Paolo Rossi Castelli 12 January 2023 17 min read

A breakthrough for sports and more: stem cells to repair tendons

A cutting-edge technique has been successfully tested (for the moment on animals) at New York’s Columbia University. It focuses on the enthesis, the membrane that attaches the tendon to the bone.

Injuries, whether sports-related or not, or even simple wear and tear due to age, can cause serious tendon lacerations that are very difficult to repair, even with surgery.

One example of this kind of damage is that of the so-called rotator cuff, the (complex) set of muscles and tendons that surround and protect the shoulder joint. In reality, what literally tears is a tough but very thin membrane, called the enthesis, which connects the tendon to the bone. Even when the tendon is surgically repaired, there is no guarantee that the enthesis will reform and that the tendon will be able to attach firmly to the bones and work as before (surgery failures range from 20% in younger people to over 94% in older people).

All this exposes the patient to the risk of new and increasingly frequent lacerations: a kind of vicious circle that those who practise high-intensity sports are very familiar with.

An innovative stem cell study 

Now, however, a study (carried out for the moment only on laboratory animals) offers hope, by using the stem cells that normally give life to the entheses itself in an innovative way to try and reproduce the whole natural process. The study was carried out by researchers from the Department of Orthopaedic Surgery at Columbia University in New York, who then published their findings in the scientific journal Cell Stem Cell.

Their study is part of intense international activity (including in Switzerland and the Ticino region) which is attempting (with as yet incomplete results) to use stem cells in orthopaedics to treat or even rebuild damaged joints.

As for the enthesis, it is created by cells called GLi1+. Therefore the NY orthopaedists decided to start with these stem cells, performing a kind of transplant on an injured area similar to a human rotator cuff. The results appeared extremely positive, because the enthesis supported by the Gli1+ regenerated far more than in animals that had not been treated with this technique, but only with traditional surgery.

Six different types of cells

Before infusing Gli1+ cells, researchers had studied in detail what happens at a cellular and molecular level when an organism creates entheses, demonstrating that six different types of stem cells are involved in the process in laboratory animals, thanks to the activation of numerous genes and biochemical mediators.

Application on humans

A similar study will also have to be carried out on humans before initial trials, and this will still require a great deal of work. It will therefore be essential to understand the roles of different cell types in the make-up of the membrane.

The possibility of multiplying these cells in the laboratory will have to be tested, so that they can also be used in older people, who do not have many stem cells (unlike younger people). Finally, further technical aspects - like those related to surgery – will have to be optimised, as well as infusions at the site and treatment and storage of Gli1+ cells. However, this study appears an important step forward.


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Paolo Rossi Castelli

Journalist since 1983, Paolo has been dealing with scientific divulgation for years, especially in the fields of medicine and biology. He is the creator of Sportello Cancro, the site created by on oncology in collaboration with the Umberto Veronesi Foundation. He collaborated with the pages of the Science of Corriere della Sera for several years. He is the founder and director of PRC-Comunicare la scienza.