A Highly Conductive 3D Cardiac Patch Fabricated Using Cardiac Myocytes Reprogrammed from Human Adipogenic Mesenchymal Stem Cells
CARDIOVASCULAR ENGINEERING AND TECHNOLOGY
Authors: Abbasgholizadeh, Reza; Islas, Jose Francisco; Navran, Stephen; Potaman, Vladimir N.; Schwartz, Robert J.; Birla, Ravi K.
Abstract
Purpose The objective of this study was to bioengineer 3D patches from cardiac myocytes that have been reprogrammed from human adipogenic mesenchymal stem cells (hADMSCs). Methods Human adipogenic mesenchymal stem cells (hADMSCs) were reprogrammed to form cardiac myocytes using transcription factors ETS2 and MESP1. Reprogrammed cardiac myocytes were cultured in a fibrin gel to bioengineer 3D patch patches. The effect of initial plating density (1-25 million cells per patch), time (28-day culture period) and treatment with 1 mu M isoproterenol and 1 mu M epinephrine were evaluated. Results 3D patches were fabricated using cardiac myocytes that have been reprogrammed from hADMSCs. Based on optimization studies, it was determined that 10 million cells were needed to bioengineer a single patch, that measured 2 x 2 cm(2). Furthermore, 3D patches fabricated 10 million cells were stable in culture for up to 28 days. Treatment of 3D patches with 1 mu M isoproterenol and 1 mu M epinephrine resulted in an increase in the electrical properties, as measured by electrical impulse amplitude and frequency. An increase in the expression of mTOR, KCNV1, GJA5, KCNJ16, CTNNT2, KCNV2, MYO3, FOXO1 and KCND2 was noted in response to treatment of 3D patches with isoproterenol and epinephrine. Conclusion Based on the results of this study, there is evidence to support the successful fabrication of a highly functional 3D patches with measurable electrical activity using cardiac myocytes reprogrammed from hADMSCs. 3D patches fabricated using optimal conductions described in this study can be used to improve the functional properties of failing hearts. Predominantly, in case of the infarcted hearts with partial loss of electrical activity, the electrical properties of the 3D patches may restore the electrical activity of the heart.
Kv4.2 autism and epilepsy mutation enhances inactivation of closed channels but impairs access to inactivated state after opening
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Authors: Lin, Meng-chin A.; Cannon, Stephen C.; Papazian, Diane M.
Abstract
A de novo mutation in the KCND2 gene, which encodes the Kv4.2 K+ channel, was identified in twin boys with intractable, infantonset epilepsy and autism. Kv4.2 channels undergo closed-state inactivation (CSI), a mechanism by which channels inactivate without opening during subthreshold depolarizations. CSI dynamically modulates neuronal excitability and action potential back propagation in response to excitatory synaptic input, controlling Ca 2(+) influx into dendrites and regulating spike timing-dependent plasticity. Here, we show that the V404M mutation specifically affects the mechanism of CSI, enhancing the inactivation of channels that have not opened while dramatically impairing the inactivation of channels that have opened. The mutation gives rise to these opposing effects by increasing the stability of the inactivated state and in parallel, profoundly slowing the closure of open channels, which according to our data, is required for CSI. The larger volume of methionine compared with valine is a major factor underlying altered inactivation gating. Our results suggest that V404M increases the strength of the physical interaction between the pore gate and the voltage sensor regardless of whether the gate is open or closed. Furthermore, in contrast to previous proposals, our data strongly suggest that physical coupling between the voltage sensor and the pore gate is maintained in the inactivated state. The state-dependent effects of V404M on CSI are expected to disturb the regulation of neuronal excitability and the induction of spike timing-dependent plasticity. Our results strongly support a role for altered CSI gating in the etiology of epilepsy and autism in the affected twins.