Stem Cell Research and Therapy Proves Problematic for Rehabilitation Patients

Physiatrists advise patients that stem cell therapy can not yet be utilized

HONOLULU—Physicians specializing in physical medicine and rehabilitation (PM&R) have been thrust into the middle of the stem cell debate as patients with spinal cord injuries request to be involved in stem research, according to David R. Gater, M.D., Ph.D., a rehabilitation specialist working with spinal cord injuries.

“Stem cell clinical trials for spinal cord injury are not being done in the United States because the Food and Drug Administration (FDA) has not found sufficient evidence to warrant moving forward with human testing,” says Dr. Gater, spinal cord injury chief at Hunter Holmes McGuire VA Medical Center and a professor at Virginia Commonwealth University in Richmond, Va. “Safety and efficacy have not yet been demonstrated in the animal models. Embryonic stem cell proliferation has led to tumors and misfirings in the central nervous system that cause significant pain, spasticity or further damage within the spinal cord.”

A group of international scientists and physicians have discussed standards for conducting clinical research in SCI, including the use of stem cells to repair spinal cord injury. “The group consensus is to have appropriate preclinical evidence before considering providing stem cell therapy to humans,” says Dr. Gater, who will speak on Nov. 12 at the American Academy of Physical Medicine and Rehabilitation’s 67th Annual Assembly as part of a panel on the ethics, politics and science of stem cell research in spinal cord injury.

Stem cells come from embryos, fetuses or adult cells. The embryonic stem cell is preprogrammed to develop into a myriad of cell and tissue types. Stem cells can also be taken from adults and grown as a single cell line as they replicate. Bone marrow, umbilical cord blood, skin and even fat cells have been used to develop neurological stem cell lines.

There are two major concerns surrounding the use of embryonic stem cells. Ethicists debate the propriety of the sacrifice of an embryo for medical treatment, while some scientists are concerned about unintended outcomes from disruption of preprogrammed stem cell cycles.

Researchers attempting to repair spinal cord damage have attempted to direct production of just a single cell type out of the multi-faceted stem cell lines, but have reached a hurdle. After several cycles of doubling, embryonic stem cells revert to their preprogrammed set and produce unwanted cells. Scientists have not been able to successfully control stem cell division to prevent tumor development.

The Art and Science of Spinal Cord Stem Cell Therapy

“Stem cells are not the magic bullet people assume they are,” states Dr. Gater. Repairing spinal cord injury is a complex process consisting of the following six components:

1. Repairing structural damage and scarring to the spinal cord and the pathways that send the neural signals to the body from the brain and from the brain to the body.

2. Bridging the gap between the damaged areas with different cell preparations including stem cells or Schwann cells.

3. Regulating the biochemical inhibitors within the cord following spinal cord injury. These enzymes prevent growth.

4. Delivering growth factors required in specific concentrations and at specific times in cell development.

5. Directing cell growth so it communicates appropriately with the cell structures above and below the damage.

6. Stimulating growth or modifying structures within the central nervous system that facilitate functional recovery such as walking through loco-motor training, or gait training.

“Each of these six items need to be addressed when spinal cord research is considered. Stem cells provide just one aspect – bridging the gap within the cord,” says Dr. Gater.

Stem cell transplantation in mice and rats with partial spinal cord injuries has demonstrated improvement in loco-motor functions, according to Dr. Gater. However, investigators have recognized that they must overcome biochemical inhibitors, provide appropriate growth factors at the correct time, while directing structural growth.

“The human central nervous system – the brain and the spinal cord – is 10 times the length of a rodent’s,” Dr. Gater illustrates. “To allow for healing you must cover ten times the distance that is present in rats and mice. Making the jump from the animal model to the human model is a fairly large leap.”

The American Academy of Physical Medicine and Rehabilitation is the national medical specialty society of more than 7,500 physical medicine and rehabilitation (PM&R) physicians, also called physiatrists. Physical medicine and rehabilitation physicians focus on restoring function. They care for patients with acute and chronic pain and musculoskeletal problems like back and neck pain, tendinitis, pinched nerves, and fibromyalgia. They also treat people who have experienced catastrophic events resulting in paraplegia, quadriplegia, or traumatic brain injury and individuals who have strokes, orthopaedic injuries, or neurological disorders such as multiple sclerosis, polio, or ALS.

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Editor’s Note: Dr. Gater has no financial interests, arrangements or affiliations to disclose that could be perceived as a real or apparent conflict of interest in the context of the subject of this presentation.

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