Ebenezar Jeyasingh, Aruna Prakasa Rao, Ganesan Singaravelu
Department of Medical Physics, Anna University, Chennai - 600025, India.
Analyst. 2015 Jun 21;140(12):4170-81. doi: 10.1039/c4an00650j. Epub 2015 Apr 24.
The objective of the study is to characterize the endogenous porphyrin fluorescence in a dimethylbenz(a)anthracene (DMBA) induced mouse skin tumor model using native fluorescence emission and excitation spectroscopy. Two intensity ratio parameters I580/I635 and I420/I515 were selected to represent the key fluorophore of endogenous porphyrins from emission and excitation spectra recorded in vivo from 31 DMBA treated animals and 5 control animals. In the emission spectrum, the endogenous porphyrin was elevated at 635 nm in different transformation lesions such as hyperplasia, papilloma, dysplasia, ESCC and WDSCC. This is corroborated by the endogenous porphyrin elevation at 420, 515, 550 and 588 nm in the WDSCC lesions from the excitation spectra. The elevation of endogenous porphyrin, probably protoporphyrin IX (PpIX), is due to biochemical and metabolic alterations in epithelial cells during tissue transformation. The loss of ferrochelatase activity might be responsible for enhanced PpIX in the transformed tissues. The sensitivity and specificity were determined for different lesion pairs from the scatter plot based on the discrimination value by validation with histopathological results. The emission intensity ratio I580/I635 at 405 nm excitation was selected to discriminate normal from hyperplasia, hyperplasia from papilloma, papilloma from dysplasia, dysplasia from early squamous cell carcinoma (ESCC), and ESCC from well differentiated squamous cell carcinoma (WDSCC) with specificities of 100%, 88%, 100%, 86%, and 100% and sensitivities of 100%, 80%, 100%, 100% and 100% respectively. Similarly, the excitation intensity ratio I420/I515 for 635 nm emission used to discriminate between WDSCC lesions and normal tissue gives 100% specificity and 100% sensitivity.
本研究的目的是利用天然荧光发射和激发光谱，对二甲基苯并(a)蒽（DMBA）诱导的小鼠皮肤肿瘤模型中的内源性卟啉荧光进行表征。从31只经DMBA处理的动物和5只对照动物体内记录的发射光谱和激发光谱中，选取两个强度比参数I580/I635和I420/I515来代表内源性卟啉的关键荧光团。在发射光谱中，内源性卟啉在不同的转化病变如增生、乳头状瘤、发育异常、食管鳞状细胞癌（ESCC）和高分化鳞状细胞癌（WDSCC）中，于635 nm处升高。激发光谱中WDSCC病变在420、515、550和588 nm处内源性卟啉的升高证实了这一点。内源性卟啉（可能是原卟啉IX，PpIX）的升高是由于组织转化过程中上皮细胞的生化和代谢改变。铁螯合酶活性的丧失可能是转化组织中PpIX增强的原因。基于与组织病理学结果验证的判别值，从散点图中确定了不同病变对的敏感性和特异性。选择405 nm激发下的发射强度比I580/I635来区分正常组织与增生组织、增生组织与乳头状瘤、乳头状瘤与发育异常、发育异常与早期鳞状细胞癌（ESCC）以及ESCC与高分化鳞状细胞癌（WDSCC），特异性分别为100%、88%、100%、86%和100%，敏感性分别为100%、80%、100%、100%和100%。同样，用于区分WDSCC病变与正常组织的635 nm发射的激发强度比I420/I515的特异性和敏感性均为100%。
