title: In vivo assessment of retinal vascular wall dimensions.
abstract: OBJECTIVE
  Retinal blood vessel diameter and arteriovenous ratio (AVR) are commonly used diagnostic parameters. Because vascular walls are typically not visible in funduscopy, clinical AVR estimation is based on the lumen rather than the entire vessel diameter. Here the authors used a transgenic mouse model to quantify AVR in vivo based on total vessel dimensions (wall and lumen).
  
  
  METHODS
  Confocal scanning laser ophthalmoscopy (cSLO) and indocyanine green angiography of the retinal vasculature were performed in wild-type and transgenic mice expressing green fluorescent protein (GFP) under the transcriptional control of the smooth muscle type α-actin (αSMA) promoter. Spectral-domain-OCT and ERG were performed to control for integrity of retinal structure and function in vivo and histology to demonstrate the location of GFP expression.
  
  
  RESULTS
  Native cSLO imaging and angiography yielded only inner vessel diameters similar to those observed through clinical funduscopy. In αSMA-GFP mice, autofluorescence imaging of the GFP-marked vascular walls also allowed the determination of outer vessel diameters. The mean AVR based on either inner diameter (AVR(id) = 0.72 ± 0.08) or outer diameter (AVR(od) = 0.97 ± 0.09) measurements were significantly different (P < 0.01).
  
  
  CONCLUSIONS
  Transgenic αSMA-GFP expression in murine vessel wall components allowed quantification of retinal vessel outer diameters in vivo. Although arterioles and venules differ in lumen and vessel wall width, they share a common outer diameter, leading to an AVR(od) close to unity. Because vessel walls are primary targets in common hypertensive and metabolic diseases, αSMA-GFP transgenic mice may prove valuable in the detailed assessment of such disorders in vivo.
authors.affiliation: Division of Ocular Neurodegeneration, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Tübingen, Germany. dominik.fischer@med.uni-tuebingen.de
authors.forename: M Dominik
authors.initials: MD
authors.lastname: Fischer
authors.forename: Gesine
authors.initials: G
authors.lastname: Huber
authors.forename: Yuxi
authors.initials: Y
authors.lastname: Feng
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Tanimoto
authors.forename: Regine
authors.initials: R
authors.lastname: Mühlfriedel
authors.forename: Susanne C
authors.initials: SC
authors.lastname: Beck
authors.forename: Eric
authors.initials: E
authors.lastname: Tröger
authors.forename: Christoph
authors.initials: C
authors.lastname: Kernstock
authors.forename: Markus N
authors.initials: MN
authors.lastname: Preising
authors.forename: Birgit
authors.initials: B
authors.lastname: Lorenz
authors.forename: Hans Peter
authors.initials: HP
authors.lastname: Hammes
authors.forename: Mathias W
authors.initials: MW
authors.lastname: Seeliger
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D001837:Body Weights and Measures; D004396:Coloring Agents; D004596:Electroretinography; D005451:Fluorescein Angiography; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D007208:Indocyanine Green; D007834:Lasers; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009887:Ophthalmoscopy; D012161:Retinal Artery / Q000033:anatomy & histology* / Q000378:metabolism; D012169:Retinal Vein / Q000033:anatomy & histology* / Q000378:metabolism; D041623:Tomography, Optical Coherence
chemical_list: D000199:Actins; D004396:Coloring Agents; C544013:alpha-smooth muscle actin, mouse; D049452:Green Fluorescent Proteins; D007208:Indocyanine Green