Podocyte protease activated receptor 1 stimulation in mice produces focal segmental glomerulosclerosis mirroring human disease signaling events.

About 30% of patients who have a kidney transplant with underlying nephrotic syndrome (NS) experience rapid relapse of disease in their new graft. This is speculated to be due to a host-derived circulating factor acting on podocytes, the target cells in the kidney, leading to focal segmental glomerulosclerosis (FSGS). Our previous work suggests that podocyte membrane protease receptor 1 (PAR-1) is activated by a circulating factor in relapsing FSGS. Here, the role of PAR-1 was studied in human podocytes in vitro, and using a mouse model with developmental or inducible expression of podocyte-specific constitutively active PAR-1, and using biopsies from patients with nephrotic syndrome. In vitro podocyte PAR-1 activation caused a pro-migratory phenotype with phosphorylation of the kinase JNK, VASP protein and docking protein Paxillin. This signaling was mirrored in podocytes exposed to patient relapse-derived NS plasma and in patient disease biopsies. Both developmental and inducible activation of transgenic PAR-1 (NPHS2 Cre PAR-1Active+/-) caused early severe nephrotic syndrome, FSGS, kidney failure and, in the developmental model, premature death. We found that the non-selective cation channel protein TRPC6 could be a key modulator of PAR-1 signaling and TRPC6 knockout in our mouse model significantly improved proteinuria and extended lifespan. Thus, our work implicates podocyte PAR-1 activation as a key initiator of human NS circulating factor and that the PAR-1 signaling effects were partly modulated through TRPC6.

Genome editing and kidney health.

Genome editing technologies, clustered regularly interspaced short palindromic repeats (CRISPR)-Cas in particular, have revolutionized the field of genetic engineering, providing promising avenues for treating various genetic diseases. Chronic kidney disease (CKD), a significant health concern affecting millions of individuals worldwide, can arise from either monogenic or polygenic mutations. With recent advancements in genomic sequencing, valuable insights into disease-causing mutations can be obtained, allowing for the development of new treatments for these genetic disorders. CRISPR-based treatments have emerged as potential therapies, especially for monogenic diseases, offering the ability to correct mutations and eliminate disease phenotypes. Innovations in genome editing have led to enhanced efficiency, specificity and ease of use, surpassing earlier editing tools such as zinc-finger nucleases and transcription activator-like effector nucleases (TALENs). Two prominent advancements in CRISPR-based gene editing are prime editing and base editing. Prime editing allows precise and efficient genome modifications without inducing double-stranded DNA breaks (DSBs), while base editing enables targeted changes to individual nucleotides in both RNA and DNA, promising disease correction in the absence of DSBs. These technologies have the potential to treat genetic kidney diseases through specific correction of disease-causing mutations, such as somatic mutations in PKD1 and PKD2 for polycystic kidney disease; NPHS1, NPHS2 and TRPC6 for focal segmental glomerulosclerosis; COL4A3, COL4A4 and COL4A5 for Alport syndrome; SLC3A1 and SLC7A9 for cystinuria and even VHL for renal cell carcinoma. Apart from editing the DNA sequence, CRISPR-mediated epigenome editing offers a cost-effective method for targeted treatment providing new avenues for therapeutic development, given that epigenetic modifications are associated with the development of various kidney disorders. However, there are challenges to overcome, including developing efficient delivery methods, improving safety and reducing off-target effects. Efforts to improve CRISPR-Cas technologies involve optimizing delivery vectors, employing viral and non-viral approaches and minimizing immunogenicity. With research in animal models providing promising results in rescuing the expression of wild-type podocin in mouse models of nephrotic syndrome and successful clinical trials in the early stages of various disorders, including cancer immunotherapy, there is hope for successful translation of genome editing to kidney diseases.