Ngoepe Malebogo, Passos Andreas, Balabani Stavroula, King Jesse, Lynn Anastasia, Moodley Jasanth, Swanson Liam, Bezuidenhout Deon, Davies Neil H, Franz Thomas
Department of Mechanical Engineering, University of Cape Town, Rondebosch, South Africa.
Wallenberg Research Centre, Stellenbosch Institute of Advanced Study, Stellenbosch University, Stellenbosch, South Africa.
Front Cardiovasc Med. 2019 Aug 7;6:104. doi: 10.3389/fcvm.2019.00104. eCollection 2019.
Myocardial infarction (MI), a type of cardiovascular disease, affects a significant proportion of people around the world. Traditionally, non-communicable chronic diseases were largely associated with aging populations in higher income countries. It is now evident that low- to middle-income countries are also affected and in these settings, younger individuals are at high risk. Currently, interventions for MI prolong the time to heart failure. Regenerative medicine and stem cell therapy have the potential to mitigate the effects of MI and to significantly improve the quality of life for patients. The main drawback with these therapies is that many of the injected cells are lost due to the vigorous motion of the heart. Great effort has been directed toward the development of scaffolds which can be injected alongside stem cells, in an attempt to improve retention and cell engraftment. In some cases, the scaffold alone has been seen to improve heart function. This study focuses on a synthetic polyethylene glycol (PEG) based hydrogel which is injected into the heart to improve left ventricular function following MI. Many studies in literature characterize PEG as a Newtonian fluid within a specified shear rate range, on the macroscale. The aim of the study is to characterize the flow of a 20 kDa PEG on the microscale, where the behavior is likely to deviate from macroscale flow patterns. Micro particle image velocimetry (μPIV) is used to observe flow behavior in microchannels, representing the gaps in myocardial tissue. The fluid exhibits non-Newtonian, shear-thinning behavior at this scale. Idealized two-dimensional computational fluid dynamics (CFD) models of PEG flow in microchannels are then developed and validated using the μPIV study. The validated computational model is applied to a realistic, microscopy-derived myocardial tissue model. From the realistic tissue reconstruction, it is evident that the myocardial flow region plays an important role in the distribution of PEG, and therefore, in the retention of material.
心肌梗死（MI）是一种心血管疾病，影响着全球相当一部分人口。传统上，非传染性慢性病在很大程度上与高收入国家的老龄人口相关。现在很明显，低收入和中等收入国家也受到影响，在这些环境中，年轻人面临高风险。目前，针对心肌梗死的干预措施可延长出现心力衰竭的时间。再生医学和干细胞疗法有潜力减轻心肌梗死的影响，并显著提高患者的生活质量。这些疗法的主要缺点是，由于心脏的剧烈运动，许多注入的细胞会流失。人们一直致力于开发可与干细胞一起注入的支架，以提高细胞的保留率和植入率。在某些情况下，单独使用支架已被证明可改善心脏功能。本研究聚焦于一种基于合成聚乙二醇（PEG）的水凝胶，将其注入心脏以改善心肌梗死后的左心室功能。文献中的许多研究在宏观尺度上把PEG在特定剪切速率范围内的特性描述为牛顿流体。该研究的目的是在微观尺度上表征20 kDa PEG的流动特性，在这个尺度下其行为可能会偏离宏观流动模式。微粒子图像测速技术（μPIV）用于观察微通道中的流动行为，这些微通道代表心肌组织中的间隙。在这个尺度下，该流体表现出非牛顿、剪切变稀行为。然后开发了PEG在微通道中流动的理想化二维计算流体动力学（CFD）模型，并使用μPIV研究进行验证。经过验证的计算模型被应用于一个基于显微镜观察得到的真实心肌组织模型。从真实的组织重建中可以明显看出，心肌流动区域在PEG的分布中起着重要作用，因此，在物质的保留方面也起着重要作用。
