Multiplex Cellular Imaging Platform for Discovery and Advancement of Novel Drugs for CNS Diseases

Developing new processes and technologies to aid the discovery and advancement of novel drugs is the objective of the imaging and biosimulation platform for new Central Nervous System drugs (BICNSD), a three-year project funded by the OSÉO, Alsace-Biovalley, and the Québec Consortium for Drug Discovery (CQDM).

Figure 1. Structure of the synapse

BICNSD Project

The focus of this France-Québec collaborative project will be to develop and validate two synergistic platforms for an innovative imaging and biosimulation-based service, to discover and develop improved drugs by gaining more insight into the fundamental mechanisms of Central Nervous System (CNS) diseases and monitoring the actions of potential drug candidates at molecular and sub-cellular levels. The key objectives of the projects include:

• Developing a drug delivery and development platform for CNS diseases using a cellular and sub-cellular imaging system that can capture images of several labels simultaneously

• Designing probes for multi-labeling of neuron receptors

• Visualizing labels using the imaging analysis software tools

• Biosimulation platform that implements and integrates signaling cascades, specific protein-protein interactions and movement of receptors along the postsynaptic membrane.

As part of the project, Rhenovia Pharma will focus on the biosimulation of drug delivery in CNS and Photon etc. will develop the multiplex cellular fluorescence imaging platform in conjunction with Professor Paul de Koninck at the Neurophotonics Centre of Université Laval.

Preliminary Results

Biosimulation Platform

Synapses (Figure 1) in the nervous system allow the passing of chemical or electrical signals between neurons. The three elements of the synapse are:

• The presynaptic terminal that discharges neurotransmitter in response to an action potential triggered in the input neuron

• The synaptic cleft where the neurotransmitter is discharged

• The postsynaptic element that belongs to the target neuron

The receptors are activated by the neurotransmitter, converting chemical signals into biochemical and electrical signals by activating intracellular secondary messenger pathways and ion channels.

The activation profile of neurotransmitter receptors is strongly influenced by their individual properties such as their kinetic characteristics and affinity towards their ligand. Besides these intrinsic specificities, the response will also be influenced by the proximity of the synapse from the release site.

Exploring interactions of glutamate receptors, their subtype receptors, and intracellular proteins with respect to the signaling pathway and protein-protein dynamics was the first step.

The migration of these receptors was studied to understand whether their migration was under specific pathological conditions or the result of the effect of drug treatment. NR1/NR2B Models of these receptors were created and subsequently compared to literature.

This is followed by the validation and implementation of these models in the glutamatergic synapse with specific characteristics.

Defining the rest of the glutamate receptors of interest is one of the future goals. Photon etc's cameras will be used to observe characteristics to determine computational environment. Dendritic branches consisting of 10-15 excitatory synapses will be the area of focus.

Multi-Labeling of Receptors in Neurons

At Paul De Koninck's lab, different combinations of quantum dots and antibodies were used to achieve specific labeling of two different synaptic receptor types, namely AMPA and NMDA (Figure 2). In addition, post-synaptic sites on live neurons were also labeled. Co-localization and correlation of proteins with different labels was also quantified as a proxy of protein-protein interactions.

Figure 2. Specific labeling of two types of synaptic receptors AMPA and NMDA (courtesy of Prof. De Koninck)

Multiplex Cellular Imaging Platform

Photon etc.’s technology has the ability to remove the limitations posed by conventional stains or labels - they can hinder simultaneous imaging of different types of tissues and molecular species.

Using the spectral imager in conjunction with innovative narrow band labels such as SERS nanospheres, quantum dots, and other Raman labels, tens of different labels can be multiplexed. This, in turn, allows simultaneous imaging and tracking of tens of signals, thereby enabling extensive in vitro analyses to explore the impact of new drug candidates on cellular signaling cascades.

The prototype design with the capability of fluorescence cellular imaging has been successfully completed and the fabrication process has begun (Figure 3). The system comprises Photon etc.’s hyperspcetral imager, the HNü 512 EMCCD camera from Nüvü Cameras, and an IX-73 Olympus microscope.

The filter allows rapid hyperspectral data acquisition in the wavelength range of 500-900nm at a bandwidth of 2nm. The combination of optical filters from Semrock and a 300W xenon lamp from Sutter Instruments provides illumination. Mirror turret and motorized focus facilitate automatic selection of illumination wavelength and acquisition of z- stack images.

Figure 3. Multiplex cellular imaging platform

The multiplex cellular imaging platform was used to characterize quantum dots at wavelengths of 605, 655 and 705nm (Figure 4).

Figure 4. Spectra of quantum dots at 605nm (blue), 655nm (green) and 705nm (red)

Conclusion

It is expected that the multiplex cellular imaging platform will take only a few seconds to capture spectrally resolved fluorescence images.

This capability helps better understanding of the fundamental mechanisms of CNS diseases and monitoring the actions of potential drug candidates at molecular and sub-cellular levels.

This, in turn, will be helpful in the discovery and development of improved CNS drugs.

About Photon etc.

Photon etc. offers state-of- the-art photonic and optical research instrumentation, from laser line tunable filters to widefield and microscopy hyperspectral imaging systems. Its patented spectral imaging and optical sensing technologies provide solutions for a wide variety of scientific and industrial applications. From material analysis to medical imaging, Photon etc.’s expertise and spirit of innovation allow the exploration of uncharted territories.

This information has been sourced, reviewed and adapted from materials provided by Photon etc.

For more information on this source, please visit Photon etc.