Poly(ɛ-caprolactone) and Polyethylene Glycol Diacrylate-based Scaffolds for TMJ Bioengineered Disc Implants

The mechanics of tissue-engineered temporomandibular joint discs: Current status and prospects for enhancement

The temporomandibular joint (TMJ) disc is an essential protective but vulnerable fibrocartilage. Their high mechanical strength is vital in absorbing loads, reducing friction, and protecting the condylar surface. Many diseases can lead to the destruction or degeneration of the mechanical function of the TMJ disc. Unfortunately, conservative treatment is ineffective in restoring the defective mechanical properties of the discs. Tissue engineering has been investigated as a promising alternative treatment approach to approximate the properties of native tissue. However, it is difficult for tissue-engineered discs to obtain sufficient mechanical properties. Several approaches have been proposed to improve the mechanical properties of tissue-engineered constructs. In this review, we summarized the mechanical properties of native TMJ discs and discussed the current mechanical testing methods. We then summarized the current advances in improving the mechanical properties of TMJ disc tissue-engineered constructs. Moreover, existing challenges and outbreak directions are discussed. This review assists future research in better understanding the mechanical properties of both native and tissue-engineered TMJ discs. It provides new insights into future mechanical property enhancement for TMJ disc tissue engineering.

Decellularized-disc based allograft and xenograft prosthesis for the long-term precise reconstruction of temporomandibular joint disc

Currently, no effective disc reconstruction treatment strategy is clinically available for temporomandibular joint (TMJ) disc-related diseases. To address this, we developed a prosthesis construct with laser-drilled decellularized natural disc reinforced by polycaprolactone, which mimics the natural morphology, and structural, biomechanical and biological property of the TMJ disc. The construct demonstrated good biocompatibility, safety and immunological tolerance both in vitro, and in a rat subcutaneous model. During 6 months implantation in an allogeneic rabbit TMJ disc reconstruction model, the disc prosthesis maintained its integrity, collagen fiber-orientation, mechanical property, joint structural stability and prevented articular cartilage and bone from damage. Furthermore, the "upgraded" disc prosthesis obtained from decellularized porcine disc was implanted into a goat TMJ disc reconstruction model. The xenograft prosthesis, with strength and viscoelasticity similar to a natural TMJ disc, was able to restore the structure and function of TMJ up to 20 weeks. These results demonstrate the translational feasibility of an allogeneic or xenogeneic decellularized disc prosthesis for treatment of advanced TMJ disc-related diseases. STATEMENT OF SIGNIFICANCE: This study makes a significant contribution to TMJ disc disease treatment both in theory and in clinics, because: (1) it provided an innovative approach to prepare an artificial TMJ disc with decent mechanical properties and long-term condyle-protecting effect; (2) it specified an advanced decellularized method for fibrocartilage decellularization and xenograft application; (3) it developed a facile and reproducible TMJ disc reconstruction model not only for middle size animal but also for large animal study; (4) the comprehensive and unreported biomechanical tests on the natural TMJ discs would act as a valuable reference for further research in the field of artificial TMJ disc materials or TMJ disc tissue engineering; (5) it suggested a potential treatment for patients with severe TMJ diseases that were commonly met but difficult to treat in clinics.

Assessment of 3D-Printed Polycaprolactone, Hydroxyapatite Nanoparticles and Diacrylate Poly(ethylene glycol) Scaffolds for Bone Regeneration

Notwithstanding the advances achieved in the last decades in the field of synthetic bone substitutes, the development of biodegradable 3D-printed scaffolds with ideal mechanical and biological properties remains an unattained challenge. In the present work, a new approach to produce synthetic bone grafts that mimic complex bone structure is explored. For the first time, three scaffolds of various composition, namely polycaprolactone (PCL), PCL/hydroxyapatite nanoparticles (HANp) and PCL/HANp/diacrylate poly(ethylene glycol) (PEGDA), were manufactured by extrusion. Following the production and characterisation of the scaffolds, an in vitro evaluation was carried out using human dental pulp stem/stromal cells (hDPSCs). Through the findings, it was possible to conclude that, in all groups, the scaffolds were successfully produced presenting networks of interconnected channels, adequate porosity for migration and proliferation of osteoblasts (approximately 50%). Furthermore, according to the in vitro analysis, all groups were considered non-cytotoxic in contact with the cells. Nevertheless, the group with PEGDA revealed hydrophilic properties (15.15° ± 4.06) and adequate mechanical performance (10.41 MPa ± 0.934) and demonstrated significantly higher cell viability than the other groups analysed. The scaffolds with PEGDA suggested an increase in cell adhesion and proliferation, thus are more appropriate for bone regeneration. To conclude, findings in this study demonstrated that PCL, HANp and PEGDA scaffolds may have promising effects on bone regeneration and might open new insights for 3D tissue substitutes.

Creating In Vitro Three-Dimensional Tumor Models: A Guide for the Biofabrication of a Primary Osteosarcoma Model

Osteosarcoma (OS) is a highly aggressive primary bone tumor. The mainstay for its treatment is multiagent chemotherapy and surgical resection, with a 50-70% 5-year survival rate. Despite the huge effort made by clinicians and researchers in the past 30 years, limited progress has been made to improve patient outcomes. As novel therapeutic approaches for OS become available, such as monoclonal antibodies, small molecules, and immunotherapies, the need for OS preclinical model development becomes equally pressing. Three-dimensional (3D) OS models represent an alternative system to study this tumor: In contrast to two-dimensional monolayers, 3D matrices can recapitulate key elements of the tumor microenvironment (TME), such as the cellular interaction with the bone mineralized matrix. The advancement of tissue engineering and biofabrication techniques enables the incorporation of specific TME aspects into 3D models, to investigate the contribution of individual components to tumor progression and enhance understanding of basic OS biology. The use of biomaterials that mimic the extracellular matrix could also facilitate the testing of drugs targeting the TME itself, allowing a larger range of therapeutics to be tested, while averting the ethical implications and high cost associated with in vivo preclinical models. This review aims at serving as a practical guide by delineating the OS TME ("what it is like") and, in turn, propose various biofabrication strategies to create a 3D model ("how to recreate it"), to improve the in vitro representation of the OS tumor and ultimately generate more accurate drug response profiles.

Tissue Engineering for the Temporomandibular Joint

Tissue engineering potentially offers new treatments for disorders of the temporomandibular joint which frequently afflict patients. Damage or disease in this area adversely affects masticatory function and speaking, reducing patients' quality of life. Effective treatment options for patients suffering from severe temporomandibular joint disorders are in high demand because surgical options are restricted to removal of damaged tissue or complete replacement of the joint with prosthetics. Tissue engineering approaches for the temporomandibular joint are a promising alternative to the limited clinical treatment options. However, tissue engineering is still a developing field and only in its formative years for the temporomandibular joint. This review outlines the anatomical and physiological characteristics of the temporomandibular joint, clinical management of temporomandibular joint disorder, and current perspectives in the tissue engineering approach for the temporomandibular joint disorder. The tissue engineering perspectives have been categorized according to the primary structures of the temporomandibular joint: the disc, the mandibular condyle, and the glenoid fossa. In each section, contemporary approaches in cellularization, growth factor selection, and scaffold fabrication strategies are reviewed in detail along with their achievements and challenges.