Abstract
Bone regeneration using a scaffold-based tissue engineering approach involves a spectrum of overlapping processes, which are driven by cell-to-cell, cell-to-extracellular matrix (ECM) and cell-to-biomaterials interactions. Traditionally, the study of osteogenesis potential of tissue-engineered constructs (TECs) in vitro only considers the osteoblasts- or mesenchymal cells (MSCs)-to-biomaterials interactions. However, this poorly recapitulates the process of bone regeneration under physiological conditions. In this study, a growth factors free co-culture model, comprising osteoblasts and monocytes was established to allow for the study of the osteogenesis potential of a TEC taking into consideration osteoblasts-to-monocytes and cells-to-biomaterials interactions. Scaffolds made of medical-grade polycaprolactone (mPCL) were fabricated by means of melt electrospinning writing technique. Subsequently, scaffolds were coated with a thin layer of calcium phosphate (CaP) by means of chemical deposition. Scaffolds with CaP coating were seeded with human-derived primary osteoblasts and monocytes and cultured for up to nine weeks. At several time-points, cells were evaluated for alkaline phosphatase and tartrate-resistant acid phosphatase activity. Additionally, cell morphology was observed through fluorescence microscopy and osteoblastic- and osteoclastic-related gene expression was analyzed by quantitative reverse transcription-polymerase chain reaction. The simultaneous presence of osteoblasts and monocytes and CaP accelerated cell matrix formation on scaffolds. Quantitative gene expression profile showed similar findings. Whereby, osteoblastic- and osteoclastic-related gene expression was highest in the PCL/CaP co-culture groups compared to other groups. This indicated synergistic effects of soluble factors secreted by cells and solubilized inorganic components from the scaffolds in promoting matrix deposition.
