Updated: May 10
Cartilage injuries affect over 6 million people per year in the United States only. Several people visit the hospitals seeking care for knee, ankle and wrist problems, and a common diagnosis is osteoarthritis, a degenerative joint disease. Once injured, cartilage is not capable of self-healing, unlike other self-repair tissues such as the bone [1,2].
The most common intervention for treating chondral injuries is chondroplasty, which removes the loose pieces for cartilage via arthroscopy. Another procedure, called microfracture, involves penetration of the subchondral bone to allow the bone marrow to fill the defect. Although these techniques provide short-term symptomatic relief, the remaining cartilage may suffer accelerated degeneration and formation of mechanically inferior fibrocartilage tissue .
Figure 1: An overview of a typical joint structure .
Using tissue engineering strategies that combine different types of cells and scaffolds as an approach to treat cartilage injuries can save millions of dollars in future healthcare costs [5,6].
Some of the latest technologies are bringing promising results in repairing cartilage from traumatic injury or chondropathies. Adult stem cells have been used in cartilage tissue engineering and many clinical trials are ongoing . The most usual and straightforward method to treat knee cartilage injuries is based on an intra-articular injection of mesenchymal stem cells (MSCs), either directly after isolation or after amplification and culture during two to four weeks. The amplification process consists of an addition of growth factors in an adapted scaffold cultured in hypoxia .
Figure 2: Schematic representation of cell therapy for cartilage based on stem cell implantation .
Advances in 3D bioprinting technology allow the development of effective treatment strategies for several kinds of health problems, including cartilage lesions, promoting efficient delivery of tissue engineered constructs.
A study by Nguyen et al. presented a prospective treatment of knee cartilage lesions using 3D bioprinting. A bioink composed of nanocellulose and alginate was used to bioprint human-derived induced pluripotent stem cells (iPSCs) into cartilage mimics. The bioink was suitable for bioprinting iPSCs to support cartilage production in co-culture with irradiated chondrocytes. After printing, viable cells increased in number over time. This research has the potential to help bring forward 3D bioprinting with iPSCs as a future treatment to repair damaged cartilage in joints like the knee .
3. Martín, A. R., Patel, J. M., Zlotnick, H. M., Carey, J. L. & Mauck, R. L. Emerging therapies for cartilage regeneration in currently excluded ‘red knee’ populations. npj Regenerative Medicine vol. 4 (2019).
6. Francis, S. L., Di Bella, C., Wallace, G. G. & Choong, P. F. M. Cartilage Tissue Engineering Using Stem Cells and Bioprinting Technology—Barriers to Clinical Translation. Frontiers in Surgery vol. 5 (2018).