title: Engineered bone culture in a perfusion bioreactor: a 2D computational study of stationary mass and momentum transport.
abstract: Successful bone cell culture in large implants still is a challenge to biologists and requires a strict control of the physicochemical and mechanical environments. This study analyses from the transport phenomena viewpoint the limiting factors of a perfusion bioreactor for bone cell culture within fibrous and porous large implants (2.5 cm in length, a few cubic centimetres in volume, 250 microm in fibre diameter with approximately 60% porosity). A two-dimensional mathematical model, based upon stationary mass and momentum transport in these implants is proposed and numerically solved. Cell oxygen consumption, in accordance theoretically with the Michaelis-Menten law, generates non linearity in the boundary conditions of the convection diffusion equation. Numerical solutions are obtained with a commercial code (Femlab 3.1; Comsol AB, Stockholm, Sweden). Moreover, based on the simplification of transport equations, a simple formula is given for estimating the length of the oxygen penetration within the implant. Results show that within a few hours of culture process and for a perfusion velocity of the order of 10(-4) m s(-1), the local oxygen concentration is everywhere sufficiently high to ensure a suitable cell metabolism. But shear stresses induced by the fluid flow with such a perfusion velocity are found to be locally too large (higher than 10(-3) Pa). Suitable shear stresses are obtained by decreasing the velocity at the inlet to around 2 x 10(-5) m s(-1). But consequently hypoxic regions (low oxygen concentrations) appear at the downstream part of the implant. Thus, it is suggested here that in the determination of the perfusion flow rate within a large implant, a compromise between oxygen supply and shear stress effects must be found in order to obtain a successful cell culture.
authors.affiliation: Laboratoire B2OA, UMR CNRS 7052, Faculté des Sciences et Technologie, Université Paris 12, Créteil Cedex, France. j.pierre@univ-paris12.fr
authors.forename: J
authors.initials: J
authors.lastname: Pierre
authors.forename: C
authors.initials: C
authors.lastname: Oddou
mesh_terms: D000818:Animals; D019149:Bioreactors; D018929:Cell Culture Techniques / Q000379:methods; D002478:Cells, Cultured; D003198:Computer Simulation; D006801:Humans; D040542:Mechanotransduction, Cellular / Q000502:physiology*; D008954:Models, Biological; D010006:Osteoblasts / Q000502:physiology*; D010012:Osteogenesis / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism*; D010477:Perfusion / Q000379:methods; D033081:Shear Strength; D023822:Tissue Engineering / Q000379:methods*
chemical_list: D010100:Oxygen