Clinical Consideration for Mesenchymal Stem Cells in Treatment of COVID-19

COVID-19, which has strongly affected the 21st century, is caused by severe acute respiratory syndrome (SARS)-CoV-2. The emergence of viral variants has rendered even vaccinated people prone to infection; thus, completely eradicating COVID-19 may be impossible. COVID-19 causes hyperinflammation, leading to organ damage and even death. SARS-CoV-2 infects not only the lungs, causing acute respiratory distress syn-drome, but also the extrapulmonary organs. Not all patients with COVID-19 respond adequately to treatments with antiviral and anti-inflammatory drugs. Therefore, new treatments are urgently needed. Mesenchymal stem cells (MSCs) exhibit immunomodulatory activity and are used to safely and effectively treat various immune disorders. Evidence has indicated the efficacy of MSCs against COVID-19. However, the safety and efficacy of MSCs must be probed further. For this reason, we explored key clinical challenges associated with MSC therapy for COVID-19, such as sources, administration routes, cell dosage, treatment timepoint, and virus reactiva-tion. We identified several challenges that must be addressed before MSCs can be clinically applied.