title: Pilot Comparative Study of the Topical Action of a Novel, Crosslinked Resilient Hyaluronic Acid on Skin Hydration and Barrier Function in a Dynamic, Three-Dimensional Human Explant Model.
abstract: BACKGROUND
  Hyaluronic acid (HA) is a popular ingredient in topical formulations for cosmetic improvement of the skin. Most formulations contain linear, non-crosslinked HA oligomers, low molecular weight (LMW) HA, and/or high molecular weight (HMW) HA. Crosslinking of HA enhances its clinical longevity and mechanical characteristics. The objective of this study was to characterize the topical effects of a new, crosslinked resilient HA (RHA) that is also available as a cohesive, tissue-integrating injectable filler, compared with non-crosslinked HMW HA and LMW HA. Living human skin explants that preserve the 3-dimensional structure of in vivo skin were used to maximize clinical relevance.
  
  
  METHODS
  Standardized doses of each HA product were applied daily for 9 days to human skin explant surfaces. Untreated explants served as controls. Water content of the stratum corneum and entire epidermis was analyzed by Raman spectroscopy. Transepidermal water loss (TEWL) was measured to assess skin barrier function. Explant morphology and microrelief were evaluated by optical and scanning electron microscopy.
  
  
  RESULTS
  Crosslinked RHA achieved a significant increase in epidermal water content (7.6%) over the control. Spectral cartography confirmed a higher epidermal water content with RHA than with HMW HA or LMW HA. TEWL was reduced by 27.8% with RHA, and by 15.6% with HMW HA, but increased by 55.5% with LMW HA. Cutaneous microrelief improved with RHA. Corneocyte cohesion improved with RHA and HMW HA.
  
  
  CONCLUSIONS
  This comparative, multimodal study demonstrated greater benefits of topical crosslinked RHA over linear HMW HA or LMW HA in reducing TEWL, retaining and redistributing water within the epidermis, maintaining skin integrity, and improving skin barrier structure and function. RHA was a more efficacious humectant than LMW HA, and a more efficacious occlusive moisturizer than HMW HA. These integrative epidermal repair activities are of significant value for addressing primary deficits of aging skin, improving tolerance to retinoids and other topical agents, and optimizing procedural outcomes. A combination of topical and injectable HA provides an elegant model of synergistic, multi-level skin restoration.
authors.forename: Hema
authors.initials: H
authors.lastname: Sundaram
authors.forename: Nicolas
authors.initials: N
authors.lastname: Mackiewicz
authors.forename: Emeline
authors.initials: E
authors.lastname: Burton
authors.forename: Laurent
authors.initials: L
authors.lastname: Peno-Mazzarino
authors.forename: Elian
authors.initials: E
authors.lastname: Lati
authors.forename: Stéphane
authors.initials: S
authors.lastname: Meunier
mesh_terms: D000279:Administration, Cutaneous; D000368:Aged; D003432:Cross-Linking Reagents / Q000008:administration & dosage* / Q000737:chemistry; D004339:Drug Compounding; D005260:Female; D006801:Humans; D006820:Hyaluronic Acid / Q000008:administration & dosage* / Q000737:chemistry; D008954:Models, Biological; D009924:Organ Culture Techniques; D010865:Pilot Projects; D015595:Skin Aging / Q000187:drug effects* / Q000473:pathology; D012879:Skin Physiological Phenomena / Q000187:drug effects*; D014870:Water Loss, Insensible / Q000187:drug effects* / Q000502:physiology
chemical_list: D003432:Cross-Linking Reagents; D006820:Hyaluronic Acid