Mechanical loading of ex vivo bovine trabecular bone in 3D printed bioreactor chambers

Previous ex vivo bone culture methods have successfully implemented polycarbonate (PC) bioreactors to investigate bone adaptation to mechanical load; however, they are difficult to fabricate and have been limited to a 5 mm maximum specimen height. The objective of this study was to validate a custom-made 3D printed MED610^TM bioreactor system that addresses the limitations of the PC bioreactor and assess its efficacy in ex vivo bone culture. Twenty-three viable trabecular bone cores (10 mm height by 10 mm diameter) from an 18-month-old bovine sternum were cultured in MED610^TM bioreactors with culture medium at 37 °C and 5% CO₂ for 21-days. Bone cores were ranked based on their day 0 apparent elastic modulus (E_app) and evenly separated into a "Load" group (n = 12) and a control group (n = 11). The Load group was loaded five times per week with a sinusoidal strain waveform between -1000 and -5000 με for 120 cycles at 2 Hz. E_app was assessed on day 0, 8, and 21 using quasi-static tests with a -4000 με applied strain. Over 21-days, the E_app of Load group samples tended to increase by more than double the control group (53.4% versus 20.9%) and no visual culture contamination was observed. This study demonstrated that bone organ culture in 3D printed MED610^TM bioreactors replicated E_app trends found in previous studies with PC bioreactors. However, further studies are warranted with a larger sample size to increase statistical power and histology to assess cell viability and bone mineral apposition rate.