Rotating-wall vessels, promising bioreactors for osteoblastic cell culture: comparison with other 3D conditions.

Osteoblastic cells cultured on microcarriers in bioreactors are a potentially useful tool to reproduce the in vivo three-dimensional (3D) bone network. The aim is to compare different types of 3D and two-dimensional (2D) osteoblastic culture. ROS17/2.8 cells are cultured in a bioreactor (rotating-wall vessel) or in two kinds of control (3D petri dish, 3D Percoll) and on two types of microcarrier (Cytodex 3 and Biosilon). Growth and morphology are determined by cell count and SEM, and differentiation is determined by dosage of alkaline phosphatase (ALP) activity and northern blots (ALP and osteocalcin (OC)). SEM shows that Biosilon microcarriers are the best substrate. Proliferation in the RWV and 3D petri dish is still in the exponential phase, whereas growth in the 2D culture reaches a plateau after eight days of culture. ALP activity and the ALP and OC mRNA levels are similar at day 8 for both the RWV and 3D petri dish. However, at day 10, cells are more differentiated in the RWV. The study shows that osteoblasts are both proliferate and differentiate in 3D structures. A BrDU immunocytochemical approach shows that only the cells in the periphery of the aggregates proliferate. Therefore the bioreactor may be a suitable tissue culture model for investigation of growth and differentiation processes in tissue engineering.