Bioreactor-based bone tissue engineering: The influence of dynamic flow on osteoblast phenotypic expression and matrix mineralization

doi:10.1073/pnas.0402532101

Bioreactor-based bone tissue engineering: The influence of dynamic flow on osteoblast phenotypic expression and matrix mineralization

Departments of ^*Orthopaedic Surgery, ^†Biomedical Engineering, and ^¶Chemical Engineering, University of Virginia, Charlottesville, VA 22903; ^‡The Wistar Institute, Philadelphia, PA 19104; and ^§Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104

Edited by Robert S. Langer, Massachusetts Institute of Technology, Cambridge, MA, and approved June 22, 2004 (received for review April 9, 2004)

Abstract

An important issue in tissue engineering concerns the possibility of limited tissue ingrowth in tissue-engineered constructs because of insufficient nutrient transport. We report a dynamic flow culture system using high-aspect-ratio vessel rotating bioreactors and 3D scaffolds for culturing rat calvarial osteoblast cells. 3D scaffolds were designed by mixing lighter-than-water (density, <1g/ml) and heavier-than-water (density, >1g/ml) microspheres of 85:15 poly(lactide-co-glycolide). We quantified the rate of 3D flow through the scaffolds by using a particle-tracking system, and the results suggest that motion trajectories and, therefore, the flow velocity around and through scaffolds in rotating bioreactors can be manipulated by varying the ratio of heavier-than-water to lighter-than-water microspheres. When rat primary calvarial cells were cultured on the scaffolds in bioreactors for 7 days, the 3D dynamic flow environment affected bone cell distribution and enhanced cell phenotypic expression and mineralized matrix synthesis within tissue-engineered constructs compared with static conditions. These studies provide a foundation for exploring the effects of dynamic flow on osteoblast function and provide important insight into the design and optimization of 3D scaffolds suitable in bioreactors for in vitro tissue engineering of bone.

Footnotes

↵ ∥ To whom correspondence should be addressed at: Department of Orthopaedic Surgery, University of Virginia, 400 Ray C. Hunt Drive, Suite 330, Charlottesville, VA 22903. E-mail: ctl3f{at}virginia.edu.
This paper was submitted directly (Track II) to the PNAS office.
Abbreviations: PLAGA, poly(lactide-co-glycolide); LTW, lighter than water; HTW, heavier than water; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide; SEM, scanning electronic microscope.