Acute IL-6 exposure triggers canonical IL6Ra signaling in hiPSC microglia, but not neural progenitor cells

BACKGROUND

Prenatal exposure to elevated interleukin (IL)-6 levels is associated with increased risk for psychiatric disorders with a putative neurodevelopmental origin, such as schizophrenia (SZ), autism spectrum condition (ASC) and bipolar disorder (BD). Although rodent models provide causal evidence for this association, we lack a detailed understanding of the cellular and molecular mechanisms in human model systems. To close this gap, we characterized the response of human induced pluripotent stem cell (hiPSC-)derived microglia-like cells (MGL) and neural progenitor cells (NPCs) to IL-6 in monoculture.

RESULTS

We observed that human forebrain NPCs did not respond to acute IL-6 exposure in monoculture at both protein and transcript levels due to the absence of IL6R expression and soluble (s)IL6Ra secretion. By contrast, acute IL-6 exposure resulted in STAT3 phosphorylation and increased IL6, JMJD3 and IL10 expression in MGL, confirming activation of canonical IL6Ra signaling. Bulk RNAseq identified 156 up-regulated genes (FDR < 0.05) in MGL following acute IL-6 exposure, including IRF8, REL, HSPA1A/B and OXTR, which significantly overlapped with an up-regulated gene set from human post-mortem brain tissue from individuals with schizophrenia. Acute IL-6 stimulation significantly increased MGL motility, consistent with gene ontology pathways highlighted from the RNAseq data and replicating rodent model indications that IRF8 regulates microglial motility. Finally, IL-6 induces MGLs to secrete CCL1, CXCL1, MIP-1α/β, IL-8, IL-13, IL-16, IL-18, MIF and Serpin-E1 after 3 h and 24 h.

CONCLUSION

Our data provide evidence for cell specific effects of acute IL-6 exposure in a human model system, ultimately suggesting that microglia-NPC co-culture models are required to study how IL-6 influences human cortical neural progenitor cell development in vitro.

Scanningless and continuous 3D bioprinting of human tissues with decellularized extracellular matrix

Decellularized extracellular matrices (dECMs) have demonstrated excellent utility as bioscaffolds in recapitulating the complex biochemical microenvironment, however, their use as bioinks in 3D bioprinting to generate functional biomimetic tissues has been limited by their printability and lack of tunable physical properties. Here, we describe a method to produce photocrosslinkable tissue-specific dECM bioinks for fabricating patient-specific tissues with high control over complex microarchitecture and mechanical properties using a digital light processing (DLP)-based scanningless and continuous 3D bioprinter. We demonstrated that tissue-matched dECM bioinks provided a conducive environment for maintaining high viability and maturation of human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes and hepatocytes. Microscale patterning also guided spontaneous cellular reorganization into predesigned striated heart and lobular liver structures through biophysical cues. Our methodology enables a light-based approach to rapidly bioprint dECM bioinks with accurate tissue-scale design to engineer physiologically-relevant functional human tissues for applications in biology, regenerative medicine, and diagnostics.