Spray on some stem cells and grow your own skin!
Ok. Bits of this film are a little grim, but it’s worth it. Well, go on then!
Amazing right? And yes, it’s real! I have to admit I double-checked the date when my friend forwarded me the National Geographic link, but April first it was not. Researchers at the University of Pittsburg’s McGowan Institute for Regenerative Medicine have made the skin cell spray gun a very real, very effective treatment for burn victims.
So how does it work? At its core, this treatment relies on the unique properties of stem cells, so that’s where I’ll begin.
Stem cells have fascinated biologists for years. They are unique amongst all other cells of the body in two ways; their capacity for self-renewal, and their ability to give rise to many different cell types.
Embryonic stem cells, which frequently (and controversially) make the news, are derived from a developing fetus. They are the ultimate in stem cell-iness because they have the potential to direct the development of an entire organism. This means that they contain all the information need to make muscles, nerves, eyes etc. And naturally this pluripotency (from the Latin pluri meaning many, and potency or potential) seemed like a fantastic quality for biologist to understand. Not only were there fundamental developmental principles to be learned, the medical applications were endless. However, glaring ethical issues arose regarding the taking of a life to save a life (that I won’t get into here) that have resulted in the stringent regulation of embryonic stem cell research.
And so researchers turned to adult stem cells. While adult stem cells are not as versatile as embryonic stem cells, they do have the potential to direct the development of certain cell lineages. For example hematopoietic stem cells, which reside in your bone marrow, can divide asymmetrically into all the different cells of your blood. Similarly, all the different layers of your skin have ancestral skin stem cells.
Research into embryonic stem cells resulted in the identification of certain genes that were expressed in, and required by, stem cells. In 2006, a Japanese group generated the first induced pluripotent stem cells. Since then much work has gone into understanding the potential of these induced stem cells. However due to genetic manipulation and lack of correct genomic imprinting (small chemical modifications in our DNA that are laid down in the egg), induced pluripotent stem cells have the unfortunate ability to become cancerous. As detailed in a recent paper in Cell however, while these cells are not yet ready for the clinic, this should not prevent them from being used in a laboratory setting.
Stem cells as a treatment
Bone marrow transplantation was the first example of a stem cell therapy. In 1959 the French surgeon Georges Mathé treated six nuclear power plant workers who had been so severely irradiated that their hematopoietic stem cell populations had been destroyed. The procedure has since been used with great success in the treatment of leukemia.
As with all transplants, the potential of the host rejecting the donor tissue exists. This rejection occurs because of subtle cellular differences between each and every one of us. Our immune system recognizes these differences as foreign, much as it would any other pathogenic invader, and mounts a formidable defense. With the development of tissue typing procedures and administration of immunosuppressive drugs, transplant rejection has significantly decreased.
By far the best way of avoiding rejection, however, is to transplant the recipient’s own tissue. In certain procedures, such as small areas of skin grafting, such auto-grafting is a viable option. But in others, such as in the case of organ transplantation, it is not. And this is where stem cells can sweep in and save the day.
Tissues in dishes
We have long had the capacity to grow cells in vitro (which literally means “within a glass”). Bacterial cells grow happily in test tubes when provided with simple nutrients and an incubator, as do yeast cells. Mammalian cells are a little more difficult to deal with, but again we have been culturing them in the lab for over a hundred years. All they require is a container to grow in that protects them from infection, liquid media containing essential amino acids and other nutrients, and a warm humid chamber in which to grow.
I am however talking about growing one type of cell at a time. Growing an organized tissue presents a far greater challenge. Not only do the cells have to grow and divide, they have to interact with one another and take on specialized roles within the tissue. Normally in our bodies external forces and small molecules send signals between cells that direct this process. Culturing a tissue in vitro requires a significant understanding of how the tissue forms, and an ability to isolate the stem cells from which the tissue is derived.
In the case of transplantation, the stem cells can be derived from the patient who will receive the cultured tissue, thus removing the chance of complications arising due to donor incompatibility. As you saw in the video, skin grafts have been performed in this way for quite some time, but with variable success.
The skin gun
And this is of course where the genius of the skin gun, and its inventor Joerg C. Gerlach, comes in; it bypasses the need for the in vitro tissue culturing. Skin stem cells that had been destroyed in the burn are replaced, and then the tissue is allowed to heal. As in the case of tissue culture in a lab, these cells require a sterile and nutrient rich environment to thrive. After the initial spraying, the wound is covered with a dressing that contains a synthetic circulatory system that brings nutrients to the infant skin and removes any toxins and waste products.
The speed and effectiveness of this treatment is out of this world. The guy in the video didn’t even have a scar after his treatment. Perhaps the spray gun as a means of stem cell delivery is unique to skin regeneration, but there are a couple of features that should be transferable to other transplants, particularly the ability to enrich a patients own stem cells and re-apply them to damaged tissue. This will likely be advanced from burgeoning knowledge on where adult stem cells reside in our body, in so-called stem cell niches. With skin stem cell therapy now a reality, what will be next? Will we be able to re-grow more complex organs such as kidneys? Or will we be able to harvest healthy stem cells from a niche before a disease such as leukemia becomes debilitating? What do you think?
Bock, C., Kiskinis, E., Verstappen, G., Gu, H., Boulting, G., Smith, Z., Ziller, M., Croft, G., Amoroso, M., & Oakley, D. (2011). Reference Maps of Human ES and iPS Cell Variation Enable High-Throughput Characterization of Pluripotent Cell Lines Cell, 144 (3), 439-452 DOI: 10.1016/j.cell.2010.12.032