Polarization of human iPSC-derived macrophages directs their immunological response to secondary pro-inflammatory stimuli

Abstract

Macrophages can be found in various tissues and play an important role in organ function by sensing and eradicating pathogens, regulating immune responses and contributing to tissue homeostasis and repair. Nowadays, increasing numbers of macrophage-based cell therapies are entering (pre-) clinical studies e.g. for the treatment of liver cirrhosis. Given limited availability of suitable donors as well as problems with variability in quantities and qualities of human monocytes that can be derived from apheresis, induced pluripotent stem cells (iPSC) offer an attractive source of therapeutic macrophages. However, considering the diverse functions, activation stages and overall plasticity of macrophages, further knowledge about (i) the potential to induce different activation stages in iPSC-derived macrophages (iPSC-Mac) as well as (ii) the stability of these phenotypes upon additional external stimuli is of high relevance. We here demonstrate that iPSC-Mac produced in a scalable differentiation platform can be polarized into defined pro- (M1) and anti-inflammatory (M2) activation stages characterized by specific surface marker expression, cytokine secretion and whole transcriptome analysis, similarly to peripheral blood-derived macrophages. Even more importantly, we show that differentially polarized iPSC-Mac maintained key characteristics of their activation status upon a subsequent inflammatory trigger. Interferon (IFN) γ polarized, M1-iPSC-Mac demonstrated an enhanced inflammatory response after additional lipopolysaccharide (LPS) stimulation, whereas Interleukin (IL)-4 stimulated M2a iPSC-Mac and IL-10/TGFβ primed M2c iPSC-Mac showed a reduced activation upon LPS treatment and maintained expression of anti-inflammatory genes. Together, our data demonstrate that defined polarized iPSC-Mac subsets can be generated. Moreover, these cells maintain key characteristics of their activation profile upon a subsequent inflammatory trigger. Thus, the use of stably polarized iPSC-Mac has the potential to further improve the applicability and efficacy of macrophage-based therapies.