Personalized disease recurrence modeling using iPSC-derived podocytes in patients with idiopathic nephrotic syndrome

Primary focal segmental glomerulosclerosis (FSGS) is characterized by podocyte injury and treatment-resistant nephrotic syndrome. Recurrence of the original disease after kidney transplantation (rFSGS) occurs in 10%-50% of patients. Unidentified circulating permeability factors (CPF) are likely involved in FSGS pathogenesis. We hypothesized that donor podocyte susceptibility to CPF is also relevant. We developed a personalized model for (r)FSGS using induced pluripotent stem cell (iPSC)-derived podocytes from patients and kidney donors.

Five patients and their respective living kidney donors were included. Three patients had developed rFSGS, and two patients manifested no symptoms of rFSGS. One patient (P5) had heterozygous mutations in NPHS2. Peripheral blood mononuclear cells were reprogrammed to iPSC, and differentiated to podocytes. iPSC-derived podocytes from either patients or donors were exposed to presumed CPF-containing plasma/serum of corresponding patients. Three assays to detect podocyte injury were performed: (i) reactive oxygen species formation, (ii) cellular granularity induction, and (iii) quantitative assessment of F-actin redistribution (FAR), a new quantitative method. Crossmatch experiments with donor iPSC-derived podocytes and patients samples assessed individual susceptibility to CPF-induced injury.

Successful podocyte differentiation was confirmed by morphology and protein expression. Only FAR differentiated consistently between patient and healthy donor samples. All pre-transplant patient samples except P5 caused significant FAR in corresponding patient podocytes. Significant FAR was observed in donor podocytes exposed to corresponding patient samples in the setting of rFSGS, and not in donor podocytes exposed to samples of patients who did not develop rFSGS. Effects of FSGS patient samples on non-corresponding donor podocytes were variable.

In vitro assays using iPSC-derived donor podocytes may allow individualized assessment of rFSGS. Prospective studies in a larger cohort are required to validate our findings.