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目的:探讨机械通气促进肺成纤维细胞活化及肺纤维化的机制，明确乳酸-转化生长因子-β1（transforming growth factor-β1, TGF-β1）途径在该过程中的作用。方法:①将C57BL/6小鼠采用随机数字表法分为假手术组（Sham组）和机械通气组（MV组），每组12只，其中Sham组仅行麻醉插管处理并保持自主呼吸，MV组采用20 ml/kg潮气量和70次/min通气频率行单次2 h机械通气，观察7 d后取材。采用H-E染色、Masson染色观察肺组织的损伤程度和纤维化程度，采用Western blot法检测肺组织Ⅰ型胶原蛋白α1链（collagen type Ⅰ alpha 1 chain, COL1A1）、α平滑肌肌动蛋白（α-smooth muscle actin, α-SMA）和TGF-β1的蛋白表达情况，采用比色法检测小鼠肺泡灌洗液（bronchial alveolar lavage fluid, BALF）和血清的乳酸浓度。②将人胚肺成纤维细胞MRC-5采用随机数字表法分为4组（每组3个孔）：PBS对照组（Con组）、1 mmol/L乳酸组（Lacn 1组）、10 mmol/L乳酸组（Lacn 10组）和20 mmol/L乳酸组（Lacn 20组），于乳酸刺激MRC-5细胞24 h后采用ELISA法检测细胞培养上清液中TGF-β1含量，同时采用细胞免疫荧光观察α-SMA的表达情况；于乳酸刺激MRC-5细胞72 h后采用Western blot法检测不同分组细胞COL1A1和α-SMA的表达情况，并通过ELISA法检测细胞培养上清液Ⅰ型前胶原羧基肽（procollagen type I carboxyl peptide, PICP）的含量变化。③另取MRC-5细胞采用随机数字表法分为3组（每组3个孔）：PBS对照组（Con组）、20 mmol/L乳酸组（Lacn 20组）和20 mmol/L乳酸+TGF-β1受体抑制剂（SB431542）组（Lacn 20+SB组），处理24 h后采用Western blot法检测不同分组细胞COL1A1和α-SMA的表达情况。n 结果:①与Sham组比较，MV组小鼠肺泡间隔增厚、胶原蛋白沉积、肺纤维化程度加重，伴有COL1A1、α-SMA和TGF-β1表达水平升高（n P<0.05），血清和BALF乳酸浓度升高（n P<0.05）。②与Con组比较，Lacn 10组和Lacn 20组细胞培养上清液中TGF-β1、PICP含量升高（n P<0.05），细胞中COL1A1和α-SMA表达水平升高（n P0.05）。③与Lacn 20组比较，Lacn 20+SB组细胞COL1A1和α-SMA表达水平降低（n P<0.05）。n 结论:机械通气可以通过乳酸-TGF-β1途径活化肺成纤维细胞，引起胶原蛋白分泌，促进机械通气相关性肺纤维化进程。“,”Objective:To explore the mechanism of mechanical ventilation to promote lung fibroblast activation and pulmonary fibrosis, and determine the role of the lactic acid-transforming growth factor-β1 (TGF-β1) pathway in the process.Methods:① C57BL/6 mice were divided into two groups according to the random number table method (n n=12): a Sham group and a mechanical ventilation (MV) group. The Sham group only underwent anesthesia intubation and maintained spontaneous breathing, while the MV group was mechanically ventilated over 2 h, with a tidal volume of 20 ml/kg and a ventilation frequency of 70 bpm. After 7 d, lung tissues were collected. The injury and fibrosis of lung tissues were observed by hematoxylin-eosin (H-E) staining and Masson staining. The levels of collagen type Ⅰ alpha 1 chain (COL1A1), α-smooth muscle action (α-SMA) and TGF-β1 were detected by Western blot. The concentrations of lactic acid in the bronchial alveolar lavage fluid (BALF) and serum were detected by colorimetry. ② Human embryonic lung fibroblasts MRC-5 cells were divided into four groups according to the random number table method ( n n=3): a PBS control (Con) group, a 1 mmol/L lactic acid (Lacn 1) group, a 10 mmol/L lactic acid (Lacn 10) group and a 20 mmol/L lactic acid (Lacn 20) group. After exposure to lactic acid for 24 h, the content of TGF-β1 in the supernatant was detected by enzyme-linked immunosorbent assay (ELISA), and the expression of α-SMA was observed by immunofluorescence. After exposure to lactic acid for 72 h, the levels of COL1A1 and α-SMA in each group were detected by Western blot, and the content of procollagen type Ⅰ carboxyl peptide (PICP) in the supernatant was detected by ELISA. ③ MRC-5 cells were divided into three groups according to the random number table method (n n=3): a PBS control (Con) group, a 20 mmol/L lactic acid (Lacn 20) group, and a 20 mmol/L lactic acid+TGF-β1 receptor inhibitor SB431542 (Lacn 20+SB) group. After treatment for 24 h, the levels of COL1A1 and α-SMA in each group were detected by Western blot.n Results:① Compared with the Sham group, the MV group presented thickened alveolar septum, collagen deposition and aggravated pulmonary fibrosis, along with increases in the levels of COL1A1, α-SMA and TGF-β1 ( n P<0.05) as well as the concentrations of lactic acid in the alveolar lavage fluid and serum (n P<0.05). ② Compared with the Con group, both the Lacn 10 and Lacn 20 groups produced increases in the content of TGF-β1 and PICP in the supernatant (n P<0.05) as well as the levels of COL1A1 and α-SMA (n P0.05). ③ Compared with the Lacn 20 group, the levels of COL1A1 and α-SMA significantly decreased in the Lac n 20+SB group (n P<0.05).n Conclusions:Mechanical ventilation can activate lung fibroblasts via the lactic acid-TGF-β1 pathway to cause the secretion of collagen, so as to accelerate the process of mechanical ventilator-associated pulmonary fibrosis.