Problem and study aim:

Millions of patients each year suffer from non-healing bone defects secondary to trauma, cancer, osteomyelitis, or congenital anomalies. The standard of care for managing these cases necessitates bone reconstruction surgery. Although using autologous bone (autograft) or banked cadaveric bone (allograft) has been considered the standard of care for decades, both come with significant attendant risks and limitations. Commercially available bone substitute materials overcome some of these challenges but do not necessarily meet the challenging anatomical and mechanical requirements of patients undergoing complex bone reconstruction surgeries. For this reason, there is a clear, unmet need for biomaterials that can support bone healing and act as bone graft substitutes for patients with challenging and non-healing bone defects.

The ultimate goal of my work is to offer a solution to non-healing bone defects with a particular focus on developing and characterising an osteoinductive, biocompatible and mechanically robust biomaterial that can act as a bone graft substitute to support bone healing for critical size (non-healing) bone defects and can be customised to patients’ specific needs.

Research Methodology:

The work in this thesis extends across five fundamental sections:
1- Isolation and characterisation of adipose-derived mesenchymal stem cells (Ad-MSCs) as a source of osteogenic precursor cells.
2- Investigating the potential use of extracorporeal shockwave therapy (ESWT) to stimulate bone healing.
3- Development of a novel 3D printable biomaterial, based on decellularised bone matrix (DCBM), for potential use as bone graft substitute and in-vitro characterisation of the scaffolds to ensure complete decellularisation, evaluate mineral content, cytocompatibility, osteoinductivity, microstructure and biomechanical properties.
4- In-vivo testing of the local biological effect of candidate biomaterials following subcutaneous implantation in rats.
5- In-vivo evaluation of the biomaterials’ ability to support bone healing in a critical-size bone defect (15 mm rabbit’s radius segmental defect).

Results and conclusion:

Our results show that Ad-MSCs were capable of differentiating towards the osteogenic lineage, as indicated by the expression of markers of both early matrix maturation markers (such as (alkaline phosphatase, RUNX2, collagen type I, osteopontin osteonectin) and late matrix mineralisation markers (such as osteocalcin, Alizarin red staining), as well as exhibiting osteoblastic morphology upon scanning electron microscopy.

While ESWT didn’t promote Ad-MSCs proliferation, the results showed that focused ESWT enhances Ad-MSCs osteogenic differentiation ability in-vitro.

The 3D-printed DCBM scaffold was shown to be cytocompatible and osteoinductive. And to have microstructure, mechanical and material properties that support clinical use as a bone graft substitute.

In-vivo testing in the rat subcutaneous model established the biocompatibility of the material, and data from the segmental bone defect study in rabbits confirmed that the scaffolds could integrate with native bone and support osteoinduction and osteoconduction by week 12 post-implantation.