Can Kidney Organoid Xenografts Accelerate Therapeutic Development for Genetic Kidney Disorders?

Kidney organoid models reveal cilium-autophagy metabolic axis as a therapeutic target for PKD both in vitro and in vivo

Human pluripotent stem cell-derived kidney organoids offer unprecedented opportunities for studying polycystic kidney disease (PKD), which still has no effective cure. Here, we developed both in vitro and in vivo organoid models of PKD that manifested tubular injury and aberrant upregulation of renin-angiotensin aldosterone system. Single-cell analysis revealed that a myriad of metabolic changes occurred during cystogenesis, including defective autophagy. Experimental activation of autophagy via ATG5 overexpression or primary cilia ablation significantly inhibited cystogenesis in PKD kidney organoids. Employing the organoid xenograft model of PKD, which spontaneously developed tubular cysts, we demonstrate that minoxidil, a potent autophagy activator and an FDA-approved drug, effectively attenuated cyst formation in vivo. This in vivo organoid model of PKD will enhance our capability to discover novel disease mechanisms and validate candidate drugs for clinical translation.

Renal Proximal Tubular Epithelial Cells: From Harvesting to Use in Studies

The kidneys are the body's main excretion organ with several additional functions, and the nephron represents their central structural unit. It is comprised of endothelial, mesangial, glomerular, and tubular epithelial cells, as well as podocytes. Treatment of acute kidney injury or chronic kidney disease (CKD) is complex due to broad etiopathogenic mechanisms and limited regeneration potential as kidney cells finish their differentiation after 34 weeks of gestation. Despite the ever-increasing prevalence of CKD, very limited treatment modalities are available. The medical community should therefore strive to improve existing treatments and develop new ones. Furthermore, polypharmacy is present in most CKD patients, while current pharmacologic study designs lack effectiveness in predicting potential drug-drug interactions and the resulting clinically relevant complications. An opportunity for addressing these issues lies in developing in vitro cell models based on patient-derived renal cells. Currently, several protocols have been described for isolating desired kidney cells, of which the most isolated are the proximal tubular epithelial cells. These play a significant role in water homeostasis, acid-base control, reabsorption of compounds, and secretion of xenobiotics and endogenous metabolites. When developing a protocol for the isolation and culture of such cells, one must focus on several steps. These include harvesting cells from biopsy specimens or after nephrectomies, using different digestion enzymes and culture mediums to facilitate the selective growth of only the desired cells. The literature reports several existing models, from simple 2D in vitro cultures to more complex ones created with bioengineering methods, such as kidney-on-a-chip models. While their creation and use depend on the target research, one should consider factors such as equipment, cost, and, even more importantly, source tissue quality and availability.