Objectives Aging causes stiffness and decreased function of the renal artery (RA). Histological study with light microscopy can reveal microscopic structural remodeling but no functional changes. The present study aimed to clarify the association between structural and functional aging of the RA through the use of scanning acoustic microscopy. Methods Formalin-fixed, paraffin-embedded cross-sections of renal arteries from 64 autopsy cases were examined. Speed-of-sound (SOS) values of three layers, which correspond to the stiffness, were compared among different age groups. SOS of the tunica media was examined in terms of blood pressure (BP) and SOS of the ascending aorta. Vulnerability to proteases was assessed by SOS reduction after collagenase treatment. Results The tunica intima presented inward hypertrophy with luminal narrowing, and the tunica media showed outward hypertrophic remodeling with aging. SOS of the tunica media and internal and external elastic laminae showed a reverse correlation with age. SOS of the tunica media was negatively correlated with BP and strongly associated with that of the aorta. The tunica media of young RAs were more sensitive to collagenase compared with the old ones. Conclusions Scanning acoustic microscopy is useful for observing the aging process of the RA. This technique simultaneously shows structural and mechanical information from each portion of the RA. In the process of aging, the RA loses contractile function and elasticity as a result of protease digestion. The tunica media and the internal and external elastic laminae exhibit reduced stiffness, but the tunica intima stiffens with atherosclerosis. As a consequence, the RA’s outer shape changes from round to oval with inward and outward hypertrophy. This indicates that the inner resistant intima supports the mechanical weakness of the tunica media to compensate for an increase in BP with aging.

中文翻译：

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薄层内膜补偿可降低衰老的肾动脉中膜的硬度，这是通过扫描声学显微镜测量的

目的衰老会导致肾动脉僵硬和功能下降。光学显微镜的组织学研究可以揭示微观结构的重塑，但没有功能性改变。本研究旨在通过使用扫描声学显微镜来阐明RA的结构和功能老化之间的关联。方法检查64例尸检病例中福尔马林固定，石蜡包埋的肾动脉横切面。在不同年龄组之间比较了对应于刚度的三层声速（SOS）值。根据血压（BP）和升主动脉的SOS检查中膜的SOS。通过胶原酶处理后SOS的降低来评估对蛋白酶的脆弱性。结果内膜内膜肥大，管腔变窄，中膜显示出随着年龄的增长而向外肥大重塑。中膜的SOS以及内部和外部弹性薄片的SOS与年龄呈反相关。中膜的SOS与BP呈负相关，与主动脉的SOS密切相关。与老年RA相比，年轻RA的中膜对胶原酶更敏感。结论扫描声学显微镜对观察RA的衰老过程很有帮助。该技术同时显示了RA各个部分的结构和机械信息。在老化过程中，由于蛋白酶消化，RA失去了收缩功能和弹性。中膜以及内部和外部弹性薄片的刚度降低，但是内膜由于动脉粥样硬化而变硬。作为结果，RA的外形从圆形变为椭圆形，向内和向外肥大。这表明内部抵抗力内膜支持中膜的机械弱点，以补偿随着年龄的增长而增加的BP。