title: [Collagen spatial distribution in rapid atrial pacing dogs with or without superior vena cava and aortic root fat pad].
abstract: OBJECTIVE
  To observe the collagen spatial distribution, collagen volume fraction (CVF) and Cx40, Cx43mRNA expressions in rapid atrial pacing dogs post vagal denervation by removing fat pad located between the medial superior vena cava and aortic root (SVC-Ao fat pad).
  
  
  METHODS
  Twenty-four dogs were randomly divided into unpaced sham operation group (S group, n = 8), Keeping SVC-Ao fat pad group (K group, n = 8) and Removing SVC-Ao fat pad group (R group, SVC-Ao fat pad was removed by surgical excision before pacing, n = 8). K and R groups were paced for six weeks. Six weeks later, all dogs were sacrificed, left atrium (LA), right atrium (RA), left atrial appendage (LAA), right atrial appendage (RAA) and atrial septum (AS) were collected and stained with HE or Masson Trichrome or frozen in liquid nitrogen for quantifying the expression of Cx40, Cx43 mRNA by Real-time quantitative Reverse Transcription Polymerase Chain Reaction (RT-PCR).
  
  
  RESULTS
  Spatial distribution of collagen fibers as well as CVF between S and R group were similar (all P > 0.05). CVF was significantly higher in K group compared to R group, especially at LAA and AS locations (all P < 0.05). Cx40mRNA expression in K group was significantly decreased in LA, RA, and significantly increased in LAA, RAA and AS compared those in S group (all P < 0.05), significantly lower in LA and RA while significantly higher in LAA and RAA compared to R group (all P < 0.05). Cx43mRNA expression in K group was significantly reduced in LA, RA, LAA and RAA while significantly increased in AS compared to S group (all P < 0.05), significantly higher in LA, RA, RAA and AS while significantly lower in LAA compared to R group.
  
  
  CONCLUSIONS
  Pacing induced collagen remodeling and modulation on Cx40mRNA and Cx43 mRNA expressions could be partially attenuated by removing SVC-Ao fat pad suggesting vagal denervation plays a key role in the initiation and preservation of atrial fibrillation.
authors.affiliation: Department of Cardiology, First Affiliated Hospital of Guangxi Medical University, Nanning 530021, China.
authors.forename: Ri-Xin
authors.initials: RX
authors.lastname: Xiong
authors.forename: Guo-Qiang
authors.initials: GQ
authors.lastname: Zhong
authors.forename: Hong-Xing
authors.initials: HX
authors.lastname: Song
authors.forename: Jing-Chang
authors.initials: JC
authors.lastname: Zhang
authors.forename: Yun
authors.initials: Y
authors.lastname: Ling
mesh_terms: D000818:Animals; D001281:Atrial Fibrillation / Q000378:metabolism* / Q000473:pathology; D002304:Cardiac Pacing, Artificial; D003094:Collagen / Q000378:metabolism*; D018031:Connexin 43 / Q000378:metabolism; D017630:Connexins / Q000378:metabolism; D004285:Dogs; D006325:Heart Atria / Q000378:metabolism* / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics; D000097003:Gap Junction alpha-5 Protein
chemical_list: D003094:Collagen; D018031:Connexin 43; D017630:Connexins; D012333:RNA, Messenger; D000097003:Gap Junction alpha-5 Protein