Bioactive scaffold-based tissue engineering strategies for orthopaedic applications

Abstract

Bone transplantation is one of the most frequent procedures performed worldwide. Common grafts include autologous, allogeneic, xenograft or synthetic grafts. The availability of autologous grafts is limited, and leads to donor site morbidities, while allografts and xenografts are associated with the risk of disease transmission, immune rejection and have poorer osteointegration than autografts. BioglassÒ is a commonly used synthetic graft that upon implantation, bonds to hard tissues through hydroxyapatite layer formation however, it comes in block or particle form. Alternatively, fibrous scaffolds are easier to handle, and they resemble the fibrillar structure of bone extracellular matrix. Cotton-wool like bioactive glass fibres can be easily packed into the defect site, however, their effect on bone formation and angiogenesis has not been evaluated. In this thesis it is hypothesised that 70S30C cotton-wool like bioactive glass fibres have osteo-stimulatory properties and are able to enhance tube like network formation which ultimately could be exploited for non-load bearing bone regeneration applications. Cotton- wool like bioactive glass fibres, were created through the electrospinning process. Several electrospinning parameters were optimised to produce bead free fibres with homogeneous diameters. Human bone marrow mesenchymal stem cells (MSCs) were used to assess in vitro effect of the fibres on cell attachment and proliferation, however the data was inconclusive. The 7osteo-stimulatory effect of bioactive glass has been credited to the ion release, hence conditioned media was obtained from the dissolution of the fibres in cell culture medium and it was shown not to inhibit cell proliferation. Furthermore, it was revealed that the conditioned media combined with the commonly used osteogenic supplements resulted in earlier and stronger osteogenic differentiation of MSCs than commercially available osteogenic media alone. Furthermore, the osteo-stimulatory ability of fibre conditioned media surpassed that of BioglassÒ. MSCs grown in the presence of fibre conditioned media produced higher levels of calcium, collagen and osteocalcin. Gene expression analysis revealed that MSCs undergo faster osteogenic differentiation in the presence of conditioned-osteogenic media than in osteogenic media alone. However, the fibre conditioned media failed to enhance tube-like network formation when human umbilical vein endothelial cells and MSCs were co-cultured in collagen gel. This thesis demonstrates, for the first time, ability of the 70S30C bioactive glass conditioned media to induce osteogenic differentiation of MSCs, which could have a broad range of applications, from bone fracture healing to osteoporosis treatments, osteosarcoma lesion healing and periodontal disease management.

Date of Award	31 Dec 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Susan Kimber (Supervisor), Philip Withers (Supervisor) & Olga Tsigkou (Supervisor)