Dynamic culture substrates that mimic the topography of the epidermal-dermal junction.

The junction between the epidermal and dermal layers of human skin undulates, the width and depth of the undulations varying with age and disease. We previously showed that when primary human epidermal keratinocytes are seeded on collagen-coated undulating static polydimethylsiloxane (PDMS) elastomer substrates, the stem cells, differentiated cells and proliferating cells become patterned in response to cues from the underlying substrate. To investigate how patterning occurs over time, we have now created a dynamic model, in which a collagen-coated PLGA membrane is placed over a polyimide sheet containing circular holes, differing in diameter and spacing. When a vacuum is applied the membrane is induced to undulate, the heights of the undulations depending on the pressure applied and the size of the holes. We observed clustering of cells with high levels of β1 integrin expression, a stem cell marker, in the base of the undulations within 48h of applying the vacuum. Differentiating, involucrin-positive cells did not cluster; however, there was clustering of cells with high E-cadherin expression and nuclear YAP. Rho kinase inhibition resulted in loss of clustering, implicating a role for Rho family members in the process.