The role of matrix properties and extrinsic loading in osteoblast-osteocyte differentiation in tissue engineered scaffolds

Abstract

Bone tissue engineering is a promising field with the potential to generate tissue substitutes, by taking advantage of mesenchymal stem cells ability to grow and produce tissue substitutes under specific physical conditions. However, to date the development of functional tissue substitutes has been limited, due to inconsistent tissue formation. Moreover, it has not yet been possible to establish osteoblast and osteocyte networks using existing tissue engineering approaches in vitro, albeit that these cell networks play a vital role in bone regeneration and long term maintenance of the bone microenvironment in vivo. Extracellular cues from the extracellular matrix have been shown to regulate osteocyte differentiation in two dimensional (2D) environments in vitro. Cell-seeding strategies (e.g. seeding density, peripheral seeding or cell encapsulation), govern tissue formation on TE scaffolds, but it has not yet been established what the optimal seeding approach is to achieve the phenotypic shift from osteoblasts to osteocytes and to establish a 3D cellular network. Mechanical stimulation in the form of fluid perfusion or mechanical strain can enhance cell distribution, osteogenic differentiation, nutrient and waste transport and hence overall bone tissue formation. However, the specific mechanical cues (both matrix-derived and extrinsically applied) required for osteoblast-osteocyte differentiation have not been identified. Therefore, the objective of this PhD thesis is to develop a bone regeneration strategy that optimises cell seeding and mimics in vivo mechanical stimulation, in particular extracellular matrix properties, compression and fluid flow, to investigate how such stimuli regulate both osteoblast and osteocyte phenotypes within porous TE constructs.