Chondrocytes
The ones that keep it all together
Credit: Art by Nelly Aghekyan. Set in motion by Dr. Emanuele Petretto. Words by Dr. Masia Maksymowicz. Project Coordinator: Dr. Masia Maksymowicz, Series Director: Dr. Radhika Patnala Sci-Illustrate, Endosymbiont
#Extraordinarycelltypes #sciart #lifescience
Shock protection
Our bodies are affected by many factors every day. We are attacked by pathogens and have to respond to light, sound, and taste. Another stressor for our body is mechanical stress, which is reduced by the presence of a special structure called cartilage. It is a resilient and flexible connective tissue that plays a crucial role in supporting and shaping various structures within the human body. Cartilage comprises specialised cells called chondrocytes embedded in a dense extracellular matrix (ECM) (1). Interestingly, fully developed cartilage lacks blood vessels, nerves, and lymphatic systems, relying on diffusion for nutrient supply (1).
This tissue is found in key locations such as joints, providing a smooth surface for frictionless movement, and in the respiratory tract, shaping the nose and trachea. The extracellular matrix of cartilage includes collagen fibres, proteoglycans, and water, granting it unique biomechanical properties, such as resistance to compression and tension (1).
The main types of cartilage are: hyaline, elastic and fibrocartilage
Hyaline cartilage has a blue-white colour and appears semi-transparent under the microscope. It occurs at the articular surfaces of most bones, the ventral parts of the ribs, and the cartilages of the trachea (2). The hyaline cartilage matrix is formed of type II collagen fibres (2). A special type of hyaline cartilage is articular cartilage, which creates connective tissue of diarthrodial joints. This type of cartilage has limited ability to regenerate (3).
Another type of cartilage, elastic, has a yellow colour, provides flexibility and is resilient to pressure. Elastic cartilage can be found in the ear, larynx, ear, and eustachian tube. The flexibility and memory within elastic cartilage are provided by the elastic fibres (made of protein elastin) that form its matrix (4).
Finally, fibrocartilage is highly resistant to compression, thanks to the high density of type I and II collagen fibres and the lower number of chondrocytes (5). It is located in tendons, ligaments, intervertebral discs, and articular surfaces of some bones (1).
Chondrocytes — little collagen factories
Now, let’s focus on the chondrocytes, which are the cells responsible for cartilage composition and functions. Their name comes from the Greek words chondros, meaning cartilage, and kytos, meaning cell. They are responsible for the production and maintenance of the extracellular matrix of cartilage (6).
Chondrocytes have a very unique shape, thanks to being located inside lacunae — a small space within the cartilage matrix. Lacunae provide a home for chondrocytes, keeping them safe and alive (6). Because of lacunae, chondrocytes have rounded or polygonal shape. During their maturation, chondrocytes become hypertrophic, which means that they become enlarged (7). Since they do not have direct access to blood vessels (they are avascular), they require diffusion of oxygen and nutrients from surrounding tissues (6).
Regeneration of cartilage
While cartilage exhibits a remarkable ability to absorb shock and distribute loads, it has limited regenerative capacity and a limited capacity for self-renewal (8). It makes cartilage prone to slow healing and susceptibility to degenerative conditions like rheumatoid arthritis (RA, 9) or osteoarthritis (OA, 10). OA is characterized by progressive degeneration of cartilage (11). Some scientists linked the development of OA with chondroptosis (apoptosis of chondrocytes), however, it is not yet known if this is a cause or a consequence of this disease (11).
Despite the challenges, ongoing research into the biology of chondrocytes and the intricate composition of the cartilage matrix holds promise for advancements in regenerative medicine and innovative treatments for cartilage-related disorders.
Recognizing and appreciating the labs working in this space
- Guilak Lab, Washington University in St. Louis, USA, https://orthopaedicresearch.wustl.edu/labs/farshid-guilak/ , Twitter: @Guilak_Lab
- Cartilage Research Laboratory, Brown University, Providence, USA, https://www.brown.edu/research/labs/cartilage/home , Twitter: @brettowensmd , Facebook: https://www.facebook.com/DrBrettOwens
- De Seny Laboratory, University of Liège, Belgium, https://orbi.uliege.be/profile?uid=p007750
- Craft Lab, Boston Children’s Hospital, USA, https://www.childrenshospital.org/research/labs/craft-lab-research/research-projects
- Laboratory of Cartilage Biology, Hospital for Special Surgery, New Your, USA, https://www.hss.edu/cartilage-biology-lab.asp
- Anie Philip Laboratory, McGill University, Canada, https://www.mcgill.ca/skinandcartilage/
- Vincent Group, University of Oxford, UK, https://www.kennedy.ox.ac.uk/research/research-groups/molecular-pathogenesis-of-osteoarthritis
References
- Chang LR, Marston G, Martin A. Anatomy, Cartilage. [Updated 2022 Oct 17]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK532964/
- Maynard RL, Downes N, Anatomy and Histology of the Laboratory Rat in Toxicology and Biomedical Research, 2019, Pages 11–22, https://doi.org/10.1016/B978-0-12-811837-5.00003-4
- Sophia Fox, Alice J et al. “The basic science of articular cartilage: structure, composition, and function.” Sports health vol. 1,6 (2009): 461–8. doi:10.1177/1941738109350438
- Monica Kesson, Elaine Atkins. “Orthopaedic Medicine (Second Edition)” (2005), Pages 33–54. https://doi.org/10.1016/B978-075065563-7.50008-4
- Buchanan, Jennifer L. “Types of Fibrocartilage.” Clinics in podiatric medicine and surgery vol. 39,3 (2022): 357–361. doi:10.1016/j.cpm.2022.02.001
- Nahian A, Sapra A. Histology, Chondrocytes. [Updated 2023 Apr 17]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK557576/
- Long, Fanxin, and David M Ornitz. “Development of the endochondral skeleton.” Cold Spring Harbor perspectives in biology vol. 5,1 a008334. 1 Jan. 2013, doi:10.1101/cshperspect.a008334
- Bačenková, Darina et al. “Human Chondrocytes, Metabolism of Articular Cartilage, and Strategies for Application to Tissue Engineering.” International journal of molecular sciences vol. 24,23 17096. 4 Dec. 2023, doi:10.3390/ijms242317096
- Tseng, Chia-Chun et al. “Dual Role of Chondrocytes in Rheumatoid Arthritis: The Chicken and the Egg.” International journal of molecular sciences vol. 21,3 1071. 6 Feb. 2020, doi:10.3390/ijms21031071
- Muthu, S., Korpershoek, J.V., Novais, E.J. et al. Failure of cartilage regeneration: emerging hypotheses and related therapeutic strategies. Nat Rev Rheumatol 19, 403–416 (2023). https://doi.org/10.1038/s41584-023-00979-5
- Charlier, Edith et al. “Insights on Molecular Mechanisms of Chondrocytes Death in Osteoarthritis.” International journal of molecular sciences vol. 17,12 2146. 20 Dec. 2016, doi:10.3390/ijms17122146
About the author:
DR. MAŁGORZATA ‘MASIA’ MAKSYMOWICZ
Content Editor The League of Extraordinary Cell Types, Sci-Illustrate Stories
Dr. Maksymowicz did her Ph.D. in Cell Biology (IIMCB, Poland) studying the intracellular trafficking and inflammatory signalling of a cytokine receptor. She did a 1-year post-doc at Nencki Institute, Poland, studying the protein- and RNA-binding properties of proteins. Currently, she is doing a post-doc at Barts Cancer Institute, UK, studying the links between endocytosis and tumorigenesis. Dr. Maksymowicz is passionate about science and loves to combine different fields of biology, always trying to seek beauty in nature.
About the artist:
NELLY AGHEKYAN
Contributing Artist The League of Extraordinary Cell Types, Sci-Illustrate Stories
Nelli Aghekyan, did a bachelor’s and master’s in Architecture in Armenia, after studying architecture and interior design for 6 years, she concentrated on her drawing skills and continued her path in the illustration world. She works mainly on children’s book illustrations, some of her books are now being published. Currently living in Italy, she works as a full-time freelance artist, collaborating with different companies and clients.
About the animator:
DR. EMANUELE PETRETTO
Animator The League of Extraordinary Cell Types, Sci-Illustrate Stories
Dr. Petretto received his Ph.D. in Biochemistry at the University of Fribourg, Switzerland, focusing on the behavior of matter at nanoscopic scales and the stability of colloidal systems. Using molecular dynamics simulations, he explored the delicate interaction among particles, interfaces, and solvents.
Currently, he is fully pursuing another delicate interaction: the intricate interplay between art and science. Through data visualization, motion design, and games, he wants to show the wonders of the complexity surrounding us.
About the series:
The League of Extraordinary Cell types
The team at Sci-Illustrate and Endosymbiont bring to you an exciting series where we dive deep into the wondrous cell types in our body, that make our hearts tick ❤.
