title: In vivo imaging of choroidal angiogenesis using fluorescence-labeled cationic liposomes.
abstract: OBJECTIVE
  Precise monitoring of active angiogenesis in neovascular eye diseases such as age-related macular degeneration (AMD) enables sensitive use of antiangiogenic drugs and reduces adverse side effects. So far, no in vivo imaging methods are available to specifically label active angiogenesis. Here, we report such a technique using fluorophore-labeled cationic liposomes (CL) detected with a standard clinical in vivo scanning laser ophthalmoscope (SLO).
  
  
  METHODS
  C57Bl/6 mice underwent laser coagulations at day 0 (d0) to induce choroidal neovascularization (CNV). Liposomes labeled with Oregon green, rhodamine (Rh), or indocyanine green (ICG) were injected into the tail vein at various time points after laser coagulation, and their fluorescence was observed in vivo 60 min later using an SLO, or afterwards in choroidal flatmounts or cryosections.
  
  
  RESULTS
  SLO detected accumulated fluorescence only in active CNV lesions with insignificant background noise. The best signal was obtained with CL-ICG. Choroidal flatmounts and cryosections of the eye confirmed the location of retained CL in CNV lesions. Neutral liposomes, in contrast, showed no accumulation.
  
  
  CONCLUSIONS
  These results establish fluorophore-labeled CL as high affinity markers to selectively stain active CNV. This novel, non-invasive SLO imaging technique could improve risk assessment and indication for current intraocular antiangiogenic drugs in neovascular eye diseases, as well as monitor therapeutic outcomes. Labeling of angiogenic vessels using CL can be of interest not only for functional imaging in ophthalmology but also for other conditions where localization of active angiogenesis is desirable.
authors.affiliation: University Eye Hospital, Albert-Ludwigs University of Freiburg, Killianstrasse 5, Freiburg im Breisgau, Germany
authors.forename: Jing
authors.initials: J
authors.lastname: Hua
authors.forename: Nikolai
authors.initials: N
authors.lastname: Gross
authors.forename: Brita
authors.initials: B
authors.lastname: Schulze
authors.forename: Uwe
authors.initials: U
authors.lastname: Michaelis
authors.forename: Hermann
authors.initials: H
authors.lastname: Bohnenkamp
authors.forename: Eric
authors.initials: E
authors.lastname: Guenzi
authors.forename: Lutz L
authors.initials: LL
authors.lastname: Hansen
authors.forename: Gottfried
authors.initials: G
authors.lastname: Martin
authors.forename: Hansjürgen T
authors.initials: HT
authors.lastname: Agostini
mesh_terms: D000818:Animals; D002264:Carboxylic Acids; D002412:Cations; D002829:Choroid / Q000098:blood supply* / Q000473:pathology / Q000601:surgery; D020256:Choroidal Neovascularization / Q000175:diagnosis* / Q000209:etiology / Q000473:pathology / Q000601:surgery; D005451:Fluorescein Angiography / Q000379:methods*; D005453:Fluorescence; D005456:Fluorescent Dyes; D007208:Indocyanine Green; D017075:Laser Coagulation / Q000009:adverse effects; D007834:Lasers; D008081:Liposomes / Q000008:administration & dosage; D051379:Mice; D008810:Mice, Inbred C57BL; D008867:Microtomy; D009887:Ophthalmoscopy; D012235:Rhodamines
chemical_list: D002264:Carboxylic Acids; D002412:Cations; D005456:Fluorescent Dyes; D008081:Liposomes; C436864:Oregon Green 488 carboxylic acid; D012235:Rhodamines; D007208:Indocyanine Green