By taking human pluripotent stem cells that are derived from skin cells and adding small molecules and growth factors, nephrology researchers at Brigham and Women’s Hospital (BWH) have created kidney organoids - miniature models in a dish that replicate many of the functions of human kidneys. These models provide a platform for intensive research into both organ growth and the response of renal tissues to injury, fibrosis, and drug therapies.
“This allows us to model disease processes with actual human tissue in a personalized way. This also represents important progress toward replacement of diseased kidney tissue. The investigators have also used advanced genome editing techniques to introduce mutations that are present in humans so that they can understand the cellular effects of those mutations that lead to the disease. It will also be possible to correct mutations that are present in the cells, differentiate them, and show what the pattern is with the mutation corrected and uncorrected. This will allow for better understanding of disease and lead to new therapies to treat these diseases,” explained Joseph V. Bonventre, MD, PhD, Chief of the Renal Division and Director of the Division of Bioengineering at BWH, who led the effort.
“The technique facilitates screening for the effects of various therapeutic compounds and combinations on renal tissues,” he added. “It also enables the determination of whether new agents are toxic to the kidney.”
The organoids are also an important stepping stone toward the goal of using human pluripotent stem-cell derived nephron progenitor cells (NPCs) placed on tissue scaffolds to generate full-sized, fully functioning organs that could one day make both kidney transplants and renal dialysis obsolete, according to Ryuji Morizane, PhD, MD, an Associate Biologist in the Renal Division at BWH. “Currently, we are applying these nephron organoids to the modeling of a number of human kidney diseases,” Dr. Morizane said.
BWH investigators have shown that NPCs can be manipulated through an intricate series of steps to differentiate into structures that mimic the fundamental unit of filtration and regulation of the body’s blood composition, the nephron. The nephron-like structures generated by this process contain populations of cells with important characteristics of functional human kidneys, including podocytes and proximal and distal tubules.
Furthermore, the investigators have demonstrated that the tubules are capable of accumulating and transporting chemicals and that they respond to nephrotoxic injury with cisplatin or gentamicin by expressing kidney injury molecule-1 (KIM-1), a biomarker for renal proximal tubule injury in humans. KIM-1, discovered by researchers in the Renal Division at BWH, is widely used by the pharmaceutical industry in drug development.
Using the CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 genome editing system, the BWH investigators mutated the gene encoding for podocalyxin, resulting in junctional reorganization of podocyte-like cells, thereby mimicking an underlying mechanism of epithelial injury in glomerulonephritis.
In a separate experiment, they used genetic editing to mutate either of the polycystic kidney disease genes PKD1 or PKD2, which resulted in induction of cyst formation in kidney tubules, a hallmark of the genetic disorder. This will provide a new system to test drugs for treatment of polycystic kidney disease.
Apart from providing insights into specific disease states, their research has important implications for the study of abnormal kidney development and function, explained Albert Q. Lam, MD, an Associate Physician in the Renal Division at BWH.
“I’m interested in using these kidney organoids to study normal and abnormal human kidney development. Because of the way these organoids form, they essentially recapitulate the stage of nephron formation in vivo, and we believe that we can use this as a tool to be able to study development of congenital kidney disease in a dish,” Dr. Lam said.
Dr. Lam, Dr. Morizane, and colleagues are currently working to generate induced pluripotent stem (iPS) cells from patients with a number of different types of genetic developmental kidney abnormalities, in order to model and better understand the mechanisms and possible methods of prevention or amelioration of such defects.
“Another of our projects is to use engineered printed structures or de-cellularized tissue scaffolds upon which nephron progenitor cells can be placed and then differentiate the cells into functional organized kidney structures,” Dr. Morizane explained.
“Ultimately, such an approach might be used to create full-sized, fully functioning kidneys, which might one day replace dialysis or transplantation,” Dr. Bonventre said. “The burden of kidney disease is so large and the scarcity of organs for transplantation so great that we must be bold in our approaches to turn these recent advances into therapies to help our patients with this devastating disease.”
These studies were funded by grants from the National Institutes of Health, the American Heart Association, the Harvard Stem Cell Institute, the National Kidney Foundation, the Uehara Memorial Foundation, and the Japan Society for the Promotion of Science.
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