In the last 5 years, we have seen an increasing number of professional athletes turning to stem cell therapies to recover from injury. Tiger Woods, Rafael Nadal, and Max Scherzer have all been reported to have undergone stem cell therapy for their sports-related injuries. 

While stem cell therapy was once prohibitively expensive for most, prices have come down significantly, making it more accessible. In this article we will discuss what stem cells are, the various treatments available and their efficacy and cost.

What are stem cells?

Stem cells are cells in the body that have the potential to self-renew, develop into other types of cells, or divide into identical cells. When there is an adequate source of resources and the right environment, stem cells have the ability to change and become cells with highly specialized functions. Moreover, stem cells are the cells that are responsible in tissue repair and injury recovery in the muscles, liver, kidneys, and lungs (1). There are several types of stem cells:

• Pluripotent stem cells could become progenitors of any type of cell in the body. For example, embryonic cells could become stomach, lung, skin, or brain cells.
  
  
  
  

• Multipotent stem cells develop into different specialized cells of a specific tissue. Unlike pluripotent cells, the fate of multipotent cells is limited.
  
  
  
  

• Mesenchymal stem cells (MSCs) are an example of multipotent cells that can develop into bone cells, cartilage cells, and muscle cells. MSCs are currently very significant in stem cell therapy because they can readily be harvested from adult donors, unlike the other types of cells.
  
  
  
  

• Unipotent stem cells have the ability to become only one type of cell. For example, the satellite cells of the skeletal muscle are limited to becoming mature skeletal muscle cells (2).

What is stem cell therapy?

Stem cell therapy is a treatment approach that utilizes stem cells grown in the laboratory. These cells are used to replace lost tissues or to assist existing tissues in performing specific functions. 

Current techniques of stem cell therapy commonly utilize MSCs because they can be derived from various adult organs and tissues, making it easier to be acquired as compared to pluripotent cells. MSCs can be harvested from the placenta, fat cells, liver, lung, or blood vessels (3). 

Stem cells are first harvested or isolated from the donor tissue. The cells are then grown or cultured in the laboratory. When successfully cultured, stem cells are then injected to the recipient and are expected to home to the target organ, in most cases, to the injured site. The recipient is then monitored for possible inflammatory reactions following the injection of stem cells (3).

Stem cell therapy for injury repair

The US Department of Health and Human Services estimates that the average annual number of sports and recreation-related injuries is at 8.6 million per year (4). The ability of MSCs to become mature bone, cartilage, or and other connective tissues make them ideal sources of regenerative tissues for injury repair, especially for sports-related injuries. MSCs could function as regulators of growth and maintenance in these tissues (1). In addition, MSCs release different substances that stimulate the existing cells in the injured tissue to undergo cell division, hence increasing the number of cells and promoting tissue survival (5).

Current regenerative medicine techniques for sports-related injuries include 3 methods:

·       Platelet-rich plasma

·       Bone marrow concentrate

·       Direct grafting of stem cells

The use of BMC and PRP injections have been effective in addressing failed healing or delayed healing fractures. Other recent developments also show BMC and PRP to be effective in rib and mandibular fractures (6). Meanwhile, through the direct grafting of tissue-specific stem cells, MSCs that have matured into the desired tissue type can be integrated into the target tissue (5). Let’s take a quick look at each of these methods.

Platelet-rich plasma

PRP contains a high concentration of platelets and various biologic substances such as platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), and many others. As the cells are derived from the patient the potential for adverse reactions and infection is very low. PRP is not made up of stem cells, but the use of PRP has been found to stimulate MSC proliferation. Thus, PRP is a vital component of stem cell-based therapy in sports-related injuries (7). 

A study published in 2012 showed that the local application of PRP in the repair of rotator cuff injury in patients reduced the pain after surgery. In addition, long-term results showed that PRP aided in the healing of rotator cuff injury in patients (8).
 

Bone marrow concentrate

Bone marrow concentrate (BMC) is another tool that is used for sports-related bone injuries and other lesions. BMC is a rich mixture of MSCs, different bioactive molecules, white blood cells, and platelets. Just like PRP, BMC is also harvested from the patient. This reduces the risk of infection and immune reactions. BMC is used to deliver stem cells to damaged bone, thus initiating repair and healing.

A clinical study done in 2016 showed that treatment of discogenic back pain with BMC injections provided relief of pain and disability improvement. BMC was delivered via disc injection to 26 patients, which showed improvement over the span of 2 years. This will not only benefit athletes with back injuries, but also the general public who could be chronically experiencing back pain (9). Another study published in 2015 reported that the use of BMC for open Achilles tendon repair resulted to excellent outcomes, characterized by early mobilization and zero re-ruptures (10).

Direct grafting of stem cells

Emerging biotech research studies have used the direct grafting of stem cells to focus on the production of tissue engineered bone bioscaffolds. These bioscaffolds are meant to function as a porous and permeable solid structure for stem cell attachment, growth, and migration. Such scaffold material would make it easier for stem cells to adhere to the injured tissue and promote growth of new cells (5). Most of the current studies on the use of stem cells on grafts to repair bone and muscle injuries are still experimental. No clinical trials have been reported so far.

How much does stem therapy cost?

The cost of stem cell therapies depends largely on the specific type of stem cells and tissues involved and the extent of injury. In the US, stem cell therapy for knee injuries range from $3000 to $5000 but the most expensive ones can reach up to $50,000. The same type of treatment costs as low as $2000 in Mexico and in Asian countries such as Thailand.

References

1. Stem cells and the evolving notion of cellular identity. Daley, G. 1680, 2015, Vol. 370.

2. Adult stem cells: hopes and hypes of regenerative medicine. Dulak, J., et al. 3, 2015, Vol. 62.

3. Browne, C., Chung, T. and Atkinson, K. The Biology of Mesenchymal Stem Cells in Health and Disease and Its Relevance to MSC-Based Cell Delivery Therapies. [book auth.] L. Chase and M. Vemuri. Mesenchymal Stem Cell Therapy. New York : Humana Press, 2013.

4. American Physical Therapy Association. Sports and Recreation-Related Injuries Top 8.6 Million Annually. APTA. [Online] January 4, 2017. https://www.apta.org/PTinMotion/News/2017/1/4/SportsInjuries/.

5. Young, M. and Doran, M. Mesenchymal Stem Cell Therapies for Bone and Tendon Conditions. [book auth.] L. Chase and M. Vemuri. Mesenchymal Stem Cell Therapy. New York : Humana Press, 2013.

6. Siddiqui, I., Mazzola, T. and Shiple, B. Techniques for Performing Regenerative Procedures for Orthopedic Conditions. [book auth.] G. Malanga and V. Ibrahim. Regenerative Treatments in Sports and Orthopedic Medicine. New York : Demos Medical Publishing, 2018.