Blood type and breed-associated differences in cell marker expression on equine bone marrow-derived mesenchymal stem cells including major histocompatibility complex class II antigen expression.
Authors: Kamm J Lacy, Parlane Natalie A, Riley Christopher B, Gee Erica K, Dittmer Keren E, McIlwraith C Wayne
Journal: PloS one
Summary
# Editorial Summary Developing an off-the-shelf mesenchymal stem cell (MSC) therapy for horses requires identifying donor sources with naturally lower immunogenicity, and this 2019 study examined whether breed and blood type influence the surface antigen profile of equine bone marrow-derived MSCs. Researchers isolated MSCs from 18 Thoroughbreds and 18 Standardbreds (including 8 universal blood donors characterised by negative Aa, Ca, and Qa antigens) and cultured them through passages 2, 4, 6, and 8, using flow cytometry to measure expression of CD11a/18, CD44, CD90, and major histocompatibility complex (MHC) class II antigens. Standardbreds demonstrated significantly lower MHC class II expression than Thoroughbreds at passages 2–6 (the critical early expansion phase), and universal blood donor Standardbreds showed substantially higher CD90 expression than non-donor Standardbreds across all passages—a combination suggesting reduced alloimmune recognition potential. For equine practitioners considering MSC therapy, these findings suggest that Standardbred universal blood donor animals at passages 2–4 represent the most immunologically favourable donor source, though the researchers emphasise that MHC class I expression (not measured here) may also influence graft survival and warrants investigation. Future work establishing the clinical relevance of these antigen expression patterns to actual transplant outcomes would significantly strengthen the case for donor-type selection in regenerative medicine protocols.
Read the full abstract on PubMed
Practical Takeaways
- •If considering allogeneic MSC therapy, sourcing cells from universal blood donor Standardbreds at early passages (2-4) may reduce immunogenic rejection risk due to lower MHC class II expression
- •Breed and blood type significantly influence MSC immunological properties; cell sourcing strategy should account for these biological variables rather than treating all equine MSC donors as equivalent
- •Cell passage number matters—MSC antigen expression changes over successive passages, so early passages appear more suitable for therapeutic application
Key Findings
- •Standardbred horses showed significantly lower MHC class II expression than Thoroughbreds at passages 2, 4, and 6
- •Universal blood donor-type Standardbreds demonstrated higher CD90 expression across all passages compared to non-donor Standardbreds
- •CD44 expression was consistently high and CD11a/18 expression was consistently low across all MSC samples
- •Universal blood donor-type Standardbred MSCs at passages 2-4 exhibited the most immunologically favorable antigen profile for potential allogeneic use