Three-dimensional in vitro models answer the right questions in ADPKD cystogenesis

Abstract

Novel technologies, new understanding of the basement membrane composition, and better comprehension of the embryonic development of the mammalian kidney have led to explosive growth in the use of three-dimensional in vitro models to study a range of human disease pathologies (Clevers H. Cell 165: 1586-1597, 2016; Shamir ER, Ewald AJ. Nat Rev Mol Cell Biol 15: 647-664, 2014). The development of these effective model systems represents a new tool to study the progressive cystogenesis of autosomal dominant polycystic kidney disease (ADPKD). ADPKD is a prevalent and complex monogenetic disease, characterized by the pathological formation of fluid fill cysts in renal tissue (Grantham JJ, Mulamalla S, Swenson-Fields KI. Nat Rev Nephrol 7: 556-566, 2011; Takiar V, Caplan MJ. Biochim Biophys Acta 1812: 1337-1343, 2011). ADPKD cystogenesis is attributed to loss of function mutations in either PKD1 or PKD2, which encode for two transmembrane proteins, polycystin-1 and polycystin-2, and progresses with loss of both copies of either gene through a proposed two-hit mechanism with secondary somatic mutations (Delmas P, Padilla F, Osorio N, Coste B, Raoux M, Crest M. Biochem Biophys Res Commun 322: 1374-1383, 2004; Pei Y, Watnick T, He N, Wang K, Liang Y, Parfrey P, Germino G, St George-Hyslop P. Am Soc Nephrol 10: 1524-1529, 1999; Wu G, D'Agati V, Cai Y, Markowitz G, Park JH, Reynolds DM, Maeda Y, Le TC, Hou H Jr, Kucherlapati R, Edelmann W, Somlo S. Cell 93: 177-188, 1998). The exaggerated consequences of large fluid filled cysts result in fibrosis and nephron injury, leading initially to functional compensation but ultimately to dysfunction (Grantham JJ. Am J Kidney Dis 28: 788-803, 1996; Norman J. Biochim Biophys Acta 1812: 1327-1336, 2011; Song CJ, Zimmerman KA, Henke SJ, Yoder BK. Results Probl Cell Differ 60: 323-344, 2017). The complicated disease progression has scattered focus and resources across the spectrum of ADPKD research.

GDNF drives rapid tubule morphogenesis in a novel 3D in vitro model for ADPKD

“…Furthermore, polycystins have a noted relationship with the microenvironment ( Cruz et al, 2017 ; Drummond, 2011 ), but there is not a current model system to determine the immediacy of these changes in response to the loss of gene function in relevant epithelial structures. Although decades of work have led to exciting advances in our understanding of disease pathology and the first FDA-approved treatments, the initiating mechanisms underlying progressive cystogenesis remain undefined in renal epithelial cells ( Dixon and Woodward, 2018 ; Torres and Harris, 2019 ; Brill and Ehrlich, 2020 ). Dissecting the complicated pathogenesis of PKD into distinct phases in an isolated tubuloid structure might allow more accurate targeting of therapeutic development and was an obvious unmet need that drove our development of a new model system.…”

“…Roadblocks of current in vitro model systems fall into categories of cost, relevancy, and translational applications, which all stem from efforts to maintain epithelial-like structures and prevent them from reverting back to innate stemness ( Dixon and Woodward, 2018 ). Despite the intricate characterization of these kidney organoids and personalization of the models to patients, the resulting structures demonstrate insufficient functional relevance and often rely on a nascent phenotype, which makes interpretation for late stage diseases, such as ADPKD, challenging ( Forbes et al, 2018 ; Takasato et al, 2015 ).…”

“…The use of a primary cell 3D system driven to a desired tubule-like phenotype could be used to isolate changes in epithelial organization following acute experimental perturbations. Therefore, we designed a system that would be inexpensive, utilize commercially available reagents, allow for differentiation and experimental protocols to be completed in less than 2 weeks, and that would allow tracking and imaging of tubuloids in situ ( Dixon and Woodward, 2018 ).…”

An American Physiological Society cross-journal Call for Papers on “Deconstructing Organs: Single-Cell Analyses, Decellularized Organs, Organoids, and Organ-on-a-Chip Models”

“…Our Journal recently published an elegant study that utilized genetic tools to develop a new cell line that will allow the study of resident renal mesenchymal stem cell-like progenitors in renal fibrotic mechanisms (47). Threedimensional in vitro models have also allowed new pathways to be identified in renal cyst development [reviewed in (12)]. The submission of manuscripts that combine new models/cell lines and that use single-cell transcriptomic, proteomic, and metabolomic studies to shed light on the cellular identification of renal progenitors, or that identify new mechanisms of normal or pathological renal function are highly encouraged.…”

Comprehensive strategy improves the genetic diagnosis of different polycystic kidney diseases

“…The onset of ADPKD occurs in adulthood in the majority of the cases, while 2%‐5% of the cases exhibit early‐onset, even foetal‐onset, and the mechanism underlying early‐onset PKD has attracted great attention 3,9 . Recent in vivo and in vitro studies on biallelic and digenic mutations have proposed a ‘two‐hit’ model for cystogenesis in PKD, which involves the inactivation of both copies of a polycystic kidney disease gene by germline and somatic mutations, thereby leading to cyst formation 10 …”