The kidney is an essential organ that eliminates waste from the human body by processing the blood supplied to it and removing waste via the production of urine. According to the United States Renal Data Service 2015 Annual Data Report, more than 661,000 Americans have kidney failure. Of these, 468,000 individuals are on dialysis, and roughly 193,000 live with a functioning kidney transplant. Unfortunately, kidney transplants are in short supply; thus, treatments for kidney disease are sorely needed.
A recent study led by researchers at the University of Manchester generated functional nephrons, the structural and functional unit of the kidney, from human pluripotent stem cells, marking a significant advance in the field of organ regeneration and tissue engineering.
First, three genetically distinct human pluripotent stem cell lines were reproducibly differentiated to kidney precursors that underwent rudimentary morphogenesis 2D in vitro cell culture. Next, the authors generated 3D organoids with more mature kidney structures. However, the glomerular structures that were formed were immature and not identical to mature glomeruli in vivo. Located at the beginning of a nephron, the glomerulus is a network of capillaries called tufts that are involved in the filtration of blood, but the engineered glomerular tufts lacked capillaries.
While the 3D organoids modestly advanced kidney morphogenesis beyond traditional 2D cell culture, the authors found that implanting differentiating cells from 2D cultures in vivo substantially improved their maturity. After twelve and nineteen days of 2D differentiation in vitro, kidney progenitors with lentiviral-transduced reporter genes were injected into immunodeficient mice. After 3 months, the kidney progenitors formed organ-like masses detectable by bioluminescence imaging. The glomeruli contained human capillaries with red blood cells, confirming their connection to the blood supply. Tubules, podocytes, mesangial cells, and other critical nephron features were also observed.
To investigate whether glomerulus filtration was functional, mice were intravenously administered with fluorescently-labeled dextran, introducing this molecule into the circulatory system. Later, the dextran was successfully detected in the tubules, indicating that the glomerulus could successfully filter this molecule from the blood supply.
The study demonstrates methods to produce kidney precursors from human pluripotent stem cells and the successful formation of functioning nephrons in vivo. These advances are critical steps in tissue engineering for treatment kidney diseases.
The article, titled “Generation of Functioning Nephrons by Implanting Human Pluripotent Stem Cell-Derived Kidney Progenitors,” was published in Stem Cell Reports.
To learn more about tissue engineering, please join Akron on March 6, 2018 for our webinar, “Tissue Engineering: A Technical and Regulatory Discussion.”