title: Relaxin 2 is functional at the ocular surface and promotes corneal wound healing.
abstract: OBJECTIVE
  We aimed to determine if the insulin-like peptide hormone relaxin 2 (RLN2) is expressed at the ocular surface and in tears and if RLN2 influences wound healing at the ocular surface, which is associated with extracellular matrix (ECM) remodeling.
  
  
  METHODS
  We analyzed transcript levels of human RLN2 and its cognate relaxin-like receptors RXFP1 and RXFP2 in tissues of the ocular surface, lacrimal apparatus, and human corneal (HCE), conjunctival (HCjE) and sebaceous (SC) cell lines. We analyzed effects of human RLN2 on cell proliferation and migration and quantified mRNA expression of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in HCE, HCjE, and SC. Using an alkali-induced corneal wounding model, we analyzed the wound healing rate in C57BL/6 mice eyes after topically applied RLN2.
  
  
  RESULTS
  The presence of RLN2, RXFP1, and RXFP2 transcripts was detected in lacrimal gland, eyelid, conjunctiva, cornea, primary corneal fibroblasts, nasolacrimal ducts, and all three cell lines. ELISA revealed RLN2 protein in all ocular surface tissues analyzed and in human tears. Stimulation of HCE, HCjE, and SC with RLN2 significantly increased cell proliferation and migration. Relative mRNA expression levels of MMP2, MMP9, TIMP1, and TIMP2 were significantly influenced by RLN2 in all three cell lines at different time points studied. The local application of RLN2 onto denuded corneal surface resulted in significantly elevated corneal wound healing.
  
  
  CONCLUSIONS
  Our data support a novel role for the RLN2 ligand-receptor system at the ocular surface and in the lacrimal apparatus as a potential future therapeutic during wound healing at the ocular surface.
authors.affiliation: Department of Anatomy II, Friedrich Alexander University of Erlangen-Nürnberg, Erlangen, Germany. ulrike.hampel@anatomie2.med.uni-erlangen.de
authors.forename: Ulrike
authors.initials: U
authors.lastname: Hampel
authors.forename: Thomas
authors.initials: T
authors.lastname: Klonisch
authors.forename: Eugenia
authors.initials: E
authors.lastname: Makrantonaki
authors.forename: Saadettin
authors.initials: S
authors.lastname: Sel
authors.forename: Ute
authors.initials: U
authors.lastname: Schulze
authors.forename: Fabian
authors.initials: F
authors.lastname: Garreis
authors.forename: Holger
authors.initials: H
authors.lastname: Seltmann
authors.forename: Christos C
authors.initials: CC
authors.lastname: Zouboulis
authors.forename: Friedrich P
authors.initials: FP
authors.lastname: Paulsen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D002460:Cell Line; D003315:Cornea / Q000378:metabolism* / Q000473:pathology; D065306:Corneal Injuries; D004797:Enzyme-Linked Immunosorbent Assay; D005109:Extracellular Matrix / Q000378:metabolism; D005131:Eye Injuries / Q000378:metabolism / Q000473:pathology; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D007765:Lacrimal Apparatus / Q000378:metabolism* / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008875:Middle Aged; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics*; D012065:Relaxin / Q000096:biosynthesis / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013666:Tears / Q000378:metabolism*; D014945:Wound Healing / Q000502:physiology*
chemical_list: C095068:RLN2 protein, human; D012333:RNA, Messenger; D012065:Relaxin