5:00pm – 5:15pm
Yuhan Helena Liu, Berj Bardakjian
“A Large-Scale Neuro-glial Network Model of Seizure Termination”
Background: How seizures terminate remains elusive. This is clinically relevant as seizure termination is sometimes followed by the postictal generalized EEG suppression state (PGES), a period with suppressed activities and has been found to be associated with sudden unexpected death in epilepsy. Method: Large-scale neuroglial network modeling was combined with EEG data analysis to elucidate the processes involved in seizure termination. Results: Dominant frequency decay, increase in cross-frequency coupling strength, as well as shift in frequency of the phase signal were observed in EEG recordings with PGES as a seizure progresses. Those experimental observations were reproduced in the simulated local field potential (LFP) by changing synaptic strengths in the model network. Different effects on dominant frequency and cross-frequency coupling were observed by varying the strengths of four different types of synapses: connections between excitatory to excitatory, excitatory to inhibitory, inhibitory to excitatory and inhibitory to inhibitory neurons. Moreover, simulations showed that microglia could modulate synaptic strengths in response to neuronal activity to produce the aforementioned experimental observations. Conclusion: Changes in the functional connectivity of the neural network could underlie the dynamics in seizure termination and microglia could play a role in shaping the connectivity. Significance: Combining computer modeling and electrophysiological observations can formulate testable hypotheses for guiding future studies to elucidate mechanisms in seizure termination.
Raeesa Matadar, Rita Kandel, Paul Santerre
“The Metabolism of Inner Annulus Fibrosus Cells Regulates Phenotype”
Introduction: Lower back pain is one of the largest causes of disability globally. It is associated with the degeneration of the intervertebral disc (IVD), a multi-tissue support structure that links the vertebral bodies. Changes in the extracellular matrix (ECM) reduce the disc’s ability to transfer loads resulting in progressive tissue degradation. As there is little capacity for self-repair, regenerating the IVD in vitro is now being explored. Previous work has shown that the addition of dexamethasone and sodium pyruvate contributes to the production and accumulation of appropriate ECM, and increases mitochondrial membrane potential in vitro. Thus, culture conditions appear to trigger metabolic changes that affect ECM accumulation, however, there have been few investigations into this link in annulus fibrosus (AF) cells. The purpose of this study was to investigate the role of the AMPK/PGC1α/PPAR/sox9 signalling axis in phenotype maintenance and appropriate ECM production without the use of a corticosteroid.
Methods: AF cells were isolated enzymatically from bovine caudal tails and seeded onto multilamellar angle-ply nanofibrous PU scaffolds in spinning bioreactors to generate AF tissues in vitro. AF tissues were cultured for up to 3 weeks in DMEM containing either 1mM (low) or 25mM (high) glucose concentrations. Tissues were evaluated histologically, biochemically, immunohistochemically and for gene expression and protein levels.
Results: IAF tissues grown in low-glucose accumulated collagen type II and aggrecan, as well as collagen type I whereas tissues grown in high glucose only accumulated collagen type I. Over time, gene expression showed an increase in PGC1α and mitochondrial transcription factor A, as well as SOX9, COL2A1 and ACAN which are components of the native IAF. We also observed an increase p-AMPK, p-ACC, PGC1α, and sox9 protein levels. ATP levels in tissue were not significantly lower in low-glucose, suggesting a non-canonical activation of AMPK. The next steps will be to inhibit AMPK to confirm its role in phenotype maintenance.
Conclusions: Here we demonstrated that low-glucose medium restored the IAF cell phenotype and activated the AMPK/PGC1α/PPAR/sox9 signalling axis when compared to high-glucose. These studies provide novel insights into the mechanisms regulating IAF phenotype which will facilitate the identification of an ideal medium formulation to enhance tissue formation appropriate for IVD regeneration and functionality.
Christopher McFaul, Christopher Yip, Rodrigo Fernandez-Gonzalez
“Understanding Cardiac Tube Formation in Developing Drosophila Embryos using Light Sheet Microscopy and Cardiac Drug Screening”
Heart development begins with the formation of a primitive tube, both in fruit flies and mammals. Tube formation is mediated by coordinated cell movements. In Drosophila, the heart is formed from 52 bi-lateral pairs of cardiac precursors that migrate dorsally and medially to join their counterparts. The cells must then undergo distinct morphological changes to control sites of adhesion and repulsion to their partner in order to form a lumen. While the genetic pathways that induce cardiac cell specification have been clearly defined, the cellular and molecular mechanisms that regulate collective cell migration during heart tube formation are not well understood. Leveraging the simplicity and pharmacological tractability of the fruit fly, Drosophila melanogaster, and the ability to perform live imaging of its embryos, we have developed a light-sheet microscopy platform and quantitative image analysis to characterize cell behaviours and molecular rearrangements during heart tube formation in living Drosophila embryos. Our system allows identification and tracking of cardiac precursors and the overlying epidermal cells. Automated image analysis allows quantitative comparison of the dynamics of tube formation across embryos. To identify the pathways that regulate collective cell movements during heart development, we are conducting a pharmacological screen for inhibitors of cardiac precursor migration. Screen hits will be followed up using our light sheet microscopy system. We are particularly interested in the role of the cytoskeleton as both actin and myosin are important for cell movements in heart development. The kinase Rho-kinase (Rok) phosphorylates and activates the myosin light chain, and thus inhibiting Rho-kinase results in impaired myosin contractility. Preliminary experiments suggest that Rok may be important for the coordinated movement of cardioblasts during Drosophila heart morphogenesis. Embryos injected with water (controls) developed normally but those injected with 10 mM Y-27632, a Rok inhibitor had disrupted coordination of cardioblasts, leading to defects in heart tube formation. Together, our novel tools will allow us to identify pathways critical for cardiac precursor migration, polarization, and cell-cell adhesion.
Shumit Saha, Muammar Kabir, Nasim Montazeri, Hisham Alshaer, Azadeh Yadollahi
“Sleep Apnea Diagnosis using Tracheal Respiratory Sounds and Movement”
Background: Sleep apnea is a chronic respiratory disorder due to intermittent partial (hypopnea) or complete (apnea) collapse of the pharyngeal airway during sleep. 26% of the Canadian adults are at high risk of sleep apnea. However, due to the complexity and limited access to polysomnography (PSG), 84% of Canadians who are at high risk of sleep apnea are not diagnosed. To address this problem, a robust and cost-effective home based technology to assess sleep apnea severity is required. Thus, we aimed to develop a new algorithm for sleep apnea diagnosis using respiratory sounds and respiratory related movement recorded over trachea.
Methods: Adults referred to the sleep lab of Toronto Rehabilitations Institute for suspected sleep apnea were recruited for this study. Simultaneously with PSG, respiratory sounds and respiratory movement were recorded over the suprasternal notch using a wearable device developed by our group, which includes a microphone and an accelerometer. We developed an algorithm to differentiate breathing and snoring segments from the respiratory sounds. The accelerometer signal was low-pass filtered to extract respiratory related movements. Energy and duration of breathing and snoring segments as well as the magnitude of respiratory related movements were extracted. Extracted features were normalized between 0 and 1 and the weighted averages of the features were compared with an adaptive threshold to detect the events. We increased the threshold in the breathing segments around the time that subject was upright which shows high probability of wakefulness, and lowered the threshold for the supine position. The number of apneas and hypopneas per hour of recording time (apnea-hypopnea index, AHI) was estimated. Estimated AHI was compared to the AHI obtained from PSG (PSG-AHI) scored by technicians according to standard criteria.
Results: Data from 59 subjects, age: 50.2±16.2 years, BMI: 29.6±5.4 kg/m2 were investigated. A high correlation was found between the estimated AHI and PSG-AHI (r = 0.84, p<0.01). Considering AHI cut-off of 15, sensitivity and specificity of diagnosing sleep apnea were 84.0% and 85.3%, respectively.
Conclusion: Utilizing a microphone and an accelerometer embedded in a small wearable device, we could achieve very high accuracies in diagnosing sleep apnea. Introduction of small, cost-effective and easily accessible wearable devices will significantly increase the diagnostic rate of sleep apnea.
Uilki Tufa, Anya Zahra, Chiping Wu, Liang Zhang, Peter L. Carlen, and Berj L. Bardakjian
“Bi-rhythmic biomimetic electrical stimulation paradigm for seizure suppression”
Epilepsy affects about 300,000 Canadians. Around 25% of patients are intractable to anticonvulsant drugs, do not meet surgical criteria and have no adequate treatment. Electrical stimulation can be an effective alternative treatment. Clinical trials have demonstrated the safety of thalamic stimulation using a high frequency stimulus with limited efficacy. Our group has previously shown, in silico, the success of stimulation with a biomimetic therapeutic signal, outperforming mono-rhythmic waveforms. In this study we aim to extend our findings in vivo and investigate a thalamic continuous stimulation paradigm using a biomimetic signal, where the amplitude of a high frequency rhythm is modulated by the phase of a low frequency rhythm forming a cross-frequency coupled (CFC) waveform, to suppress seizure-like events (SLEs) in a kindled mouse model. Bipolar electrodes were implanted in the CA3 of the hippocampus and in the ipsilateral medial dorsal nucleus of the thalamus, allowing for stimulation and iEEG recordings. A webcam was used for monitoring animal motor behavior. Mice were kindled daily through unilateral CA3 stimulations, reaching convulsive SLEs. To test suppression, thalamic stimulation using a CFC waveform was applied continuously for 15 minutes, followed by hippocampal stimulation to evoke an SLE. We found a 1Hz-100Hz phase-amplitude CFC waveform to be effective in suppressing SLEs (confirmed by iEEG and video analysis) and increasing after discharge threshold. Low frequency suppression was found as a marker to assess the effective stimulus amplitude. We aim to fine tune parameters and investigate this effect in a spontaneous recurrent seizure mouse model. These findings are important in the development of therapeutic strategies for epileptic patients.
“mRNA as Medicine”
Moderna is a clinical stage pioneer of messenger RNA Therapeutics™, an entirely new in vivo drug technology that produces human proteins, antibodies and entirely novel protein constructs inside patient cells, which are in turn secreted or active intracellularly. This breakthrough platform addresses currently undruggable targets and offers a superior alternative to existing drug modalities for a wide range of diseases and conditions. Moderna is developing and plans to commercialize its innovative mRNA drugs through its own ventures and its strategic relationships with established pharmaceutical and biotech companies. Its current ventures are: Onkaido, focused on oncology, Valera, focused on infectious diseases, Elpidera, focused on rare diseases, and Caperna, focused on personalized cancer vaccines. Founded by Flagship VentureLabs™, Cambridge-based Moderna is privately held and currently has strategic agreements with AstraZeneca, Alexion Pharmaceuticals, Merck and Vertex Pharmaceuticals. To learn more, visit www.modernatx.com.
“Neural Representations of Natural Self-Motion: Implications for Perception & Action”
Dr. Cullen received a bachelor’s degree in Biomedical Engineering and Neuroscience from Brown University and a PhD in Neuroscience from the University of Chicago. After doctoral studies, Dr. Cullen was a Fellow at the Montreal Neurological Institute where she worked in the Department of Neurology and Neurosurgy. In 1994, Dr. Cullen became an assistant professor in the Department of Physiology at McGill University, with appointments in Biomedical Engineering, Neuroscience, and Otolaryngology. In 2002, Cullen was appointed a William Dawson Chair in recognition of her work in Systems Neuroscience and Neural Engineering, and served as Director of McGill’s Aerospace Medical Research Unit comprising four faculty and their research labs.
In 2016, Dr. Cullen moved to Johns Hopkins University, where she is now a Professor in Biomedical Engineering, and holds joint appointments in the Departments of Neuroscience and in Otolaryngology – Head and Neck Surgery. In addition to her research activities, Dr. Cullen currently serves as the Program Chair and Vice President of the Society for the Neural Control of Movement. Dr. Cullen has been an active member of the Scientific Advisory Board of the National Space Biomedical Research Institute, which works with NASA to identify health risks in extended space flight. She has also served as a reviewing editor on numerous Editorial Boards including the Journal of Neuroscience, the Journal of Neurophysiology, and the Journal of Research in Otolaryngology. Dr. Cullen has received awards including the Halpike-Nylen medal of the Barany Society for “outstanding contributions to basic vestibular science”, the Sarrazin Award Lectureship from the Canadian Physiological Society (CPS), and was elected Chair of the Gordon Research Conference on eye movement system biology. Cullen has served as Communications Lead for the Brain@McGill, and was Chair of the 2016 Canadian Association for Neuroscience meeting. She has published over 120 articles, book chapters, and patent applications and given over 140 national and international invited lectures.
Xian Wang, Yonit Tsatskis, Sevan Hopyan, Helen McNeill, Yu Sun
“Robotic Intracellular Manipulation and Measurement with Multi-Pole Magnetic Tweezers”
The capability to directly interrogate intracellular structures inside a single cell for measurement and manipulation has significant implications in the understanding of subcellular and sub-organelle activities, diagnosing diseases, and developing new therapeutic approaches. Compared to measurements of single cells, physical measurement and manipulation of sub-cellular structures and organelles remain underexplored. To spearhead an exciting new era of intracellular physical measurement and manipulation, we have developed a multi-pole magnetic tweezers system for micromanipulation involving sub-micrometer position control and picoNewton force control of a sub-micron magnetic bead inside a single cell for measurement on different locations (spatial) and different time points (temporal). The bead was three-dimensionally positioned in the cell using a generalized predictive controller that tackles the control challenge caused by the low bandwidth of visual feedback from high-resolution confocal imaging. The average positioning error was quantified to be 0.4 µm, slightly larger than Brownian motion-imposed constraint (0.31 µm, 1 µm = 〖10〗^(-6) m). The system is also capable of applying a force up to 60 pN with a resolution of 4 pN (1 pN = 〖10〗^(-12) N) for a period of time longer than 30 mins. The measurement results revealed significantly higher stiffness exists in the nucleus’ major axis than in the minor axis. This stiffness polarity is likely attributed to the aligned actin filament. We also proved that the nucleus stiffens upon the application of an intracellularly applied force, which can be attributed to the response of structural protein lamin A/C and the intracellular stress fiber actin filaments.
Ryan Koh, Adrian Nachman, Jose Zariffa
“Classification of naturally evoked compound action potentials in peripheral nerve recordings via convolutional neural networks”
Objective: Recording and stimulation from the peripheral nervous system are becoming important components in a new generation of bioelectronics systems. Neurostimulation in humans using implanted peripheral neural interfaces has seen a long history of success, including in applications such as reducing phantom pain in amputees, treatment for overactive bladder, and implanted functional electrical stimulation for movement. Unfortunately, recording applications using implanted peripheral neural interfaces has not been as successful and remains a challenge. Improvements to recording devices and signal processing techniques to extract useful information from those devices are needed. With the objective of recording selectively and reliably from different neural pathways in a peripheral nerve, we propose to use a convolutional neural network to exploit the spatiotemporal structure of compound action potentials (CAPs) recorded from a 56-channel nerve cuff.
Approach: 9 Long-Evan rats were implanted with a 56-channel spiral nerve cuff electrode on the sciatic nerve. Afferent activity was selectively evoked in three fascicles of the sciatic nerve (tibial, peroneal, sural) using mechanical stimuli. Spatiotemporal signatures of recorded CAPs were used to train the CNN. A recurrent neural network was then trained to predict the joint angle based on predicted firing patterns from the CNN. Performance was measured based on the CNN’s classification accuracy and F1-score, and correlation between the ground truth and predicted joint angle of the rat’s ankle.
Main Results: Our novel technique using CNNs yielded a mean classification accuracy of 0.808 ±0.104 with corresponding mean F1-score of 0.747 ±0.114. In contrast, the mean classification accuracy and F1-score for the previous state-of-the-art were 0.686 ±0.126 and 0.605 ±0.212, respectively. Using the CNN classification results, the mean Pearson correlation coefficient was 0.826 ± 0.176 for the ankle angle predicted using the estimated firing rate vs the manually labelled ankle angle.
Significance: The proposed method demonstrates that CAP-based classification can be used to track a physiological meaningful measure (e.g. joint angle) and will allow for more precise control signals in neuroprosthetic systems.
Eric Ho, Jaclyn Obermeyer, Anup Tuladhar, Samantha Payne, Molly Shoichet
“Non-Invasive, Epicortical Delivery of Brain-Derived Neurotrophic Factor for Recovery after Stroke”
Stroke affects over 15 million people worldwide, and despite significant research patients are faced with limited treatment options. This is due, in part, to the blood brain barrier (BBB). To address this roadblock, our group has developed a non-invasive, epicortical drug delivery vehicle that circumvents the BBB to provide therapeutic effects to the central nervous system. The system was used to deliver brain-derived neurotrophic factor (BDNF), a promising protein therapeutic for stroke therapy that does not readily cross the BBB. We have shown that BDNF can be electrostatically adsorbed onto the negative surface of poly(lactic co-glycolic acid) (PLGA) nanoparticles dispersed in a hyaluronan-methylcellulose hydrogel, limiting protein denaturation while achieving a similar release profile to encapsulation in vitro. We hypothesized that the vehicle could be applied in vivo to deliver BDNF in an endothelin-1 rat model of stroke injury.
Release from the vehicle in vitro resulted in a sustained, burst free release for 30 days, with the discharged BDNF bioactive when released from the vehicle. In vivo, significant BDNF diffusion into the tissue was observed, with the protein detected up to a depth 3000 µm up to 21 days post treatment. BDNF delivery augmented plasticity after stroke, as evidenced by increased synaptophysin staining in the contralesional hemisphere of BDNF-treated rats, as well as reduced lesion volume, indicating a neuroprotective effect. When assessing behavioural recovery, hindlimb function was significantly enhanced at 7 weeks with local BDNF delivery.
This vehicle is highly tunable for the delivery of many therapeutic proteins. The controlled release is encapsulation free and governed by electrostatic interactions between PLGA and charged proteins, enabling significantly higher protein loading and lower loss of bioactivity. Release rate and dose can be controlled through modification of the PLGA nanoparticles. In vivo, a therapeutically relevant concentration of BDNF was delivered to the brains of stroke injured rats with an epicortical hydrogel-nanoparticle composite. With local, sustained delivery directly to the brain, we demonstrate the benefit of BNDF and the potential for use of this platform strategy with other biotherapeutics.
Tianhao Chen, Zia Saadatnia, Hani Naguib
“A novel, flexible and ultra-thin pressure sensor for concentric tube manipulators in intra-ventricular neurosurgery robotic tools”
Minimally invasive endoscopic intraventricular surgery is a robot-assisted technique that has improved patient outcomes with less wound healing time due to small size of incisions. Small and dexterous surgical tool can be designed and miniaturized to a size of 2 mm while maintaining its dexterity and force required to resect brain tumors without open-skull surgery. To provide instrument-tissue interaction information for this tool, force feedback is required to ensure safety and effective operation. In this study, a small and highly sensitive smart material-based sensor was designed and integrated to the tool shaft, known as the concentric tube manipulators. A 200 um- ultrathin layer of micropatterned resistive carbon-filled polyvinylidene fluoride (PVDF) conductive polymer was wrapped spirally around the 2 mm-diameter concentric tube for static and quasi-static force sensing. A layer of interdigitated electrodes was designed to achieve pressure readings with both directional and locational information. Optimizations were performed on the size, pitch and shape of the microstructures as well as the width and spacing of the electrodes to improve sensitivity with reduced hysteresis. The finalized design can sense a pressure down to 0.55 kPa while retaining its flexibility, biocompatibility and sterilizability. The sensor will also enhance more intuitive force feedback for surgeons to use the dexterous neurosurgical tool, which will have a significant impact on brain tumor and epilepsy practice.
"Human organs on a chip with perfusable vasculature"
Dr. Vunjak-Novakovic and her team of engineers, clinicians, and scientists are developing innovative technologies for engineering and studying human tissues. They are interested in regenerative medicine, tissue models for stem cell research, and “organs-on-a-chip” platforms for use in precision medicine.
Their laboratory is located in the Columbia University Medical Center, and has state of the art facilities for human stem cell and tissue engineering research. They are a founding member of the Stem Cell Core and Stem Cell Imaging Core, and are serving as the Bioreactor-Imaging Core of the national Tissue Engineering Resource Center founded to foster tissue engineering for medical impact. They are actively collaborating with colleagues at Columbia University, nationwide, and around the world. To translate their science into new therapeutic modalities, their lab has launched three biotech companies: epiBone (epibone.com), Tara(tarabiosystems.com), and East River Biosolutions (eastriverbio.com) that are all based in New York City.
To engineer a range of human tissue/organ systems, they provide the cells with native-like environments, using biomaterial scaffolds (templates for tissue formation) and bioreactors (culture systems enabling environmental control and signaling). They design biomaterial scaffolds by processing the native tissue matrix to recapitulate the composition, architecture, and mechanical properties of the native cell niche, for applications ranging from biological research to clinical delivery of therapeutic materials and cells. They design bioreactors for engineering human-scale tissues for regenerative medicine: bone, cartilage, heart muscle, and lung. In each case, the bioreactor is custom-designed to accommodate a specific tissue (such as the exact anatomy of a bone graft), to provide perfusion (such as air ventilation and vascular perfusion for supporting the lung), and to apply physical forces (such as dynamic loading to cartilage and bone, electromechanical conditioning to the heart muscle, hydrodynamic shear to bone and vasculature). They are also developing microscale bioreactors for studies of stem cell differentiation, modeling of diseases, and drug development. Bioreactors are integrated with imaging so that the changes in tissue structure and function can be monitored in real time.