#chondrocytes

Restoring Cartilage

Upset in a molecular pathway called Wnt signalling in cartilage cells called chondrocytes underlies the breakdown of cartilage in the painful joint disease osteoarthritis. Here, researchers have identified how the molecular signals are normally balanced and have developed StemJEL an injectable hydrogel therapy which restores the balance and cartilage and joint function

Read the published research paper here

Image from work by Angela Ruscitto and colleagues

Cartilage Biology and Regenerative Medicine Laboratory, Section of Growth and Development, Division of Orthodontics, College of Dental Medicine, Columbia University Irving Medical Center, New York, NY, USA

Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in Cell Stem Cell, September 2023

All Knees

It’s tough, it’s rubbery, it’s your cartilage. Your joints contain two types: articular cartilage, which covers the ends of your bones, and growth-plate cartilage, which forms the ends of long bones. Both comprise cells called chondrocytes. How these types of cartilage develop isn’t clear. Researchers now investigate in mice genetically engineered with fluorescently-tagged NFATc1 – a protein which when inactivated interferes with cartilage development. Using fluorescent microscopy of developing mouse knee joints, they found NFATc1-containing cells (progenitors) matured into articular chondrocytes but not growth-plate chondrocytes. NFATc1-containing progenitors also matured into cells that contribute to the joint lining, ligaments and developing kneecap (pictured, green). Analysing the RNA of articular chondrocytes revealed that NFATc1 levels dropped as the cells matured. Reducing NFATc1 levels in progenitors triggered articular cartilage formation while increasing levels blocked this from happening. NFATc1 is therefore vital for articular — but not growth-plate — cartilage development.

Written by Lux Fatimathas

Image from work by Fan Zhang and Yuanyuan Wang, and colleagues

Xuanwu Hospital, Capital Medical University, China; National Clinical Research Center for Geriatric Diseases, China

Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in eLife, February 2023

Muscle Support

Whenever you fracture a bone, progenitor cells in your damaged bone jump into action, forming a callus – a mass of fibroblasts and cartilage-producing cells called chondrocytes. New cartilage and bone is then laid down. Researchers now reveal that progenitor cells in the surrounding skeletal muscle are also involved. Mice were genetically modified to track these progenitor cells using fluorescence microscopy, focusing on the muscle surrounding the tibia bone (pictured) before fracture of the bone (left, blue), and then 3 days (middle) and 3 weeks after fracture (right). Combined with RNA analysis, the team found some progenitors matured into fibroblasts and later others matured into chondrocytes, forming a callous (right, blue). However, in mice where the bone and muscle were injured, these progenitors interfered with bone healing by producing excess fibrous tissue – administering the drug imatinib prevented this. Skeletal muscle therefore has a vital role in the effectiveness of bone healing.

Written by Lux Fatimathas

Image from work by Anais Julien and colleagues

Univ Paris Est Creteil, INSERM, IMRB, Creteil, France

Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in Nature Communications, May 2021

Propaganda!

Chondrocytes are the only cells found in healthy cartilage. They produce and maintain the cartilaginous matrix, which consists mainly of collagen and proteoglycans.