Tendon Healing
Scar tissue makes the restoration of injured tendons a painful and complex process, often leading to secondary ruptures.
A new study conducted by Chen-Min Fan and his colleagues from the Carnegie Institute for Science and published in the journal Nature Cell Biology demonstrates the existence of tendon stem cells that can be used to effectively heal tendons even without surgery.
Tendons are connective tissue that attaches muscles to bones. They participate in movement, facilitating the transfer of force that allows a person to move. Unfortunately, they are also particularly prone to injury and damage, after which they rarely fully recover. A patient with an injured tendon needs long-term treatment, including surgery, and he often retains limited mobility. This is due to the formation of fibrous scars that destroy the structure of the tendon.
Fan and colleagues identified all types of cells present in the tendons around the knee joint and found previously unexplored tendon stem cells. It was believed that such cells do not exist, since tendon injuries rarely heal completely.
Patellar tendon 30 days after injury. The upper layer of red cells is tendon stem cells, green cells under them are tendon cells (tendocytes). In the process of regeneration, tendon stem cells differentiate into tendon cells, yellow and orange colored cells in a transitional state. Photo: Tyler Harvey, Carnegie Institution for Science.
Surprisingly, the fibrous scar tissue cells and tendon stem cells were located in the same space – in the protective layer that surrounds the tendon. Moreover, the team found that tendon stem cells are part of a competitive system with the precursors of fibrous scars – this explains why tendon healing is such a long and complex process.
Both tendon stem cells and scar tissue progenitor cells are activated by a single protein, platelet-derived growth factor A (platelet–derived growth factor-A). When researchers changed tendon stem cells in such a way that they stopped responding to platelet growth factor, only scar tissue grew after injury and no new tendocytes appeared.
Thus, tendon stem cells must displace the precursors of scar tissue in order to prevent the formation of complex scars. The search for a therapeutic way to block scar cells and stimulate tendon stem cells can bring the treatment of tendon injuries to a qualitatively new level.
Article T.Harvey et al. A Tppp3+Pdgfra+tendon stem cell population contributes to regeneration and reveals a shared role for PDGF signaling in regeneration and fibrosis published in the journal Nature Cell Biology.
Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru Based on Carnegie Science: Tendon Stem Cells Could Revolutionize Injury Recovery.