I reviewed a 2020 study in Frontiers in Veterinary Science that compared autologous conditioned serum (ACS), autologous protein solution (APS), and triamcinolone in an inflamed equine joint model. The goal was to see how these orthobiologics stacked up against a common corticosteroid when it comes to reducing inflammation and protecting cartilage in horses with osteoarthritis.
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Why This Matters
Lameness caused by osteoarthritis is one of the biggest reasons horses lose performance, and it affects more than 80% of the geriatric equine population. Corticosteroids like triamcinolone are still a common first-line treatment because they reduce inflammation quickly, but repeated long-term use remains a concern. That is why blood-derived orthobiologics like ACS and APS are getting so much attention.
This paper is especially helpful because it does not just compare ACS and APS to each other. It compares them to what they are actually up against in practice: triamcinolone.
Study Overview
- Design: Ex vivo co-culture study using inflamed equine cartilage and synovial membrane
- Subjects: 6 healthy Quarter Horses (1 mare, 5 geldings; average age 14.9 years)
- Model: IL-1β-stimulated cartilage and synovial explants cultured together to mimic an OA environment
- Treatments:
- ACS at 25% and 50%
- APS at 25% and 50%
- Triamcinolone (TA)
- Stimulated and unstimulated controls
- Measures: Cell counts, cytokines, growth factors, PGE2, and gene expression in cartilage and synovial membrane
Key Findings
Product Profiles
ACS and APS had very different cellular profiles.
- ACS had lower RBCs, WBCs, and platelets
- APS had higher WBCs and platelets, but lower RBCs than whole blood
- Compared directly, APS had significantly higher WBCs, RBCs, and platelets than ACS
Interestingly, despite those cellular differences, the cytokine and growth factor content between ACS and APS was fairly similar, although ACS was significantly higher in TGF-β and soluble TNF receptor 1.
Inflammation
The study looked closely at PGE2, a major pro-inflammatory mediator in OA.
After stimulation with IL-1β, PGE2 increased 4.7-fold. Triamcinolone reduced PGE2, but not significantly. Both ACS and APS significantly reduced PGE2, with APS at 50% being the most effective.
That matters because lower PGE2 may help explain why horses treated clinically with ACS or APS often show improvement in lameness.
Gene Expression
Triamcinolone was the only treatment that significantly downregulated IL-1β in the synovial membrane, and it trended toward reducing IL-6. But it did not broadly change many of the other inflammatory genes measured.
ACS and APS had a broader effect in cartilage:
- both downregulated IL-1β and TNF-α
- both trended toward upregulating COL2A1 and ACAN, which are associated with cartilage matrix support
- APS also downregulated MMP-1 in synovial membrane
My Takeaway
The big takeaway from the paper is that triamcinolone looked stronger in a narrow anti-inflammatory sense, but ACS and APS appeared to create a broader, more chondroprotective response.
The authors concluded that both ACS and APS may offer a more disease-modifying approach by reducing inflammatory mediators tied to cartilage destruction and by supporting a more reparative environment.
Overall, I really liked this study. I thought the design was strong for an ex vivo paper, and I especially appreciated that the authors compared orthobiologics to the standard treatment clinicians actually use, not just to each other. ACS and APS both outperformed triamcinolone in reducing PGE2, and both showed a more favorable cartilage response, which is exactly what you want in osteoarthritis.
Of course, this is still not an in vivo study, so I would love to see a clinical follow-up. But for anyone interested in equine OA, this paper gives a really useful look at how orthobiologics may work differently from steroids — and why that difference might matter over time.
If you have questions, or if there is a paper you would like Dr. Adrienne Wright to review next, reach out at adrienne@ardentanimalhealth.com.
