Abstract
The global population is experiencing a progressive increase in the ageing demographic. Many elderly individuals are significantly impacted in terms of their quality of life due to bone and cartilage injuries. With advancing age, the articular cartilage undergoes abnormal friction due to reduced synovial fluid in the joint, leading to cartilage degradation and wear. The subchondral bone, devoid of the protective cartilage layer, also experiences wear, resulting in symptoms associated with osteoarthritis, such as joint pain and morning stiffness, thereby affecting patients' mobility patterns. In advanced stages of osteoarthritis, joint replacement surgery, utilising prosthetic scaffolds to replace the diseased joint, is commonly employed in clinical practice to improve patients’ quality of life. In recent years, novel materials for bone and cartilage repair have gained significant attention from researchers. It has been reported that research teams have explored the use of stem cells for bone and cartilage regeneration, as well as the application of biomaterials such as hydrogels and decellularised bone for tissue repair. This thesis describes different treatment methods for decellularised natural transparent cartilage scaffolds (dLhCG) as a biological material and evaluates the effectiveness of dLhCG treated with various methods for bone and cartilage repair.In the first chapter of this thesis, the current research status of bone and cartilage defects and osteoarthritis will be outlined. The existing treatment methods for osteoarthritis, evaluation of the characteristics and pros and cons of various joint replacement materials will be discussed. The biological processes related to bone regeneration will be explored, along with the preparation methods of decellularised natural transparent cartilage scaffolds and the fundamental design approach for this study.
The second chapter of this thesis will provide a literature review focusing on bone tissue engineering and related biomaterials. The main content will cover the current development status of tissue engineering, bone structure, an introduction to bone formation and regeneration, as well as several types of materials commonly used for bone regeneration. This chapter will emphasise the application of tissue-engineered bone materials and briefly discuss the use of cells in tissue engineering, providing an outlook on their future development.
In the third chapter of this thesis, the focus will be on describing the method and effectiveness of preparing artificial bone scaffolds using decellularised natural hyaline cartilage scaffolds (dLhCG) in vitro. The experimental design is based on the in vivo process of endochondral ossification. Mesenchymal stem cells derived from bone marrow were implanted into dLhCG in vitro, and the dLhCG scaffold provided a cartilage environment that closely simulated the in vivo process of endochondral ossification. The recellularised dLhCG (rLhCG) was treated with different differentiation mediums to induce the mesenchymal stem cells to differentiate into chondrocytes, undergo hypertrophy and transdifferentiation, ultimately differentiating into osteoblasts and achieve their corresponding functions. The mesenchymal stem cells were also directly induced to differentiate into osteoblasts through an osteogenic differentiation medium, serving as a control group to the chondrogenic differentiation process mentioned above. After the completion of the in vitro preparation process, the obtained product (OsLhCG) is characterised using qPCR, immunohistochemistry, RNA-Seq, etc. The treated OsLhCG was also implanted into the omentum of nude mice to observe its angiogenic capability. Furthermore, the treated OsLhCG was decellularised and implanted into rat femoral defects, and after 30 days, the bone tissue was harvested and characterised to evaluate its bone repair ability. From the experimental results, it can be concluded that the process of simulating in vivo endochondral ossification, where mesenchymal stem cells differentiate into chondrocytes, hypertrophic chondrocytes, and transdifferentiate into osteoblasts, and replace the cartilage matrix with newly deposited bone matrix, can be achieved with a cartilaginous scaffold (dLhCG) as the growth environment. The OsLhCG obtained through this method exhibits properties similar to natural bone tissue, including vascularisation and the ability to repair bone defects.
The fourth chapter of this thesis will focus on the application of transglutaminase (TGase) catalysis to achieve gelation of gelatine, thereby integrating dLhCG powders into a hydrogel and achieving in situ repair of cartilage defects. Due to the use of fixed-shaped moulds in the production process, dLhCG often maintains its original shape after preparation, which may not perfectly fit the shape of the affected area, resulting in poor integration with natural cartilage tissue. TGase can catalyse the reaction between the γ-glutamylamide groups of the glutamine residue side chain and the ε-amino groups of lysine residues at 37 degrees Celsius. Compared to thermo-induced gelatine hydrogel, the hydrogel formed through transglutaminase-catalysed cross-linking remains unchanged in terms of flowability and inherent structure at physiological temperature, approximately 37 degrees Celsius. Furthermore, it retains sufficient mechanical strength to enable cartilage repair. When encapsulating dLhCG powder, the hydrogel initially retains its flowability, allowing it to form a hydrogel with a suitable shape for the cartilage defect site, promoting better repair and regeneration of the cartilage defect. Based on the aforementioned design concept, a Gelatine-dLhCG powder (TgCOL2-G) model was established in vitro, and its relevant characteristics were tested with and without cell encapsulation, such as mechanical properties, cytotoxicity, swelling ratio, etc. The experimental results indicate that TgCOL2-G is non-toxic to cells and supports the proliferation and functionality of chondrocytes, including matrix secretion. Furthermore, TgCOL2-G exhibits appropriate mechanical properties and is biodegradable, demonstrating its potential for application in the field of cartilage defect repair at the performance level.
Chapter 5 of this thesis serves as the conclusion, providing a concise summary of the research findings and outlining the future experimental plans.
In conclusion, this study provides a comprehensive overview of the current applications of biomaterials and stem cells in bone and cartilage defect repair. Through the utilisation of chemical and biological methods, the original materials have been modified and optimised to achieve enhanced tissue repair outcomes. This research offers valuable insights and serves as a significant reference for addressing the challenges associated with bone and cartilage repair.
| Date of Award | 10 Jan 2024 |
|---|---|
| Original language | English |
| Awarding Institution |
|
| Supervisor | Dongan WANG (Supervisor) |