Osteoarthritis (OA) is currently an incurable and progressive condition in dogs causing chronic joint pain and possibly increasing disability. Due to the poor healing capacity of cartilage lesions that occur with OA, development of effective therapeutics is difficult. For this reason, current OA therapy is mostly limited to the management of pain and inflammation, but not directed ad disease modification. In the search for a safe and effective OA treatment, mesenchymal stem cells (MSCs) have been of great interest since these cells might be able to restore cartilage defects. The designs of OA studies on MSC usage, however, are not always consistent and complete, which limits a clear evaluation of MSC efficacy. The general study results show a tendency to improve lameness, joint pain and range of motion in dogs suffering from naturally-occurring OA. Assessment of the cartilage surface demonstrated the ability of MSCs to promote cartilage-like tissue formation in artificially created cartilage defects. Immunomodulatory capacities of MSCs also seem to play an important role in reducing pain and inflammation in dogs. It should be mentioned, however, that in the current studies in literature there are specific design limitations and further research is warranted to confirm these findings.

Background Mesenchymal stem cell treatments in dogs have been investigated as a potential innovative alternative to current conventional therapies for a variety of conditions. So far, the precise mode of action of the MSCs has yet to be determined. The aim of this study was to gain more insights into the pharmacokinetics of MSCs by evaluating their biodistribution in healthy dogs after different injection routes. Methods Three different studies were performed in healthy dogs to evaluate the biodistribution pattern of radiolabelled equine peripheral blood-derived mesenchymal stem cells following intravenous, intramuscular and subcutaneous administration in comparison with free 99mTechnetium. The labelling of the equine peripheral blood-derived mesenchymal stem cells was performed using stannous chloride as a reducing agent. Whole-body scans were obtained using a gamma camera during a 24-h follow-up. Results The labelling efficiency ranged between 59.58 and 83.82%. Free 99mTechnetium accumulation was predominantly observed in the stomach, thyroid, bladder and salivary glands, while following intravenous injection, the 99mTechnetium-labelled equine peripheral blood-derived mesenchymal stem cells majorly accumulated in the liver throughout the follow-up period. After intramuscular and subcutaneous injection, the injected dose percentage remained very high at the injection site. Conclusions A distinct difference was noted in the biodistribution pattern of the radiolabelled equine peripheral blood-derived mesenchymal stem cells compared to free 99mTechnetium indicating equine peripheral blood-derived mesenchymal stem cells have a specific pharmacokinetic pattern after systemic administration in healthy dogs. Furthermore, the biodistribution pattern of the used xenogeneic equine peripheral blood-derived mesenchymal stem cells appeared to be different from previously reported experiments using different sources of mesenchymal stem cells.

Preclinical research has been indispensable in the exploration of the neurological basis of major depressive disorder (MDD). The present study aimed to examine effects on regional brain activity of two frequently used depression models, the chronic unpredictable mild stress (CUMS)- and the chronic corticosterone (CORT) depression model. The CUMS and CORT depression model were induced by exposing male Long-Evans rats to a 4-week procedure of unpredictable mild stressors or a 3-week procedure of chronic corticosterone, respectively. Positron emission tomography with [F]FDG was performed to determine alterations in regional brain activity. In addition, depressive- and anxiety-like behaviour was assessed via the forced swim test and the open field test, respectively. The chronic CORT administration, but not the CUMS model, significantly induced depressive-like behaviour and elevated plasma corticosterone levels. Compared to control, induction of the CORT depression model resulted in a significantly reduced glucose consumption in the insular cortex and the striatum, and a significantly elevated consumption in the cerebellum and the midbrain. Induction of the CUMS model replicated the findings with respect to the activity in the striatum region, and cerebellum, but missed significance in the insular cortex and the midbrain. Based on the alterations in behaviour and regional [F]FDG uptake, a superior face validity and construct validity can be observed after induction of depression via chronic CORT injections, compared to the used CUMS paradigm.

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