Regional myocardial ablation enabled by radio-frequency or other energies is currently the main treatment modality for drug-refractory arrhythmias. However, the highly unspecific nature of current ablation methodologies is responsible for unnecessary damage to cardiac or peri-cardiac tissue, thus severely hampering ablation safety and efficacy. Photodynamic therapy (PDT) has been extensively studied for treating cancerous cells. In PDT, after activation by light, photosensitizer agents transfer energy to oxygen molecules and generate reactive oxygen species which induce cell death exquisitely confined to photosensitized cells, while adjacent non photosensitized cells are spared.
In specific aim 1, we will use a recently developed cardiac targeting peptide (CTP) that binds to myocytes while it does not attach to other cardiac cells. In preliminary experiments, we have demonstrated that CTP-PDT-NPs delivered in co-cultures of adult rat ventricular myocytes and fibroblasts, led to myocytes-specific damage after laser illumination. Thus, we hypothesize that in isolated Langendorff-perfused rat hearts, CTP- conjugated-PDT-NPs (CTP-PDT-NPs) will enable obtaining myocyte-specific ablation while fibroblasts will be spared. With optical mapping techniques, we will determine how myocyte-specific ablation after illumination of a ventricular region with a 671 nm Laser, compares with non-specific ablation in terms of impulse propagation during pacing and during reentry.
In specific aim 2, we will determine whether myocyte-specific ablation with PDT-NPs could be implemented in the whole animal. In this aim, CTP-PDT-NPs will be injected intravenously in an anesthetized rat open chest model. After 10-30 minutes, we will illuminate a small region of the ventricular epicardium and subsequently, the heart will be removed and an immunohistological investigation with myocyte and fibroblast cell-specific antibody staining will be conducted. This will enable to assess the degree of damage induced to myocytes, and the extent to which fibroblasts and other non-myocyte cells were spared. Also, in a subgroup of rats, the chest wall will be sutured after ablation and animals will be followed-up for one month. Then, after heart removal, histological testing will be conducted to detect inflammatory infiltrates and fibrosis and assess fibroblast proliferation. Results will be compared with those of rats that underwent radiofrequency ablation or were sham operated. In this aim, we hypothesize that myocyte-specific ablation in vivo will associate with a decreased inflammatory reaction and fibroblast differentiation into myofibroblasts, as well as a dampened fibroblast proliferation and fibrosis formation.

Public Health Relevance

Regional myocardial ablation enabled by radio-frequency or other energies is currently the main treatment modality for drug-refractory arrhythmias which are cardiac conditions affecting several million Americans each year. However, the highly unspecific nature of current ablation methodologies is responsible for unnecessary damage to cardiac or peri-cardiac tissue, thus severely hampering ablation safety and efficacy. Here, we propose to investigate an innovative ablation approach that will enable targeting specifically those cardiac cells involved in the initiation and perpetuation of arrhythmic conditions. Thus, this project coul pave the way for developing safer and more efficient therapies for cardiac arrhythmias.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Exploratory/Developmental Grants (R21)
Project #
5R21HL111876-02
Application #
8511808
Study Section
Myocardial Ischemia and Metabolism Study Section (MIM)
Program Officer
Danthi, Narasimhan
Project Start
2012-07-16
Project End
2014-06-30
Budget Start
2013-07-01
Budget End
2014-06-30
Support Year
2
Fiscal Year
2013
Total Cost
$222,054
Indirect Cost
$79,254
Name
University of Michigan Ann Arbor
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
Kalifa, Jérôme; Avula, Uma Mahesh R (2014) Bisphosphonates and cardiac electrophysiology: should the red flag be raised higher? J Cardiovasc Electrophysiol 25:307-8