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01 August 2014, at 1:00am

HYPE or hope: which word will best sum up the story of stem cell therapies in veterinary medicine over the coming years?

Leading veterinary orthopaedic surgeon Professor John Innes gave a guarded verdict of the future utility of these much talked about techniques in small animal patients in one of his presentations at VetsNorth 2014.

In some respects, regenerative medicine was progressing faster and offered more promise in small animals than in human patients, but he had concerns about whether there was sufficient understanding of the underlying science to provide reliable clinical results.

Moreover, he was worried that the provision of veterinary services is being driven too much by commercial interests and that this might be so damaging to the reputation of this form of therapy that it never achieves its potential.

Encouraging signs

Prof. Innes described a number of studies carried out in university centres around the world which have been published in recent months.

Some have certainly shown encouraging signs that stem cells, usually harvested from bone marrow or adipose tissue, can produce clinical benefits when delivered locally to repair bone, cartilage or ligaments. Yet other workers have experienced much more disappointing results.

“That is because we don’t fully understand the basic biology and I would imagine that it may be decades before we reach that stage. We have to be careful about going straight into the clinic and applying this technology when it is poorly characterised, as that way we might miss something,” he said.

Certainly there is evidence that the available techniques for harvesting, purifying and applying stem cells can be helpful in therapy in horses with tendon injuries and in a few small-scale studies in dogs.

Progress could be faster in small animal than in human medicine as there are fewer regulatory constraints on the developing science. Dogs may also provide a suitable model for testing potential human therapies, he noted.

But with current techniques, it would seem unlikely that stem cell therapies will enter routine use in humans or animals. Prof. Innes pointed out that using stem cells in treating osteoarthritis, using autologous stem cells derived from the patient’s own cartilage, would require two separate surgical procedures. 

Together with the expense of growing and purifying the cells, a single treatment would probably cost more than £20,000. Even if cheaper methods can be developed for veterinary use, the costs are still likely to be prohibitive for most patients.

Not all the same

There was a widely-held belief that all stem cells are the same but that is far from the truth, he said. Different cells from different organs vary in the extent that they can undergo cycles of development without differentiating into a single form of adult cell. And when the transformation does occur, there are often limitations to the types of cells that can be formed.

Disappointingly, those older patients that are at greatest need of regenerative medicine techniques will usually produce smallest numbers and the least vigorous stem cells, he said.

Prof. Innes believed that overly optimistic and uncritical forecasts of the potential value of stem cell therapies have encouraged commercial practices that he regards as suspect. “There are companies that offer parents the opportunity to bank the stem cells contained in the dental pulp of their child’s milk teeth for future use. I think that is preying on people’s fears and it is not something I would choose to do if I was to have more children.”

There was also the possibility that stem cell treatment using either the patient’s own cells or those from donors could result in the development of neoplasms or the transmission of infectious diseases. This was one area that would have to be thoroughly investigated before these therapies are offered for routine use, he said.

In questions, however, he said he did not believe that there is a risk to patients if lipoma cells are contained in the adipose tissue extracted from their own bodies and used as a source of stem cells.

He believed that the processing and purification process will remove both normal fat cells and those from normally benign fatty growths.

Amazing results

Prof. Innes accepted the findings of Yorkshire practitioner Pred Prokic who said he had witnessed “amazing results” when treating a dog with arthritic stifle joints with cells extracted from its own fat deposits.

He said that in some of his own patients treated with a similar technique he had also seen impressive clinical improvements. But there was considerable variation in the results achieved in different cases which could not be easily explained and histological samples showed that only a small number of stem cells injected into a joint migrated to the area of the osteoarthritic lesion.

He wondered whether the clinical benefits seen in such procedures were a result of the cells having paracrine effects – perhaps by releasing proteins that mediate the inflammatory process – rather than the physical reconstruction of damaged tissue.

This would help explain the results of earlier surgeons using injections of whole blood into affected joints and the more recent emergence of platelet rich plasma as a treatment option in osteoarthritis, he said.