Immunological response to bolus versus multiple injections of hylan G-F 20 (Synvisc) in a murine biocompatibility model.

Local tissue reactivity to intra-articular injections of hyaluronic acid hylan G-F 20 (Synvisc) has been described. We used a murine biocompatibility model to study the inflammatory response to Synvisc after a single bolus injection versus the traditional three shot series of injections. Air pouches were established subcutaneously in BALB/c mice, which were injected with phosphate-buffered saline (PBS), 5 mg ultra-high molecular weight polyethylene particles (to simulate synthetic joint wear debris, positive control), 0.5 mL Synvisc (one injection/week for three weeks, harvested 14 days after last injection), or 1.5 mL Synvisc bolus (harvested either 14 or 28 days after last injection). Inflammatory gene expression and inflammation of air pouch tissue, and serum antibody titers to Synvisc were determined. Inflammation was observed with all Synvisc treatments relative to PBS (p < 0.01). However, the three injection series of Synvisc resulted in significantly (p < 0.05) greater tumor necrosis factor-alpha gene expression compared to both PBS and bolus single shot Synvisc harvested after 14 or 28 days. While all Synvisc treatments resulted in serum antibodies to Synvisc (p < 0.02 compared to PBS control group), mice that received three injections of Synvisc had higher levels than mice receiving a single injection (p < 0.01). These results demonstrate that a single bolus injection of Synvisc led to less inflammation and a lower antibody response when compared to the three-shot series of injections, supporting the current change in treatment from multiple injections to a single injection of Synvisc .