Harvey Lui

All living cells are dynamic machines that continuously adapt and respond to their local environment. Serial analysis of cellular dynamics over time offers new insights into human skin responses to solar radiation. However, most of the previous studies are based on multiple biopsies and ex vivo analysis, which precludes the monitoring of the same sites and cells over time. In this thesis, a novel methodology based on in vivo real-time multi-modality microscopy is developed to image and quantify cellular dynamics. This imaging system integrates reflectance confocal microscopy (RCM), two-photon excitation fluorescence microscopy (TPF), and second harmonic generation microscopy (SHG) to provide complimentary tissue information. Furthermore, a method for precise serial micro-registration was created for in vivo microscopy imaging of human skin. This method solved the challenges for relocalization repeatedly and efficiently in multiple imaging sessions, enabling quantitative imaging monitoring of the same cells/tissue microstructures over a long period of days and weeks. Concurrently, an automatic segmentation algorithm was established for image analysis; epidermal-dermal junction (DEJ) was delineated in 3D, and epidermal melanin was also segmented. I applied this analysis and precise relocalization method in conjunction with in vivo multimodality multiphoton microscopy to study skin response to UV challenges. The behavior of human skin cells such as cell proliferation, melanin upward migration, blood flow dynamics, and epidermal thickness adaptation can be recorded over time, enabling quantitative cellular dynamics analysis. These results demonstrate that our label-free, automated assessments relying solely on endogenous contrast could be useful for accurate, non-invasive longitudinal skin dynamics study.

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