Articular cartilage is a load-bearing tissue that lines the surface of bones in diarthrodial joints. The location of articular cartilage gives reason for its function as a shock absorbing tissue that provides low friction movement during articulation, protecting the ends of bones and allowing pain-free articulation. It is commonly described as a tissue that is made of up to 80% water, is devoid of blood vessels, nerves, and lymphatics, and is populated by only one cell type, the chondrocyte, leading to this avascular tissue having a limited capacity for intrinsic repair. According to the 2018 WHO Global Burden of Disease Study, over 300 million people have suffered from osteoarthritis (OA) from 1990 to 2017. Patients that respond poorly to conventional therapies are ultimately treated with surgical procedures to promote cartilage repair by the implantation of artificial joint structures (arthroplasty) or total joint replacement (TJR).

This poor repair capability, coupled with the high frequency of injuries and high cost, positions cartilage repair at the forefront of stem cell-driven regenerative medicine approaches. Although many attempts, ranging from bone marrow stimulation techniques to more complex autologous chondrocyte implantation (ACI), have been made to repair articular cartilage defects, no strategy has yet succeeded in generating tissue that adequately restores damaged cartilage. The limitations of current treatments for cartilage defects have prompted the field of cartilage tissue engineering to seek to integrate engineering and biological principles to promote the growth of new cartilage to replace damaged tissue. However, significant challenges remain in translating basic bioscience into clinical applications.

The aim of this Special Issue is to solicit original research articles focusing on recent progress in mechanistic understanding and enhancement of existing and potential therapies for cartilage regeneration. Review articles which describe the current state of cartilage tissue engineering are also welcomed.

Potential topics include but are not limited to the following:

• Stem cell-driven models of cartilage differentiation
• Cartilage stem/progenitor cells
• Cross talk between mesenchymal stem cells (MSCs), their secretome, and the microenvironment
• Immunomodulation properties of stem cells
• Additive manufacturing approaches
• Synthetic extracellular matrix (ECM) generation
• Interplay of ECM components, cells, and molecules in cartilage regeneration
• The role of immunomodulation in cartilage regeneration
• In vivo models of cartilage repair
• Discovery of potential therapeutic methods targeting resident stem/progenitor cells in joints, including small molecular drugs
• Incorporation of biomimetic materials into cartilage repair strategies
• Micro and nanotechnology approaches to repair and drug delivery
• Studies of the developmental mechanisms of chondrogenesis
• In situ cartilage tissue engineering