Therapeutic stem cell cloning uses two methods to try and produce healthy tissue which will not be rejected for people who have diseases ranging from diabetes to Alzheimer’s.

The first step is to produce cloned cells from the affected person. The nucleus is removed from a normal body cell of the patient. It is transferred to a unfertilised human ovum which has had its original nucleus removed. After a mild electric shock the new pre-embryo cell starts to develop, producing a collection of embryonic cells with the same genetic information as the patient. This is a cloned human embryo, but it has been formed with no intention to clone a whole human being. The embryo is not allowed to grow beyond 14 days (after which the nervous system begins to develop). Scientists working with embryos have to be licensed by the Human Fertilisation and Embryology Authority.

The embryo produced in this way is simply a source of stem cells with DNA which matches the patient perfectly. The idea is that stem cells will be harvested from the embryo, hence destroying it. The embryonic stem cells will then be cultured and directed to form the needed tissue, whether that is new brain cells, heart muscle, insulin producing pancreas cells or whatever. These potentially healing cells will then be transferred to the patient, where they can do their job without any fear of rejection.

Just like the work on embryonic stem cells and adult stem cells, therapeutic stem cell cloning is still in the very early stages of development. There are many technical barriers still to be overcome – getting the cloned embryo to develop, successfully culturing the cells and finding ways to direct the differentiation of the stem cells into the required adult tissue. There are many ethical considerations too, from producing cloned embryos to using them purely as a source of stem cells. The technique of therapeutic stem cell cloning still has a long way to go before it is a widely used and accepted technique in hospitals everywhere – but its medical potential is enormous.