Inflammatory response following intra-articular injection of decellularized porcine amnion/chorion in horses.

Objective: The objective of the study was to evaluate effects of intra-articular decellularized porcine amnion/chorion suspension (dPACLS) in horses.

Study design: Controlled, randomized, prospective study.

Animals: A total of 10 adult horses.

Methods: One randomly selected radiocarpal joint (RCJ) was injected with a high dose (HD) of 50 mg (n = 5) or low dose (LD) of 5 mg of dPACLS (n = 5). The contralateral RCJ received saline as control. Systemic serum amyloid A (SAA), synovial fluid analysis (including SAA) and subjective lameness evaluation were performed prior to injection (time 0) and 24, 48, 72, 96, 168 h post-injection.

Results: Synovial fluid nucleated cell count (NCC) in both groups was higher than controls at 24 and 48 h post-injection. The HD group had significantly higher synovial fluid SAA values than the LD group and the controls. Systemic SAA was higher in HD group than baseline at all timepoints except 168 h, but no difference was detected from baseline in LD group at any timepoint. Systemic SAA was significantly greater in the HD group than the LD group at all timepoints except at baseline and 168 h. Three HD horses were lame and had elevated NCC at 168 h.

Conclusion: The HD group had more clinically evident inflammation in comparison to the LD group based on systemic and synovial SAA, subjective lameness scores, and carpal flexion.

Clinical significance: Intra-articular injection of dPACLS at the doses studied is not recommended for intra-articular injection due to the inflammatory response.