Conclusion

The study was successful in determining that the immunosuppressant drug tacrolimus, in concentrations that are currently used for transplant patients, has no visible detrimental affects on stem cell proliferation, viability or the number of cells that differentiate after exposure. Most of the stem cells differentiated into immature neurons. No cells differentiated into astrocytes or dopaminergic neurons. Whether tacrolimus caused the specific differentiation path to be taken is a question that requires further study.

The immunosuppressant drug cyclosporin, studied originally in concentrations that are currently used following transplants, was found to prevent cells from proliferating. The concentrations were lowered significantly, but viability remained low. Following exposure to the drug, the stem cells differentiated into immature neurons, and Ig staining was negative for both astrocytes and dopaminergic neurons. Fewer cells differentiated and there was low cell viability.

As background research confirmed, in the case of stem cell transplants, tacrolimus has fewer side effects and is a better option for immunosuppression. Cyclosporin in any concentration has negative effects on stem cell proliferation and differentiation. Although the drug works well as an immunosuppressant, its negative effects on the transplant seriously diminishes its usefulness.

Relevant Application:

It has been determined that the current literature stating that tacrolimus has fewer side effects than cyclosporin is true. It is much more potent than cyclosporin as well, and should be considered as an alternative to this widely used drug. Through our experimentation, we have also discovered that neither cyclosporin nor tacrolimus are harmful to undifferentiated stem cells provided they are administered in the correct doses. Since they do not seem to aid neural stem cells to differentiate into dopaminergic cells, they may not be very beneficial in the treatment of Parkinson’s disease when cells are transplanted before differentiation, and in this case other drugs should be studied for consideration.

Since this experiment was carried out in vitro, there are many other variables which must be considered if the results achieved are to apply in vivo. When cyclosporin is administered to rats after an experimental neural stem cell transplant, the drug is injected into the animal’s stomach. Similarly, when taken by a human patient, the drug does not enter directly into the brain but is either taken orally or injected into the blood stream. For these reasons, the precise quantity of the drug that reaches the brain is unknown, though the doses administered are regulated. The brain tissue concentration of the drugs in rats should be compared to the concentrations administered to determine how much of the drug actually reaches the brain.

Although these immunosuppressive agents are mainly used to prevent rejection, based on our results they may be beneficial in manipulating neural stem cells to differentiate into neurons. The manipulation of differentiation opens up a whole new realm of possibilities in the area of transplantation. This project is a pilot-project for further research which will be conducted at the Dalhousie Brain Lab in the Tupper Building in further studying this potential of cyclosporin and tacrolimus.