iPSC-derived M2-like ALS macrophages suppress pro-Inflammatory phenotype of M1-like macrophages (S25.008)

Objective: To determine whether M2-like macrophages differentiated from human induced pluripotent stem cells (iPSC) are immune-suppressive and relevant mechanisms Background: Neuroinflammation is a prominent pathological finding in amyotrophic lateral sclerosis (ALS). Numerous studies have confirmed that activated microglia contribute to motoneuron injury and participate in ALS disease progression. These activated microglia are pro-inflammatory and classified as M1-like macrophages. In contrast, M2-like macrophages produce high levels of anti-inflammatory cytokines and neurotrophins. However, it is not known whether iPSC-derived M2-like macrophages are immune-suppressive and by what mechanisms. Design/Methods: M1-like and M2-like macrophages were differentiated from human iPSC. Specific mRNAs from the macrophage phenotypes were assayed by qRT-PCR. ELISAs were performed to identify pro- or anti-inflammatory cytokines secreted by two different macrophages. M1-like and M2-like macrophages were also co-cultured for their immune-stimulatory or immune-suppressive attributes. Results: Fibroblasts obtained from an ALS patient with a C9orf72 mutation and a healthy volunteer were reprogrammed to iPSC. The iPSC-derived monocytes were further differentiated to M1-like and M2-like macrophages. M1-like macrophages up-regulated the pro-inflammatory cytokines, IL-6, IL-8, and TNFα. M2-like macrophages released higher level of the anti-inflammatory cytokine IL-10 than M0 resting macrophages. M2-like macrophages from a healthy volunteer also produced more TGF-β protein than M0 resting macrophages. TGF-β protein was not detectable in the supernatants of M2-like macrophages from ALS iPSC. Functionally, both C9orf72 ALS and healthy volunteer M2-like macrophages were able to suppress the activation of M1-like macrophages by down-regulating IL-6, IL-8, and TNF-α expression. Blocking antibodies against IL-10 and TGF-β did not reverse the suppressive effects of M2-like macrophages on M1 activation. Conclusions: iPSCs can be differentiated into M1-like and M2-like macrophages. M2-like macrophages are able to suppress the pro-inflammatory phenotype of M1-like macrophages. Therefore, M2-like human macrophages differentiated from iPSC may serve as a candidate for immune-cell-based therapy to mitigate neuroinflammation and slow ALS disease progression. Study Supported by: ALS Finding a Cure Disclosure: Dr. Zhao has nothing to disclose. Dr. Beers has nothing to disclose. Dr. Thonhoff has nothing to disclose. Dr. Ornelas has nothing to disclose. Dr. Svendsen has nothing to disclose. Dr. Appel has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Avanir Pharmaceuticals Speaker’s Bureau, Mitsubishi Tanabe Pharma America, Inc. and Neuraltus.