The buildup of scar tissue makes recovery from torn rotator cuffs, jumpers knee, and other tendon injuries a painful, challenging process, often leading to secondary tendon ruptures. New research led by Carnegies Chen-Ming Fan and published inNature Cell Biologyreveals the existence of tendon stem cells that could potentially be harnessed to improve tendon healing and even to avoid surgery.

Tendons are connective tissue that tether our muscles to our bones, Fan explained. They improve our stability and facilitate the transfer of force that allows us to move. But they are also particularly susceptible to injury and damage.

Unfortunately, once tendons are injured, they rarely fully recover, which can result in limited mobility and require long-term pain management or even surgery. The culprit is fibrous scars, which disrupt the tissue structure of the tendon.

Working with Carnegies Tyler Harvey and Sara Flamenco, Fan revealed all of the cell types present in the Patellar tendon, found below the kneecap, including previously undefined tendon stem cells.

Because tendon injuries rarely heal completely, it was thought that tendon stem cells might not exist, said lead author Harvey. Many searched for them to no avail, but our work defined them for the first time.

Stem cells are blank cells associated with nearly every type of tissue, which have not fully differentiated into a specific functionality. They can also self-renew, creating a pool from which newly differentiated cell types can form to support a specific tissues function. For example, muscle stem cells can differentiate into muscle cells. But until now, stem cells for the tendon were unknown.

Surprisingly, the teams research showed that both fibrous scar tissue cells and tendon stem cells originate in the same spacethe protective cells that surround a tendon. Whats more, these tendon stem cells are part of a competitive system with precursors of fibrous scars, which explains why tendon healing is such a challenge.

The team demonstrated that both tendon stem cells and scar tissue precursor cells are stimulated into action by a protein called platelet-derived growth factor-A. When tendon stem cells are altered so that they dont respond to this growth factor, then only scar tissue and no new tendon cells form after an injury.

Tendon stem cells exist, but they must outcompete the scar tissue precursors in order to prevent the formation of difficult, fibrous scars, Fan explained. Finding a therapeutic way to block the scar-forming cells and enhance the tendon stem cells could be a game-changer when it comes to treating tendon injuries.

Reference: Harvey, Flamenco and Fan. 2019.A Tppp3+Pdgfra+ tendon stem cell population contributes to regeneration and reveals a shared role for PDGF signalling in regeneration and fibrosis. Nature Cell Biology.DOI: https://doi.org/10.1038/s41556-019-0417-z.

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Revolutionizing Injury Recovery With Tendon Stem Cells - Technology Networks