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

有许多报道描述了激光激发人体动脉的自身荧光光谱。然而，光谱数据是有限的，因为所得信号只是光强度和发射光谱轮廓。本文应用纳秒荧光法检测人体动脉的衰老。作为检查，从尸体上取两条动脉：(1)主动脉和(2)基底动脉。检测了荧光衰减曲线的年龄依赖性异质性。荧光在450nm处最大。在脉冲光激发下，时间荧光的衰减时间为纳秒级。除1例外，基底动脉荧光衰减时间呈年龄依赖性。主动脉无年龄依赖性。我们认为，由于高血压的脉动引起的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，脑动脉内机械应力不强，不影响组织老化。由此产生的荧光衰减曲线反映了实际年龄。45岁基底动脉荧光衰减明显快于92岁基底动脉。从钙含量的检查中，我们发现45年基底动脉含有大量的钙。因为组织中钙含量是衰老的一个指标，所以45岁动脉的荧光衰减如此之快是合理的解释：45岁动脉的生理年龄大于90岁。我们的结果是首次报道了动脉荧光衰减曲线随年龄的变化。然而，什么物质在动脉壁上发出荧光，以及为什么荧光衰减时间随着年龄的增长而减少，目前还不清楚。死亡原因可能与荧光密切相关。为了进一步将动脉自身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.