Tissue engineering of different cartilage types: a review of different approaches and recent advances

Cartilage is a connective tissue that serves as a structural support for maintaining the shape for specific appendices (nose, ear) and also helps for shock absorption when present in joints. Different types of cartilage coexist in the body: hyaline, elastic and fibrocartilage. Due to their different embryologic origin, they produce distinct extracellular matrix and therefore have specific functions according to their location. Cartilage is frequently subjected to many different lesions. Those include traumatic, metabolic and congenital forms, concerning all regions where this tissue is present: joints, head and neck area, intervertebral disks, etc. Increasing number of cancers also affects cartilage; especially in ear, nose and trachea. Unfortunately, this tissue has a poor regeneration ability. Few therapeutic options exist for cartilaginous lesions and most of them concern articular cartilage. They include micro fracture, autologous chondrocytes implantation, mosaicplasty, allograft and prosthesis. Ear and trachea are also targeted for reconstruction with lesser extent. Therefore, cartilage engineering highly addresses increasing number of pathologies associated to this tissue. In the last two decades, several trials were investigated using both progenitor cells and scaffolds. Even bone marrow derived stem cells were widely used and served as gold standard. Many progenitors from different areas are investigated for their capacity of chondrogenesis. On the other hand, biomaterials, natural and synthetic, are used to induce a 3D environment that allows proper growth and differentiation toward cartilage formation. Their characteristics depend on the location of the expected graft where porosity, biodegradability, ability to support strength and large scale use are the key points. Favorable environments are also needed to achieve appropriate chondrogenesis, including biochemical or mechanical stimuli and low oxygen tension. Bioprinting showed also encouraging outcomes in cartilage reconstruction with the investigation of several scaffolds