Therapeutic impact of mesenchymal stem cells on idiopathic pneumonia syndrome after allogeneic hematopoietic stem cell transplantation.

Mesenchymal stem cells (MSCs) effectively treat steroid-refractory acute graft-versus-host disease (aGVHD). However, their impact on patients with both steroid-refractory aGVHD (SR-aGVHD) and idiopathic pneumonia syndrome (IPS) is unclear. This retrospective study analyzed 24 patients who received MSCs as a secondary treatment for SR-aGVHD, including 6 who also had IPS. The 180-day overall survival rate was 52.0%, with a relapse rate of 13.3% and non-relapse mortality at 34.7%. The clinical course was compared between the six patients with concurrent IPS and SR-aGVHD who received MSCs and the 36 IPS patients who did not receive MSCs. The 6 MSC-treated patients had a higher 2-year overall survival rate than the control group, at 83.3% versus 61.1%, with all patients showing reduced oxygen requirements and improved imaging findings. Among the five patients who survived longer than 2 months after MSC therapy, the median time to complete oxygen therapy was 28 days, and steroid doses were reduced by 25% at the 2-month mark. Some patients showed improved pulmonary function after MSC therapy. These findings support MSCs as a promising treatment for SR-aGVHD and suggest potential benefits in IPS.