Kruithof Boudewijn P T, van Wijngaarden Aniek L, Mousavi Gourabi Babak, Hjortnaes Jesper, Palmen Meindert, Ajmone Marsan Nina
Department of Cardiology, Leiden University Medical Center, 2333 ZA Leiden, The Netherlands.
Department of Cell and Chemical Biology, Leiden University Medical Center, 2333 ZA Leiden, The Netherlands.
J Cardiovasc Dev Dis. 2021 Jul 8;8(7):79. doi: 10.3390/jcdd8070079.
The formation of superimposed tissue (SIT), a layer on top of the original valve leaflet, has been described in patients with mitral regurgitation as a major contributor to valve thickening and possibly as a result of increased mechanical stresses. However, little is known whether SIT formation also occurs in aortic valve disease. We therefore performed histological analyses to assess SIT formation in aortic valve leaflets ( = 31) from patients with aortic stenosis ( = 17) or aortic regurgitation due to aortic dilatation ( = 14). SIT was observed in both stenotic and regurgitant aortic valves, both on the ventricular and aortic sides, but with significant differences in distribution and composition. Regurgitant aortic valves showed more SIT formation in the free edge, leading to a thicker leaflet at that level, while stenotic aortic valves showed relatively more SIT formation on the aortic side of the body part of the leaflet. SIT appeared to be a highly active area, as determined by large populations of myofibroblasts, with varied extracellular matrix composition (higher collagen content in stenotic valves). Further, the identification of the SIT revealed the presence of foldings of the free edge in the diseased aortic valves. Insights into SIT regulation may further help in understanding the pathophysiology of aortic valve disease and potentially lead to the development of new therapeutic treatments.
叠加组织（SIT）的形成是指在原始瓣膜小叶上方形成一层组织，在二尖瓣反流患者中，它被认为是瓣膜增厚的主要原因，可能是机械应力增加的结果。然而，对于SIT的形成是否也发生在主动脉瓣疾病中，人们知之甚少。因此，我们进行了组织学分析，以评估主动脉狭窄患者（n = 17）或因主动脉扩张导致主动脉反流患者（n = 14）的主动脉瓣小叶（n = 31）中SIT的形成情况。在狭窄和反流的主动脉瓣中均观察到SIT，在心室侧和主动脉侧均有，但在分布和组成上存在显著差异。反流性主动脉瓣在游离缘显示出更多的SIT形成，导致该水平的小叶更厚，而狭窄性主动脉瓣在小叶体部的主动脉侧显示出相对更多的SIT形成。SIT似乎是一个高度活跃的区域，这由大量的肌成纤维细胞决定，其细胞外基质组成各不相同（狭窄瓣膜中的胶原蛋白含量更高）。此外，对SIT的识别揭示了病变主动脉瓣中游离缘的折叠情况。对SIT调节的深入了解可能有助于进一步理解主动脉瓣疾病的病理生理学，并有可能导致新治疗方法的开发。
