Gene therapy remains a fairly new and still experimental procedure for the treatment of disease. In addition stem cells are still a relatively new concept and remain a confusing and complicated technology that much of the public struggles to understand. The potential for stem cells to be used in gene therapies is however, a valid one that has important ramifications for treating a range of diseases, many of which currently have no cure.
Understanding Gene Therapy
Gene therapy involves inserting genes into a person’s cells with the aim of providing treatment for a particular disease. At a very simplistic level, gene therapy is the use of a person’s own cells to provide a therapeutic effect. In most types of gene therapy, a healthy and normal gene is inserted into a cell or tissue to replace a gene that is abnormal and thus, produces disease. Delivery of the gene can be difficult and viruses are commonly used to ‘carry’ the normal gene into the cell.
Because a virus places its own genetic material into the host as part of its own replication cycle, it is an effective way to deliver the normal gene into the cell, thereby replacing the abnormal one. It may seem odd to imagine a virus – which we associate with poor health and disease – as a delivery mechanism for a gene, but it’s quite an interesting and successful concept. The disease causing genes of the virus are first removed and then the desired normal gene for the host is introduced. This allows the virus to ‘infect’ the host’s cell with the normal gene, which then replaces the abnormal one, assuming the procedure works as intended.
Using Stem Cells for Gene Therapy
There are many reasons why stem cells hold great potential for successful use in gene therapies. Stem cells have the ability to self-renew, which means that the need to provide repeated administrations of gene therapy can be reduced or possibly even eliminated. In particular, hematopoietic stem cells are an ideal choice because they can easily be removed from the blood, bone marrow or umbilical cord. They are not as difficult to identify and isolate as other stem cells and can be more readily coaxed to differentiate in a laboratory setting before injection into the patient.
Other stem cells that suggest promise for gene therapy include myoblasts and neural stem cells. Researchers have found that myoblasts work particularly well for injection into muscle tissue because they readily join with other muscle fibers and therefore integrate well into the network of muscle fibers.
Neural stem cells appear to hold potential for treating gliomas, which are a difficult type of brain tumour to treat. When a patient suffers from a glioma, the tumour cells attack the healthy brain tissue and travel throughout the brain. In studies thus far, scientists have been able to take neural stem cells and then genetically modify them to create a protein that activates a precursor drug that is not toxic to one that destroys tumour cells. After injecting these genetically modified stem cells into mice who had human-derived gliomas, there was a significant reduction in tumour size within only two weeks.
Research involving embryonic stem cells and gene therapy rather than the previously mentioned adult stem cells is another area that is currently under investigation. Because embryonic stem cells have a greater potential for self renewal as opposed to adult stem cells, repeated administrations of gene therapy are less likely to be necessary. This means that over the long-term, embryonic stem cells could provide better maintenance of therapeutic effects in comparison with adult stem cells.
Overall, there are benefits and challenges to both embryonic and adult stem cell use in gene therapies. Both sources of stem cells, however, hold potential for treating diseases in this manner and the continuation of research will hopefully yield tangible therapies one day soon.