Stem Cell Therapy for Thyroid Disease in Cats and Dogs

Questions:
Stem cell therapy is coming into the limelight for animals and humans. I've read of its success treating diabetes, so wonder about the thyroid as well.

Do you have any knowledge of this, or can you point me in a direction to explore? Can stem cell transplantation help cure my older cat with hyperthyroidism? He hates taking the daily methimazole!

My Response:
Stem cells are biological cells found in all multicellular organisms (including humans, dogs, and cats). They are characterized by the ability to renew themselves through mitotic cell division and differentiating into a diverse range of specialized cell types. Stem cells may one day be used to make cells and tissues for therapy of many diseases, including Parkinson's disease, Alzheimer's disease, spinal cord injury, heart disease, diabetes and arthritis (1).

Stem Cells (Picture from: http://biologyblog.edublogs.org/)

Diabetes mellitus is the main endocrine disorder in which research in stem cell therapy has been investigated (2). In many human patients, as in our canine and feline diabetics, diabetes mellitus will frequently reach the stage of life threatening and severely disabling complications, which cannot be controlled by insulin alone.

Several other hormone deficiency disorders (hypothyroidism, Addison's disease) could potentially be helped by stem cell transplantation However, it is relatively easy to provide hormone replacement for these disorders, so there is not a huge incentive to use stem cell therapy for these diseases.

There is ongoing research concerning stem cell therapy for thyroid disease in people (3-6), but I do not know of anyone working on stem cell therapy for thyroid disease in cats. However, notice that — even in people — they are concentrating on stem cell therapy for thyroid cancer (4,6).  Again, it's relatively cheap and easy to provide thyroid supplements for hypothyroidism. Hyperthyroidism is relatively easy to cure with radioiodine (7-10), so investigators aren't overly concerned with stem cell transplantation for that condition.

References:

1. Sharma S, Vyas G, Gawarikar SB, et al. Stem cell transplantation: brief review and current status. Journal of the Indian Medical Association 2011;109:570-574, 579-581. 
2. Fiorina P, Voltarelli J, Zavazava N. Immunological applications of stem cells in type 1 diabetes. Endocrine Reviews 2011;32:725-754.
3. Lin RY. New insights into thyroid stem cells. Thyroid 2007;17:1019-1023.
4. Thomas D, Friedman S, Lin RY. Thyroid stem cells: lessons from normal development and thyroid cancer. Endocrine-Related Cancer 2008;15:51-58. 
5. Davies TF, Latif R, Minsky NC, et al. Clinical review: The emerging cell biology of thyroid stem cells. The Journal of Clinical Endocrinology and Metabolism 2011;96:2692-2702.
6. Lin RY. Thyroid cancer stem cells. Nature Reviews: Endocrinology 2011;7:609-616.
7. Radioiodine therapy for hyperthyroidism. Drug and Therapeutics Bulletin 2006;44:44-48. 
8. Franklyn JA, Boelaert K. Thyrotoxicosis. Lancet 2012;379:1155-1166.
9. Peterson ME: Radioiodine treatment for hyperthyroidism. Clinical Techniques in Small Animal Practice 2006;21:34-39.
10. Peterson ME, Broome MR: Radioiodine for hyperthyroidism. In: Bonagura JD, Twedt DC (eds): Current Veterinary Therapy XV. Philadelphia, Saunders Elsevier, 2012, in press.