title: Selective matrix (hyaluronan) interaction with CD44 and RhoGTPase signaling promotes keratinocyte functions and overcomes age-related epidermal dysfunction.
abstract: BACKGROUND
  Mouse epidermal chronologic aging is closely associated with aberrant matrix (hyaluronan, HA)-size distribution/production and impaired keratinocyte proliferation/differentiation, leading to a marked thinning of the epidermis with functional consequence that causes a slower recovery of permeability barrier function.
  
  
  OBJECTIVE
  The goal of this study is to demonstrate mechanism-based, corrective therapeutic strategies using topical applications of small HA (HAS) and/or large HA (HAL) [or a sequential small HA (HAS) and large HA(HAL) (HAs→HAL) treatment] as well as RhoGTPase signaling perturbation agents to regulate HA/CD44-mediated signaling, thereby restoring normal epidermal function, and permeability barrier homeostasis in aged mouse skin.
  
  
  METHODS
  A number of biochemical, cell biological/molecular, pharmacological and physiological approaches were used to investigate matrix HA-CD44-mediated RhoGTPase signaling in regulating epidermal functions and skin aging.
  
  
  RESULTS
  In this study we demonstrated that topical application of small HA (HAS) promotes keratinocyte proliferation and increases skin thickness, while it fails to upregulate keratinocyte differentiation or permeability barrier repair in aged mouse skin. In contrast, large HA (HAL) induces only minimal changes in keratinocyte proliferation and skin thickness, but restores keratinocyte differentiation and improves permeability barrier function in aged epidermis. Since neither HAS nor HAL corrects these epidermal defects in aged CD44 knock-out mice, CD44 likely mediates HA-associated epidermal functions in aged mouse skin. Finally, blockade of Rho-kinase activity with Y27632 or protein kinase-Nγ activity with Ro31-8220 significantly decreased the HA (HAS or HAL)-mediated changes in epidermal function in aged mouse skin.
  
  
  CONCLUSIONS
  The results of our study show first that HA application of different sizes regulates epidermal proliferation, differentiation and barrier function in aged mouse skin. Second, manipulation of matrix (HA) interaction with CD44 and RhoGTPase signaling could provide further novel therapeutic approaches that could be targeted for the treatment of various aging-related skin disorders.
authors.affiliation: Department of Medicine, University of California San Francisco and VA Medical Center, United States. Electronic address: lilly.bourguignon@ucsf.edu.
authors.forename: Lilly Y W
authors.initials: LY
authors.lastname: Bourguignon
authors.forename: Gabriel
authors.initials: G
authors.lastname: Wong
authors.forename: Weiliang
authors.initials: W
authors.lastname: Xia
authors.forename: Mao-Qiang
authors.initials: MQ
authors.lastname: Man
authors.forename: Walter M
authors.initials: WM
authors.lastname: Holleran
authors.forename: Peter M
authors.initials: PM
authors.lastname: Elias
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D049109:Cell Proliferation; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004817:Epidermis / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology; D005109:Extracellular Matrix / Q000276:immunology / Q000502:physiology; D000091344:Filaggrin Proteins; D006801:Humans; D018960:Hyaluronan Receptors / Q000235:genetics / Q000378:metabolism*; D006820:Hyaluronic Acid / Q000008:administration & dosage / Q000737:chemistry / Q000378:metabolism*; D007381:Intermediate Filament Proteins / Q000235:genetics; D015603:Keratinocytes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008970:Molecular Weight; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011498:Protein Precursors / Q000235:genetics; D015398:Signal Transduction; D015595:Skin Aging / Q000187:drug effects / Q000473:pathology / Q000502:physiology*; D020741:rho GTP-Binding Proteins / Q000378:metabolism*; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors
chemical_list: C476399:Cd44 protein, mouse; D004791:Enzyme Inhibitors; D000091344:Filaggrin Proteins; D018960:Hyaluronan Receptors; D007381:Intermediate Filament Proteins; D011498:Protein Precursors; C032253:involucrin; D006820:Hyaluronic Acid; C061570:protein kinase N; D054460:rho-Associated Kinases; D011493:Protein Kinase C; D020741:rho GTP-Binding Proteins
keywords: CD44; Keratinocyte functions; Matrix hyaluronan; RhoGTPase signaling; Skin aging