LAUSR

OBJECTIVE We aimed at explaining the mechanism of therapeutic effect of Umbilical Cord Mesenchymal Stem Cells (UC-MSC) in subjects with COVID-19 Acute Respiratory Distress Syndrome (ARDS). Patients with COVID-19 ARDS present with a hyperinflammatory response characterized by high levels of circulating pro-inflammatory mediators, including tumor necrosis factor α and β (TNFα and TNFβ). Inflammatory functions of these TNFs can be inhibited by soluble TNF Receptor 2 (sTNFR2). In patients with COVID-19 ARDS, UC-MSC appear to impart a robust anti-inflammatory effect, and treatment is associated with remarkable clinical improvements. We investigated the levels of TNFα, TNFβ and sTNFR2 in blood plasma samples collected from subjects with COVID-19 ARDS enrolled in our trial of UC-MSC treatment. PATIENTS AND METHODS We analyzed plasma samples from subjects with COVID-19 ARDS (n=24) enrolled in a Phase 1/2a randomized controlled trial of UC-MSC treatment. Plasma samples were obtained at Day 0 (baseline, before UC-MSC or control infusion), and Day 6 post infusion. Plasma concentrations of sTNFR2, TNFα, and TNFβ were evaluated using a quantitative multiplex protein array. RESULTS Our data indicate that at Day 6 after infusion, UC-MSC recipients develop significantly increased levels of plasma sTNFR2 and significantly decreased levels of TNFα and TNFβ, compared to controls. CONCLUSIONS These observations suggest that sTNFR2 plays a mechanistic role in mediating UC-MSC effect on TNFα and TNFβ plasma levels, determining a decrease in inflammation in COVID-19 ARDS.