Abstract 2966: Brown Adipose Tissue Derived-cells Differentiate Into Cardiac Conduction and Pace-maker Cells in vitro and Improve Complete AV Block in vivo
An adipose tissue is one of the sources of mesenchymal stem cells, which have the potential to differentiate into various types of cells. Here we report that adipose tissue-derived mesenchymal stem cells differentiate into cardiac conduction system and pacemaker-like cells. Brown adipose tissue (BAT) were isolated from interscapular area of mice and enzymatically digested before culture. The cell surface marker analysis of isolated BAT-derived cells showed CD29 100%, CD31 17%, and CD45 6.4%. Round or tube-like cells in some of the colonies showed spontaneous beating at 4–7 days after culturing of BAT-derived cells. RT-PCR analyses revealed that BAT-derived cells expressed Nkx2.5, GATA6, Tbx5, ANF, MEF2C, cardiac alpha actin and MyoD, but not GATA4. Immunocytochemical analysis revealed that the most of round and tube-like cells in beating colonies expressed sarcomeric alpha actinin (SA) and cardiac Troponin T. Some of the tube-like cells showed fine sarcomeric structures. Patch-clamp techniques revealed that spontaneous electrical activity appeared between −40 and −60 mV. The shape of action potential from beating round and tube like cells showed properties of both cardiac pacemaker and neuronal cells. BAT-derived cells expressed several cardiac conduction system and pace-maker cell marker genes, such as Tbx5, HF-1b, connexin 40, connexin 45, MinK, and HCN1 to 4, which are necessary for pace-maker activity. To examine the regenerative potential, we created complete atrioventricular(AV) block in mice and injected GFP positive primary beating BAT-derived cells or passaged white adipose tissue (WAT) derived cells which did not show any cardiac or skeletal characters, intramyocardially into around the AV node. At 1weeks after transplantation, 50% of BAT-derived cells injected mice improved sinus rhythm or 2:1 AV block(n=8), but all WAT-derived cells injected mice continued complete AV block(n=4). Immunocytochemical analysis revealed that GFP and SA positive cells exist in atriam and ventricular septum in BAT-derived cells injected heart. These findings suggest that BAT-derived cells differentiate into cardiac conduction system and pacemaker-like cells in vitro and in vivo, and may become a useful cell source for arrhythmia therapy.