Fig. 5. Pathologic findings in MCT-induced PAH rats according to dose of hUCB-MSCs at week 4. (A) Low-dose of hUCB-MSCs also effectively decreased pulmonary arteriole medial wall thickening. (B) The number of intra-acinar arteries was decreased in UA and UB groups. (C) Low-dose hUCB-MSCs also attenuated pulmonary pathological changes in MCT-induced PAH rat (Victoria blue staining, ×400). ^*p<0.05, compared with C, ^†p<0.05, compared with M. No, number; C, control group; M, monocrotaline group; UA, 3×10⁶ cells/rat; UB, 1.5×10⁶ cells/rat; UC, 3×10⁵ cells/rat; MCT, monocrotaline; PAH, pulmonary arterial hypertension; hUCB-MSCs, human umbilical cord blood derived mesenchymal stem cells.