Development of time- and spectro-resolved microfluorometer and its application to detect arterial aging

有许多报道描述了人体动脉的激光激发自体荧光光谱。然而，光谱数据是有限的，因为合成的信号只是光强度和发射光谱轮廓。在这里，我们应用纳秒荧光法来检测人体动脉的衰老。检查标本为两条动脉：(1)大动脉和(2)基底动脉。研究了荧光衰减曲线随年龄变化的不均一性。荧光在450 nm处有最大发射峰。在脉冲光激发下，时间荧光的衰减时间为纳秒量级。基底动脉荧光衰减时间除1例外，其余均呈年龄依赖性。然而，主动脉并未表现出年龄依赖性。我们假设，由于高血压的脉动，机械应力加速了主动脉壁的老化，导致无法区分的衰减曲线。另一方面，脑动脉内的机械应力不强，不影响组织的老化。由此得到的荧光衰减曲线反映了实际年龄。45年的基底动脉荧光衰减比92年的快得多。从钙含量的检测发现，45年的基底动脉含有大量的钙。由于组织中的钙含量是衰老的一个指标，因此可以合理地解释45年动脉的快速荧光衰减：45年动脉的生理年龄大于90岁。我们的结果是首次报道了动脉的荧光衰减曲线随年龄的变化。然而，目前仍不清楚动脉壁中的荧光物质是什么，以及为什么荧光衰减时间随着年龄的增长而减少。死亡原因可能与荧光有很大关系。为了进一步将动脉自体荧光技术应用于组织衰老的研究，有必要澄清这些问题。

There are many reports that describe laser excited autofluorescence spectroscopy of human arteries. However, spectroscopic data are limited, since resultant signals are only light intensity and emission spectral profile. Here we applied the nanosecond fluorometry to detect aging in human artery. As the examination, two arteries from cadavers were subjected : (1) aorta and (2) basilar artery. The age dependent heterogeneity of the fluorescence decay curve was examined. The fluorescence had emission maximum at 450 nm. The decay time of the temporal fluorescence was in nanosecond scale when excited with a pulsed light. The fluorescence decay time of basilar artery showed the age-dependency, except for one case. However, aorta did not show the age dependency. We assume that aging of aortic wall is accelerated by mechanical stress due to pulsation of the high blood pressure, resulting in indistinguishable decay curves. On the other hand, the mechanical stress inside cerebral artery is not strong and does not influence the tissue aging. Resultant fluorescence decay curve thus reflects the actual age. The fluorescence decay of the 45 years basilar artery was extraordinarily faster than that of 92 years. From the examination of Ca content, we found the 45 years basilar artery contained a large amount of calcium. Because calcium content in the tissue is one indicator of aging, such the fast fluorescence decay of the 45 years artery is reasonably explained : the physiological age of the 45 years artery was older than 90 years.Our result is the first report that the fluorescence decay curve of artery changes with respect to the age. However, it is still ambiguous what substance fluoresces in the arterial wall and why fluorescence decay time decreases with age. The cause of death may strongly relate to the fluorescence. It is necessary to clarify these for further application of the arterial autofluorescence to the study of tissue aging.