June 2015
Volume 56, Issue 7
Free
ARVO Annual Meeting Abstract  |   June 2015
Two-photon Microscopy to Visualize Amyloid Plaques in Unstained Retinas from Alzheimer’s Disease
Author Affiliations & Notes
  • Francisco J. Avila
    Laboratorio de Optica, Universidad de Murcia, Murcia, Spain
    Physics and Astronomy, University of Waterloo, Waterloo, ON, Canada
  • Laura Emptage
    Physics and Astronomy, University of Waterloo, Waterloo, ON, Canada
  • Oscar del Barco
    Laboratorio de Optica, Universidad de Murcia, Murcia, Spain
  • Pablo Artal
    Laboratorio de Optica, Universidad de Murcia, Murcia, Spain
  • Melanie C W Campbell
    Physics and Astronomy, University of Waterloo, Waterloo, ON, Canada
    School of Optometry and Vision Science, University of Waterloo, Waterloo, ON, Canada
  • Juan M Bueno
    Laboratorio de Optica, Universidad de Murcia, Murcia, Spain
  • Footnotes
    Commercial Relationships Francisco Avila, None; Laura Emptage, None; Oscar del Barco, None; Pablo Artal, None; Melanie Campbell, None; Juan Bueno, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science June 2015, Vol.56, 3372. doi:
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      Francisco J. Avila, Laura Emptage, Oscar del Barco, Pablo Artal, Melanie C W Campbell, Juan M Bueno; Two-photon Microscopy to Visualize Amyloid Plaques in Unstained Retinas from Alzheimer’s Disease. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3372.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: Alzheimer’s disease (AD) is a neurodegenerative process characterized by the formation of insoluble plaques of amyloid β (Aβ) proteins in brain tissues. Classical microscopy techniques have shown Aβ deposits in stained retinal tissues of human donors and dogs, often used as animal models of AD. Although these Aβ deposits can be seen in unstained retinas using polarized light (Campbell et al., 2013), alternative non-invasive methods to image Aβ deposits in unstained retinal tissues are of interest. We explored here two-photon microscopy as a new tool to visualize Aβ deposits.

Methods: A research two-photon microscope (Bueno et al., 2010) was used to record two-photon excitation fluorescence (TPEF) images originating from flat-mounted, fixed, unstained retinas of human donors with a diagnosis of AD. Another set of retina samples from dogs suffering progressive cognitive impairment that is paired with Aβ accumulation (Mutsuga et al., 2012) was also examined. Different areas across the retina containing presumed Aβ deposits (first identified with polarized light) were imaged. At each location a Z-scan motor coupled to the microscope objective allowed optical sectioning of the samples.

Results: Aβ plaques provided a stronger TPEF signal than the surrounded retinal structures. Deposits could easily be distinguished and were found to be lying in front of nerve fiber layer and slightly penetrating into it. 3D volume renderings of the imaged areas were reconstructed from the set of images. This provided valuable and detailed information on the shape and distribution of deposits within the retina.

Conclusions: Two-photon microscopy is a useful alternative method to visualize Aβ deposits within unstained retinas. This technique offers high resolution imaging and avoids photo-damage. Optical sectioning allows accurate Aβ depth location tracking, as well as detailed information on morphology and geometrical characterization. Possible future clinical implementations of this technique in vivo might help to establish early diagnoses of AD and to quantify the progression the disease.

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