title: Development of stratum corneum chymotrypsin-like protease activity and natural moisturizing factors from birth to 4 weeks of age compared with adults.
abstract: BACKGROUND
  From birth, the functional properties of the neonatal epidermal barrier mature whereby the stratum corneum (SC) hydrates and the skin surface acidifies. The identification of a thinner infant SC compared with adults suggests underdeveloped mechanisms underlying differentiation and desquamation.
  
  
  OBJECTIVE
  To assess the functional properties of the neonatal SC from birth, in conjunction with the quantification of superficial chymotrypsin-like protease activity [kallikrein-7 (KLK-7)] and filaggrin-derived natural moisturizing factors (NMF).
  
  
  METHODS
  A total of 115 neonates recruited to the Oil in Baby SkincaRE (OBSeRvE) randomized controlled trial underwent a full evaluation of the SC at birth (< 72 h old) and at 4 weeks of age (n = 39, no oil control group) using minimally invasive instrumentation and methodology. A cohort of 20 unrelated adults was recruited for comparison.
  
  
  RESULTS
  At birth NMF levels correlated with SC hydration (r = 0·50) and skin-surface pH (r = -0·54). From birth to 4 weeks, transepidermal water loss (TEWL), superficial KLK-7 activity and filaggrin-derived NMF significantly elevated. Impaired epidermal barrier function at birth (> 75th percentile TEWL) was accompanied by significantly elevated chymotrypsin-like protease activity and reduced levels of NMF.
  
  
  CONCLUSIONS
  The biophysical, biological and functional properties of the developing neonatal SC are transitional from birth to 4 weeks of age and differ significantly from adults. The presence of impaired barrier function with elevated protease activity and reduced NMF at birth suggests why certain infants are predisposed to epidermal barrier breakdown and the development of atopic dermatitis.
authors.affiliation: The Academic Unit of Dermatology Research, Department of Infection and Immunity, Faculty of Medicine, Dentistry and Health, The University of Sheffield Medical School, Beech Hill Road, Sheffield, S10 2RX, U.K.. j.chittock@sheffield.ac.uk.
authors.forename: J
authors.initials: J
authors.lastname: Chittock
authors.affiliation: School of Nursing, Midwifery and Social Work, The University of Manchester, Manchester, U.K.
authors.forename: A
authors.initials: A
authors.lastname: Cooke
authors.affiliation: School of Nursing, Midwifery and Social Work, The University of Manchester, Manchester, U.K.
authors.forename: T
authors.initials: T
authors.lastname: Lavender
authors.affiliation: The Academic Unit of Dermatology Research, Department of Infection and Immunity, Faculty of Medicine, Dentistry and Health, The University of Sheffield Medical School, Beech Hill Road, Sheffield, S10 2RX, U.K.
authors.forename: K
authors.initials: K
authors.lastname: Brown
authors.affiliation: The Academic Unit of Dermatology Research, Department of Infection and Immunity, Faculty of Medicine, Dentistry and Health, The University of Sheffield Medical School, Beech Hill Road, Sheffield, S10 2RX, U.K.
authors.forename: A
authors.initials: A
authors.lastname: Wigley
authors.affiliation: Institute of Human Development, The University of Manchester, Manchester, U.K.|Sidra Neonatology Center of Excellence, Sidra Medical and Research Center, Doha, Qatar.
authors.forename: S
authors.initials: S
authors.lastname: Victor
authors.affiliation: The Academic Unit of Dermatology Research, Department of Infection and Immunity, Faculty of Medicine, Dentistry and Health, The University of Sheffield Medical School, Beech Hill Road, Sheffield, S10 2RX, U.K.|The Pediatric Dermatology Clinic, Sheffield Children's Hospital, Sheffield, U.K.
authors.forename: M J
authors.initials: MJ
authors.lastname: Cork
authors.affiliation: The Academic Unit of Dermatology Research, Department of Infection and Immunity, Faculty of Medicine, Dentistry and Health, The University of Sheffield Medical School, Beech Hill Road, Sheffield, S10 2RX, U.K.
authors.forename: S G
authors.initials: SG
authors.lastname: Danby
mesh_terms: D000328:Adult; D055592:Biophysical Phenomena / Q000502:physiology; D001834:Body Water / Q000502:physiology; D053818:Chymases / Q000378:metabolism*; D015331:Cohort Studies; D004817:Epidermis / Q000201:enzymology*; D005260:Female; D000091344:Filaggrin Proteins; D064368:Healthy Volunteers; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D014870:Water Loss, Insensible / Q000502:physiology
chemical_list: C000717249:FLG protein, human; D000091344:Filaggrin Proteins; D053818:Chymases