RESUMO
<p><b>OBJECTIVE</b>To 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.</p><p><b>METHODS</b>Two 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.</p><p><b>RESULTS</b>Compared 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).</p><p><b>CONCLUSION</b>BMSCs 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.</p>