Deformation strain is the main physical driver for skeletal precursors to undergo osteogenesis in earlier stages of osteogenic cell maturation

Abstract

Mesenchymal stem cells play a major role during bone remodelling and are thus of high interest for tissue engineering and regenerative medicine applications. Mechanical stimuli, that is, deformation strain and interstitial fluid-flow-induced shear stress, promote osteogenic lineage commitment. However, the predominant physical stimulus that drives early osteogenic cell maturation is not clearly identified. The evaluation of each stimulus is challenging, as deformation and fluid-flow-induced shear stress interdepend. In this study, we developed a bioreactor that was used to culture mesenchymal stem cells harbouring a strain-responsive AP-1 luciferase reporter construct, on porous scaffolds. In addition to the reporter, mineralization and vitality of the cells was investigated by alizarin red staining and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. Quantification of the expression of genes associated to bone regeneration and bone remodelling was used to confirm alizarin red measurements. Controlled perfusion and deformation of the 3-dimensional scaffold facilitated the alteration of the expression of osteogenic markers, luciferase activity, and calcification. To isolate the specific impact of scaffold deformation, a computational model was developed to derive a perfusion flow profile that results in dynamic shear stress conditions present in periodically loaded scaffolds. In comparison to actually deformed scaffolds, a lower expression of all measured readout parameters indicated that deformation strain is the predominant stimulus for skeletal precursors to undergo osteogenesis in earlier stages of osteogenic cell maturation.

Modeling of the Human Bone Environment: Mechanical Stimuli Guide Mesenchymal Stem Cell–Extracellular Matrix Interactions

“…A custom-made bioreactor system, previously described in [ 36 ], was designed to mimic the mechanical environment to which bone tissue is subjected in vivo, where both shear stress and cyclic compression can be applied to the cell-seeded scaffolds. Briefly, the system can be separated into three compartments—(1) the bioreactor cartridge, where the cell-seeded scaffolds are harbored inside a 10.4 mm diameter silicone housing, which allows gas exchange while avoiding fluid extravasation; (2) a computer-controllable peristaltic pump that ensures the continuous fluid flow of the cell culture medium through a unidirectional closed-circuit centered between the bioreactor-cartridge and the medium reservoir; and (3) an uniaxial loading unit directly connected with the bioreactor cartridge, where frequency and magnitude of the piston displacement can be tailored.…”

Journey into Bone Models: A Review

“…Yet, it served as a successful demonstration of the beneficial effects of mechanical load in the context of 3D in vitro bone formation. In this regard, the bioreactor model used by Kleinhans et al was further modified to allow cyclic compression while perfusing the tissue construct [ 189 ]. Since bioreactor experiments are rather expensive regarding time and cost, parallelization can help to reduce these expenses per experiment while the overall throughput is enhanced.…”

Multiphysics simulation of a compression–perfusion combined bioreactor to predict the mechanical microenvironment during bone metastatic breast cancer loading experiments

“…Matrix deformations and fluid flow occur together (Robling & Turner, 2009), thus delineating the individual roles of each signal in cancer cell mechanobiology studies is challenging. One approach is to apply perfusion and compression in combination and isolation, and several recent studies using this approach report that fluid flow‐ and compression‐induced signals together enhance bone anabolism (Ramani‐Mohan et al, 2018; Zhao et al, 2015, 2018). For example, multiscale computational modeling of a hydrogel scaffold undergoing perfusion, compression, or both predicted that the combination of low magnitude (0.5% peak strain) compression and pore pressure (10 kPa) would induce more osteogenic differentiation and bone mass (Zhao et al, 2018), perhaps as a result of greater cell deformation (Zhao et al, 2015).…”