Enhanced osteogenic differentiation and biomineralization in mouse mesenchymal stromal cells on a β-TCP robocast scaffold modified with collagen nanofibers

Abstract

Calcium phosphate ceramics have been widely used in clinics as bone grafts. However, according to traditional techniques, it is difficult to create calcium phosphate bone grafts with tailored internal porous structures that may ensure optimal biocompatibility and sufficient mechanical properties. In this study, β-TCP bone scaffolds with well-defined inter-connective porous structures were fabricated by robocasting. With the aim of better mimicking the native extracellular matrix of bone without sacrificing the mechanical strength, type I collagen gel was coated on the filaments of the sintered β-TCP scaffolds to form an ultrafine fibrous network that was similar to the natural collagen nanofibers in bone. Both sintered β-TCP scaffolds and collagen gel coated scaffolds supported the growth of mouse mesenchymal stromal cells (mMSCs). Meanwhile, the thin layer of biomimetic collagen nanofibers on the β-TCP scaffolds significantly stimulated the osteoblastic differentiation of mMSCs by up-regulating the expression of ALP, Runx-2, collagen I, OPN, BSP and BMP-2. Additionally, a more active biogenesis of matrix vesicles (MVs) was induced in the mMSCs on the collagen gel coated scaffolds, evidenced by SEM and TEM results together with a significant increase of the gene expression of matrix vesicle components, indicating an enhanced initiation of matrix mineralization. Our study not only illustrates the potential use of the collagen gel coated β-TCP robocast scaffold for bone repair but also highlights the significance of the incorporation of collagen nanofibers in the scaffolds.