title: Imaging mitochondrial dynamics in human skin reveals depth-dependent hypoxia and malignant potential for diagnosis.
abstract: Active changes in mitochondrial structure and organization facilitate cellular homeostasis. Because aberrant mitochondrial dynamics are implicated in a variety of human diseases, their assessment is potentially useful for diagnosis, therapy, and disease monitoring. Because current techniques for evaluating mitochondrial morphology are invasive or necessitate mitochondria-specific dyes, their clinical translation is limited. We report that mitochondrial dynamics can be monitored in vivo, within intact human skin by relying entirely on endogenous two-photon-excited fluorescence from the reduced metabolic coenzyme nicotinamide adenine dinucleotide (NADH). We established the sensitivity of this approach with in vivo, fast temporal studies of arterial occlusion-reperfusion, which revealed acute changes in the mitochondrial metabolism and dynamics of the lower human epidermal layers. In vitro hypoxic-reperfusion studies validated that the in vivo outcomes were a result of NADH fluorescence changes. To demonstrate the diagnostic potential of this approach, we evaluated healthy and cancerous human skin epithelia. Healthy tissues displayed consistent, depth-dependent morphological and mitochondrial organization patterns that varied with histological stratification and intraepithelial mitochondrial protein expression. In contrast, these consistent patterns were absent in cancerous skin lesions. We exploited these differences to successfully differentiate healthy from cancerous tissues using a predictive classification approach. Collectively, these results demonstrate that our label-free, automated, near real-time assessments of mitochondrial organization-relying solely on endogenous contrast-could be useful for accurate, noninvasive in vivo diagnosis.
authors.affiliation: Department of Biomedical Engineering, Tufts University, 4 Colby Street, Medford, MA 02155, USA.
authors.forename: Dimitra
authors.initials: D
authors.lastname: Pouli
authors.affiliation: Laser Microbeam and Medical Program, Beckman Laser Institute, University of California, Irvine, Irvine, CA 92612, USA.
authors.forename: Mihaela
authors.initials: M
authors.lastname: Balu
authors.affiliation: Department of Biomedical Engineering, Tufts University, 4 Colby Street, Medford, MA 02155, USA.
authors.forename: Carlo A
authors.initials: CA
authors.lastname: Alonzo
authors.affiliation: Department of Biomedical Engineering, Tufts University, 4 Colby Street, Medford, MA 02155, USA.
authors.forename: Zhiyi
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Department of Biomedical Engineering, Tufts University, 4 Colby Street, Medford, MA 02155, USA.|Department of Biomedical Engineering, University of Arkansas, 120 John A. White Jr. Engineering Hall, Fayetteville, AR 72701, USA.
authors.forename: Kyle P
authors.initials: KP
authors.lastname: Quinn
authors.affiliation: Department of Preventive Medicine and Public Health, Faculty of Medicine, University of Malaga, 32 Louis Pasteur Boulevard, 29071 Málaga, Spain.
authors.forename: Francisca
authors.initials: F
authors.lastname: Rius-Diaz
authors.affiliation: Department of Dermatology, University of California, Irvine, 1 Medical Plaza Drive, Irvine, CA 92697, USA.
authors.forename: Ronald M
authors.initials: RM
authors.lastname: Harris
authors.affiliation: Department of Dermatology, University of California, Irvine, 1 Medical Plaza Drive, Irvine, CA 92697, USA.
authors.forename: Kristen M
authors.initials: KM
authors.lastname: Kelly
authors.affiliation: Laser Microbeam and Medical Program, Beckman Laser Institute, University of California, Irvine, Irvine, CA 92612, USA.
authors.forename: Bruce J
authors.initials: BJ
authors.lastname: Tromberg
authors.affiliation: Department of Biomedical Engineering, Tufts University, 4 Colby Street, Medford, MA 02155, USA. irene.georgakoudi@tufts.edu.
authors.forename: Irene
authors.initials: I
authors.lastname: Georgakoudi
mesh_terms: D015415:Biomarkers / Q000737:chemistry; D002280:Basal Cell Carcinoma / Q000000981:diagnostic imaging* / Q000473:pathology; D004817:Epidermis / Q000473:pathology; D006706:Homeostasis; D006801:Humans; D000860:Hypoxia / Q000473:pathology*; D015603:Keratinocytes / Q000166:cytology; D008545:Melanoma / Q000000981:diagnostic imaging* / Q000473:pathology; D036641:Microscopy, Fluorescence, Multiphoton; D008928:Mitochondria / Q000378:metabolism* / Q000473:pathology; D063154:Mitochondrial Dynamics; D009243:NAD / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D017785:Photons; D012867:Skin / Q000378:metabolism* / Q000473:pathology
chemical_list: D015415:Biomarkers; D009243:NAD; D010100:Oxygen