Stem Cell Therapy for Tendon and Ligament Injuries

Professional and recreational sport practice is increasing but unfortunately so is the rate of sports injuries as mentioned in many epidemiological studies. Aside from medical consequences, the economic burden related to costs of conservative treatment, surgery and rehabilitation is very high.

Sport injuries, most of the time affect muscles, tendons, ligaments, cartilage and bones and range from very mild to severe, prompting different therapeutic approaches. Overuse is the most common cause of sport injuries and half of those injuries affect tendon, tendon sheath and tendon insertion to the bone. The number of ligament injuries, particularly anterior cruciate ligament (ACL) is increasing.

What are Tendon and Ligament? 

Tendons and ligaments are thick bands of tissue comprising collagen. They both help stabilize body structures and facilitate body movements. The main difference between tendon and ligaments is that they connect different parts of the anatomy. Tendons connect muscles to bones, while ligaments connect bones to other bones. 

Tendons contain bundles of fiber, which a type of tissue called endontendon surrounds. This tissue enables bundles of tendon fibers to move against one another, supporting body movement. 

Ligaments are typically more elastic than tendons. There are two different types of ligament: white and yellow. Wghite ligaments are rich in sturdy collagen fibers, which are not very elastic. Yellow ligaments contain more elastic fibers, which allow more movement. 

Ligaments are located at joints, whereas tendons provide the connection between muscle and bone that allows the muscles  to move different parts of the body. 

Ligament and tendons can stretch or tear relatively easily and the symptoms of tendon and ligament injuries tend to be very similar. 

What are Common Injuries that Affect Them? 

Tendon and ligament injuries are common. Several factors can increase the risk of injury, including:

• Overuse.
• Trauma from a fall or blow. 
• Twisting the tendon or ligament into an abnormal position.
• Weakness in the surrounding muscles due to sedentary lifestyle. 

Tendon Injuries 

Tendon injuries are common, especially in people who play sports. An estimated 30-50% of sporting injuries involve tendon problems. A common injury is a strain, which is damage to a tendon or the muscle to which it connects. They can take weeks to months to heal. 

Tendinitis happens when a tendon becomes inflamed and irritated. Tendinitis can develop following trauma, such as a strain, but it is most commonly an overuse injury. People with tendinitis may notice that the area is painful, swollen, and warm to the touch.

Subluxation happens when a tendon moves out of place. A person might hear a popping or snapping sound when it happens and then experience pain and weakness in the affected joint. Sometimes, the pain will come and go. Subluxation is more likely in people with certain genetic anatomical differences, but tendons can also snap out of place as a result of an injury.

Tendon ruptures can also occur. These injuries may be due to a combination of immediate trauma and chronic trauma.

Ligament Injuries

A sprain occurs when a ligament stretches or tears. It can be a temporary, minor inconvenience or a debilitating injury that takes months to heal. The knee, ankles and wrist are the more commonly affected joints. 

They can be classified based on their severity in 3 categories:

• Grade 1: mild sprains in which the fibers of the ligament stretch, but the ligament does not tear.
• Grade 2: moderate sprains where the ligament partially tears.
• Grade 3: severe sprains in which the ligament completely tears. This type renders the joint completely unstable and often requires surgical treatment. 

One of the more common types of ligament injuries is a torn anterior cruciate ligament (ACL), which is a ligament located in the knee. 

What is a Strain and Sprain? 

A sprain is a stretch or tear in a ligament and a strain is also a stretch or tear, but it happens in a muscle or tendon. 

Sprains usually happen when a person falls, twists or is hit in a way that forces the body out of its normal position. The most common type is a sprained ankle. About 25,000 people sprain an ankle every year. 

Strains on the other hand are more common in athletes in contact sports, like football, hockey and boxing. Even in noncontact sports like tennis or rowing, doing the same motions over and over can lead to strains of the hand and forearm. They are common even at home or workplace when you are doing a lot of heavy lifting.  

Current Treatment Options

Standard treatment options include rest, ice, compression, elevation, short course of pain modulators and anti-inflammatory medications that provide relief of symptoms without complete healing. It is known that poor vascular supply of tendons and ligaments slows down the healing process and extends the time of recovery. An injured player wants to return to sport as soon as possible because prolonged rest has a detrimental effect on the body. 

Regenerative Medicine Treatment

The concept of regenerative medicine attracts the attention of researchers and clinicians offering a promising potential to regenerate the damaged tissue rather than to alleviate symptoms. One of the more promising therapies is the use of stem cells.

Stem cells are undifferentiated cells with potential to differentiate under certain conditions into other types of cells. This allows them to regenerate damaged parts of the body and eventually to restore impaired functions. 

Mesenchymal stem cells (MSCs) have self renewal and differentiation potential. They are able to differentiate into mesodermal lineages forming osteocytes, chondrocytes and adipocytes. They can be harvested from the patient’s own body (autologous cells), mainly from bone marrow and adipose tissue. They can also be obtained from other tissues like umbilical cord, which are easier to obtain and have some advantages over autologous cells. 

Studies have documented the positive therapeutic effect of stem cells on tendon injuries in humans. Clinical improvement and in some studies structural changes detected by MRI and US were reported. Also, the positive effects were maintained even 3 to 4 years after the treatment. 

Other studies have reported the effect of MSCs on ACL injuries. In these studies MSCs were combined with Hyaluronic acid in one, and with dextrose and PRP in the other. Clinical and MRI improvement was documented as well. 

Mesenchymal stem cells are the front runner in the field of regenerative medicine with thousands of scientific papers in the last 10 years. Clinical application of MSCs for treatment of tendon and ligament injuries might be a good alternative option for athletes due to their anti-inflammatory and regenerative properties.

Sources: 

Trebinjac S, Gharairi M. Mesenchymal Stem Cells for Treatment of Tendon and Ligament Injuries-clinical Evidence. Med Arch. 2020 Oct;74(5): 387-390. 
DOI:10.5455/medarh.2020.74.387-390.

Marina Basina, M.D. (2019, Oct 31) Tendons and ligaments: What is the difference? Medical News Today. Retrieved from: https://www.medicalnewstoday.com/articles/326858 

Image from: https://www.myfootdr.com.au/knee-ligament-injuries-causes-treatment/