【Objective】To investigate the therapeutic effect of bone marrow mesenchymal stem cells (MSC) in hyperoxic lung injury of neonatal rats.【Methods】 Bone marrow MSC cultures were prepared from bone marrow of SD rats by adherent culture

and were transfected by lentiviral vector carrying GFP gene. Newborn rat pups from four different litters were randomized to A

B

C

D

and E groups. Different dose of bone marrow MSC (1 × 105 per pup or 1 × 104 per pup) were injected via the tail vein respectively for A and B groups after 7 days oxygen exposure

and phosphate buffered saline (PBS) for C group. MSCs and PBS were injected respectively for D and E groups as normoxia groups. The engraftment of MSCs in neonatal rat lungs

weight gaining

lung coefficient

radical alveolar counts and lung histology were assessed. 【Results】 GFP positive cells were found in rats lungs of A

B

D groups; the ratio of GFP-positive cells in A and B groups were higher than that of D group (31.3±2.6% vs 11.8±1.3%

A group vs D group

22.7 ± 1.3% vs 11.8 ± 1.3%

B group vs D group

P < 0.05); the ratio of A group was also higher than that of B group

P < 0.05) . Bone marrow MSC exerted their therapeutic benefit of improving weight gaining (66 ± 9 g vs 48 ± 7 g

A group vs C group

P < 0.05)

radical alveolar counts (9.2 ± 0.7 vs 7.4 ± 0.4

A group vs C group

P < 0.05)

decreasing lung coefficient (2.26 ± 0.23% vs 2.9 ± 0.4%

A group vs C group

P < 0.05) and suppressing lung inflammation of neonatal rats

and which were significant better in the high dose group of MSCs treatment than that of low dose group.【Conclusion】 Both two doses of bone marrow MSC treatment could attenuate hyperoxia-induced lung injury in newborn rats

and the therapeutic effect of high dose group was more obviously.