Autologous conditioned serum and subsequent synovial fluid concentrations of cytokines, matrix metalloproteinases, and tissue inhibitors of metalloproteinases after injection into equine osteoarthritic distal interphalangeal joints

Abstract

INTRODUCTION: Autologous conditioned serum (ACS) is used for treatment of osteoarthritis in horses. However, there is a lack of critical knowledge of the contents of ACS and any biological effects after injection into osteoarthritic joints. OBJECTIVE: The specific aims of this study were to (1) evaluate content of cytokine, matrix metalloproteinases (MMP), and tissue inhibitors of matrix metalloproteinases (TIMP) in ACS, (2) validate/refute that ACS increases anti-inflammatory or pro- inflammatory biomarkers in synovial fluid from naturally occurring osteoarthritic joints, (3) demonstrate whether freeze/thaw effects IL-1ra concentrations in ACS, and (4) evaluate for clinical improvement in lameness following ACS therapy. METHODS: Eleven horses with naturally occurring osteoarthritis in a forelimb distal inter-phalangeal joint were given 3 consecutive intra-articular doses of ACS separated by 7-day intervals. Synovial fluid was collected before administration of each dose at day 0, 7, 14, and 21. Concentrations of cytokines (IL-1ra, IL-1Beta, TNF�, IL-4, IL-6, IL-8, IL-10), MMPs (-1, -3, -9, -13), and TIMPs (-1, -2, -3, -4) were quantified using ELISA and multiplex assays. Serum was compared to unincubated and incubated controls and synovial fluid was compared to baseline (day 0). Horses were videotaped trotting (at day 0, 7, 14, and 21) and graded blindly for degree of lameness. RESULTS: Concentrations of IL-1ra, as well as MMP-1 to TIMP (-1, -2, -3, -4) and MMP-9 to TIMP (-1, -2, -4) ratios were increased in ACS (vs. unincubated control), and IL-4, IL-6, and IL-8 were decreased in ACS (vs. incubated control). Freeze/thaw did not affect biomarker concentrations in ACS. Although ACS contained high concentrations of IL-1ra, no changes in IL-1ra concentrations were observed in synovial fluid 7 days after each injection. No change in median lameness grade was noted throughout study duration (median grade of 1/5 at all time points).