RAAS-Deficient Organoids Reveal that Delayed Angiogenesis Is The Pathomechanism Underlying Autosomal Recessive Renal Tubular Dysplasia
Autosomal Recessive Renal Tubular Dysgenesis (AR-RTD) is a fatal genetic disorder affecting proximal tubule (PT) development in patients harboring mutations in genes comprising the Renin–Angiotensin–Aldosterone System (RAAS). To uncover the pathomechanism of AR-RTD, we differentiated ACE and AGTR1 deficient pluripotent stem cells and reprogrammed AR-RTD patient cells into kidney organoids. Marker analyses confirmed that all mutant and control organoids generated PT in room air (21% O2) or under hypoxic conditions (2% O2). Mature (d24) AGTR1-/- and control organoids transplanted under the kidney capsule of immunodeficient mice engrafted and differentiated well, as did renal vesicle stage (d14) control organoids. By contrast, d14 AGTR1-/- organoids failed to engraft due to insufficient pro-angiogenic VEGF-A expression. When grown under hypoxic conditions VEGF-A expression was stimulated and organoids engrafted. Thus, PT dysgenesis in AR-RTD is a non-autonomous consequence of a developmental delay in VEGF-A induction linking ANGII pro angiogenic role to PT dysgenesis. Overall design: Bulk RNA-seq was performed comparing unmodified iPSCs to those with CRISPR/Cas9 deletion of either ACE or ATGR1 genes.