IL-18 is a new type of inflammatory cytokine similar to but distinct from IL-12 and IL-1beta. One intriguing property of IL-18 is synergism with IL-12 in many respects. In this study we examined the in vivo synergistic effects of IL-18/IL-12 in mice and found lethal toxicity accompanying an elevated IFN-gamma level in the serum. Since treatment with IL-18 alone did not have any apparent toxicity, and treatment with IL-12 alone showed only limited toxicity in our system, the synergy between the two cytokines was all the more remarkable. The major symptoms of the toxicity were weight loss, diarrhea, hemorrhagic colitis, splenomegaly, fatty liver, and atrophic thymus, most of which are similarly found in endotoxin-induced septic shock. However, in contrast to septic shock, TNF-alpha was not induced. The involvement of IFN-gamma in the toxicity was further studied in detail. Treatment of athymic nude mice with anti-asialo-GM1 did not reduce the toxicity, whereas anti-IFN-gamma treatment of wild-type mice alleviated it. When IFN-gamma-deficient mice were treated with IL-18/IL-12, the majority of them showed mortality and toxicity with severe pulmonary edema. These results indicate that IL-18/IL-12 treatment induces severe adverse effects through not only IFN-gamma-dependent mechanisms but also IFN-gamma-independent processes.
Recent regenerative studies using human pluripotent stem cells (hPSCs) have developed multiple kidney-lineage cells and organoids. However, to further form functional segments of the kidney, interactions of epithelial and interstitial cells are required. Here we describe a selective differentiation of renal interstitial progenitor-like cells (IPLCs) from human induced pluripotent stem cells (hiPSCs) by modifying our previous induction method for nephron progenitor cells (NPCs) and analyzing mouse embryonic interstitial progenitor cell (IPC) development. Our IPLCs combined with hiPSC-derived NPCs and nephric duct cells form nephrogenic niche- and mesangium-like structures in vitro. Furthermore, we successfully induce hiPSC-derived IPLCs to differentiate into mesangial and erythropoietin-producing cell lineages in vitro by screening differentiation-inducing factors and confirm that p38 MAPK, hypoxia, and VEGF signaling pathways are involved in the differentiation of mesangial-lineage cells. These findings indicate that our IPC-lineage induction method contributes to kidney regeneration and developmental research.
Cell therapies using human induced pluripotent stem cell (hiPSC)-derived nephron progenitor cells (NPCs) are expected to ameliorate acute kidney injury (AKI). However, using hiPSC-derived NPCs clinically is a challenge because hiPSCs themselves are tumorigenic. LIN28A , ESRG , CNMD and SFRP2 transcripts have been used as a marker of residual hiPSCs for a variety of cell types undergoing clinical trials. In this study, by reanalyzing public databases, we found a baseline expression of LIN28A , ESRG , CNMD and SFRP2 in hiPSC-derived NPCs and several other cell types, suggesting LIN28A , ESRG , CNMD and SFRP2 are not always reliable markers for iPSC detection. As an alternative, we discovered a lncRNA marker gene, MIR302CHG , among many known and unknown iPSC markers, as highly differentially expressed between hiPSCs and NPCs, by RNA sequencing and quantitative RT-PCR (qRT-PCR) analyses. Using MIR302CHG as an hiPSC marker, we constructed two assay methods, a combination of magnetic bead-based enrichment and qRT-PCR and digital droplet PCR alone, to detect a small number of residual hiPSCs in NPC populations. The use of these in vitro assays could contribute to patient safety in treatments using hiPSC-derived cells.
