Stem cells originally came from two main sources, embryonic stem cells and adult tissue which contain adult stem cells.
This is an area of ethical debate because scientists can generate human embryonic stem cells from embryos created during in vitro fertilization. These cells can divide in cell culture to generate millions of potential cells for transplantation. The core of the ethical debate centers on the discussion of when life begins and the ethics of destroying human embryos. Amongst the many aspects of this debate are the controversies surrounding the researchers themselves and whether they are complicit in the destruction of embryos.
Adult stem cells are also a potential source of transplant material and these can be found in many organs including the pancreas. They are unspecialized cells thought to be capable of differentiating into cells involved in damage repair in that particular tissue. Their capacity to divide in the laboratory is quite limited and this makes the generation of large quantities of stem cells difficult. There are however very successful although limited programmes, the bone marrow transplants for hematology based diseases being the best example. Furthermore mesenchymal stem cells can now be harvested and used to differentiate into cells for bone, cartilage and fat based transplants.
Scientists have more recently been able to take adult cells and genetically reprogramming them into what are called
induced pluripotent stem cells (iPSC’s)
. These behave and grow like embryonic stem cells. This eliminates the need to derive cellular material from a developing embryo and provides a source of cells with the potential to develop a tissue specific function. Promising areas include the treatment of Parkinson’s disease or macular degeneration but making a viable insulin producing pancreatic beta cell for human use has so far proved elusive.
For any patient exploring the idea that stem cell transplants could eventually provide a cure for diabetes the main message at the moment is beware of the potential dangers of over hype. The main strength of stem cell research is that it represents exciting science. The concepts are only promising for the future of medicine. They may prove to be too toxic, that will probably turn out to represent the main weakness. However, new developments such as stem cells to repair the damaged heart are beginning to emerge but we need time to assess the risks.
There are currently many potential barriers. The generation of sufficient quality stem cells for a transplant and their differentiation into insulin secreting cells is still a scientific discipline. This area is in its infancy even in the laboratory, curing diabetes is not a current clinical reality.
The science behind the survival of the stem cells after transplant and the safety associated with long-term integration into the recipient’s body needs much more study in order to overcome what are significant technical hurdles. We really don’t know at this stage if stem cell transplants will function appropriately for the duration of the patient’s life. We don’t know if they will turn out to be safe