Cellular Changes That Accompany Shedding of Human Corneocytes

J Invest Dermatol. 2012 Oct;132(10):2430-2439. doi: 10.1038/jid.2012.173. Epub 2012 Jun 28.

Abstract

Corneocyte desquamation has been ascribed to the following: 1) proteolytic degradation of corneodesmosomes (CDs); 2) disorganization of extracellular lamellar bilayers; and/or 3) "swell-shrinkage-slough" from hydration/dehydration. To address the cellular basis for normal exfoliation, we compared changes in lamellar bilayer architecture and CD structure in D-Squame strips from the first versus fifth stripping ("outer" vs. "mid"-stratum corneum (SC), respectively) from nine normal adult forearms. Strippings were either processed for standard electron microscopy (EM) or for ruthenium-, or osmium-tetroxide vapor fixation, followed by immediate epoxy embedment, an artifact-free protocol, which, to our knowledge, is previously unreported. CDs are largely intact in the mid-SC, but replaced by electron-dense (hydrophilic) clefts (lacunae) that expand laterally, splitting lamellar arrays in the outer SC. Some undegraded desmoglein 1/desmocollin 1 redistribute uniformly into corneocyte envelopes (CEs) in the outer SC (shown by proteomics, Z-stack confocal imaging, and immunoEM). CEs then thicken, likely facilitating exfoliation by increasing corneocyte rigidity. In vapor-fixed images, hydration only altered the volume of the extracellular compartment, expanding lacunae, further separating membrane arrays. During dehydration, air replaced water, maintaining the expanded extracellular compartment. Hydration also provoked degradation of membranes by activating contiguous acidic ceramidase activity. Together, these studies identify several parallel mechanisms that orchestrate exfoliation from the surface of normal human skin.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adult
  • Dehydration / metabolism
  • Dehydration / pathology
  • Desmocollins / metabolism
  • Desmoglein 1 / metabolism
  • Desmosomes / metabolism
  • Desmosomes / pathology*
  • Desmosomes / ultrastructure
  • Epidermis / metabolism
  • Epidermis / pathology*
  • Epidermis / ultrastructure*
  • Extracellular Matrix / metabolism
  • Extracellular Matrix / pathology*
  • Extracellular Matrix / ultrastructure*
  • Fixatives
  • Glycoproteins / metabolism
  • Humans
  • Intercellular Signaling Peptides and Proteins
  • Microscopy, Electron

Substances

  • CDSN protein, human
  • DSC1 protein, human
  • Desmocollins
  • Desmoglein 1
  • Fixatives
  • Glycoproteins
  • Intercellular Signaling Peptides and Proteins