LIMITS OF CELL THERAPY

Among the many avenues in use to assure the health of individuals, cell therapy is probably the most promising avenue. This explains the many examples of cell uses in research projects around the world. In fact, cell therapy has been present in our living environments for a very long time. For more than 50 years, it has been used in particular to treat hematological cancers and other disorders of the blood system.

The first bone marrow transplant was performed by Dr. E. Donnall Thomas in New York in 1956. The patient with leukemia then received a bone marrow transplant from his identical twin, who was healthy. At the same time, the first transplants were performed in France. The practice then gradually spread elsewhere in the world. In 2009, more than 58,000 blood stem cell transplants were performed worldwide. In Quebec, approximately 500 stem cell transplants are performed annually. Differentiated cells are also transplanted to fight cancer cells or to fight infections after a stem cell transplant.

The Maisonneuve-Rosemont Hospital (HMR) proudly highlighted last fall, the first transplant performed within it, 30 years ago. This intervention was at the time the work of pioneers in the field, hematologists Yvette Bonny, Claude Perreault, Jacques Boileau and Michel Lacombe. This application of cell therapy as performed in the cell therapy laboratory at Maisonneuve-Rosemont Hospital, uses blood stem cells also called hematopoietic stem cells. These are the source of all blood cells. They are present in the bone marrow. The first transplants therefore consisted of puncturing the bones and removing them from the bone marrow (spinal aspirations).

This procedure performed in the operating room is long, mobilizes a large medical team and requires the patient’s general anesthesia. In the 1990s, it became possible to use a drug that causes stem cells to detach from the bone marrow, relocate and circulate in the blood. This is called “stem cell mobilization”. The stem cell collection is then done by apheresis technique. This technique involves enriching the blood circulating outside the body to obtain a concentrate of stem cells. Apheresis is performed by a nurse and does not require anesthesia. Finally, blood stem cells are also present in the umbilical cord blood. They are collected at the time of delivery and are frozen, then stored until a need is expressed.

To date, the use of cord blood is limited and more common in children due to the small number of stem cells required for transplantation, but its applications are increasing. For transplantation in adults, the mobilized cells from the blood and obtained by apheresis are mainly used. Less than 10% of transplants are performed with cells taken by aspiration of bone marrow and 1% from cord blood.

Some current research projects in the world

1. Repair of the heart muscle following an infartus
2. Repair of articular cartilage following trauma
3. Regeneration of the cornea in macular degeneration
4. Treatment of degenerative diseases of the nervous system
5. Treatment of diabetes
6. Skin replacement
7. Repair of vessels
8. Bone grafting or consolidation to counter bone loss
9. Alternative to liver transplant
10. Fight against cancer
11. Reconstruction of the blood system

Depending on the disease, its stage of development and the patient’s condition, several approaches can be considered to treat blood cancer or a dysfunction of the blood system. When a transplant is necessary, it can be autologous or allogenic. In the case of an autologous or autograft transplant, the patient receives his own stem cells after his cancer cells have been destroyed. In other circumstances, it is necessary to use a healthy donor for the transplant.

This is called an allogeneic transplant or an allograft. If a compatible donor related to the patient is available, the patient will be the first choice. However, since contemporary families have fewer children, transplants involving a compatible sibling are not always possible. Another solution is a transplant with an unrelated compatible donor. In this case, the existence of a donor compatible with the patient in international banks is verified. When there is no unrelated donor, it is also possible to consider a cord blood transplant.

However, the limit of this type of transplant often lies in the number of cells available. The majority of cord blood transplants are currently performed in children. When standard protocols no longer meet the patient’s needs, manipulation of the grafts is often necessary, and it is at this point that clinical studies are required to provide innovative solutions.