Experimental Models to Study Podocyte Biology: Stock-Taking the Toolbox of Glomerular Research

Abstract

Diseases affecting the glomeruli of the kidney, the renal filtration units, are a leading cause of chronic kidney disease and end-stage renal failure. Despite recent advances in the understanding of glomerular biology, treatment of these disorders has remained extraordinarily challenging in many cases. The use of experimental models has proven invaluable to study renal, and in particular, glomerular biology and disease. Over the past 15 years, studies identified different and very distinct pathogenic mechanisms that result in damage, loss of glomerular visceral epithelial cells (podocytes) and progressive renal disease. However, animal studies and, in particular, mouse studies are often protracted and cumbersome due to the long reproductive cycle and high keeping costs. Transgenic and heterologous expression models have been speeded-up by novel gene editing techniques, yet they still take months. In addition, given the complex cellular biology of the filtration barrier, certain questions may not be directly addressed using mouse models due to the limited accessibility of podocytes for analysis and imaging. In this review, we will describe alternative models to study podocyte biology experimentally. We specifically discuss current podocyte cell culture models, their role in experimental strategies to analyze pathophysiologic mechanisms as well as limitations with regard to transferability of results. We introduce current models in Caenorhabditis elegans, Drosophila melanogaster, and Danio rerio that allow for analysis of protein interactions, and principle signaling pathways in functional biological structures, and enable high-throughput transgenic expression or compound screens in multicellular organisms.

Human pluripotent stem cell-derived kidney organoids for personalized congenital and idiopathic nephrotic syndrome modeling

“…For decades, murine and human 2D conditionally immortalized podocytes (ciPOD) have been used to unravel NS pathophysiology. Although these models have expanded our knowledge regarding podocytopathies in NS, we and others showed that in vitro 2D conditionally immortalized podocyte models do not meet in vivo podocyte characteristics (Hagmann and Brinkkoetter, 2018; Hale et al, 2018; Rinschen et al, 2018; van den Broek et al, 2021). Here, we showed that kidney organoids are a promising tool to study both congenital and idiopathic nephrotic syndrome since organoid podocytes express essential proteins, with a morphology closely resembling in vivo podocytes, and respond similarly to injury triggers.…”

Urine Single-Cell RNA Sequencing in Focal Segmental Glomerulosclerosis Reveals Inflammatory Signatures

“…The protein products of these canonical podocyte genes are essential for the proper podocyte function. In cell culture, human and mouse podocytes also lose expression of NPHS1 and NPHS2, 23,24 and this downregulation or loss in FSGS urinary podocytes could be due to podocyte injury or dedifferentiation. EMT is important in cancer biology, in which it contributes to increased mobility of cancer cells.…”

From Infancy to Fancy: A Glimpse into the Evolutionary Journey of Podocytes in Culture

“…The podocytes in culture encounter neither the conventional mechanical stretch nor the flow of primary urine filtrate. Thus, it is not surprising that they do lack SDs in between neighboring cells (51) and also express only a limited amount of specific marker proteins such as nephrin, podocin, or transient receptor potential cation channel 6 (TRPC6) (52). In order to test if these conditionally immortalized podocytes can tolerate the physiological intraglomerular conditions, several mechanical and fluid shear stress models were generated to imitate the in vivo conditions (53)(54)(55).…”