Regenerative medicine holds great promise for the repair of damaged tissues and organs and the restoration of functionality by stimulating the body's own regenerative capacity.
One of the most commonly used treatments in regenerative medicine is the use of stem cells because they have incredible potential to regenerate and induce healing in the human body.
Clinicaltrials.gov is a website maintained by the National Institutes of Health (NIH) and the National Library of Medicine which lists all medical studies that are required by law to be registered. Currently, there are over 7,000 clinical trials registered in the U.S. that involve stem cells. Various types of stem cell therapies are being studied for their impact on an extensive range of conditions such as joint injuries, heart conditions, Parkinson’s disease, ALS, Autism, Alzheimer’s, Multiple Sclerosis, Rheumatoid Arthritis, and Osteoarthritis. How can one little thing like a stem cell potentially treat such a varied spectrum of problems?
How does a stem cell heal?
Stem cells are unspecialized, meaning that they have the potential to become another type of cell. In an embryo, the stem cells divide rapidly and differentiate, which is when they become all the different types of specialized cells necessary to make up the entire organism. Some divide into other stem cells and remain in the body after birth to continue their work of replicating and differentiating to help the body regenerate and heal as needed.
Stem cells have another incredible ability. They can lie dormant for a long time, then suddenly begin dividing and renewing themselves when needed, and they can go on dividing as long as necessary. It is possible that a single stem cell can proliferate, which means divide into two identical daughter cells, throughout a person’s entire life. However, our diminishing amount of available stem cells fuels one of the theories behind aging.
Where are stem cells found?
Stem cells are found in humans at any age. Early embryonic stem cells can be obtained from fertilized eggs that are a few days old and then grown in the lab for research. Due to obvious ethical concerns with these types of stem cells, embryonic stem cell use is not legal in the United States.
Stem cells obtained from adult human tissues are known as somatic (non-reproductive) stem cells. There are several different types of somatic stem cells. Hematopoietic Stem Cells become different types of cells in the blood. Mesenchymal Stem Cells have the ability to regenerate bone cells, fat cells, muscle cells, and cartilage cells. Neural Stem Cells help to regenerate nerve tissue in the brain and spinal cord. Epithelial Stem Cells help to regenerate the skin and Intestinal Stem Cells help in repairing the gut lining. Compared with embryonic stem cells, somatic stem cells have lost the ability to continue to multiply and become different types of tissue, but still retain an amazing capacity for dividing and restoring tissue. There are many sources of adult stem cells, but some are safer to use than others. Currently, the most common three sources of stem cells that are allowed in the United States come from bone marrow, adipose, and amniotic tissue (specifically from the umbilical cord and the placenta).
Bone marrow contains both hematopoietic and mesenchymal stem cells. Bone marrow transplant of stem cells is a commonly known type of stem cell therapy which has been used for over 50 years. High doses of chemotherapy or radiation therapy used to fight cancer cells often destroy bone marrow stem cells. Bone marrow derived mesenchymal stem cells (BM-MSC’s) are the most commonly used mesenchymal stem cells for scientific and clinical purposes (1). However, BM-MSC’s decrease significantly with age, as does their differentiation potential (2). In addition, the process of obtaining BM-MSC’s carries the high costs, risks, and pain associated with surgery and therefore may not be the best option for regenerative procedures.
Adipose derived mesenchymal stem cells are an easier source to obtain and have demonstrated in vitro studies to be as effective as either of the other types of stem cells. However, there are concerns about safety. Adipose is where the body stores toxins and these toxins may influence the effectiveness of these stem cells. Additionally, of the 22 cases of adverse effects noted in the literature, almost all have been from adipose derived mesenchymal stem cells. Three individuals lost their vision from the use of adipose derived msc’s, and one died from complications in the liposuction surgery part of the stem cell acquisition.
Mesenchymal stem cells derived from amniotic tissue of the umbilical cord and placenta are more easily acquired. They are also safer because they do not carry the risk of including toxins, do not require surgery to acquire, and have no documented adverse events to date. Reputable cord banks acquire this tissue from mothers who have consented to donate it. The effectiveness of umbilical cord derived mesenchymal stem cells has proven to be equal or superior to adipose and bone marrow mesenchymal stem cells (1).