNA were significantly increased under both polarizing conditions.

CONCLUSION

The present in vitro study found that Ad-MSCs from healthy participants were able to correct the imbalance between Th17 and Treg found in PBMCs of PD patients, which were correlated with an increase in LIF secretion and a decrease in expression of IL-6R, IL-23R, and RORγt. These findings should be confirmed by in vivo experiments.