Current Research Projects

Micromechanics of Cardiomyocytes and Intact Tissue

Kevin D. Costa, PhD, Department of Medicine (Cardiology)
Research in the Costa lab is concerned with understanding how global pump function of the heart relates to the micro-scale mechanical and structural properties of underlying cardiovascular cells and tissues. The atomic force microscope allows high-resolution imaging and elastographic mapping of sample viscoelastic properties, with molecular specificity obtained by combination with confocal microscopy. Finite element analysis is used to help interpret measurements, develop new data analysis methods, and improve experimental protocols to maximize the information that can be extracted from AFM tests.

Structural Bases of High Fidelity of DNA Polymerase Delta

Aneel K. Aggarwal, PhD, Department of Structural Biology
DNA polymerase δ (Polδ) plays a crucial role in replication, and mutations that lower the fidelity of Polδ cause cancers in mice and humans. The Aggarwal group is utilizing the AFM to image Polδ and its interaction with DNA at the molecular level. Their aim is to identify high-resolution structures of Polδ and other components involved in replication and answer questions about the arrangement of DNA around these purified components by taking advantage of the single molecule imaging capabilities of the AFM system.

Nanoparticles for Molecular MRI of Atherosclerosis

Zahi A. Fayad, PhD, Departments of Radiology and Medicine (Cardiology)
The Fayad group has worked to develop multifunctional lipid-based nanoparticles for molecular imaging. The platforms are either fluorescent or magnetic to enable high contrast detection with optical techniques and MRI. One of their aims is to develop HDL mimicking nanoparticles for the in vivo detection of atherosclerosis using MRI and other imaging modalities. The AFM will be used to visualize the molecular surface structure of the HDL nanoparticles, track the real time process of their uptake by macrophage cells through scans of the cell surface, and characterize the surface structure and micromechanical properties of atherosclerotic lesions in vascular tissue sections that have been exposed to the HDL nanoparticles.

Functions of Regulatory Motifs in Signaling Networks

Ravi Iyengar, PhD, Department of Pharmacology and Systems Therapeutics
The Iyengar group utilizes system level approaches to study how multiple cellular signals can be integrated to stimulate and sustain neurite outgrowth in Neuro2A cells. In particular, they are interested in understanding how signals from G protein coupled receptors and those from membrane forces transduced by the integrin receptor integrate in real time to control the outgrowth processes in neurons. They will use the AFM in force mode to apply targeted mechanical stimuli along the length of the neurite while simultaneously measuring the intracellular signaling response using integrated FRET probes. The goal is to understand the spatial basis for the signal integration process, which will lead to the development of novel spatially specified networks to define the integration of mechanical and chemical signals.

Mechanisms Underlying Mitochondrial Dysfunction in the Diabetic Heart

Fadi G. Akar, PhD, Department of Medicine (Cardiology)
Mitochondrial dysfunction is a hallmark of a wide range of human pathologies including being at the origin of many cardiovascular disorders. The overall goal of the Akar group is to identify the mechanistic inter-relationship between altered mitochondrial energetics and arrhythmias in cardiovascular disorders that are associated with oxidative stress, such as diabetes. The group will employ AFM techniques to apply targeted mechanical stressors to isolated cardiac cells to induce physiologically relevant biochemical and mitochondrial oscillations. The goal is to determine the critical threshold of mechanical stress required for pathological mitochondrial membrane potential oscillations in normal and diabetic animals. By probing at the subcellular level with the AFM, the group hopes to uncover mechanisms by which these targeted mechanical perturbations scale to the entire mitochondrial network and how these mechanisms are affected by the disease process itself.

Control of Local Calcium Signaling in the Heart

Eric A. Sobie, PhD, Department of Pharmacology & Systems Therapeutics.
The research aims of the Sobie group concern the mechanisms by which calcium release from intracellular stores is controlled in the heart, and how this process is disrupted in disease states. Interests are focused to the elementary unit of calcium release, Ca2+ sparks, and particularly the coordinated opening of ryanodine receptors that facilitate these sparks. The group has found that heart failure can disrupt the association between these receptors and the cell membrane because of severe alterations to the membrane structure. Fluorescence imaging can provide an overview of the gross changes in myocyte structure, however limited optical resolution does not allow for more quantitative information, such as the organization of transverse tubules which could lead to better modeling of their role in calcium signaling. The group will utilize the AFM to provide a high resolution characterization of these subcellular structures that are thought to play a role in cell signaling. Targeted physical disruption will also be performed, such as indentation of the transverse tubules to study the effect on calcium release in the myocyte.

PICOT and Cardiac Hypertrophy

Roger J. Hajjar, MD, Department of Medicine (Cardiology)
Pressure overload-induced cardiac hypertrophy due to valvular or hypertensive heart diseases is one of the most common causes of congestive heart failure. Past studies have suggested roles for protein kinase C (PKC) in the hypertrophic response. The Hajjar group has demonstrated that the elevated PKC activity in development of cardiac hypertrophy is counteracted by a feedback inhibitor mechanism that is dependent on a cytosolic PKC inhibitor protein PICOT (PKC-Interacting Cousin of Thioredoxin). The group has characterized the molecular mechanism of PICOT activity in PKC regulation and evaluated the physiological consequences of PICOT overexpression in rodent models of cardiac hypertrophy and heart failure. The group hypothesizes that PICOT overexpression can also lead to alterations in sarcomere structure, which promotes ventricular dilation. In light of this, the AFM will be utilized to study the effects of PICOT on the elastic properties of beating isolated cardiomyocytes and intact mouse hearts. The goal is to better understand PICOT signaling mechanisms, which will allow the design of novel therapeutic strategies to block the development of cardiac hypetrophy and the progression to heart failure.

Tendon Response to In Vivo Fatigue Damage

Evan L. Flatow, MD, Department of Orthopaedics
Critical to the prevention of tendinopathies is an understanding of local tendon response to pre-rupture fatigue. The Flatow lab has shown an increase in structural damage associated with higher levels of tendon fatigue through evaluation of the temporal response of the tendon to low-level fatigue applied by in vivo cyclic loading of the patellar tendon of rats. An early transient response was detected, followed by stabilizing of the bulk mechanics of the tendon. Thus, there is an unknown connection between the micro- and macromechanical responses of the tendon. The group plans to use AFM indentation techniques to measure the structural and mechanical effects of the in vivo cyclic fatigue protocol at the micro level along with second harmonic generation imaging to evaluate the level of damage at the test site.

Contact Us

AFM Core Facility
Tel: 212-241-2362 (x4AFMC)
Fax: 212-241-4080

Atran Berg Laboratory Building, Rm 3-23
1428 Madison Avenue
New York, NY 10029