ABSTRACT
To investigate the effect of overexpression of microRNA-21-5p (miR-21-5p) on early apoptosis of type Ⅱalveolar epithelial cells (AECⅡ) in rats with hyperoxic acute lung injury (HALI). Methods The Sprague-Dawley (SD) rats were randomly divided into four groups: control group (CON group), hyperoxia group (H group), overexpression group (OE group) and empty vector group (EV group), with 20 rats in each group. HALI animal model was made by inhaling high concentration oxygen (oxygen concentration ≥90%); CON group was arranged to inhale room air. The miR-21-5p adeno-associated virus-6 (AAV-6) overexpression vectors or empty vectors were dripped into the lungs of OE group and EV group through tracheal tube, respectively. The hyperoxia model was prepared after 3 weeks of feeding. At 0, 24, 48 and 60 hours after making model, 5 rats were selected to detect lung injury parameters:oxygenation index (OI), respiratory index (RI), wet/dry ratio (W/D), pathological injury score of lung tissue; real-time quantitative polymerase chain reaction (RT-qPCR) was used to detect the expression of miR-21-5p in AECⅡ, and flow cytometry was used to detect the early apoptotic rate of AECⅡ. Results ① The lung injury parameters: in H group, the OI gradually decreased with time, but the RI, lung W/D ratio and pathological score increased gradually with time, the difference between CON group was statistically significant at 24 hours [OI (mmHg, 1 mmHg = 0.133 kPa):336.04±5.79 vs. 400.22±19.70, RI: 0.20±0.02 vs. 0.10±0.06, lung W/D ratio: 5.04±0.09 vs. 4.85±0.09, lung tissue pathological score: 0.13±0.01 vs. 0.07±0.01, all P < 0.05]. It indicated that HALI model could be successfully established by inhaling high concentration oxygen continuously. ② The expression of miR-21-5p: the miR-21-5p was gradually increased in H, OE and EV groups, and the expression of miR-21-5p was significantly higher than that in CON group at 24, 48 and 60 hours. Compared with H group, the expression of miR-21-5p was significantly increased further in OE group at 0, 24, 48 and 60 hours (2-ΔΔCt: 3.75±0.11 vs. 0.98±0.14, 3.98±0.12 vs. 1.18±0.13, 4.28±0.18 vs. 1.49±0.06, 4.66±0.12 vs. 1.80±0.12, all P < 0.05). ③ The early apoptosis of AECⅡ: the early apoptosis rate gradually increased with time in H, OE and EV groups, and the early apoptosis of AECⅡ was significantly higher than that in CON group at 24, 48 and 60 hours. Compared with H group, the early apoptosis rate was significantly decreased in OE group at 24, 48 and 60 hours [(1.22±0.63)% vs. (2.84±0.59)%, (5.76±0.18)% vs. (13.10±2.01)%, (29.48±0.48)% vs. (49.04±1.36)%, all P < 0.05]. ④ There was no significant difference in the expression of miR-21-5p and the early apoptosis of AECⅡ cells between EV group and H group at each time point. Conclusion Overexpression of miR-21-5p could inhibit the early apoptosis of AECⅡ in rats with HALI.
ABSTRACT
Objective To investigate the effects of microRNA-21-5p (miR-21-5p) on hyperoxic acute lung injury (HALI) in rats and provide a theoretical basis for HALI gene therapy. Methods One hundred and sixty Sprague-Dawley (SD) rats were randomly divided into four groups with number table:hyperoxia control group, phosphate buffer saline (PBS) group, blank virus group and miRNA-21-5p group (each, n = 40). The rats in hyperoxia control group were fed directly in the hyperoxia box (oxygen concentration > 90%); in the other three groups, 200 μL PBS, 200μL slow virus and 200μL miRNA-21-5p slow virus were dropped into the nose respectively, and then they were fed in the hyperoxia box. The rats were exposed to hyperoxia in the boxes for 0, 24, 48 and 72 hours in all the groups, and at each time point, 10 rats were taken randomly from each group to perform arterial blood-gas analysis, calculate oxygenation index (OI) and respiratory index (RI). Afterwards the rats were sacrificed by blood-letting from carotid artery under intra-peritoneal anesthesia, and the lung tissues were obtained to measure the left lung wet/dry weight (W/D) ratio, hemotoxylin-eosin (HE) staining was made and the pathological changes of the right lung were observed under light microscope and the pathological score was measured. Results At 0 hour, the OI, RI, lung W/D ratio and the lung tissue pathology score in rats with hyperoxic injury had no statistically significant differences among the four groups (all P>0.05). With the extension of time, the level of OI was gradually reduced, and the levels of RI, pathologic score and W/D ratio of lung tissues were gradually increased. Compared with the hyperoxia control group, in miRNA-21-5p group, the levels of OI were increased significantly at 24, 48 and 72 hours after the exposure to hyperoxia [mmHg (1 mmHg = 0.133 kPa): 24 hours 358.10±29.25 vs. 306.19±37.23, 48 hours 336.67±29.27 vs. 269.70±29.00, 72 hours 323.81±19.05 vs. 203.81±43.40, all P 0.05). Under the optical microscope, along with the prolongation of exposure to hyperoxia, the structure of alveoli was gradually disturbed, their walls fractured and damaged, alveolar septa widened, edematous, infiltrated with inflammatory cells and in part of the rats a small amount of red blood cell exudates could be seen, but the degree of lung pathological injury in miRNA-21-5p group was much milder than that of the other groups. Conclusion The rat persistently exposed to hyperoxia for 24 hours can establish the rat model of HALI successfully, and the miRNA-21-5p can protect the lung tissue from the damage to some degrees in HALI rats.