Stem cell therapy for haematological disorders is a longstanding successful procedure. Over the past few years it has been realised that stem cells originate from tissues other than bone marrow and it is generally accepted that these cells and products derived from them offer the possibility of new treatment for many diverse conditions. Currently the relative therapeutic benefits of stem cells obtained from embryos, fetal cord blood, bone marrow or other tissues have yet to be determined. A common problem for all these options is the potential rejection due to incompatibility between the donor and patient. Nuclear reprogramming may be the solution.
It is possible to reprogram a somatic nucleus by transferring it into an enucleated egg. This construct is then activated and embryonic stem cells isolated from the resulting blastocyst. Products derived from these ES cells would be compatible with the patient who donates the nucleus and thus not be rejected. This technique is known as therapeutic cloning. Consequently the major burden to the development of this promising new medical treatment is the ethical, political and regulatory hurdles that need to be overcome.
The UK has led the world by legislating to permit nuclear programming. The approval is associated with rigorous regulation and this itself is a significant barrier to development. In particular the source of eggs donors is controversial and is the major rate limiting step in the research at present.
Evidence now suggests that the eggs with competence to reprogram that the nucleus are those which are most difficult to obtain i.e. those used immediately after retrieval from the donor. New strategies are being developed to increase the supply of these eggs.