Proceedings of The Physiological Society
University of Oxford (2011) Proc Physiol Soc 23, C1
Ischaemic preconditioning prevents the differentiation induced by ischaemia/reperfusion injury of rat cardiac fibroblasts into myofibroblasts
K. Pertiwi1, E. Chilton2
1. Biology Education Department, Faculty of Mathematics and Natural Sciences, Yogyakarta State University, Yogyakarta, Indonesia. 2. Veterinary and Biomedical Sciences, James Cook University, Townsville, Queensland, Australia.
Effect of ischaemia reperfusion injury, ischaemic preconditioning, and glibenclamide on rat cardiac fibroblast to myofibroblast differentiation. Following 60 minutes of ischaemia and 60 minutes of reperfusion, a significant percentage of fibroblasts were stimulated to differentiation into myofibroblasts, compared to time control. If cells were preconditioned with 15 minutes ischaemia and 30 minutes reperfusion prior to the 60 minutes ischaemia/60 minutes reperfusion, significantly fewer cells differentiated. Glibenclamide (10 μM) significantly limited the beneficial effect of IPC.
Ischaemia/reperfusion (IR) injury is a key source of myocardial damage in humans following acute myocardial infarction, post-cardiac arrest, and heart transplantation (1). The beneficial effects of ischaemic preconditioning (IPC) in minimising IR-induced damage to cardiac muscle have been extensively studied, and involve activation of ATP-sensitive potassium (KATP) channels (2). No previous studies have investigated the effects of IR injury or IPC in cardiac fibroblasts. Fibroblasts are responsible for maintaining the extracellular matrix in healthy hearts, and differentiate into the wound-healing phenotype, myofibroblasts, following cardiac injury (3). Our goals were to determine if: (a) IR injury induces cardiac fibroblasts to differentiate into myofibroblasts; and if so, (b) does IPC ameliorate the IR-induced myofibroblast differentiation? Hearts were removed from isoflurane-anaesthetised (5% induction, 2% maintenance; 1 l/min oxygen) adult female Sprague Dawley rats, and fibroblasts dissociated by standard enzymatic digestion (4). Freshly dissociated fibroblasts were exposed to 30, 60 or 120 minutes of ischaemia by coating pelleted cells with mineral oil (modified from 5), followed by 60 minutes of reperfusion when mineral oil was replaced with culture media. Fibroblasts were then placed under culture conditions and allowed to grow to ~70% confluency. Cultures were stained for expression of α-smooth muscle actin, a marker of myofibroblast differentiation (3). IR of all durations evoked significant differentiation of fibroblasts into myofibroblasts, with 88±1% (mean±S.E.M., n=5) of cells differentiating following 30 minutes of ischaemia, 93±2% (n=4) following 60 minutes of ischaemia, and 92±1% (n=5) following 120 minutes of ischaemia. In contrast, time controls indicated that only 37±2% (n=5, 30 min), 30±1% (n=5, 60 min), and 45±2% (n=4, 120 min.) of cells differentiated from fibroblasts into myofibroblasts without IR. IPC produced by 15 minutes ischaemia and 30 minutes reperfusion, prior to 60 minutes of ischaemia and 60 minutes of reperfusion, significantly reduced the differentiation of fibroblasts into myofibroblasts from 88±2% (n=7, no IPC) to 46±4% (n=7, IPC)(Fig. 1). The beneficial effect of IPC was reduced if cells were treated with 10 μM glibenclamide, a KATP channel blocker; in this protocol, 77±4% (n=8) of fibroblasts differentiated into myofibroblasts despite preconditioning (Fig. 1). These data indicate that IR injury strongly stimulates differentiation of cardiac fibroblasts into the wound-healing phenotype, the myofibroblast. IPC prevented IR-induced differentiation in a glibenclamide-sensitive manner, suggesting that activation of KATP channels is part of the mechanism by which IPC protects cardiac fibroblasts.
Where applicable, experiments conform with Society ethical requirements