Sep 15 2014

Stem Cell Transplant First

NeurologicaBlog is very meta. I like to not only communicate science, but explore how best to communicate science, including thinking about how to communicate the need to think about thinking. (Cue the endless meta-regression.)

For example, there is often much to criticize about how science news is reported in the general media. Part of the problem is that science mostly advances by accumulating baby steps. ┬áBaby steps, however, don’t always make for compelling headlines, and so every advance becomes a “breakthrough,” every mystery has scientists “baffled,” and every study may some day lead to the cure for cancer, rid us of the common cold, or produce a piece of technology similar to that found in popular science fiction.

Part of the challenge of being a skeptical science communicator is to convey simultaneously the deserved awe of cool science, including the potential implications of genuine advances, while also discussing the need for caution in interpreting results, and essentially throwing a wet blanket on premature hype. It can be a delicate balancing act.

I had all this in mind when I approached the main topic of today’s post – a rather exciting and anticipated advance in stem-cell technology. Japanese researchers have created a sheet of retinal epithelial cells from a patient’s own skin cells. First they had to induce pulripotency on the skin cells, which essentially turns them into stem cells (iPS cells). Then they had to coax these created stem cells into becoming the desired cell type which in this case is retinal epithelial cells.

The researchers have just surgically implanted this sheet of cells into the eye of the patient from whom the skin cells were taken – she is getting a transplant of her own tissue. She suffers from macular degeneration, a common cause of loss of vision resulting from loss of the retinal epithelial cells. The surgery is not expected to restore the patient’s lost vision, but it is hoped that the transplanted tissue may decrease further degeneration of the retina.

Why is this such an exciting advance? It is just a baby step, to be sure, but it is a noteworthy milestone and a good time to review where we are with stem cell technology.

Stem cells are any cell population that can differentiate into various mature cell types. There are many types of stem cells that are partially differentiated and serve as a source of new cells. For example, bone marrow contains blood stem cells that can differentiate into the various types of blood cells. A stem cell that can turn into many different types of cells is called pluripotent.

Embryonic stem cells are totipotent, meaning they can potentially turn into any cell type in the body. This is why they are so useful for research and have such promise therapeutically. They remain controversial, however, because they are harvested from embryos.

In the last decade, however, researchers have discovered how to induce at least pluripotency. By making just a few genetic changes, they can take adult derived skin cells and revert them to pluripotent stem cells. These are not as useful as embryonic stem cells, but they are still quite useful and have the advantage of not being controversial.

Stem cells derived from adult cells also have a huge potential therapeutic advantage – if you can induce stem cells from a recipient’s own cells, then you can ultimately give them a transplant of their own cells. This could eliminate the problem of rejection (which results from the immune system of the recipient recognizing the transplanted cells as foreign).

This, then, is the “holy grail” of stem cell therapeutics. Imagine a day when doctors can take a sampling of your skin cells or a cheek swab to gather a few epithelial cells, then culture those cells and revert them to a pluripotent state. They could then essentially have a vat of your own stem cells, from which they can make cells of any type they wish.

Such stem cells would have multiple possible uses. One use would be similar to the recent report – forming a tissue or even a full organ for transplant into the patient. A patient could theoretically receive an implant of their own kidney, eliminating the need for a donor, ensuring organ availability, and further eliminating the need for anti-rejection drugs. This would certainly be a game-changer for organ transplantation. The same could be done for blood transfusions, bone marrow transplant, skin grafts, or any organ that could be grown from the stem cells.

A second application is to inject the engineered stem cells into the body where they will repair or replace tissue in the body. Rather than growing a heart and then transplanting into a patient, therefore, you could inject cardiac stem cells into the existing heart, and those cells will form cardiac cells that will repair a damaged or weakened heart. There are already preliminary clinical trials of such treatments. Similarly, neural stem cells could be injected into a brain following a stroke, and those cells could repair the damaged brain tissue.

A third potential application is using stem cells not to directly replace damaged or lost tissue, but to support it in order to cure or mitigate the effects of disease. An engineered stem cell could be designed to deliver a steady dose of a drug, hormone, neurotransmitter, or other desired chemical. These nurse stem cells could keep a cell population from dying, preventing the progression of disease. Or they might just serve as an excellent drug delivery system.

It’s difficult to overstate the potential of stem cells (pun intended) – fully realized, stem cell technology could be an incredibly powerful therapeutic tool. This is exactly why there is so much hype surrounding stem cells.

But we also have to clearly state the reasons for caution. While the technology is advancing, this is very complex technology with many hurdles to overcome. The applications I listed above are still very experimental. One major potential problem is that transplanted stem cells might have the potential to form tumors and cancer. The reason our bodies are not naturally full of stem cells allowing us to regenerate any damage, disease, or degeneration is because of the neoplastic potential of stem cells. We evolved to get rid of them as soon as they were not absolutely necessary, to minimize the risk of cancer.

Further, it remains to be seen if adult-derived induced pluripotent stem cells will actually eliminate the possibility of rejection. Perhaps the process by which cells are made pluripotent and then made to differentiate into the desired cell type will also change them enough to still trigger rejection to some degree. Hopefully not, but until we do the research we won’t know for sure.

All this, of course, is on top of the basic technology of knowing how to get stem cells to become the exact kind of cell that we want. Creating organs is even more challenging – we need more than a sheet or clump of the desired cell type, we need to construct a three-dimensional complex structure. Researchers have been trying to do this using scaffolding, which is basically a donated organ denuded of its own cells. Results so far have been encouraging, but a long way away from transplantable organs.

Premature hype can be a problem. It created unrealistic expectations in the public, who then might become discouraged when the promised applications are not being realized. Perhaps worse, however, it can make some people vulnerable to exploitation. There are essentially phony stem cell clinics popping up around the world (in countries with poor regulation) promising stem cell treatments long before the technology actually exists.


Stem cells are a very exciting technology that has the potential to transform modern medicine. The current study represents a noteworthy milestone – the first implantation of tissue from induced pluripotent stem cells taken from the tissue recipient. It’s encouraging to see the technology continuing to advance.

We have to keep this one case and the potential for stem cells in perspective, however. Science advances by baby steps, and there are many incremental advances between where we are now and the dramatic stem cell therapeutics we hope to have one day. The applications we are waiting for will likely take longer than the general public realizes (or hopes).

Like many technologies, stem cells are likely to be disappointing in the short term, but then exceed our expectations in the long term.

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