Influence of Incubation Time and Incubation Tube on the Cytokine and Growth Factor Concentrations of Autologous Conditioned Serum in Horses.

Autologous conditioned serum (ACS) is commonly used for the treatment of human and equine osteoarthritis (OA). The objective of this study was to investigate the influence of incubation time and incubation tube on concentrations of interleukin-1 receptor antagonist (IL-1ra), interleukin-1 beta (IL-1β), and insulin-like growth factor-1 (IGF-1) in ACS of horses with and without OA. Blood samples of 7 control horses and 6 horses with naturally occurring OA were obtained. The concentration of serum IL-1ra, IL-1β, and IGF-1 was determined after 12, 24, and 36 hours of incubation using commercial serum vacutainer glass tubes (incubated serum [IS]) or a specific equine ACS system. There was no significant difference in IL-1ra, IL-1β, and IGF-1 concentrations between IS and ACS samples detectable at 24 or 36 hours of incubation. The ACS of horses with OA and control horses did not contain significantly different cytokine or growth factor concentrations. In conclusion, an incubation time exceeding 24 hours does not lead to a significant increase in cytokine and growth factor concentrations in equine ACS. Incubation of whole blood in commercial serum glass tubes has similar effects on the IL-1ra, IL-1β, and IGF-1 concentrations when compared with the incubation in specialized equine ACS kits. Interleukin-1 receptor antagonist, IL-1β, and IGF-1 concentrations in ACS of OA horses is not significantly increased when compared with control horses.