title: Luminescent dual sensors reveal extracellular pH-gradients and hypoxia on chronic wounds that disrupt epidermal repair.
abstract: Wound repair is a quiescent mechanism to restore barriers in multicellular organisms upon injury. In chronic wounds, however, this program prematurely stalls. It is known that patterns of extracellular signals within the wound fluid are crucial to healing. Extracellular pH (pHe) is precisely regulated and potentially important in signaling within wounds due to its diverse cellular effects. Additionally, sufficient oxygenation is a prerequisite for cell proliferation and protein synthesis during tissue repair. It was, however, impossible to study these parameters in vivo due to the lack of imaging tools. Here, we present luminescent biocompatible sensor foils for dual imaging of pHe and oxygenation in vivo. To visualize pHe and oxygen, we used time-domain dual lifetime referencing (tdDLR) and luminescence lifetime imaging (LLI), respectively. With these dual sensors, we discovered centripetally increasing pHe-gradients on human chronic wound surfaces. In a therapeutic approach, we identify pHe-gradients as pivotal governors of cell proliferation and migration, and show that these pHe-gradients disrupt epidermal barrier repair, thus wound closure. Parallel oxygen imaging also revealed marked hypoxia, albeit with no correlating oxygen partial pressure (pO2)-gradient. This highlights the distinct role of pHe-gradients in perturbed healing. We also found that pHe-gradients on chronic wounds of humans are predominantly generated via centrifugally increasing pHe-regulatory Na+/H+-exchanger-1 (NHE1)-expression. We show that the modification of pHe on chronic wound surfaces poses a promising strategy to improve healing. The study has broad implications for cell science where spatial pHe-variations play key roles, e.g. in tumor growth. Furthermore, the novel dual sensors presented herein can be used to visualize pHe and oxygenation in various biomedical fields.
authors.affiliation: 1. Department of Dermatology, University Medical Center Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Schreml
authors.affiliation: 2. Institute of Analytical Chemistry, Chemo- and Biosensors, University of Regensburg, Universitätsstraße 31, 93053 Regensburg, Germany.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Meier
authors.affiliation: 3. Fraunhofer Institute for Biomedical Engineering, Branch Potsdam, Am Mühlenberg 13, 14476 Potsdam, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Kirschbaum
authors.affiliation: 4. Department of Biology, University of Copenhagen, 13 Universitetsparken, DK-2100 Copenhagen, Denmark.
authors.forename: Su Chii
authors.initials: SC
authors.lastname: Kong
authors.affiliation: 5. Center of Plastic Surgery, Department of Trauma Surgery, University Medical Center Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Gehmert
authors.affiliation: 6. Department of Maxillofacial Surgery, University Medical Center Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Felthaus
authors.affiliation: 7. Department of Pharmacy, Freie Universität Berlin, Königin-Luise-Str. 2-4, 14195 Berlin, Germany.
authors.forename: Sarah
authors.initials: S
authors.lastname: Küchler
authors.affiliation: 8. Blond McIndoe Research Foundation, Queen Victoria Hospital, Holtye Road, East Grinstead RH19 3DZ, England, UK.
authors.forename: Justin R
authors.initials: JR
authors.lastname: Sharpe
authors.affiliation: 3. Fraunhofer Institute for Biomedical Engineering, Branch Potsdam, Am Mühlenberg 13, 14476 Potsdam, Germany.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Wöltje
authors.affiliation: 1. Department of Dermatology, University Medical Center Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany.
authors.forename: Katharina T
authors.initials: KT
authors.lastname: Weiß
authors.affiliation: 1. Department of Dermatology, University Medical Center Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Albert
authors.affiliation: 1. Department of Dermatology, University Medical Center Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany.
authors.forename: Uwe
authors.initials: U
authors.lastname: Seidl
authors.affiliation: 9. Center for Electron Microscopy at the Institute of Pathology, University Medical Center Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany.
authors.forename: Josef
authors.initials: J
authors.lastname: Schröder
authors.affiliation: 6. Department of Maxillofacial Surgery, University Medical Center Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Morsczeck
authors.affiliation: 5. Center of Plastic Surgery, Department of Trauma Surgery, University Medical Center Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany.
authors.forename: Lukas
authors.initials: L
authors.lastname: Prantl
authors.affiliation: 3. Fraunhofer Institute for Biomedical Engineering, Branch Potsdam, Am Mühlenberg 13, 14476 Potsdam, Germany.
authors.forename: Claus
authors.initials: C
authors.lastname: Duschl
authors.affiliation: 4. Department of Biology, University of Copenhagen, 13 Universitetsparken, DK-2100 Copenhagen, Denmark.
authors.forename: Stine F
authors.initials: SF
authors.lastname: Pedersen
authors.affiliation: 6. Department of Maxillofacial Surgery, University Medical Center Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Gosau
authors.affiliation: 1. Department of Dermatology, University Medical Center Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany.
authors.forename: Mark
authors.initials: M
authors.lastname: Berneburg
authors.affiliation: 2. Institute of Analytical Chemistry, Chemo- and Biosensors, University of Regensburg, Universitätsstraße 31, 93053 Regensburg, Germany.
authors.forename: Otto S
authors.initials: OS
authors.lastname: Wolfbeis
authors.affiliation: 1. Department of Dermatology, University Medical Center Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Landthaler
authors.affiliation: 1. Department of Dermatology, University Medical Center Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Babilas
mesh_terms: D000368:Aged; D015374:Biosensing Techniques / Q000379:methods*; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism; D015687:Cell Hypoxia; D002460:Cell Line; D002465:Cell Movement; D049109:Cell Proliferation; D005260:Female; D005456:Fluorescent Dyes; D006801:Humans; D006863:Hydrogen-Ion Concentration; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D008297:Male; D008856:Microscopy, Fluorescence / Q000379:methods; D008875:Middle Aged; D061848:Optical Imaging / Q000379:methods; D062326:Re-Epithelialization; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism; D014647:Varicose Ulcer / Q000378:metabolism* / Q000473:pathology
chemical_list: D027682:Cation Transport Proteins; D005456:Fluorescent Dyes; C490998:SLC9A1 protein, human; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers
keywords: cell migration; fluorescence imaging; gradient sensing; proton transporters; wound healing