Movement of joints is facilitated by structures in the body called tendons that connect muscle and bone. They are grouped under the category of “dense connective tissues” and are made of mainly collagen type I. the junction of the attachment of the bone and a tendon is called “enthesis” that has such an arrangement to allow transmission of contracting muscles to the collagen of the tendon while lowering the stress exerted on the tendon to prevent its damage.
A clinical problem associated with tendons is damage due to age or overuse. According to research published by Wu and team in 2017 in EFORT open reviews, 50% of 33 million reported muscle injuries are due to tendon and ligament damage! Statistics also show that the probability of injury to certain tendons is more such as the Achilles tendon, forearm extensors, rotator cuff, tibialis posterior and patellar tendons. There has been a spike in the number of Achilles damage due to increased participation in physical activities and a rise in the elderly population.
Contrary to belief, Wu and team reported that the damage to tendons occurs in people who are sedentary apart from those who are active physically. These conditions are due to sport, age, nutrition, body weight and also genetics.
Though tendons have the ability to heal themselves, the process is slow and the strength of the tendon is often lost leading to challenging lifestyles. The treatment options include rehabilitation that takes a long time, not to mention the associated pain. According to Rees (Rheumatology (Oxford)), around 60% of such restorations are successful. Another alternative is surgically suturing the tendon that requires long rehabilitation. The side effects of non-steroidal anti-inflammatory drugs that are taken for pain relief are another challenge. Other options are ultrasound treatment, shock treatment and exercise whose efficacy lags behind.
The use of stem cells to treat such damage has attracted the attention of scientists. These stem cells have also been isolated from the tendon. In order to explore this exciting option, a team led by Yang cultured these cells and studied their properties that were published in the journal calledin vitro cellular & developmental biology.
The connective tissues of the tendon from foetal bovine were removed followed by washing and cutting into 1-mm3 bits. Digestion of these bits was done using 0.1% collagenase I followed by filtering through a 70-μm mesh filter. Following centrifugation, the cells were seeded in L-DMEM complete culture medium plus 15% FBS, penicillin, streptomycin, bFGF, and 2 mM L-glutamine.
48 h after seeding the primary cells of the Achilles tendon tissues showed attachment with homogenous morphology. The cells showed genetic stability and the expression of markers such as collagen I and a protein that controls cell morphology called tenascin-C, as shown by PCR and fluorescence.
Further studies showed that these stem cells called tendon-derived stem cells (TDSCs)could be differentiated into chondrocytes, adipocytes and also osteocytes.
Such ease of culture coupled with the ability of these cells isolated from culturing to form other cells under appropriate conditions opens up the avenue of using these cells to address the “yet to be 100%” successful treatment of tendon damage.
Wu, F., Nerlich, M., &Docheva, D. (2017). Tendon injuries: Basic science and new repair proposals. EFORT open reviews, 2(7), 332–342.
Rees JD, Wilson AM, Wolman RL. Current concepts in the management of tendon disorders. Rheumatology (Oxford) 2006;45:508-521.
Yang, J., Zhao, Q., Wang, K., Liu, H., Ma, C., Huang, H., & Liu, Y. (2016).Isolation and biological characterization of tendon-derived stem cells from fetal bovine. In vitro cellular & developmental biology. Animal, 52(8), 846–856. https://doi.org/10.1007/s11626-016-0043-z