Retrospective analysis of local injection site adverse reactions associated with 230 allogenic administrations of bone marrow-derived mesenchymal stem cells in 164 horses.
Authors: Ursini T L, Amelse L L, Elkhenany H A, Odoi A, Carter-Arnold J L, Adair H S, Dhar M S
Journal: Equine veterinary journal
Summary
# Editorial Summary: Allogenic Bone Marrow-Derived Mesenchymal Stem Cell Safety in Equine Practice A single donor's bone marrow-derived mesenchymal stem cells (BM-MSCs) were characterised in vitro, then administered allogeneically to 164 horses across 230 injections, with the research team investigating whether cells lacking major histocompatibility complex class II expression could be used without triggering significant immune reactions. The cells demonstrated appropriate proliferation and differentiation capacity, remained viable following cryopreservation and shipping, and possessed minimal MHC-II expression (<2%), meeting the theoretical criteria for immunological tolerance. Post-injection adverse reactions—defined as increased pain, swelling, heat at the injection site, or worsening lameness—occurred in only 10 of 230 administrations (4.35%), affecting three synovial structures and seven soft tissue sites. This reaction rate aligns with historical data for autologous BM-MSC use, suggesting that allogenic stem cell therapy from a single, well-characterised donor presents a clinically acceptable safety profile whilst offering the significant advantage of rapid availability without the delay of autologous cell harvesting and expansion. However, the retrospective design and routine use of anti-inflammatory medication post-injection likely masked mild reactions such as transient synovitis, meaning the true incidence of adverse effects may be somewhat higher than reported—a consideration worth noting when counselling clients on realistic expectations.
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Practical Takeaways
- •Allogenic BM-MSCs from a characterized donor can be used clinically with a low adverse reaction rate (~4%), providing a practical alternative to autologous harvesting when rapid treatment is needed
- •Be vigilant for post-injection reactions at injection sites, particularly increased pain, swelling, heat, or lameness, though these may be masked by routine anti-inflammatory therapy
- •Recognize that synovitis and mild inflammatory reactions may be underreported in clinical practice and consider baseline imaging and careful monitoring when administering allogeneic cell therapy
Key Findings
- •Allogenic bone marrow-derived mesenchymal stem cells from a single donor were successfully proliferated, characterized as MHC-II negative (<2%), and remained viable after cryopreservation
- •10 of 230 injections (4.35%) were associated with adverse local reactions, occurring in both synovial structures (n=3) and soft tissues (n=7)
- •Adverse reaction rate for allogenic BM-MSCs was similar to previously reported rates for autologous BM-MSCs
- •Study likely underestimated mild reactions such as synovitis due to retrospective design and anti-inflammatory drug use masking clinical signs