■横向(t)-小管驱动心肌细胞中Ca2+的快速和同步上升。心力衰竭(HF)中的虚拟完全心房t-小管损失减少Ca2+释放。尚不清楚是否或如何恢复心房t小管,以及这如何影响收缩期Ca2。
■通过快速心室起搏在绵羊中诱发HF,并在快速起搏终止后恢复。连续的面块扫描电子显微镜和共聚焦成像用于研究t管超微结构。使用膜片钳评估功能,Ca2+,和共聚焦成像。通过Westernblot鉴定了参与心房t管恢复的候选蛋白,并在大鼠新生心室肌细胞中表达,以确定它们是否改变t管结构。
■心房t小管在HF中丢失,但在HF恢复后再次出现。恢复的t小管紊乱,采用不同的形态,t管长度和分枝增加。T管障碍与线粒体障碍有关。恢复的t小管是有功能的,触发细胞内部的Ca2+释放。收缩压Ca2+,ICa-L,肌浆网Ca2+含量,从HF恢复后恢复SERCA功能。共聚焦显微镜显示ryanodine受体染色的片段化和在HF中远离z线的运动,从HF中回收后逆转。急性拔管,为了去除恢复的T管,证实了它们在恢复收缩期Ca2+瞬变中的关键作用,Ca2+去除率,和峰值L型Ca2+电流。在HF期间,端黄素和肌管蛋白的丰度降低,在恢复期间增加。这些蛋白质的转染改变了新生肌细胞中小管的密度和结构。肌管蛋白的作用更大,增加小管长度和分支,复制在复苏心房中看到的。
■我们表明,从HF恢复可以恢复心房t小管,这促进了ICa-L的恢复,肌浆网Ca2+含量,和收缩压Ca2+。我们证明了肌管蛋白在t管恢复中的重要作用。我们的发现揭示了一种新的可行的治疗策略。
UNASSIGNED: Transverse (t)-tubules drive the rapid and synchronous Ca2+ rise in cardiac myocytes. The virtual complete atrial t-tubule loss in heart failure (HF) decreases Ca2+ release. It is unknown if or how atrial t-tubules can be restored and how this affects systolic Ca2+.
UNASSIGNED: HF was induced in sheep by rapid ventricular pacing and recovered following termination of rapid pacing. Serial block-face scanning electron microscopy and confocal imaging were used to study t-tubule ultrastructure. Function was assessed using patchclamp, Ca2+, and confocal imaging. Candidate proteins involved in atrial t-tubule recovery were identified by western blot and expressed in rat neonatal ventricular myocytes to determine if they altered t-tubule structure.
UNASSIGNED: Atrial t-tubules were lost in HF but reappeared following recovery from HF. Recovered t-tubules were disordered, adopting distinct morphologies with increased t-tubule length and branching. T-tubule disorder was associated with mitochondrial disorder. Recovered t-tubules were functional, triggering Ca2+ release in the cell interior. Systolic Ca2+, ICa-L, sarcoplasmic reticulum Ca2+ content, and SERCA function were restored following recovery from HF. Confocal microscopy showed fragmentation of ryanodine receptor staining and movement away from the z-line in HF, which was reversed following recovery from HF. Acute detubulation, to remove recovered t-tubules, confirmed their key role in restoration of the systolic Ca2+ transient, the rate of Ca2+ removal, and the peak L-type Ca2+ current. The abundance of telethonin and myotubularin decreased during HF and increased during recovery. Transfection with these proteins altered the density and structure of tubules in neonatal myocytes. Myotubularin had a greater effect, increasing tubule length and branching, replicating that seen in the recovery atria.
UNASSIGNED: We show that recovery from HF restores atrial t-tubules, and this promotes recovery of ICa-L, sarcoplasmic reticulum Ca2+ content, and systolic Ca2+. We demonstrate an important role for myotubularin in t-tubule restoration. Our findings reveal a new and viable therapeutic strategy.