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

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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.