PHYSICAL, BIOCHEMICAL AND CYTOLOGICAL CHARACTERISTICS OF SYNOVIAL FLUID WITH INDUCED SYNOVITIS MODEL IN PONIES

Abstract

The aim of this study was to describe the changes of the synovial fluid caused by experimental synovitis induced by an intra-articular injection of 0.5 mL of Freund’s complete adjuvant in six adult ponies. The physical-chemical and cytological parameters were evaluated before the synovitis induction (T0), 5 days after induction (T1) and, after that, at 12 (T2), 24 (T3), 48 (T4), 72 (T5), 96 (T6) and 120 hours (T7). The contra lateral joint served as healthy control. The protein, viscosity and mucin precipitation quality did not differ (P>0.05) among the joints in T0. At T1, the synovial fluid of the joints with synovitis showed an increased protein concentration (6.5 g/dl), low viscosity and low mucin precipitate quality, which remained stable until T7. Viscosity and mucin precipitate quality did not change in the synovial fluid of healthy joints until the end of the experiment. Due to repeated arthrocentesis, protein increased (p <0.05) at T6 and T7. Joints with synovitis had an increased total nucleated cell count (>700 cells/mm3, p <0.05) at T1, that decreased at T3, remaining on an inflammatory level during the observation period. The differential cell count showed neutrophil predominance and presence of reactive mesothelial cells. The intra-articular injection of 0.5 mL of Freund’s complete adjuvant produced a neutrophilic synovitis of moderate to severe intensity, similar to the natural synovitis, reinforcing the effectiveness of this model in the study of the pathophysiology and treatment of joint diseases.
KEY WORDS: Equine orthopedics, synovitis, synovial fluid.