Adult stem cells have been saving many lives for decades. However, the question remains open as to whether they are also suitable for new applications.
Bone marrow and skin transplants are so successful because they use the regenerative powers of adult stem cells. But the capabilities of these cells are limited, and moreover their numbers are usually rather small. Can adult stem cells keep up with their pluripotent cousins in the future?
Pros and cons are compiled here
1. Therapy with adult stem cells is proven and safe
Bone marrow transplantation has been used in hospitals for decades; doctors can draw on a wealth of experience. Tolerability is usually very good, and serious complications are rare – except for the problem of rejection reactions (more under point 2). It can be assumed that no serious side effects occur with other adult stem cells either.
2. Own stem cells can be used for therapy
When it comes to questions of tolerability, own stem cells are the best choice for therapies: They are not rejected by the immune system, and patients are spared lifelong treatment with drugs. The risk of spreading infections or tumours can also be eliminated.
3. Adult stem cells are not ethically controversial
The harvesting of adult stem cells does not cause controversy – no one objects to adults voluntarily donating tissue. In a society that seeks consensus, this is an important plus point.
But what is usually concealed: Especially in the treatment of brain diseases, stem cells are isolated from aborted foetuses – adult and foetal stem cells are often not strictly distinguished. And when abortion comes into play, the potential for conflict is hardly less than with embryonic stem cells.
1. Adult stem cells are not suitable for all body tissues
The number of adult stem cells is usually negligible, especially in slow-growing organs. Since adult stem cells are difficult to multiply in the laboratory, there are usually too few cells available for therapy. Recourse to stem cells from aborted foetuses could partially solve the quantity problem, but spark an ethical debate with an outcome that is difficult to predict.
2. Adult stem cells are difficult to obtain
Stem cells are deeply embedded in body tissues. If you want to isolate them, you have to destroy the organ – certainly not the goal of medical treatment. Only stem cells from bone marrow, blood and skin are easy to obtain, but they are also usually already committed to blood and skin cells. Mesenchymal stem cells can still develop into other tissues and first studies are trying to use this for medicine. But the chances of success can hardly be predicted at the moment.
3. Genetic damage accumulates in adult stem cells
Stem cells also age. The genetic material of the cells is constantly attacked by aggressive substances and not every damage can be repaired. Therefore, old stem cells are less functional than young ones, and the risk of cancer also increases significantly. An optimal donor would therefore be as young as possible, but recruiting children as donors is probably neither desirable nor enforceable.
Adult stem cells from bone marrow and skin have become an indispensable part of medicine. Recently, niche applications for eye injuries, Crohn’s disease and transplant rejection have been added. But beyond that, there is stagnation: great hopes for heart attacks, for example, have been treading water for years.
Moreover, adult stem cells are usually small in number and well hidden in the body. They cannot compete with pluripotent stem cells in terms of growth and developmental capacity. Embryonic cells carry a heavy ethical burden, but the future could belong to the similarly powerful iPS cells.