In developing mouse kidneys, orientation of loop of Henle growth is adaptive and guided by long-range cues from medullary collecting ducts

Effective and new technologies in kidney tissue engineering

Kidney disease encompasses a wide spectrum of conditions, ranging from simple infections to chronic kidney disease. When the kidneys are unable to filter blood and remove waste products, these abnormalities can lead to kidney failure. In severe cases of kidney failure, kidney transplantation is considered the only definitive treatment. Worldwide, the World Health Organization (WHO) repeatedly emphasizes the importance of organ donation and increasing transplantation rates. Many countries implement national programs to promote the culture of organ donation and improve patient access to kidney transplantation. The extent to which this procedure is performed varies across countries and is influenced by several factors, including the volume of organ donation, medical infrastructure, access to technology and health policies. However, a kidney transplant comes with challenges and problems that impact its success. Kidney tissue engineering is a new approach that shows promise for repairing and replacing damaged kidney tissue. This article reviews recent advances in kidney tissue engineering, focusing on engineered structures such as hydrogels, electrospinning, 3D bioprinting, and microfluidic systems. By mimicking the extracellular environment of the kidney, these structures provide suitable conditions for the growth and development of kidney cells. The role of these structures in the formation of blood vessels, the mimicry of kidney functions and the challenges in this field were also discussed. The results of this study show that kidney tissue engineering has high potential for treating kidney diseases and reducing the need for kidney transplantation. However, to achieve clinical application of this technology, further research is required to improve the biocompatibility, vascularization and long-term performance of engineered tissues.

Production of kidney organoids arranged around single ureteric bud trees, and containing endogenous blood vessels, solely from embryonic stem cells

There is intense worldwide effort in generating kidney organoids from pluripotent stem cells, for research, for disease modelling and, perhaps, for making transplantable organs. Organoids generated from pluripotent stem cells (PSC) possess accurate micro-anatomy, but they lack higher-organization. This is a problem, especially for transplantation, as such organoids will not be able to perform their physiological functions. In this study, we develop a method for generating murine kidney organoids with improved higher-order structure, through stages using chimaeras of ex-fetu and PSC-derived cells to a system that works entirely from embryonic stem cells. These organoids have nephrons organised around a single ureteric bud tree and also make vessels, with the endothelial network approaching podocytes.

Single-cell RNA sequencing reveals differential cell cycle activity in key cell populations during nephrogenesis

The kidney is a complex organ composed of more than 30 terminally differentiated cell types that all are required to perform its numerous homeostatic functions. Defects in kidney development are a significant cause of chronic kidney disease in children, which can lead to kidney failure that can only be treated by transplant or dialysis. A better understanding of molecular mechanisms that drive kidney development is important for designing strategies to enhance renal repair and regeneration. In this study, we profiled gene expression in the developing mouse kidney at embryonic day 14.5 at single-cell resolution. Consistent with previous studies, clusters with distinct transcriptional signatures clearly identify major compartments and cell types of the developing kidney. Cell cycle activity distinguishes between the "primed" and "self-renewing" sub-populations of nephron progenitors, with increased expression of the cell cycle-related genes Birc5, Cdca3, Smc2 and Smc4 in "primed" nephron progenitors. In addition, augmented expression of cell cycle related genes Birc5, Cks2, Ccnb1, Ccnd1 and Tuba1a/b was detected in immature distal tubules, suggesting cell cycle regulation may be required for early events of nephron patterning and tubular fusion between the distal nephron and collecting duct epithelia.

Kctd15 regulates nephron segment development by repressing Tfap2a activity

A functional vertebrate kidney relies on structural units called nephrons, which are epithelial tubules with a sequence of segments each expressing a distinct repertoire of solute transporters. The transcriptiona`l codes driving regional specification, solute transporter program activation and terminal differentiation of segment populations remain poorly understood. Here, we demonstrate that the KCTD15 paralogs kctd15a and kctd15b function in concert to restrict distal early (DE)/thick ascending limb (TAL) segment lineage assignment in the developing zebrafish pronephros by repressing Tfap2a activity. During renal ontogeny, expression of these factors colocalized with tfap2a in distal tubule precursors. kctd15a/b loss primed nephron cells to adopt distal fates by driving slc12a1, kcnj1a.1 and stc1 expression. These phenotypes were the result of Tfap2a hyperactivity, where kctd15a/b-deficient embryos exhibited increased abundance of this transcription factor. Interestingly, tfap2a reciprocally promoted kctd15a and kctd15b transcription, unveiling a circuit of autoregulation operating in nephron progenitors. Concomitant kctd15b knockdown with tfap2a overexpression further expanded the DE population. Our study reveals that a transcription factor-repressor feedback module employs tight regulation of Tfap2a and Kctd15 kinetics to control nephron segment fate choice and differentiation during kidney development.