Kidney organoids derived from human pluripotent stem cells exhibit glomerular- and tubular-like compartments that are largely avascular and immature in static culture. Here, we report an in vitro method for culturing kidney organoids under flow on millifluidic chips, which greatly expands their endogenous pool of endothelial progenitor cells (EPCs) and generates vascular networks with perfusable lumens surrounded by mural cells. Vascularized kidney organoids cultured under flow exhibit more mature podocyte and tubular compartments with enhanced cellular polarity and adult gene expression, compared to static controls. However, the association of vessels with these compartments is reduced upon disrupting the endogenous VEGF gradient. Glomerular vascular development progresses through intermediate stages akin to the embryonic mammalian kidney’s formation of capillary loops abutting foot processes. The ability to induce substantial vascularization and morphological maturation of kidney organoids in vitro under flow opens new avenues for studying kidney development, disease, and regeneration.

Kidney injury is characterized by persisting inflammation and fibrosis, yet mechanisms by which inflammatory signals drive fibrogenesis remain poorly defined. RNA sequencing of fibrotic kidneys from patients with CKD identified a metabolic gene signature comprising loss of mitochondrial and oxidative phosphorylation gene expression with a concomitant increase in regulators and enzymes of glycolysis under the control of PGC1 and MYC transcription factors, respectively. We modeled this metabolic switch , in experimental murine models of kidney injury, and in human kidney stromal cells (SCs) and human kidney organoids. In mice, MYC and the target genes thereof became activated in resident SCs early after kidney injury, suggesting that acute innate immune signals regulate this transcriptional switch. , stimulation of purified human kidney SCs and human kidney organoids with IL-1 recapitulated the molecular events observed , inducing functional metabolic derangement characterized by increased MYC-dependent glycolysis, the latter proving necessary to drive proliferation and matrix production. MYC interacted directly with sequestosome 1/p62, which is involved in proteasomal degradation, and modulation of p62 expression caused inverse effects on MYC expression. IL-1 stimulated autophagy flux, causing degradation of p62 and accumulation of MYC. Inhibition of the IL-1R signal transducer kinase IRAK4 or inhibition of MYC as well as in human kidney organoids abrogated fibrosis and reduced tubular injury. Our findings define a connection between IL-1 and metabolic switch in fibrosis initiation and progression and highlight IL-1 and MYC as potential therapeutic targets in tubulointerstitial diseases.

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In mouse embryos, the Zfhx1 transcription factor genes, Sip1 and ␦EF1, are expressed in complementary domains in many tissues. Their possible synergism in embryogenesis was investigated by comparing the phenotype of Sip1؊/؊;␦EF1؊/؊ double homozygotes with single homozygous embryos. Unexpectedly, in Sip1؊/؊ embryos ␦EF1 was ectopically activated, suggesting a negative regulation of ␦EF1 expression by Sip1. Sip1؊/؊;␦EF1؊/؊ embryos were similar to Sip1؊/؊ embryos in short somite production and developmental arrest around E8.5, but showed more severe defects in dorsal neural tube morphogenesis accompanied by a larger reduction of Sox2 expression, ascribable to the loss of the ectopic ␦EF1 expression. Sip1؉/؊;␦EF1؊/؊ embryos develop various morphological defects after E10 that were absent in ␦EF1؊/؊ embryos even in tissues without significant overlap of Sip1 and ␦EF1 expression, and arrested during mid gestation earlier than ␦EF1؊/؊ embryos. These findings indicate that complex synergistic interactions occur between Zfhx1 transcription factor genes during mouse embryogenesis. Developmental Dynamics 235: 1941-1952, 2006.