The effect of hyaluronan on mouse intramembranous osteogenesis in vitro.

Hyaluronan (HA) is an almost ubiquitous component of extracellular matrices. Early in embryogenesis mesenchymal cells migrate, proliferate and differentiate, in part, because of the influence of HA. Because many of the features of embryogenesis are revisited during wound repair, including bone fracture repair, this study was initiated to evaluate whether HA has an effect on calcification and bone formation in an in vitro system of osteogenesis. Enzyme-digested calvarial mesenchymal cells from 13-day-old mouse embryos were cultured in BGJb medium with rooster comb hyaluronan in seven different molecular weights (30, 40, 90, 160, 550, 660, and 1300 kDa). The dosages for each molecular weight were 0.5, 1.0 and 2. 0 mg/ml. HA was added once to the medium at the plating of cells. After 10 days in culture, with low molecular weight hyaluronan (30 and 40 kDa) bone colonies were identifiable on a base of confluent fibroblasts. The number of colonies was larger than controls, particularly in the 1.0 and 2.0 mg/ml dosages of both 30 and 40 kDa of HA. Hyaluronan of high molecular weight, no matter what the dose, showed no significant bone colony formation, with apparent cell growth inhibition. Higher molecular weights were thereafter not included in this study. No statistically significant difference in the size of colonies was found when compared to controls in the 30 and 40 kDa bone colonies no matter what the dose.