Abstract
Articular cartilage is a highly specialised connective tissue of diarthrodial joints which provides a smooth, lubricated surface for joint articulation and plays a crucial role in the transmission of loads. In vivo cartilage is subjected to mechanical stimuli that are essential for cartilage development and the maintenance of a chondrocytic phenotype. Cartilage damage caused by traumatic injuries, ageing, or degradative diseases leads to impaired loading resistance and progressive degeneration of both the articular cartilage and the underlying subchondral bone. Since the tissue has limited self-repairing capacity due its avascular nature, restoration of its mechanical properties is still a major challenge. Tissue engineering techniques have the potential to heal osteochondral defects using a combination of stem cells, growth factors, and biomaterials that could produce a biomechanically functional tissue, representative of native hyaline cartilage. However, current clinical approaches fail to repair full-thickness defects that include the underlying subchondral bone. Moreover, when tested in vivo, current tissue-engineered grafts show limited capacity to regenerate the damaged tissue due to poor integration with host cartilage and the failure to retain structural integrity after insertion, resulting in reduced mechanical function. The aim of this review is to examine the optimal characteristics of osteochondral scaffolds. Additionally, an overview on the latest biomaterials potentially able to replicate the natural mechanical environment of articular cartilage and their role in maintaining mechanical cues to drive chondrogenesis will be detailed, as well as the overall mechanical performance of grafts engineered using different technologies.
Highlights
Specialty section: This article was submitted to Biomaterials, a section of the journal Frontiers in Bioengineering and Biotechnology
This study reported that unconfined compression at 10% strain and 0.5 Hz for 1 h/day significantly reduced GAG production and collagen type II (Col II) synthesis compared to static culture
Synthetic materials provide high tensile stress and compressive modulus, but they are modified, facilitating the creation of layered scaffolds which is a requirement for osteochondral grafts
Summary
Specialty section: This article was submitted to Biomaterials, a section of the journal Frontiers in Bioengineering and Biotechnology. Repetitive overloading or trauma is thought to disrupt the blood supply resulting in osteonecrosis This in turn, may induce microcracks in the subchondral bone plate and underlying bone, resulting in fragmentation of bone and cartilage, causing inflammation, and joint pain. It has been demonstrated that excessive loading, either as single acute event or repetitive stresses, induces the expression of degradative enzymes such as metallopeptidase with a thrombospondin type 1 motif 5 (ADAMTS5) and matrix metalloproteinase-13 (MMP13), affecting matrix composition and playing a pivotal role in pathogenesis (Nakagawa et al, 2012; Buckwalter et al, 2013; Houard et al, 2013; Chang et al, 2019) Both OA ( post-traumatic osteoarthritis: PTOA) and OCD are associated with high-impact sports and abnormal loading/ joint injury, and tend to affect highly stressed joints such as the knee and elbow. Since mechanical loading plays such a vital role in the initiation and progression of osteochondral defects and associated conditions, a deeper understanding of cartilagebone mechanics is essential for developing better diagnosis and treatment methods
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