Canine mesenchymal stem cells: state of the art, perspectives as therapy for dogs and as a model for man.

Interest in mesenchymal stem cells (MSCs) both for regenerative and reparative therapies in dogs is emerging, as the current treatment options for several conditions often do not result either in the desired clinical outcome or in the patients' return to normal function. In addition, canine MSCs have been evaluated in some experimental and preclinical studies on efficacy and safety testing of novel treatments for humans, since the dog is considered to be a superior model for humans than rodents. Although these MSCs can be derived from several sources, clinical use has favoured bone marrow and adipose tissue because of their relative ease of stem cell recovery and the minimal donor-site morbidity. Before any type of stem cell can be applied clinically, its unequivocal characterization by a set of specific functional or phenotypic markers is crucial. However, no uniform characterization criteria are available for canine MSCs so far. Moreover, although multi-lineage potential of canine MSCs has been demonstrated in a limited number of studies, research on the differentiation potential of MSCs towards tenocytes is still lacking in canine medicine. In contrast, this latter subject has been explored already in human as well as in equine medicine, demonstrating the need for a specific 'niche', i.e. factors with a positive influence on the MSC differentiation. Since most of these factors are still unknown regarding canine MSC, critical basic knowledge is urgently required to motivate and correctly translate the potential therapeutic applications of these stem cells in both dog and man.