OBJECTIVETo investigate the effect of bone marrow mesenchymal stem cell (BMSC) transplantation on acute lung injury induced by paraquat (PQ) poisoning in rats, and to identify the optimal transplantation conditions.

METHODSTwo hundred female rats were randomly divided into six groups, i.e., PQ group (n = 15), BMSC treatment group 1 (n = 15 for each subgroup), BMSC treatment group 2 (n = 15 for each subgroup), BMSC control group 1 (n = 15 for each subgroup), BMSC control group 2 (n = 15), and normal control group (n = 5). In the PQ group, each rat was intraperitoneally injected with 20% PQ solution (15 mg/kg). In BMSC treatment group 1, each rat was injected via the caudal vein with 1×10(5), 10(6), 10(7)or 10(8) BMSCs (1 ml) after 6 hours of PQ exposure. In BMSC treatment group 2, each rat was injected via the caudal vein with 1×10(7) BMSCs (1 ml) after 1, 6, 12, or 24 hours of PQ exposure. In BMSC control group 1, each rat was injected via the caudal vein with 1×10(5), 10(6), 10(7), or 10(8) BMSCs (1 ml). In BMSC control group 2, each rat was injected via the caudal vein with 1×10(7) BMSCs (1 ml). In the normal control group, each rat was intraperitoneally injected with an equal volume of 0.9% saline. The lung wet/dry weight ratio and plasma tumor necrosis factor-α (TNF-α) and malondialdehyde (MDA) levels were measured at 1, 3, and 7 days after various treatments.

RESULTSCompared with the normal control group, the PQ group showed significantly higher lung wet/dry weight ratios at 3 and 7 days after PQ exposure and significantly higher plasma TNF-α and MDA levels at 1, 3, and 7 days after PQ exposure (P < 0.01). Compared with the PQ group, BMSC treatment group 1 showed significantly lower lung wet/dry weight ratios at 7 days after injection of 1×10(6) and 10(7) BMSCs, significantly lower plasma TNF-α levels at 3 and 7 days after injection of 1×10(5), 10(6), and 10(7) BMSCs, and significantly lower plasma MDA levels at 3 days after injection of 1×10(6) and 10(7) BMSCs and at 7 days after injection of 1×10(5), 10(6), and 10(7) BMSCs (P < 0.05 or P < 0.01). Compared with the PQ group, BMSC treatment group 2 showed significantly lower lung wet/dry weight ratios at 7 days after injection of BMSCs following 1, 6, and 12 hours of PQ exposure, significantly lower plasma TNF-α levels at 3 and 7 days after injection of BMSCs following 1, 6, and 12 hours of PQ exposure, and significantly lower plasma MDA levels at 3 days after injection of BMSCs following 6 hours of PQ exposure and at 7 days after injection of BMSCs following 1, 6, and 12 hours of PQ exposure (P < 0.01).

CONCLUSIONBMSCs have a protective effect on the lung in rats with PQ poisoning, and the effect is closely related to the transplantation time and number of transplanted BMSCs. After 6 hours of PQ exposure, intravenous injection of 1×10(7) BMSCs can result in significant decreases in lung wet/dry weight ratio and plasma TNF-α and MDA levels.