title: Macrophage imbalance (M1 vs. M2) and upregulation of mast cells in wall of ruptured human cerebral aneurysms: preliminary results.
abstract: BACKGROUND
  M1 and M2 cells are two major subsets of human macrophages that exert opposite effects on the inflammatory response. This study aims to investigate the role of macrophage M1/M2 imbalance and mast cells in the progression of human cerebral aneurysms to rupture.
  
  
  METHODS
  Ten patients with cerebral aneurysms (five ruptured and five unruptured) underwent microsurgical clipping. During the procedure, a segment of the aneurysm dome was resected and immunostained with monoclonal antibodies for M1 cells (anti-HLA DR), M2 cells (anti-CD 163), and mast cells (anti-tryptase clone AA). A segment of the superficial temporal artery (STA) was also removed and immunostained with monoclonal antibodies for M1, M2, and mast cells.
  
  
  RESULTS
  All ten aneurysm tissues stained positive for M1, M2, and mast cells. M1 and M2 cells were present in equal proportions in unruptured aneurysms. This contrasted with a marked predominance of M1 over M2 cells in ruptured aneurysms (p = 0.045). Mast cells were also prominently upregulated in ruptured aneurysms (p = 0.001). Few M1 and M2 cells were present in STA samples.
  
  
  CONCLUSIONS
  M1/M2 macrophages and mast cells are found in human cerebral aneurysms; however, M1 and mast cell expression seems to markedly increase in ruptured aneurysms. These findings suggest that macrophage M1/M2 imbalance and upregulation of mast cells may have a role in the progression of cerebral aneurysms to rupture.
authors.affiliation: Department of Neurosurgery, Carver College of Medicine, University of Iowa, Iowa City, IA, USA. david-hasan@uiowa.edu
authors.forename: David
authors.initials: D
authors.lastname: Hasan
authors.forename: Nohra
authors.initials: N
authors.lastname: Chalouhi
authors.forename: Pascal
authors.initials: P
authors.lastname: Jabbour
authors.forename: Tomoki
authors.initials: T
authors.lastname: Hashimoto
mesh_terms: D000328:Adult; D000368:Aged; D017542:Aneurysm, Ruptured / Q000150:complications / Q000473:pathology*; D015703:Antigens, CD / Q000378:metabolism; D015214:Antigens, Differentiation, Myelomonocytic / Q000378:metabolism; D005260:Female; D006684:HLA-DR Antigens / Q000378:metabolism; D006801:Humans; D002532:Intracranial Aneurysm / Q000150:complications / Q000473:pathology*; D008264:Macrophages / Q000378:metabolism*; D008297:Male; D008407:Mast Cells / Q000145:classification / Q000378:metabolism* / Q000473:pathology; D008875:Middle Aged; D011956:Receptors, Cell Surface / Q000378:metabolism; D013699:Temporal Arteries / Q000473:pathology*; D015854:Up-Regulation / Q000502:physiology*; D000098902:CD163 Antigen
chemical_list: D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D000098902:CD163 Antigen; D006684:HLA-DR Antigens; D011956:Receptors, Cell Surface