Stem cell therapies for treating osteoarthritis: prescient or premature?

There has been unprecedented interest in recent years in the use of stem cells as therapy for an array of diseases in companion animals. Stem cells have already been deployed therapeutically in a number of clinical settings, in particular the use of mesenchymal stem cells to treat osteoarthritis in horses and dogs. However, an assessment of the scientific literature highlights a marked disparity between the purported benefits of stem cell therapies and their proven abilities as defined by rigorously controlled scientific studies. Although preliminary data generated from clinical trials in human patients are encouraging, therapies currently available to treat animals are supported by very limited clinical evidence, and the commercialisation of these treatments may be premature. This review introduces the three main types of stem cells relevant to veterinary applications, namely, embryonic stem cells, induced pluripotent stem cells, and mesenchymal stem cells, and draws together research findings from in vitro and in vivo studies to give an overview of current stem cell therapies for the treatment of osteoarthritis in animals. Recent advances in tissue engineering, which is proposed as the future direction of stem cell-based therapy for osteoarthritis, are also discussed.