Exogenous connexin43‐expressing autologous skeletal myoblasts ameliorate mechanical function and electrical activity of the rabbit heart after experimental infarction

Abstract

Acute myocardial infarction is one of the major causes of mortality worldwide. For regeneration of the rabbit heart after experimentally induced infarction we used autologous skeletal myoblasts (SMs) due to their high proliferative potential, resistance to ischaemia and absence of immunological and ethical concerns. The cells were characterized with muscle-specific and myogenic markers. Cell transplantation was performed by injection of cell suspension (0.5 ml) containing approximately 6 million myoblasts into the infarction zone. The animals were divided into four groups: (i) no injection; (ii) sham injected; (iii) injected with wild-type SMs; and (iv) injected with SMs expressing connexin43 fused with green fluorescent protein (Cx43EGFP). Left ventricular ejection fraction (LVEF) was evaluated by 2D echocardiography in vivo before infarction, when myocardium has stabilized after infarction, and 3 months after infarction. Electrical activity in the healthy and infarction zones of the heart was examined ex vivo in Langendorff-perfused hearts by optical mapping using di-4-ANEPPS, a potential sensitive fluorescent dye. We demonstrate that SMs in the coculture can couple electrically not only to abutted but also to remote acutely isolated allogenic cardiac myocytes through membranous tunnelling tubes. The beneficial effect of cellular therapy on LVEF and electrical activity was observed in the group of animals injected with Cx43EGFP-expressing SMs. L-type Ca(2+) current amplitude was approximately fivefold smaller in the isolated SMs compared to healthy myocytes suggesting that limited recovery of LVEF may be related to inadequate expression or function of L-type Ca(2+) channels in transplanted differentiating SMs.

Peering into tunneling nanotubes—The path forward

“…Various malignant tumors, including those of lung‐, ovarian‐, and laryngeal cancer, mesothelioma, and neuroblastoma, were shown to form TNT‐like connections (Antanavičiūtė et al , 2014, 2015; Ady et al , 2016; Desir et al , 2016). Mesothelioma cells forming TNTs of > 70 μm in length contained microvesicles labeled with MitoTracker (Lou et al , 2012).…”

Tunneling Nanotubes and Gap Junctions–Their Role in Long-Range Intercellular Communication during Development, Health, and Disease Conditions

“…These include the cytonemes found in Drosophila (Kornberg, 1999 ; Hsiung et al, 2005 ). TNT like structures between immune cells in lymph nodes (see review by Onfelt et al, 2004 ; Gerdes et al, 2007 ), and between MHC class II + cells in the mouse cornea (Chinnery et al, 2008 ), as well as the bridges TNT-like structures observed in several models of malignant tumors (cancer) such as mesothelioma, lung cancer, ovarian cancer, and laryngeal cancer (Ady et al, 2014 ; Antanaviciute et al, 2014 , 2015 ; Thayanithy et al, 2014b ; Desir et al, 2016 ) or capable of crossing the dense tubular basement membrane in the kidney of the cystinosis mouse model (Naphade et al, 2015 ) or in their cornea and thyroid (Rocca et al, 2015 ; Gaide Chevronnay et al, 2016 ). One major issue in performing these in vivo and ex vivo studies is the difficulties in identifying the precise nature of the structures and clearly determining their role in the transfer.…”

Restoring heart function and electrical integrity: closing the circuit

“… 77 – 81 Myocardial delivery of these cells in a cryoinjury MI murine model improved electrical coupling between skeletal myoblasts and host CM, with lower incidence of sustained arrhythmias and the ventricular arrhythmia inducibility decreased when compared to regular skeletal myoblast injection. 78 Conversely, although an amelioration of electrical coupling and improved electrical activity was observed, other studies involving rat 81 and rabbit 79 MI models reported that this coupling was insufficient to prevent arrhythmic events and that LV functional improvement was modest. This may relate to distinct AP characteristics of skeletal myoblasts which, in a cardiac environment, may also undergo downregulation of voltage-gated sodium, potassium, and calcium channels, 82 affecting their excitability and function.…”