急性呼吸窘迫综合征( acute respiratory distress syndrome, ARDS)的常见病因,包括细菌性或病毒性肺炎、脓毒症、严重创伤和胃内容物误吸等,临床表现为呼吸窘迫和难治性低氧血症.ARDS目前缺乏有效的治疗措施,预后差、病死率高[1-3].间充质干细胞( mesenchymal stem cell, MSC)通过多种机制调控ARDS的炎症反应,参与肺血管内皮细胞损伤的修复,从而减轻肺损伤[4].MSC的免疫调节作用主要是通过细胞外囊泡( extracellular vesicle, EV)介导的[5] ,MSC-EV具有免疫原性低、存储简单等优点,可替代MSC细胞治疗,减轻肺损伤,促进组织修复.本文将对MSC 的免疫调节作用及其在 ARDS中的应用进展作一综述,为寻求ARDS的有效治疗手段提供新的思路和方向.

Objective:To evaluate the value of high-throughput sequencing (HTS) technology for bronchoalveolar lavage fluid (BALF) in diagnosing pulmonary infection pathogen and corresponding effects on the prognosis of patients.Methods:A computer retrieval was performed in Pubmed, Embase, Cochrane Library, Wanfang database, Web of Science, clinical trials.gov, CNKI, Wanfang database, and China biology medicine dise (CBM) from the setup date of the database to December 8, 2021.The positive rate, sensitivity and specificity of BALF metagenomic sequencing and traditional pathogen detection method on pulmonary infection detection were compared.The intensity of antibiotics used, length of hospital stay, 28/30 day mortality, and 90-day mortality were compared by adjusting the therapeutic regimen according to pathogenic test results.Review Manager 5.4.1 software was used for meta-analysis on the abovementioned indexes.Results:A total of 35 papers with 2 624 patients were included, involving 2 248 cases in the HTS group and 2 493 cases in the traditional pathogen detection group.The results of the meta-analysis showed that the positive rate of the HTS group was 79.8%(1 793/2 248), being significantly higher than that of the traditional pathogen detection group at 41.7%(1 039/2 493)( OR=6.84, 95% CI: 4.84~9.67, Z=10.88, P<0.001). The sensitivity, specificity, and the area under the curve of receiver operating characteristic curves by BALF metagenomic sequencing was higher than those by traditional pathogen detection method.The patients enrolled in nine papers were patients with severe pneumonia, and the subgroup analysis showed that the positive rate of BALF high-throughput sequencing in patients with severe pneumonia was 85.8%(495/577), being significantly higher than that in the traditional pathogen detection group at 42.9% (282/657)( OR=6.52, 95% CI: 4.04~10.52, Z=7.69, P<0.001). According to the results of pathogen detection, the intensity of antibiotic use in the high-throughput sequencing group was significantly lower than that in the traditional detection group(SMD=-40.04, 95% CI: -47.05~-33.03, Z=11.19, P<0.001); and the everage length of stay was shortened(SMD=-4.68, 95% CI: -6.12~-3.25, Z=6.40, P<0.001). The 28/30-day mortality and 90-day mortality of the HTS group was 9.09% and 12.82%, respectively, both of which were lower than those of the traditional detection group at 26.44%( OR=0.26, 95% CI: 0.13~0.51, Z=3.89, P<0.001) and 38.30%( OR=0.21, 95% CI: 0.07~0.66, Z=2.67, P=0.008). Conclusions:Compared with traditional pathogen detection methods, using BALF for HTS is found to have higher diagnostic value for pulmonary infection.The adjustment on the therapeutic regimenbased on HTS results for BALFcan reduce the intensity of antibiotic use, shorten the length of hospital stay, reduce mortality, and improve the prognosis of patients.