This study was divided into two parts. The first part is an investigation of dose-dependent effect. hUCB-MSCs were administered into 3 groups of rats (UA 3×10⁶ cells, UB 1.5×10⁶ cells, UC 3×10⁵ cells) via the external jugular vein at week 1 after monocrotaline (MCT) injection. The second part is a search for optimal treatment timing in 3×10⁵ cellsdose of hUCB-MSCs administered at day 1 for UD group (low dose of hUCB-MSCs at day 1), at day 1 and week 1 for the UE group (dual transfusion of low dose of hUCB-MSCs at day 1 and week 1) and at 1 week for the UF group (reversal treatment of low dose hUCB-MSC at week 1) after MCT injection.
Low-dose early treatment of hUCB-MSCs is as effective as a high dosetreatment of hUCB-MSCs in improving PAH although dual or reversal treatment is still more effective.