The epidermal barrier undergoes continuous renewal through a process called homeostasis, during which epidermal stem cells provide new keratinocytes that will go through a complex maturation process to replace corneocytes that are constantly lost during the desquamation and tissue turnover.

Active ingredients with an effect on the epidermal homeostasis can be screened by monitoring tissue cohesion markers and differentiation markers. The biological endpoints are assessed by immunofluorescence of proteins involved in:

  • Tight junctions (claudins, occluding, ZO-1)
  • Corneo-desmosomes (corneodesmosin, desmogleins)
  • Cornified envelope (involucrin, loricrin, filaggrin)

The effects of a test item on the skin barrier can also be evaluated by measuring:

  • Trans-epidermal electric resistance (TEER)
  • Skin diffusion of chromogenic dyes

StratiCELL has also designed a TaqMan low density qPCR array to study the expression levels of 96 target genes carefully selected and identified as key factors in the epidermal barrier and homeostasis functions.