Nancy E. Larsen

Clearance kinetics of a hylan-based viscosupplement after intra-articular and intravenous administration in animal models.

Clearance of hylan fluid and hylan gel, components of the hyaluronan (HA)-derived viscosupplement hylan G-F 20, following intra-articular injection into normal, healthy rabbits was evaluated. Radiolabeled hylan G-F 20 was injected at a volume of 0.3 mL into both knee joints of 12 rabbits. At sacrifice, synovial fluid, joint tissues, blood, popliteal lymph nodes, liver, spleen, kidney, and lung were analyzed for radioactivity. The half-life of the fluid component, a high-molecular weight hylan, was 1.5 ± 0.2 days while the half-life of the hylan gel component, a crosslinked hylan, was 8.8 ± 0.9 days. There was no radioactivity detected in the blood or the major internal organs following intra-articular injection. A rat model was used to evaluate the clearance of a large intravenous bolus of solubilized hylan gel. No accumulation of hylan gel degradation products was observed in any major organs and the half-life of hylan elimination from the blood was within normal ranges for HA elimination. The dosing used in the nonclinical rabbit intra-articular study was equivalent (v/w) to a single 6 mL dose in humans. These results are consistent with the current clinical data that demonstrates safety and effectiveness of an increased volume of hylan G-F 20 injected into the osteoarthritis knee.

Hylan Gel for Soft Tissue Augmentation

Hylan, a hyaluronan derivative, was chemically crosslinked with divinyl sulfone to produce water insoluble, elastoviscous hylan gel slurries. The physical and biological properties of this gel slurry were examined by rheological and particle size analysis and by in vivo studies. Hylan gel slurries are made up of pseudoplastic, deformable gel particles with greater elasticity (at all frequencies) and greater viscosity (at low shear rate, e.g. 0.01 s−1) than the soluble hylan polymer.

CELL ATTACHMENT AND GROWTH ON SOLID HYALURONAN (HYLAN B GEL)

ABSTRACT Hylan B is a water-insoluble hyaluronan produced by bis-ethyl sulfone covalent crosslinks. Hylan B gels containing 0.5% hyaluronan polymers are heat stable, but degradable by various hyaluronidase. They are more resistant to degradation by free radicals than high molecular weight (average MW > 4 million) hyaluronan of hylan A (avg. MW 6 million). Cells after trypsin treatment were seeded on the surface of hylan B gels imbibed with tissue culture media supplemented with fetal bovine serum. Cells from eight established cell lines originating from fibroblasts, epithelial or endothelial cells, chondrocytes, tumor cells and stem cells were used. All but the endothelial-origin cells attach to the gel, but only the L929 fibroblasts and stem cells multiplied. Fibronectins (plasma or cellular) added to the media-imbibed gel promoted the spread of the cells of some of these cell lines, while sulfated glycosaminoglycans inhibited the spread and growth of some of these cells. Some poly-lysines, on the other hand, promoted their growth. First explant chicken embryonic cells were also cultured on hylan B gels. Embryonic fibroblasts from the heart migrated and multiplied on the gel surface when homologous embryo extract was added to the culture medium. The results form these in vitro cell culture studies suggest that hylan B gel matrices may be modified by the addition of various types of cell attachment molecules as a means to promote cell attachment and growth.

DRY FILM MADE OF HYLAN TO PREVENT ADHESION BETWEEN TWO HEALING TISSUE SURFACES

ABSTRACT When the epithelial cell layer covering two adjacent tissues is removed accidentally or intentionally during surgical procedures, the underlying connective tissue will grow together during the wound- healing process. Similarly, when two connective tissue surfaces not covered by endothelium but separated by elastoviscous fluid containing high molecular weight hyaluronan are wounded by trauma or during surgical procedures, they can grow together during the healing process. Such adhesion between two tissue surfaces may interfere with function and the excessive new connective tissue formed (scar tissue) may exert pressure on adjacent nerves, causing chronic pain. This paper describes the use of new formulations of dry films containing only hylan. In animal models, this film prevented adhesion formation between two tissue surfaces denuded from their mesothelial or epithelial cell cover. The most important property of this film after it is hydrated by tissue fluids was that it still adhered to the tissue surface, ensuring its stay in place. Thus, it functions as a barrier material, separating the healing tissues. The films do not cause inflammation or foreign body reaction and they do not interfere with the healing of adjacent tissues. These films successfully prevented adhesions between tissue surfaces in liver and cecal abrasion models in rat and uterine horn abrasion models in rabbits. Such films can also be used as delivery vehicles for various drugs, influencing them by combining their physical barrier effect with regulation effects on the healing process.