Characterization of Mesenchymal Stem Cells in Musculoskeletal Injury

The main goal of regenerative medicine is to enhance the innate healing response to more closely mimic tissue development. This may include cell-based, trophic, or small molecule therapies. In cell-based therapies, the initial premise was one of tissue replacement. Mesenchymal stem cells (MSCs) are adult-derived stem cells present throughout the body and easily harvested from individual patients. After over a decade of veterinary and human medical use of MSCs and medical research, the function of MSCs after therapeutic use in injury remains unclear. Elucidating engraftment location and longevity of MSCs post injection may provide insight to their mechanism of action. We developed a protocol for labeling MSCs with a fluorocarbon nanoparticle that allows for non-invasive longitudinal tracking and evaluated cellular viability, proliferation, and morphology. A dose dependent cell association of the nanoparticle was seen in our study but it was not repeatable between individuals. Prior to use of this technique to track MSCs, further study is needed to elucidate where the failure occurred: uptake of label by MSCs, maintenance of label within the cell cytoplasm or loss of conjugation of the fluorophore. Despite the use of MSCs as a therapeutic in horses for many years, there is little information on the best techniques for cryopreserving these cells for immediate use post thaw. We tested several freezing mediums for the short-term cryopreservation of equine MSCs. We found that 95% autologous serum and 5% DMSO did not negatively affect post thaw viability, growth kinetics, or morphology. Bisphosphonates were approved for use in horses in the United States in 2014. Since, they have become wildly popular due to improvements in lameness in treated horses. We suspected that the efficacy in lameness reduction could be due to an off target effect such as an effect on the MSC because the approved dose is so low compared to the anti- resorptive dose of the same drugs in people. We investigated the impact of bisphosphonates on bone remodeling and bone cells including MSCs. We observed reduction in lameness but no changes in bone turnover or MSC characteristics