Evaluation of Repeated Intralesional Injection of Allogeneic Umbilical Equine Cord Blood Mesenchymal Stromal Cells for Treatment of Equine Superficial Digital Flexor Tendonitis

Abstract

This thesis is a continuation of the investigations of cryopreserved allogeneic equine umbilical cord blood (CB) derived mesenchymal stromal cells (MSC) by its use in the treatment of superficial digital flexor tendon (SDFT) injuries in horses. In the course of time, the thesis concludes evaluating the efficacy and safety of repeated intralesional injection of CB-MSC in SDFT lesions in client-owned horses and its comparison to the control group receiving platelet rich plasma (PRP). We confirmed the safety of the CB-MSC with the results of the flow cytometry for lymphocytes CD4+ and CD8+ on the blood samples taken at 0, 24, 72 and 168 hours post-injection. There was no clinical systemic immune reaction to repeated CB-MSC treatment and there were no paraclinical significant changes as measured by the expression of lymphocytes CD4+ and CD8+ between groups, treatments, and injections times. We identified that the intralesional treatment of CB-MSC induced an inflammatory reaction at the injection site that resolved within 24 to 72 hours. Along with the inflammatory response, the patients displayed an expansion of the needle tract that was noticeable throughout the length of the study. In all horses, we used a 20-gauge needle to inject. Possibly, the horses had a mild reaction to the commercial cryomedium. Ultrasonographic evaluations revealed that circumferences of the lesion region decreased faster in the CB-MSC group compared to the PRP group. Four out of five horses in the CB-MSC group returned to racing as defined by one or more starts and one out of three patients in the PRP group returned to race training. Based on our results, the repeated intralesional treatment with allogeneic equine CB-MSC is safe, despite the inflammation and needle tract observed. We believe that an alternative delivery method of allogeneic equine CB-MSC that avoids the risk of needle-tracts is desirable. For that reason, we proposed the continuation of the current thesis with a clinical prospective study to investigate the use of repeated intra-arterial injections of allogeneic equine CB MSC for SDFT lesions, and to evaluate its utility.