Autologous conditioned serum: the comparative cytokine profiles of two commercial methods (IRAP and IRAP II) using equine blood

Reasons for performing study: Osteoarthritis (OA) is one of the most prevalent and debilitating conditions affecting the horse. Autologous conditioned serum (ACS), commercially available as IRAP and IRAP II, is a recently developed treatment for OA in which plasma is prepared from venous blood by incubation with glass beads for 24 h. This product has been shown to increase anti‐inflammatory cytokines and growth factors in human blood. However, data for equine ACS preparations are lacking. Objectives: To characterise the protein profiles produced by commercially available ACS systems in equine blood. Methods: Blood was drawn from 5 horses into 6 groups: red top vacutainer (control), IRAP and IRAP II, with and without heparin. Samples were collected 1 or 24 h post draw and analysed for IL‐1ra, IL‐10, IGF‐1, TGF‐β, TNF‐α and IL‐1β using ELISAs. Results: Twenty‐four hour IRAP and IRAP II samples contained significantly higher levels of all cytokines relative to 1 h serum controls. At 24 h, IRAP II contained significantly higher levels of IL‐1ra and IRAP contained significantly higher levels of TNF‐α, compared to 24 h controls. In addition, TGF‐β, IL‐10 and IL‐1β in IRAP and IRAP II sera were similar to 24 h serum controls. The addition of heparin significantly reduced levels of IGF‐1, TNF‐α and TGF‐β, and significantly elevated levels of IL‐1ra. Conclusions: The cytokine profile that IRAP II produced is modestly better than IRAP. Incubation of whole blood in glass tubes stimulated cytokine synthesis, although not as efficiently as IRAP II. Potential relevance: Although high levels of IL‐1ra were found in ACS, elevation of other factors suggests these cytokines play a previously understated role in clinical improvements. Because ACS has been shown to alleviate clinical symptoms of OA, the present study suggests that factors other than IL‐1ra alone might be involved in its clinical efficacy. Species‐dependent elevations of cytokines warrant further investigation and optimisation of the systems appears to be necessary based on the differences between human and equine blood.