Immunosuppressive Functions of M2 Macrophages Derived from iPSCs of ALS Patients

Abstract

Amyotrophic lateral sclerosis (ALS), an adult-onset neurodegenerative disease, is a systemic inflammatory disorder that augments disease burden and rates of disease progression, and is pathologically characterized by activated leukocytes. Activated macrophages are members of this family and can be simplistically separated into M1 and M2 cells. M2 macrophages (M2) have been shown to provide therapeutic benefits in mouse models of diabetes and Adriamycin nephrosis by suppressing the pro-inflammatory state. However, the suppressive functions of M2 have not been investigated in ALS, nor have M2 derived from human iPSCs (Induced Pluripotent Stem Cells) been studied for their immunosuppressive potential. In this study, human iPSCs from ALS patients with C9orf72 (C9) mutation or from sporadic ALS patients were differentiated into M2 macrophages, which suppressed activation of pro-inflammatory M1 macrophages as-well-as proliferation of pro-inflammatory CD4⁺CD25^- T lymphocytes (Teffs) of ALS patients. These M2 macrophages also converted ALS Teffs into CD4⁺CD25⁺Foxp3⁺ regulatory T cells (Tregs), and rescued ALS patients’ Tregs from the loss of functional markers CD25 and Foxp3. Furthermore, the ALS Tregs induced or rescued by iPSC-derived M2 cells had strong suppressive functions. Without influence of C9 mutation or disease insult, immunomodulatory effects of ALS iPSC-derived M2 cells behaved similarly to control iPSC-derived M2 cells. This study demonstrates that M2 cells differentiated from ALS patients’ iPSCs have immunosuppressive functions and boost ALS Tregs, and may serve as a candidate for immune-cell-based therapy to mitigate the systemic inflammation occurring in patients with ALS.

Keywords: ALS, M2 macrophages, immunosuppression, induced pluripotent stem cells (iPSC)