title: Opioid growth factor modulation of corneal epithelium: uppers and downers.
abstract: OBJECTIVE
  This paper presents a concise review of the role of the intrinsic opioid growth regulation system (IOGRS) in homeostasis and wound repair of the corneal epithelium.
  
  
  METHODS
  The article is a summary of published research on the topic.
  
  
  RESULTS
  The native opioid peptide, [Met(5)]-enkephalin, also termed opioid growth factor (OGF), has been demonstrated to be present in a wide variety of classes of the phylum. Chordata, and acts as an autocrine/paracrine produced, tonically active, receptor specific, negative growth modulating factor in homeostatic (uninjured) corneal epithelium in humans and non-primates. Similarly, OGF acts to down-regulate epithelial cell division and migration of corneal epithelium in the closing of corneal epithelial abrasions. Such repair can be up-regulated (hastened) in non-diabetic animals by treatment with exogenous administration of the potent opioid antagonist, naltrexone (NTX). The system also is functional in diabetic animals and can be manipulated to restore epithelial wound healing rates to normal.
  
  
  CONCLUSIONS
  The IOGRS plays a vital role in supporting corneal epithelial homeostasis, and in modulating closure of epithelial wounds. The system should provide opportunities for novel therapies especially for corneal epithelial wound healing disorders.
authors.affiliation: Department of Ophthalmology, Penn State's Milton S. Hershey Medical Center, 500 University Drive, Hershey, PA 17033, USA. jxs14@psu.edu
authors.forename: Joseph W
authors.initials: JW
authors.lastname: Sassani
authors.forename: Ian S
authors.initials: IS
authors.lastname: Zagon
authors.forename: Patricia J
authors.initials: PJ
authors.lastname: McLaughlin
mesh_terms: D000818:Animals; D003315:Cornea / Q000502:physiology; D004247:DNA / Q000096:biosynthesis; D003920:Diabetes Mellitus / Q000503:physiopathology; D004723:Endorphins / Q000502:physiology*; D019573:Epithelium, Corneal / Q000293:injuries / Q000502:physiology*; D006133:Growth Substances / Q000502:physiology*; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D011957:Receptors, Opioid / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D014945:Wound Healing / Q000502:physiology
chemical_list: D004723:Endorphins; D006133:Growth Substances; D011957:Receptors, Opioid; D004247:DNA