After a tendon, ligament, or muscle has been injured, it is very common for scar tissue to develop at the site of injury. Scar tissue is thick and fibrous which can result in loss of flexibility and movement along with long-term pain. Tendons are extremely prone to the development of scar tissue following an injury, and inefficient healing of a tendon often demands surgical interventions in order to try to improve recovery. A team of researchers from the Carnegie Institution for Science have identified a new population of tendon stem cells that are able to contribute to tendon regeneration following injury.
The researchers’ first goal was to try and identify a stem cell population in the tendons of a living mouse model, as previous attempts have been done in artificial tissue culture. In order to find this population, the researchers first categorized all cell types found in the tendons by analyzing the tendon cells’ RNA and then looking at differences in gene expression. These differences in gene expression refer to the amount of RNA that is present in the cell — genes that are actively being expressed will result in higher RNA levels compared to genes that are not as expressed. From this analysis, the researchers were able to identify a subset of cells that operated as a self-renewing stem cell population. The fact that these cells are self-renewing is an important property of stem cells as it enables them to not only maintain a population of stem cells but also contribute to tendon regeneration.
Image source: Jan-Otto
Next, the research team introduced injury to the mouse tendon in order to determine whether or not these tendon stem cells could regenerate the damaged tissue. From this experiment, the researchers discovered something extremely interesting. They were able to confirm that tendon stem cells were able to aid in the healing process and help regrow tendons; however, the stem cells’ ability to do this is not always guaranteed. It was discovered that the tendon stem cells mostly compete with the cells that contribute to the formation of scar tissue. Therefore, the ability of tendon stem cells to contribute to regeneration relies both on timing and the presence of certain cellular signals. The competition between tendon stem cells and scar tissue cells helps to explain why recovering from a tendon injury is challenging and often times not fully possible.
This research provides new insights both on injury repair mechanisms along with the identification of a resident stem cell population. These discoveries could possibly translate into further avenues of research as well. The work to block scar tissue precursor cells could remove cell competition and enable tendon stem cells to contribute more towards regeneration after injury. If this avenue is successful, it could entail fewer people having to live with long-term complications and pain from their injuries. New treatment options like this are extremely promising due to the fact that they would be a less invasive treatment method as patients could potentially forgo surgical intervention.
Featured Image Source: Chinnapong
