Intra-articular injections of hyaluronan solutions of different elastoviscosity reduce nociceptive nerve activity in a model of osteoarthritic knee joint of the guinea pig

Objective: To study in guinea pigs knee joints the effects of intra-articular injection of HYADD®4-G (Fidia-Farmaceutici), a novel hyaluronan (HA)-derived elastoviscous material and of Hyalgan® (Fidia-Farmaceutici), a HA product with very low viscoelasticity, on movement-evoked nociceptor impulse activity from normal and inflamed knee joints. Design: Nociceptor impulse activity was recorded from single Aδ and C fibers of the medial articular nerve either under control conditions or after induction of an experimental knee joint osteoarthritis (OA) by partial medial menisectomy and transection of the anterior cruciate ligament (PMM-TACL). The stimuli consisted of standardized innocuous and noxious inward and outward rotations of the tibia against the femur of 50 s duration, repeated every 5 min for 1.5 h. Results: The number of movement-evoked impulses was significantly augmented 1 day and 1 week after PMM-TACL compared with intact knee joint. The enhanced impulse response to joint movements 1 week following surgery was attenuated by repeated intra-articular injection of HYADD®4-G and even more prominently by Hyalgan®. Conclusions: HA products have a reducing action on joint nociceptor discharges that appears to depend predominantly on their role as an elastoviscous filter associated with their rheological properties, but also on a chemical effect on sensitized nociceptive terminals of inflamed joint tissues, possibly linked to the HA concentration.This work was supported by funds from FIDIA (Italy), and by grants BFU2005-08741 (CB) and BFU2005-03986 (AG) and CONSOLIDER-INGENIO 2010 CSD2007-00023 to C.B., from the Spanish Ministry of Science and Education.Peer Reviewe