The novel coronavirus (SARS-CoV-2) has affected over 28 million people across the United States, according to the CDC. At the present time, there is no effective cure for COVID-19 (2, 3). While widely publicized drugs like remdesivir and chloroquine have shown promising results in treating symptoms of COVID-19 in some instances, other studies have found that they make no significant difference (3). The lack of headway in finding an effective treatment is leading scientists across the world to turn to alternative regenerative therapies. The use of stem cells to treat COVID-19, including mesenchymal cells, is now being studied in over 34 clinical trials across the world (4).
Difficulties in Finding a Treatment for COVID-19
Before diving into how mesenchymal cells may be a promising therapy for treating COVID-19, it is helpful to understand what makes treating the disease so difficult in the first place. Lung diseases have long been a source of study for clinicians, especially those caused by viral infections or those that lead to acute respiratory distress syndrome (ARDS) (2, 5). ARDS occurs due to an extreme pro-inflammatory response that creates a cytokine storm, often causing lung damage, respiratory failure, inflammation, and damage to the cardiovascular system (4). Other disease-causing viruses, such as SARS-CoV-1, MERS-CoV (Middle East Respiratory Syndrome), and H7N9 (avian flu) can cause ARDS or ARDS-like effects, just as the current SARS-CoV-2 does (2, 6). Treatments of choice up to this point have been antibiotic therapy, ventilation, and anti-inflammatory pharmaceuticals, though these have all presented low success rates (5). Because these treatments do not meet efficacy standards, research to find other potential cures for respiratory diseases via modalities such as cell therapies has been underway for years (2, 5).
What are Cell Therapies?
There are a variety of cell therapies, including many different kinds of ethically-donated stem and progenitor cells (5). Though cell therapies generally show potential for repairing tissue damage and promoting tissue regeneration for a variety of ailments, mesenchymal stromal/stem cell (MSC) therapies have risen to the forefront of study, specifically for the treatment of lung diseases such as COVID-19 (4, 5). Even so, it is important to note that while previous clinical trials have determined cell therapies to be safe, any claims about stem cells have not been approved by the FDA.
Interestingly, while the debate continues as to whether mesenchymal cells can actually be classified as stem cells, they undoubtedly show the same characteristics that are traditionally attributed to stem cells in clinical trials (7). MSCs are naturally found in bone marrow, fat, and other tissues and, when isolated and introduced into the body, make their way to sites of damage or inflammation in the body (7). While the exact interactions of MSCs with their surroundings on the cellular level are still being determined, the effects on a variety of conditions have been shown as largely positive long-term (2, 3, 4, 5, 7).
In the instances that mesenchymal cells have been specifically studied as a treatment for lung-related diseases, ARDS, and even for COVID-19 specifically, MSCs show the ability to work with the body’s natural processes. In this way, they have the ability to address and prevent immune-mediated effects, restore damaged tissue, reduce inflammation, and more (3, 4).
Effects of COVID-19 on the Immune System
What has been determined about COVID-19 so far tells us that the body’s immune system can respond quickly and very severely. In its overreaction, the immune system can send too many destructive, antigen-destroying cells such as macrophages and neutrophils to attack (4, 5). This leads to an over-production of pro-inflammatory cytokine proteins, which can create a generally dysregulated inflammatory response (4, 5). As a result of this dysregulation, the immune system may signal the body to produce more macrophages, leading to an even greater imbalance over time (4, 5). Many clinicians believe this process of respiratory dysregulation can directly contribute to the lung damage and respiratory failure that is at the root of ARDS, many viral lung-based diseases, and importantly, severe cases of COVID-19 (4).
How MSCs Can Work to Combat Infection and Damage