A kidney organoid-based readout to assess disease activity in primary and recurrent focal segmental glomerulosclerosis.

Primary focal segmental glomerulosclerosis (pFSGS) is an acquired kidney disorder that frequently leads to kidney failure and confers an elevated risk of recurrence after kidney transplantation, termed recurrent pFSGS. Unfortunately, there is no diagnostic method to foresee recurrence of pFSGS after kidney transplantation. Progress in developing assays to test disease activity is hampered by few preclinical models to replicate disease and inability of in vitro cultured primary podocytes to remain terminally differentiated. In recent years, advancements in kidney organoid biology have led to the development of kidney tissues with glomeruli and major nephron segments including podocytes. To develop a pFSGS model, we studied the effect of plasma from patients diagnosed with pFSGS on kidney organoids differentiated from human pluripotent stem cells. The pFSGS plasma treatment induced podocytopathy, extracellular matrix protein deposition, fibrosis and apoptosis within organoids, whereas non-recurrent plasma did not affect organoid structure. pFSGS plasma also led to loss of normal expression patterns of podocyte specific proteins, nephrin and podocin within podocytes. Further, cytokine array profiling revealed that pFSGS plasma induced secretion of cytokines associated with inflammation and angiogenesis. Additionally, kidney organoids treated with plasma obtained after therapeutic plasma exchange for recurrent pFSGS led to lower cell death in organoids after sequential exchanges with the final exchange showing the least apoptotic cells without morphological abnormality. Overall, our results demonstrate the potential of kidney organoids in advancing kidney disease modeling. These insights could be applied in clinical settings to assist in gauging FSGS recurrence risk prior to kidney transplantation.