Differentiating mesenchymal stromal cells into healthy chondrocytes for articular cartilage requires a variety of biochemical and biomechanical stimuli. While the effects of such stimuli on chondrogenic markers are well-studied, no bioreactor has thus far collected real-time data from mRNA expression for use in closed-loop control. Here, we present the design of an automated bioreactor that applies perfusion, oscillating hydrostatic pressure, and varying concentrations of multiple biochemical growth factors to the cell cultures while measuring fluorescent markers of gene expression in real-time. Our system achieves a gradated hydrodynamic environment across the length of cell cultures with flow rates between 0.46 and 3.2 cm s-1 and shear stresses between 5.0 and 60 mPa, can apply oscillating hydrostatic pressure at up to 0.5 Hz and 4.83 MPa, and can dynamically control the concentrations of two biochemical growth factors. The integrated fluorescent fiberscope system can measure fluorescent dye concentrations as low as 3 nᴍ within the cell chamber. Our LNA/DNA nano-biosensor is designed to track Sox9 mRNA, a gene critical to the chondrogenic process. The reactor is controlled via MATLAB Simulink and includes remote observation and control features to increase flexibility and minimize downtime. This novel bioreactor provides a platform for further articular cartilage research with the ultimate design goal of generating a transfer function that maps growth factor inputs to mRNA expression outputs for real-time control.
Schuler et al. (Thu,) studied this question.