Islet-1 gene delivery improves myocardial performance after experimental infarction Aya Barzelay a , Edith Hochhauser b , Michal Entin-Meer a , Yelena Chepurko b , Einat Birk c , Arnon Afek d , Iris Barshack d , Lidya Pinhas c , Yulia Rivo a , Jeremy Ben-Shoshan a , Sofia Maysel-Auslender a , Gad Keren a , Jacob George e, * a The Cardiology Department, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel b The Cardiac Research Laboratory, Felsenstein Medical Research Center, Rabin Medical Center, Petah Tikva, Israel c The Department of Cardiology, Schneider Children’s Medical Center, Petah Tiqva, Israel d The Institute of Pathology, Sheba Medical Center, Tel Hashomer, Israel e Department of Cardiology, Kaplan Medical Center, Rehovot 76100, Israel 1 article info Article history: Received 24 December 2011 Received in revised form 9 May 2012 Accepted 21 May 2012 Available online 30 May 2012 Keywords: Gene therapy Myocardial infarction Angiogenesis abstract Objective: The LIM-homeobox transcription factor Isl1 plays a crucial role during heart embryogenesis and later on gives rise to adult resident cardiac stem cells. In this study, we aimed to discover new extra cardiac populations of Isl1 stem cells. We then investigated endogenous Isl1 kinetics after myocardial infarction (MI), and the effect of intra-myocardial gene transfer of naked DNA encoding Isl1 on functional recovery after MI. Methods: We used the transgenic mice Isl1/cre/Z/EG for lineage tracing of extra cardiac Isl1 stem cells. Non transgenic mice were used to study Isl1 kinetics post-MI by RT-PCR and FACS analysis. MI was induced in non transgenic mice by permanent ligation of the left anterior descending coronary artery (LAD). Naked DNA encoding Isl1 was injected to the peri-infarct region. Evaluation of cardiac performance was con- ducted by echocardiogram. Analysis of myocardial fibrosis and number of vessels was performed on histological cryosections. Results and conclusions: Isl1 gives rise to subpopulations of progenitors in both the bone marrow and spleen, and is re-expressed in the spleen and left ventricle following MI. Intramyocardial gene transfer of Isl1 to the border zone of the infarcted hearts resulted in partial salvage of left ventricular function, enhanced vascularization, and reduced myocardial fibrosis. The Isl1 gene appears to be an attractive reparative target for future management of myocardial dysfunction. Ó 2012 Elsevier Ireland Ltd. All rights reserved. 1. Introduction Following MI, endogenous regeneration attempts do occur as the number of stem cells in the circulation increase [1]. Interest- ingly, Myocardial dysfunction has been shown to lead to re- expression of several embryonic genes, including ANF, b-MHC and a-actinin [2]. The use of activating embryonic signaling path- ways in cardiovascular gene therapy was shown to be efficient in both MI and hind limb ischemia [3]. These observations lend support to the hypothesis that re-activation of embryonic genes may be beneficial for cardiac repair. One of the earliest steps in cardiogenesis occurs when the cells of the cardiogenic mesoderm form the cardiac crescent. Isl1 progenitors which comprise the cardiac crescent migrate into the developing heart and give rise to the outflow tract, right ventricle and both atria [4e6]. Isl1 expression is then turned off [5,7e9] except in a small population of resident cardiac stem cells which maintains Isl1 expression throughout adulthood [5]. The aim of the current study was to assess whether Isl1 gives rise to additional progenitor populations outside the heart and to determine whether the Isl1 gene is re-expressed endogenously as a response to MI. A second aim was to study the effect of Isl1 gene transfer to the infarcted heart. 2. Methods Detailed materials and methods are in the supplemental online data. Isl1/cre/Z/EG mouse was used for lineage tracing. FVB mice were used for Isl1 detection post-MI, and for intra-myocardial gene * Corresponding author. Tel.: þ972 8 9441335; fax: þ972 9411590. E-mail addresses: jgeorge@bezeqint.net, jacobg@post.tau.ac.il (J. George). 1 Affiliated to the Hebrew University, Jerusalem, Israel. Contents lists available at SciVerse ScienceDirect Atherosclerosis journal homepage: www.elsevier.com/locate/atherosclerosis 0021-9150/$ e see front matter Ó 2012 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.atherosclerosis.2012.05.025 Atherosclerosis 223 (2012) 284e290