Patterning of human epidermal stem cells on undulating elastomer substrates reflects differences in cell stiffness

Area of Science:

• Biomaterials Science
• Cell Biology
• Dermatology

Background:

• The epidermal-dermal junction in human skin undulates, with variations linked to age and disease.
• Epidermal stem cells organize in patterns reflecting this junction's topography in vivo.

Purpose of the Study:

• To investigate how topographical cues from an engineered epidermal-dermal interface influence epidermal stem cell organization and behavior.
• To elucidate the role of mechanical forces and cell stiffness in epidermal stem cell patterning.

Main Methods:

• Primary human epidermal keratinocytes cultured on collagen-coated polydimethylsiloxane (PDMS) substrates mimicking skin topography.
• Atomic Force Microscopy (AFM) to measure cell stiffness (Young's modulus).
• Analysis of cell density, nuclear height, and expression of key proteins (β1 integrin, E-cadherin, Desmoglein 3, F-actin, MAL).

Main Results:

• Keratinocytes patterned on PDMS substrates within 24 hours, with higher cell density and nuclear height at the base versus tips.
• Cells on tips showed increased β1 integrin, E-cadherin, Desmoglein 3, and F-actin, while cells at the base had higher MAL levels.
• Cell stiffness (Young's modulus) was lower on tips compared to the base or flat substrates, dependent on Rho kinase activity and intercellular adhesion.

Conclusions:

• Epidermal stem cell patterning on undulating surfaces is driven by mechanical forces at intercellular junctions.
• Substrate topography significantly influences cell mechanics and protein expression, mimicking in vivo organization.
• Rho kinase activity and intercellular adhesion are critical regulators of cell stiffness and patterning in response to mechanical cues.