Introduction: The declarations of the emergency situation by the Up to now, World Health Organization (WHO) has declared emergency situation due to several extensive outbreaks of infectious diseases, especially in the new century. Considering this fact, as well as the mortality of these outbreaks and the chance of future re-emergence, have prompted researchers to seek effective therapeutic strategies for proper management of infectious, epidemic-prone diseases. One of these strategies is the application of stem cells, showing good effectiveness in the Coronavirus Disease 2019 (COVID-19) pandemic. The present review aimed to investigate the latest available literature on the therapeutic potential of stem cells in outbreaks caused by the following viral diseases: Severe Acute Respiratory Syndrome (SARS, 2003), Influenza (2009), Middle East Respiratory Syndrome (MERS, 2012), Ebola Virus Disease (EVD, 2014), Zika Virus Disease (ZIKV, 2016), and COVID-19 (2019).
Methods: In order to find the studies on the therapeutic potential of stem cells on the mentioned epidemic-prone diseases, the databases of Google Scholar, PubMed, and Scopus were searched using the following keywords and phrases: "stem cells and SARS-CoV", "stem cells and SARS-CoV-2", "stem cells and MERS-CoV", "stem cells and Ebola virus", "stem cells and Influenza virus", and "stem cells and Zika virus". A total of 125 studies, which were published before July 11, 2021, were collected. Afterward, the related abstracts and titles were evaluated, and the duplicated studies were omitted. Moreover, those not following our eligibility criteria were omitted. Eventually, 78 studies were selected for translation and complete analysis. The data on the effectiveness and side effects of this therapeutic intervention were classified in a table and underwent analysis.
Results: According to our findings, stem cells and their derivatives, such as exosomes, can be used as an effective therapeutic strategy for COVID-19. There are several ongoing and completed clinical trials on this topic. Various types of stem cells, especially mesenchymal stem cells, are used to manage the fatal complications of these diseases, such as ARDS (Acute Respiratory Distress Syndrome).
However, there is limited research on the efficacy of stem cells in SARS and MERS, which are highly similar to COVID-19 in pathogenesis. Moreover, the literature on stem cell therapy in influenza is controversial. Some studies have recommended this treatment, while others reported it as ineffective and with considerable side effects. Therefore, these controversies highlight the need for further studies with higher comprehensiveness and accuracy.
In addition, stem cells have helped the researchers illustrate the available ambiguities in the pathogenesis of the influenza virus, especially the relationship between influenza and some congenital abnormalities. Also, some studies have used stem cell models to identify the mechanisms involved in the pathogenesis and transmission of Zika and Ebola viruses. It is expected that these studies can be used in effective antiviral therapy developments against these pathogens.
Conclusion: The present study provides new insights into the effects of stem cells on emerging epidemic-prone diseases. Therefore, stem cell therapy can help us overcome challenges caused by these epidemic-prone diseases, such as re-emergence and functional ambiguities. Clinical trials during the COVID-19 pandemic have shown the potential benefits of stem cells and their derivatives in mortality reduction and recovery acceleration of the patients. It has been shown that stem cells can regulate immune responses, leading to reduced inflammation. Moreover, these cells play an effective role in tissue repair. Due to their differentiation ability, they are suitable for laboratory simulation. Thus, they can be essential tools for investigating the functions of Zika, Ebola, and Influenza viruses. Despite these promising findings, however, further studies are needed to evaluate the long-term effects and safety of this method. With recent advances, stem cells have revolutionized the medical sciences. These cells are expected to be an effective weapon for fighting microbial threats against the human population.