Biomimetic fetal rotation bioreactor for engineering bone tissues—Effect of cyclic strains on upregulation of osteogenic gene expression

Abstract

Cells respond to physiological mechanical stresses especially during early fetal development. Adopting a biomimetic approach, it is necessary to develop bioreactor systems to explore the effects of physiologically relevant mechanical strains and shear stresses for functional tissue growth and development. This study introduces a multimodal bioreactor system that allows application of cyclic compressive strains on premature bone grafts that are cultured under biaxial rotation (chamber rotation about 2 axes) conditions for bone tissue engineering. The bioreactor is integrated with sensors for dissolved oxygen levels and pH that allow real-time, non-invasive monitoring of the culture parameters. Mesenchymal stem cells-seeded polycaprolactone-β-tricalcium phosphate scaffolds were cultured in this bioreactor over 2 weeks in 4 different modes-static, cyclic compression, biaxial rotation, and multimodal (combination of cyclic compression and biaxial rotation). The multimodal culture resulted in 1.8-fold higher cellular proliferation in comparison with the static controls within the first week. Two weeks of culture in the multimodal bioreactor utilizing the combined effects of optimal fluid flow conditions and cyclic compression led to the upregulation of osteogenic genes alkaline phosphatase (3.2-fold), osteonectin (2.4-fold), osteocalcin (10-fold), and collagen type 1 α1 (2-fold) in comparison with static cultures. We report for the first time, the independent and combined effects of mechanical stimulation and biaxial rotation for bone tissue engineering using a bioreactor platform with non-invasive sensing modalities. The demonstrated results show leaning towards the futuristic vision of using a physiologically relevant bioreactor system for generation of autologous bone grafts for clinical implantation.

Comparative Craniofacial Bone Regeneration Capacities of Mesenchymal Stem Cells Derived from Human Neural Crest Stem Cells and Bone Marrow

“…On days 1, 7, 14 and 21 of culture, cells were harvested from the scaffold and lysed by freeze-thawing as described in Section . The cell lysates were then assessed for DNA content using a PicoGreen DNA quantification kit (Molecular Probes, USA) following manufacturer’s instructions and as described previously …”

“…On day 21 of the scaffold studies, cell lysates from scaffolds were obtained by the freeze-thaw method as stated above and acellular PCL-TCP scaffolds were used as a control to offset the calcium eluted from the scaffold. Calcium deposits were dissolved in 0.5 N acetic acid and the amount of calcium was quantified using the QuantiChrom Calcium Assay kit (Bioassay systems, USA), following manufacturer’s instructions and as described previously …”

A Materials Perspective on the Design of Damage-Resilient Bone Implants Through Additive/Advanced Manufacturing

“…Some of these simulators can be operated during a large number of cycles, under various temperatures and hydration conditions. Finally, bioreactors are being developed to study the response of cells and materials under shear flow in physiological environment (Figure 13E) [140]. Such 3D, complex and varying loading conditions simulators are still to be exploited by scientists and engineers to study the fracture mechanics and resistance of bone and its potential implants, way earlier in the design and fabrication process.…”

Bioengineered Living Bone Grafts—A Concise Review on Bioreactors and Production Techniques In Vitro

“…Results of the studies performed using either commercially available or custom-made rotating bioreactors are summarized in Table 3. Ravichandran et al [85] cultured human BMDSCs on the surface of polycaprolactone/β-tricalcium phosphate-based biomaterials in a multimodal bioreactor system that allows for the application of cyclic compressive strains and biaxial rotation of a chamber. After two weeks of culture, they showed that cells exhibited increased expression of osteogenesis-related genes (ALP, OC, OCN, and COL 1) in comparison with static cultures.…”