Investigating the cardiomyocyte rigidity sensing mechanism with micro patterned surfaces and nanopillars

最近的发现表明，细胞在一个被称为机械感应的过程中受到环境硬度的引导。这会影响细胞的命运，从而形成心脏、血管或其他组织。心脏的硬度在发育、疾病和衰老过程中都会发生变化，从而影响心脏细胞的跳动。然而，目前还不清楚心脏中的细胞是如何测量硬度的，或者来自健康和患病心脏的细胞是否能以同样的方式感知硬度。在之前的一项研究中，我们发现细胞通过可拉伸蛋白测量特定粘附结构的刚度，称为黏附体和黏附灶。如果这些蛋白质被拉伸，其他蛋白质就会被激活，重塑某些细胞结构，即肌动蛋白丝。肌动蛋白丝有不同的种类。其中一些是心肌细胞所特有的，而另一些也存在于其他类型的细胞中，如皮肤或免疫细胞，它们需要锚定细胞或用于迁移。在坚硬的表面上，我们发现后一种结构的形成增加了，我们相信这将减少前一种结构的形成（这是心脏跳动所必需的）。此外，基于其他人和我们之前的工作，我们假设黏附结构的组成在发育和疾病期间会发生变化。因此，具有不同特性的可拉伸蛋白可以在不同时间定位在粘附处。为了了解心脏细胞是如何感知硬度的，我们需要更清楚地了解粘附处存在哪些蛋白质，以及这些蛋白质如何影响不同肌动蛋白细丝的形成。在这里，我们想要回答这些问题，通过把心脏细胞放在合成基质上，我们可以制造出具有一定刚度的基质，或者我们可以用来测量细胞力。我们还可以在这些表面上打印图案，在上面形成粘合结构。这将使我们能够精确地监测，有多少蛋白质定位在粘连处。此外，我们将干扰不同的信号通路，这些信号通路在与健康或患病心脏相当的硬度上被激活，并观察细胞对治疗的反应方式的变化。这些实验的结果将使我们更深入地了解心脏是如何感知僵硬的。这将使生物材料的设计能够在体外或体内培养心脏细胞，以修复心肌梗死或其他心脏病造成的损伤。

Recent discoveries have shown that cells are guided by the stiffness of their environment in a process, called mechanosensing. This influences the fate of the cells in order to form a heart, a blood vessel or other tissue. The stiffness of the heart changes during development, in disease and also during ageing, thereby affecting how well the cells in the heart can beat. However, it is still unclear how the cells in the heart measure the stiffness, or if cells from healthy and diseased hearts can sense it in the same way.In a previous study we found evidence that cells measure the stiffness at specific adhesive structures, known as costameres and focal adhesions through stretchable proteins. If the proteins are stretched, other proteins are activated to remodel certain cellular structures, called actin filaments. The actin filaments come in different varieties. Some of them are specific for cardiomyocytes, while others are also found in other cell types, such as skin or immune cells and needed to anchor the cell, or for migration. On stiff surfaces we find an increased formation of the latter structures and we believe that this will reduce the formation of the former structures (which are needed for the heart to beat). Moreover, based on others and our previous work we hypothesize that the composition of the adhesive structures changes during development and disease. Therefore, stretchable proteins with different characteristics could be located at adhesions at different times.In order to understand how the cells in the heart sense the stiffness we need a clearer picture of what proteins are present at the adhesions and how this affects the formation of the different actin filaments. Here, we want to answer these questions, by placing heart cells on synthetic substrates, which we can produce to have certain stiffnesses, or which we can use to measure the cellular forces. We can also print pattern onto these surfaces, on which the adhesive structures will form. This will allow us to monitor precisely, how much of which protein localizes to the adhesions.Further, we will disturb different signalling pathways that are activated on stiffness comparable to a healthy or diseased heart and observe the changes in the way the cells behave in response to the treatment.Together results from these experiments will lead to a deeper understanding how the heart senses the stiffness. This will allow the design of biomaterials to grow heart cells outside or inside the body to repair injuries from myocardial infarctions or other heart disease.