Circulating mesenchymal stem cells in sulfur mustard-exposed patients with long-term pulmonary complications

Sulfur mustard (SM) is a toxic agent that causes acute and long-term pulmonary complications. Recent evidence has shown the impact of SM on mesenchymal stem cells (MSCs). These cells have a critical role in repairing the damaged tissues. In this study, we evaluated the mobilization of MSCs in SM-exposed patients with long-term pulmonary complications. Fifty-nine SM-injured patients with prolonged pulmonary complications and 20 healthy individuals were included. Patients were classified based on taking drugs, having comorbidities, and severity of respiratory consequence. MSCs with phenotype of CD45-CD44⁺CD29⁺CD105⁺ were evaluated in peripheral blood using flow cytometry. Circulating MSCs were lower in SM-exposed patients compared to the control group (0.93 vs. 2.72 respectively, P = 0.005). No significant difference was observed in the MSC count between patients taking corticosteroids or antibiotics and those patients not taking them. Comorbidities like liver and kidney diseases had changed the count of MSCs in SM-exposed subjects. In addition, the frequency of MSCs did not show any association with the severity of long-term pulmonary complications. In conclusion, SM-exposure causes a decline in the frequency of circulating MSCs in survivors. The lower number of the peripheral MSC population in SM-exposed patients was not affected by taking corticosteroids or antibiotics, but comorbidities are probably involved in MSC frequency. The decreases observed in the number of circulating MSCs was not associated with the severity of the pulmonary complications; however, further studies in mustard lung models are required to demonstrate the therapeutic or pathologic role of MSCs in SM injuries.