MassGeneral Institute of Neurodegenerative Disease                                Massachusetts General Hospital   Harvard Medical School

Brian Bacskai Lab - Optical Imaging Approaches for Alzheimer's Disease

Lab Members        Postdoctoral Fellows : Graduate Students : Research Technicians

Brian Bacskai, Ph.D.

Meenakshi Subramaniam, Ph.D.

Monica Garcia-Alloza, Ph.D.

Anand Kumar, Ph.D.

I am involved in the development of optical tomographic techniques for the non-invasive detection and diagnosis of diseases. In particular, my work with the Bacskai group is focused on the non-invasive imaging of amyloid plaques, which are widely considered to be a hallmark of Alzheimer's disease, in transgenic mouse models.

We recently showed that time domain imaging technology allows the detection of in-vivo lifetime changes directly from surface measurements. Moreover, multiple lifetime components could be separated based on surface-decay-amplitude measurements. Contingent upon the development of fluorescent compounds that specifically change their lifetime upon binding to amyloid beta in the brain, lifetime based sensing could prove to be a powerful tool for quantifying plaque load and studying drug treatment responses in the same animal.

The application of optical tomography to Alzheimer's disease poses additional challenges, since amyloid plaques are very small (~10s of microns) and distributed across the small volume of the brain. The use of lifetime as a contrast mechanism is likely to prove very useful in this scenario, where multiple fluorophore distributions (plaque bound and free) occupying the same region in the brain may be separately recovered based on their lifetime.

Home Page: http://www.nmr.mgh.harvard.edu/~ankumar/

Kishore Kuchibotla, Ph.D. candidate

Kishore Kuchibhotla is investigating the effect of Alzheimer's Disease related pathologies on neural function.  The specific functional effects of amyloid-beta plaques to their micro-environment, or of neurofibrillary tangles to a specific neuron, are not well understood in-vivo.  Combining in vivo multiphoton imaging with calcium-imaging techniques, he is trying determine the spatial specificity of functional deficits in animals who develop either plaques or tangles.  He uses two primary techniques for introducing calcium-sensitive probes in vivo.  The first involves the direct injection of calcium-sensitive AM-ester dyes (BAPTA-derivatives) into the brain under multiphoton-guidance.  This technique allows for hundreds of neurons to be analyzed with single-cell resolution.  The second uses gene-transfer techniques to introduce a genetically-encoded calcium indicator, yellow cameleon 3.6, into cortical neurons, allowing longitudinal observation of neural function with spine-level spatial resolution.  Yellow cameleon is a FRET-based ratiometric indicator that might also permit investigation of calcium dyshomeostasis near plaques or in tangle-bearing neurons.

Scott Raymond, Ph.D. candidate

Recently, a NIR (near-infrared) dye (AOI987) has emerged that effectively crosses the BBB and binds plaques. Detection in vivo, however, can be confounded by autoflourescence and background, non-bound dye. I am interested in exploiting changes in lifetime and emission spectra that occur on binding, potentially allowing higher contrast for imaging. Currently, I am using a Monte Carlo simulation to model the detection potential given specific parameters, including plaque density, dye quantum yield and specificity, lifetime and spectral shifts, etc. I am also testing available dyes for in vivo imaging capabilities, using multiphoton microscopy, FLIM, spectral unmixing, and an in-house time-resolved system that uses a picosecond-gated intensifier for wide-field lifetime measurements. Our goal is to develop a NIR probe that allows rapid diagnosis of plaque burden, non-invasively.

Home Page: http://web.mit.edu/sbr/www/homepage/index.htm
 

Sarah Dodwell

Alex Hoang

Chronic in-vivo imaging of diffuse plaques.

We have shown previously by in-vivo two-photon microscopy that topical application of anti-amyloid antibodies 3d6 and 10d5 onto the cortex of transgenic mice leads to the reduction and clearance of diffuse plaques.  Because the antibodies used to label and image the diffuse plaques also lead to clearance, we cannot use these antibodies to track the history of these diffuse plaques over time.  I have identified an antibody 32.1.3 that can label the diffuse plaques but does not lead to clearance.  It is my hope to use this antibody for chronic imaging of diffuse amyloid.

 Laura Borrelli

 Brian Ferrara