The effect of hyaluronan on osteogenesis in allogeneic bone grafting

ABSTRACT

Hyaluronan is an essential component of extracellular matrices. Early in embryogenesis mesenchymal cells migrate, proliferate and differentiate, in part, because of the influence of hyaluronan. Since the features of embryogenesis are revisited during wound healing, including bone fracture repair, this study was initiated to evaluate whether hyaluronan has an effect on osteogenesis in early stage of wound healing. Grafting bone chip was applied on the two squared shaped bone defects on the total 60 rat calvarium about 7x7 mm size which were made with electric drill intentionally, the right side was grafted with allogeneic bone and the left side was autogenous bone grafting. In experimental groups, grafting materials were hydrated with 1.0 mg/ml concentration of hyaluronan solution before surgery for 30 minutes. The calvarial bone defects were covered with layer suture. In postoperative 1, 2, 4, 6 and 8 weeks, total experimental rats were sacrificed and evaluated under light microscope with routine H&E, Masson Trichrome and toluidine blue stain and found initial osteogenesis at postoperative 1 and 2 weeks under electric microscope. In postoperative 1 and 2 weeks, inflammatory changes in the wound sites were more prominent in bones to which hyaluronan had been applied. But, new bone formation had been induced by day 7 on both periand endosteal surfaces of the grafted areas. Newly formed trabecular bones were filled in grafted wound and the active bone remodeling by osteoblast and osteoclast had occurred till postoperative 4 weeks. The mature bone formation on both calvarial bone defects after 4 weeks without distinctive difference between control and hyaluronan groups. These results suggest that high-molecular hyaluronan is capable of accelerating new bone formation through mesenchymal cell differentiation in bone grafting.