title: Downregulated Smad4 Affects Extracellular Matrix Remodeling in Ventilator-induced Lung Injury.
abstract: OBJECTIVE
  To explore the effect of Smad4 on the extracellular matrix remodeling in ventilator-induced lung injury (VILI).
  
  
  METHODS
  We randomized 24 C57BL/6 mice to 4 groups for treatment (n=6/group): control, ventilation, non-targeted (scramble) lentivirus transfection plus ventilation, and Smad4 small interfering RNA (siRNA) lentivirus transfection plus ventilation. Lentivirus was delivered by intranasal instillation. Four weeks later, the 3 ventilated groups underwent high tidal volume (VT 40mL/kg) ventilation to induce lung injury. After 72 hours, lungs were collected from the anesthetized live mice. Histological changes in lungs were evaluated by hematoxylin and eosin and Masson's staining. The expression of α-smooth muscle actin (α-SMA) was determined by immunohistochemistry, and the mRNA and protein levels of Smad4, α-SMA, and collagen I and III were detected by quantitative real-time PCR and western blotting analysis.
  
  
  RESULTS
  Smad4 siRNAs significantly knocked down Smad4 expression (P<.05), which was increased with ventilation, thereby alleviating inflammatory cell infiltration. It also inhibited accumulation of α-SMA-positive myofibroblasts and pulmonary fibrosis, as seen by reduced collagen I and III expression (P<.05), induced by ventilation. Scramble siRNA treatment had no effect (P>.05).
  
  
  CONCLUSIONS
  Smad4 gene silencing may be a therapeutic target for treating ventilator-induced lung injury and pulmonary fibrosis.
authors.affiliation: Department of Intensive Care Unit, Qilu Hospital, Shandong University, Shandong Province, China.
authors.forename: Xiaofang
authors.initials: X
authors.lastname: Huang
authors.affiliation: Department of Ultrasound, Qilu Hospital, Shandong University, Shandong Province, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhou
authors.affiliation: Department of Intensive Care Unit, Qilu Hospital, Shandong University, Shandong Province, China Dingshifang123@aliyun.com.
authors.forename: Shifang
authors.initials: S
authors.lastname: Ding
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D024042:Collagen Type I / Q000235:genetics / Q000378:metabolism; D024061:Collagen Type III / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation / Q000235:genetics*; D005109:Extracellular Matrix / Q000378:metabolism*; D007150:Immunohistochemistry; D008168:Lung / Q000378:metabolism / Q000473:pathology; D008297:Male; D008810:Mice, Inbred C57BL; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D051901:Smad4 Protein / Q000235:genetics* / Q000378:metabolism; D055397:Ventilator-Induced Lung Injury / Q000235:genetics*
chemical_list: C541116:ACTA2 protein, human; D000199:Actins; D024042:Collagen Type I; D024061:Collagen Type III; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D051901:Smad4 Protein
keywords: extracellular matrix; mechanical ventilation; pulmonary fibrosis; ventilator-induced lung injury