Adipose-Derived Stem Cells: A Review

Imagine a veterinarian harvesting stem cells from a horse: He or she inserts a needle into the horse’s sternum or hip, and thick red bone marrow fills the syringe. But can you picture a veterinarian harvesting less commonly-used adipose-, or fat-, derived stem cells? And how effective are they? Joseph Yocum, DVM, Dipl. AVBP, owner of Green Tree Veterinary Service and the Centre for Regenerative Medicine in Danville, Ky., presented a review of adipose-derived stem cells at the 2011 North American Veterinary Regenerative Medicine Conference held June 2-4 in Lexington, Ky.

Yocum explained that research indicates adipose tissue is a reliable source from which to collect stem cell aspirates.

“Adipose tissue is easy to harvest, yields a large number of cells, and, thus, does not require tissue expansion and has the potential to differentiate into a number of specialized cells of mesodermal origin,” Yocum explained.

Adipose-derived cells can be harvested from a few different areas on the horse’s body; however, the most common place from which to harvest is the hindquarters–particularly from the fat located near the horse’s tailhead. Yocum noted that, “Fat can be harvested from the inguinal (groin) area, and there is some discussion of harvesting from the neck, but I don’t know of anyone that has tried that yet. The tailhead area is the easiest since the inguinal area requires general anesthesia.”

Yocum explained that there are two ways to harvest adipose-derived stem cells: a surgical linear incision and liposuction. He noted that the linear incision is the most straightforward; however, liposuction is more cosmetic. Both approaches yield about the same amount of nucleated cells per gram and the same cell viability, he added, indicating there’s little difference between the two methods’ efficacy.

“Recent advances, including improved enzymatic digestion that allows us to increase cell yield, in the processing of adipose tissue have substantially improved the cell concentration and total cell counts from harvested fat,” Yocum added. “This precludes the need for cell expansion (the process by which stem cells are proliferated until enough are available for a treatment, which can take days or weeks to complete with other types of stem cells). In most cases, cells are available for same day injection.”

Yocum also noted that adipose-derived cells have shown:

  • The ability to develop into osteocytes (bone cells), chondrocytes (cartilage cells), myocytes (muscle cells), and tenocytes (tendon cells);
  • The ability to transdifferentiate (when an already differentiated stem cell creates cells outside its established differentiation path) into cells of other germ origins (“This is new, but via transdifferentiation cells from other germ origin other than mesenchymal origin have been experimentally produced,” Yocum noted.); and
  • That they have large numbers of growth factors, proteins, pericytes (a connective tissue cell that occurs about small blood vessels), blood cells, and fibroblasts (cells that form connective tissues). Yocum explained that, “Growth factors are essential to stimulate stem cells to differentiate into the target cell.”

Finally, Yocum explained that when platelet-rich plasma therapy is used in conjunction with adipose-derived stem cells, the stem cells are further stimulated to proliferate and differentiate. Also, evidence suggests that photostimulation (the process whereby certain wavelengths of light stimulate cell proliferation) activates the adipose-derived stem cells. However, he noted that the reason behind this remains to be discovered.

Yocum noted that while some parties favor using bone marrow-derived cells and others favor adipose-derived stem cells, current research indicates that both stem cells are likely equally effective in helping injuries heal.

Often, he added, a veterinarian bases his or her decision to use bone marrow- or adipose-derived stem cells on several factors: “The decision is based on a number of factors including ease of harvest, cell numbers, and the interval between harvest and injection (adipose-derived cells can be ready within hours whereas bone marrow-derived cells must be expanded, which can take weeks).”

Cost is another consideration: “I am not sure about the cost of collecting and expanding bone marrow-derived stem cells, but I feel that adipose-derived stem cells are reasonably priced,” said Yocum, who charges $1,495 at his practice for adipose collection, processing, and the first treatment. “Also, since we get such large numbers of cells we have the option of freezing a portion of the collection, which allows multiple treatments from a single collection.”

Regardless of whether the treating veterinarian chooses bone marrow- or adipose-derived stem cells, Yocum said that the future of regenerative medicine is bright, but more research is needed to determine the best applications.

“I am excited about the potential of regenerative medicine,” he concluded. “We have developed novel treatments using stem cell for musculoskeletal injuries–injuries that before had no effective treatment–and we’re getting excellent results.

“In addition to this area of medicine I believe we will discover new applications for a number of other medical conditions as well,” he continued. “It is important to me that we approach this with a practical mindset as we develop treatment protocols for these other conditions, muscle disease, liver disease, pulmonary disease, neurologic disease, as examples. All the time moving forward and learning what works and what does not work.”

Courtesy of Joseph Hall


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