Scaffold topography alters intracellular calcium dynamics in cultured cardiomyocyte networks

Abstract

Structural and functional changes ensue in cardiac cell networks when cells are guided by three-dimensional scaffold topography. We report enhanced synchronous pacemaking activity in association with slow diastolic rise in intracellular Ca2+ concentration ([Ca2+]i) in cell networks grown on microgrooved scaffolds. Topography-driven changes in cardiac electromechanics were characterized by the frequency dependence of [Ca2+]i in syncytial structures formed of ventricular myocytes cultured on microgrooved elastic scaffolds (G). Cells were electrically paced at 0.5-5 Hz, and [Ca2+]i was determined using microscale ratiometric (fura 2) fluorescence. Compared with flat (F) controls, the G networks exhibited elevated diastolic [Ca2+]i at higher frequencies, increased systolic [Ca2+]i across the entire frequency range, and steeper restitution of Ca2+ transient half-width (n = 15 and 7 for G and F, respectively, P < 0.02). Significant differences in the frequency response of force-related parameters were also found, e.g., overall larger total area under the Ca2+ transients and faster adaptation of relaxation time to pacing rate (P < 0.02). Altered [Ca2+]i dynamics were paralleled by higher occurrence of spontaneous Ca2+ release and increased sarcoplasmic reticulum load (P < 0.02), indirectly assessed by caffeine-triggered release. Electromechanical instabilities, i.e., Ca2+ and voltage alternans, were more often observed in G samples. Taken together, these findings 1) represent some of the first functional electromechanical data for this in vitro system and 2) demonstrate direct influence of the microstructure on cardiac function and susceptibility to arrhythmias via Ca(2+)-dependent mechanisms. Overall, our results substantiate the idea of guiding cellular phenotype by cellular microenvironment, e.g., scaffold design in the context of tissue engineering.

Mechanotransduction: the role of mechanical stress, myocyte shape, and cytoskeletal architecture on cardiac function

“…The expression of the calcium channel α1C subunit and peak values for I to , I Na , and I Ca are all increased for aligned neonatal rat ventricular myocytes compared to pleomorphic cultures [181]. Furthermore, tissues aligned with microgrooved substrates show increased systolic intracellular Ca 2+ and decreased diastolic rise time [187]. These studies suggest that cytoskeletal architecture can regulate electrophysiology and furthermore indicate that an aligned phenotype similar to that observed in vivo is optimal for ion channel expression and function.…”

Surface Chemistry and Microtopography of Parylene C Films Control the Morphology and Microtubule Density of Cardiac Myocytes

“…Many studies have previously associated cellular alignment and sarcomeric organization with improved Ca 2+ physiology of NRVM on structured tissue substrates. 11,[25][26][27] These observations have been primarily attributed to changes in the sarcoplasmic reticulum organization 28 and voltage-gated Ca 2+ currents. 3 Therefore, it is not surprising that Ca 2+ handling parameters of NRVM were similar for cells cultured on both film thickness groups.…”

Quantitative evaluation of cardiomyocyte contractility in a 3D microenvironment

“…Three-dimensional (3D) cell cultures have a wide variety of applications in basic cell and tissue studies (Yin et al, 2004;Entcheva and Bien, 2003;Motlagh et al, 2003), in vivo tissue repair and clinical practice (Curtis et al, 2005;Stoklosowa, 2001). Previous studies have attempted to provide grooved surfaces for cardiomyocytes to mimic their in vivo 3D circumstances, and have shown that the alignment, orientation and shape of the cells were guided by the grooved surfaces (Yin et al, 2004;Entcheva and Bien, 2003;Motlagh et al, 2003).…”