[Marrow-derived mesenchymal stem cells protect the lung injury caused by exposure to high oxygen: experiment with rats].

Objective: To investigate the influence of marrow-derived mesenchymal stem cells (MSCs) on the lung injury caused by exposure to high oxygen.

Methods: MSCs were extracted from the femurs of Sprague-Dawley (SD) rat, cultured, amplified, and labeled with 5-bromo-2'-deoxy-uridine (BrdU). Thirty-two 3-day-old SD rats were randomly divided into 4 equal groups: Group A, exposed to high oxygen (95%) for 7 days and then injected intra-peritoneally with 50 microl phosphate buffered solution (PBS) containing 5 x 10(4) MSCs; Group B, exposed to ordinary air for 7 days and then injected intra-peritoneally with PBS containing 5 x 10(4) MSCs; Group C, exposed to high oxygen (95%) for 7 days and then injected intra-peritoneally with PBS without MSC; and Group D, exposed to ordinary air for 7 days and then injected intra-peritoneally with PBS without MSC. 72 h later, when the rats were 13 days old they were killed Bronchoalveolar lavage fluid (BALF) was obtained to count the numbers of white blood cells and neutrophils. Lung homogenate was made. ELISA was used to examine the contents of tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta. Radial alveolar count (RAC) of the lungs was conducted under light microscope. Double-staining immunocytochemistry was used to detect the expression of surfactant protein A (SP-A) and BrdU.

Results: (1) The RAC values of Groups A and C were (11.0 +/- 1.0) and (9.6 +/- 0.7) cells/10 fields, both significantly lower than those of Group B and D [(13.9 +/- 1.1) and (14.0 +/- 1.1) cells/10 fields respectively, F = 40.41, P = 0.000]. The RAC of Group A was significantly higher than that of Group C (P < 0.05). (2) The white blood cell numbers in BALF of Groups A and C were (0.85 +/- 0.21) and (1.44 +/- 0.69) x 10(5)/ml respectively, both significantly higher than those of Groups B and D [(0.18 +/- 0.10) and (0.21 +/- 0.06) x 10(5)/ml respectively, F = 21.52, P = 0.000]. The neutrophil numbers of Groups A and C were (0.32 +/- 0.12) and (0.73 +/- 0.35) x 10(5)/ml respectively, both significantly higher than those of Groups B and D [(0.06 +/- 0.02) and (0.07 +/- 0.02) x 10(5)/ml respectively, F = 22.91, P = 0.000]. (3) The TNF-alpha levels in the homogenate of Groups A and C were (173 +/- 20) and (224 +/- 42) pg/m respectively, both significantly higher than those of Group B and D [(34 +/- 4) and (35 +/- 4) pg/ml respectively, F = 138.1, P = 0.000]. The IL-1beta levels in the homogenate of Groups A and C were (530 +/- 74) and (948 +/- 82) pg/ml respectively, both significantly higher than those of Group B and D [(210 +/- 33) and (216 +/- 30) pg/ml respectively, F = 247.4, P = 0.000]. (4) BrdU-positive cells and SP-A-positive cells were seen in both Groups A and B, a few double-stained cells were found in Group A, but only SP-A-positive cells, and none BrdU positive cells and double-stained cells were seen in Groups C and D.

Conclusion: MSC administration has protective effect on the ling injury caused by exposure to high oxygen via different mechanisms.