Bone tissue engineering bioreactors: dynamic culture and the influence of shear stress

A bone tissue engineering strategy involving the in vitro expansion of cells on a scaffold before implantation into the body represents a promising alternative to current clinical treatments. To improve in vitro culture, bioreactor systems have been widely researched for bone tissue engineering purposes. Spinner flask, rotating wall bioreactors, and perfusion systems have all been the focus of experiments, and each system has advantages and disadvantages. This review seeks to summarize these efforts and provide the current status of research in this area. Research using spinner flasks and rotating wall bioreactors is discussed, but focus is placed on perfusion bioreactor systems. While spinner flasks and rotating wall bioreactors have been shown to improve in vitro culture conditions by increasing homogeneity of nutrients in the media, perfusion systems expose cells to shear stress and more efficiently enhance nutrient transfer. Enhanced mineralized matrix deposition and enhancement of osteoblastic signal expression in response to culture in these systems have been widely reported. This review provides analysis of the causes of these changes in signal expression as well as reports on bioreactor systems that have been commercialized.