Table 4 Challenges for testing mesenchymal stromal cells for ARDS

Source and production methods

Bone marrow, umbilical cord, iPSC-derived

Optimal dose (intravenous)

2, 4, or 10 × 10⁶/kg (ideal body weight)

Number of doses and timing

One dose versus two doses

Dose spacing 36–72 h apart?

Inclusion criteria

High-flow nasal oxygen versus invasive mechanical ventilation

Identifying treatment responsive phenotypes

Potential variables—age, viral, bacterial pneumonia, shock or not shock, biological variables (IL-8, Protein C, bicarbonate)