Stems Cells in Kidney Disease-The Renal Stem Cell

Diagram of stem cell division and differentiation. A - stem cell; B - progenitor cell; C - differentiated cell; 1 - symmetric stem cell division; 2 - asymmetric stem cell division; 3 - progenitor division; 4 - terminal differentiation (Photo credit: Wikipedia)

One of the challenges of medicine and the hope of all those who turn to practitioners of the art of medicine is the search for a cure, something that makes you whole again. It is for this reason that research surrounding stem cells and the potential therapies to be derived from stem cells inspires strong emotional responses from lay persons as well as experienced research scientists. The fact is that we have never been closer than we are now to being able to cure many types of diseases that were previously considered chronic. The converse however is that much work needs to be done, some of that work being fundamental basic research into the nature of cell replication and the mechanism of determination of cell roles that make one cell a stem cell and another cell not.

The kidney has been regarded as an organ incapable of true regeneration. This label has resulted in the doctrine that renal diseases are never truly totally reversible. In fact to support this argument we see where researchers have now made it known that child hood nephrotic syndrome secondary to minimal change disease, once considered one of the most reversible types of renal damage may alter the kidney for life in ways that we do not understand, predisposing for further kidney disease in the future. We note with some trepidation research that shows that patients hospitalized with acute renal failure, even with recovery of renal function have an unexpectedly high rate of progression to require dialysis in the years ahead. Is anything truly acute in kidney disease anymore?

When we speak to patients about their condition we are trained to avoid mentioning the word cure or reversal and lean more towards statements such as slow and retard progression of kidney disease. The impression we give is that chronic kidney disease tends to be an ominous relentless process that all of our technology and treatment methods combined will only slow.

This is why the promise of stem cell therapy for the kidney becomes so important. This explains why people will fly across the globe spending large sums of money for pseudoscientific therapy. It is because the proponents of pseudoscientific stem cell therapies make it their business to use the words that we are told not to, "cure", "reverses all damage", "regenerate", to name a few.

It therefore becomes vital to separate the pseudoscience from the science. That is exactly what Little and Bertram's article in the Journal of The American Society of Nephrology seeks to do while lighting the way for future research. Unfortunately the people in need of this knowledge are most unlikely to ever read it.

So where is the kidney stem cell, the one true cell that can become all other parts of the kidney. The cell that by itself if necessary will regrow the entire organ. Such a cell sadly has never been found and is unlikely to exist anywhere outside of science fiction. What does exist however is a cell with some classic features of a stem cell in that it may divide indefinately and has not been predetermined to become one specific type of cell only.

The hope is that cells of this nature will still be useful in kidney disease either by being able to replace diseased cells with new healthy cells or by just being in the same vicinity of diseased cells somehow produce chemicals that stimulate the diseased cells to shrug off the damage and get back to doing their job. One area of the kidney where the process of regeneration does occur is the tubule of the kidney. One of the most recognizable renal diseases and most common cause of acute renal failure is ATN, acute tubular necrosis. In this disease cells within the tubules of the kidney spontaneously die falling into the tubule and blocking them in the process. This causes renal failure, however in time brand new cells grow and replace the cells lost and the tubule is as good as new.

Diseases and conditions where stem cell treatment is promising or emerging. (See Wikipedia:Stem cell#Treatments). Bone marrow transplantation is, as of 2009, the only established use of stem cells. Model: Mikael Häggström. To discuss image, please see Template talk:Häggström diagrams (Photo credit: Wikipedia)

Where do these new cells come from? do they travel from the bone marrow from a stem cell source located there that produces the exact kind of tubule cell needed? Are they derived from the border of the glomerulus and the tubule implying a source of cells similar to stem cells within the kidney itself. Recently Appel et. al. have suggested the latter is actually the case. This may explain why the kidney cannot regenerate the tubule too many times. If this source or pool of "stem like" cells are used up with repeated acute diseases of the kidney then the kidney may lose its ability to regenerate. It is even possible that these cells are there to repair some of the natural damage of aging and by forcing them to be used in an episode of ATN we reduce the kidney's resistance to the wear and tear of the aging process.

Stem cell therapy is a very important evolving area of medical science. Understanding stem cells increases our understanding of many areas of medical physiology that had lagged behind the frontier of medicine. It is likely to continue to drive research at a rapid pace based on the perceived light at the end of the tunnel....the ability to use the word cure more readily and frequently.