Renal disease threatens approximately 2 million Canadians nationwide. The Kidney Foundation of Canada estimates that each day, an average of 14 Canadians learn that their kidneys have failed.
Most diseases of the kidneys affect the nephrons, the functional unit of the kidney. Nephrons fulfill a variety of functions including regulating blood volume, filtering the blood, and reabsorbing nutrients. Renal diseases often manifest as a loss of kidney function over time, because as the nephrons become damaged, their ability to eliminate wastes and regulate fluids is reduced.
In the past, studies focusing on kidney repair have used hematopoietic stem cells or embryonic stem cells due to the lack of an identified adult kidney stem cell population. Kidney regeneration is limited in adult mammals. Humans for example, are able to repair damaged nephrons somewhat, but cannot regenerate new ones. In contrast, many teleost fishes show remarkable regenerative abilities and are able to produce new nephrons throughout their lives If a fish nephron stem cell could be found, it would pave the way for the identification or creation of equivalent cells in humans. A recent paper in the journal Nature explored this issue and identified a possible renal progenitor cell in zebrafish.
Through a series of transplantation experiments, researchers were able to identify a population of long-lived cells which had the ability to self-renew –- the hallmark of stem cells. When these cells were fluorescently tagged with either red or green and allowed to develop, the nephrons that resulted were a mix of red and green as well. This seems to indicate that a single progenitor cell does not become a single nephron, but rather that aggregates of progenitor cells contribute to the development of each nephron.
The authors speculate that if the mammalian kidney contained equivalent cells, they would most likely be dormant in adults. Further study into the zebrafish system may eventually identify a method of reactivating or engineering the similar cells in human adults, leading to better treatments for chronic kidney disease.
Zebrafish are already used in other areas of stem cell research, such as hematopoietic stem cell development, cardiac repair, and retinal regeneration for age-related macular degeneration and retinal injury.