Although treatment outcomes for acute respiratory distress syndrome (ARDS) remain controversial, treatment with bone-marrow-derived mesenchymal stromal cells (MSCs) has shown positive outcomes. However, the safety of MSCs in critically ill patients with ARDS has not been determined. This study aims to investigate the safety profile of MSCs in patients with moderate-severe ARDS.

This multicenter, prospective, double-blind, randomized trial included a total of 60 ventilated patients with moderate to severe ARDS. The patients were randomly assigned in a 2:1 ratio to receive MSCs or a placebo. The primary outcome of the study was the safety of MSCs.

No predefined MSC-related hemodynamic or respiratory adverse events occurred in any of the patients. 1 death occurred in the MSC group within 24 hours of the MSC infusion, but the death was considered to be unrelated to the treatment. 28-day mortality was almost similar in the two groups: 30% in the MSC group and 15% in the placebo group. The findings further suggested that the MSC group had higher mean Acute Physiology and Chronic Health Evaluation III scores than placebo (104 vs. 89). The hazard ratio for mortality at 28 days was 1.43.

The research concluded that a single dose of intravenous MSC had an acceptable safety profile in patients with moderate-severe ARDS.