title: Morphology and topography of retinal pericytes in the living mouse retina using in vivo adaptive optics imaging and ex vivo characterization.
abstract: OBJECTIVE
  To noninvasively image retinal pericytes in the living eye and characterize NG2-positive cell topography and morphology in the adult mouse retina.
  
  
  METHODS
  Transgenic mice expressing fluorescent pericytes (NG2, DsRed) were imaged using a two-channel, adaptive optics scanning laser ophthalmoscope (AOSLO). One channel imaged vascular perfusion with near infrared light. A second channel simultaneously imaged fluorescent retinal pericytes. Mice were also imaged using wide-field ophthalmoscopy. To confirm in vivo imaging, five eyes were enucleated and imaged in flat mount with conventional fluorescent microscopy. Cell topography was quantified relative to the optic disc.
  
  
  RESULTS
  We observed strong DsRed fluorescence from NG2-positive cells. AOSLO revealed fluorescent vascular mural cells enveloping all vessels in the living retina. Cells were stellate on larger venules, and showed banded morphology on arterioles. NG2-positive cells indicative of pericytes were found on the smallest capillaries of the retinal circulation. Wide-field SLO enabled quick assessment of NG2-positive distribution, but provided insufficient resolution for cell counts. Ex vivo microscopy showed relatively even topography of NG2-positive capillary pericytes at eccentricities more than 0.3 mm from the optic disc (515 ± 94 cells/mm(2) of retinal area).
  
  
  CONCLUSIONS
  We provide the first high-resolution images of retinal pericytes in the living animal. Subcellular resolution enabled morphological identification of NG2-positive cells on capillaries showing classic features and topography of retinal pericytes. This report provides foundational basis for future studies that will track and quantify pericyte topography, morphology, and function in the living retina over time, especially in the progression of microvascular disease.
authors.affiliation: Center for Visual Science, University of Rochester, Rochester, New York.
authors.forename: Jesse
authors.initials: J
authors.lastname: Schallek
authors.forename: Ying
authors.initials: Y
authors.lastname: Geng
authors.forename: HoanVu
authors.initials: H
authors.lastname: Nguyen
authors.forename: David R
authors.initials: DR
authors.lastname: Williams
mesh_terms: D000818:Animals; D000941:Antigens / Q000378:metabolism; D002452:Cell Count; D004730:Endothelium, Vascular / Q000166:cytology; D005456:Fluorescent Dyes; D008164:Luminescent Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D009887:Ophthalmoscopy; D061848:Optical Imaging / Q000379:methods*; D020286:Pericytes / Q000166:cytology* / Q000378:metabolism; D011509:Proteoglycans / Q000378:metabolism; D012171:Retinal Vessels / Q000166:cytology*; D000099216:Chondroitin Sulfate Proteoglycan 4
chemical_list: D000941:Antigens; D005456:Fluorescent Dyes; D008164:Luminescent Proteins; D011509:Proteoglycans; D000099216:Chondroitin Sulfate Proteoglycan 4; C413663:fluorescent protein 583
keywords: adaptive optics; capillaries; diabetic retinopathy; microvascular network; neurovascular coupling