Vitiligo is an immune skin disorder consisting of depigmented skin patches caused by the destruction of epidermal melanocytes. Vitiligo treatment represents a clinical challenge since the re-pigmentation mechanism is not fully understood. In this pilot study, we employ in-vivo multiphoton microscopy to evaluate epidermal keratinocyte metabolic state before and during treatment, in-vivo reflectance confocal microscopy to track melanocyte migration after treatment initiation, and single cell transcriptomics to identify unique cell populations more abundant in stable vitiligo lesions compared to normal skin. The findings provide insights into the role of certain cell populations in the viability of micro-grafting treatments.
Vitiligo is characterized by white patches on skin due to the loss of melanocytes. Treatments are not uniformly successful and re-pigmentation is rarely complete. Optical laser scanning microscopy techniques have great potential to advance our understanding of the repigmentation process of vitiligo.
In this pilot study, we employ in-vivo multiphoton microscopy (MPM) to assess potential changes in the metabolic state of epidermal keratinocytes involved in vitiligo before and throughout treatment, and in-vivo reflectance confocal microscopy (RCM) to assess the initiation of the re-pigmentation process and monitor wound healing after micro-grafting treatment.
Temporal changes in macrophage metabolism are likely crucial to their role in inflammatory diseases. Label-free two-photon excited fluorescence (TPEF) and fluorescence lifetime imaging microscopy are well suited to track dynamic changes in macrophage metabolism. We performed TPEF imaging of human macrophages following either pro- or an anti-inflammatory stimulation. Two endogenous fluorophores, NAD(P)H and FAD, coenzymes involved in key metabolic pathways, provided contrast. We used the corresponding intensity images to determine the optical redox ratio of FAD to FAD + NAD(P)H. We also analyzed the intensity fluctuation patterns within NAD(P)H TPEF images to determine mitochondrial clustering patterns. Finally, we acquired NAD(P)H TPEF lifetime images to assess the relative levels of bound NAD(P)H. Our studies indicate that the redox ratio increases, whereas mitochondrial clustering decreases in response to both pro- and anti-inflammatory stimuli; however, these changes are enhanced in pro-inflammatory macrophages. Interestingly, we did not detect any significant changes in the corresponding NAD(P)H bound fraction. A combination of optical metabolic metrics could be used to classify pro- and anti-inflammatory macrophages with high accuracy. Contributions from alterations in different metabolic pathways may explain our findings, which highlight the potential of label-free two-photon imaging to assess nondestructively macrophage functional state.
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