title: Real-time PCR study of Ang1, Ang2, Tie-2, VEGF, and KDR expression in human erectile tissue during aging.
abstract: BACKGROUND
  Aging is a recognized risk factor for erectile dysfunction (ED), contributing independently to vascular damage of penile tissue. Vascular maintenance depends on angiogenic balance in tissues. Vascular endothelial growth factor (VEGF) is a modulator of endothelial cells functions, after engagement to specific receptor kinase domain region (KDR). Other factors, such as angiopoietins, cross talk with VEGF, modulating its effects. Angiopoietin-1 (Ang1) and angiopoietin-2 (Ang2) compete for binding to Tie-2 and, while Ang1 promotes vascular stabilization, Ang2 acts as a partial agonist or antagonist of Ang1 signaling, depending on VEGF bioavailability.
  
  
  OBJECTIVE
  To quantify the expression of Ang1, Ang2, Tie-2, VEGF, and KDR by real-time polymerase chain reaction (PCR) in human corpus cavernosum (CC) from young and aged healthy individuals.
  
  
  METHODS
  Human CC fragments were obtained from organ donors without known risk factors to ED and divided in two groups: young (16-35 years) and aged (59-74 years). RNA was extracted and converted to cDNA. Real-time PCR reactions employed appropriate primers. KDR, Tie-2, Akt, and phospho-Akt protein levels were also assessed by Western blotting (WB). Computer-assisted evaluation of vascular areas was performed.
  
  
  METHODS
  Study of angiopoietins-Tie-2 and VEGF-KDR systems in human CC during aging by real-time PCR and WB. The ratios Ang1/Tie-2 and VEGF/KDR and Akt levels were also determined.
  
  
  RESULTS
  Real-time PCR results showed a sixfold significant reduction in the Ang1/Tie-2 ratio during aging. Ang2, VEGF, and KDR expression results were highly variable. Nevertheless, the ratio VEGF/KDR was significantly higher in the aged individuals. Akt and phospho-Akt levels were similar in both groups. Immunohistological evaluation revealed a significant decrease in vascular areas and endothelial surface in CC with aging, despite no differences found in vessel number.
  
  
  CONCLUSIONS
  The obtained results suggest an aging-associated downregulation of angiopoietins/Tie-2 system and an apparent compensatory upregulation of the VEGF/KDR system.
authors.affiliation: Faculty of Medicine of Universidade do Porto, Porto, Portugal. antonio.f.figueiredo@gmail.com
authors.forename: António
authors.initials: A
authors.lastname: Figueiredo
authors.forename: Ana Lúcia
authors.initials: AL
authors.lastname: Cordeiro
authors.forename: Nuno
authors.initials: N
authors.lastname: Tomada
authors.forename: Inês
authors.initials: I
authors.lastname: Tomada
authors.forename: Adriana
authors.initials: A
authors.lastname: Rodrigues
authors.forename: Alexandra
authors.initials: A
authors.lastname: Gouveia
authors.forename: Delminda
authors.initials: D
authors.lastname: Neves
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging / Q000378:metabolism* / Q000502:physiology; D042683:Angiopoietin-1 / Q000032:analysis* / Q000502:physiology; D042702:Angiopoietin-2 / Q000032:analysis* / Q000502:physiology; D015153:Blotting, Western; D006801:Humans; D008297:Male; D008875:Middle Aged; D010413:Penis / Q000098:blood supply / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D016133:Polymerase Chain Reaction; D042787:Receptor, TIE-2 / Q000032:analysis* / Q000502:physiology; D042461:Vascular Endothelial Growth Factor A / Q000032:analysis* / Q000502:physiology; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000032:analysis* / Q000502:physiology; D055815:Young Adult
chemical_list: C467630:ANGPT1 protein, human; D042683:Angiopoietin-1; D042702:Angiopoietin-2; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D042787:Receptor, TIE-2; D040301:Vascular Endothelial Growth Factor Receptor-2