Allogenic Mesenchymal Stem Cells as a Treatment for Equine Degenerative Joint Disease: A Pilot Study

Cell-based therapies, such as treatments with mesenchymal stem cells (MSCs) and platelet-rich plasma (PRP) are thought to have beneficial effects on the clinical outcome of orthopedic injuries, but very few animal studies with large sample size are published so far. Therefore, the aim of this study was to assess the safety and report the clinical outcome of allogenic, immature or chondrogenic induced MSCs in combination with PRP for the treatment of degenerative joint disease (DJD) in 165 horses. MSCs and PRP were isolated from a 6-year-old donor horse and transplanted either in their native state or after chondrogenic induction in combination with PRP into degenerated stifle (n=30), fetlock (n=58), pastern (n=34) and coffin (n=43) joints. Safety was assessed by means of clinical evaluation and the outcome was defined as failure to return to work (score 0), rehabilitation (score 1), return to work (score 2) and return to previous level (score 3), shortly (6 weeks) after treatment or at 18 weeks for the patients that returned for long-term follow-up (n=91). No adverse effects were noticed, except for three patients who showed a moderate flare reaction within one week after treatment of the fetlock joint without long-term effects (1.8% of 165 horses). Already after 6 weeks, 45% (native MSCs) and 60% (chondrogenic induced MSCs) of the treated patients returned to work (-> score 2+3) and the beneficial effects of the treatment further increased after 18 weeks (78% for native MSCs and 86% for chondrogenic induced MSCs). With the odds ratio of 1.47 for short-term and 1.24 for long-term, higher average scores (but statistically not significant) could be noticed using chondrogenic induced MSCs as compared to native MSCs. For all three lower limb joints a higher percentage of the treated patients returned to work after chondrogenic induced MSC treatment, whereas the opposite trend could be noticed for stifle joints. Nevertheless, more protracted follow-up data should confirm the sustainability of these joints.