Simple method for the production of rete ridges in human dermo-epidermal skin substitutes

The engineering of autologous dermo-epidermal skin substitutes aims to replicate the functional and structural properties of normal human skin for treating severe burns, trauma, congenital giant nevi, and necrosis-inducing diseases. We established autologous dermo-epidermal skin analogues, the quality of which is presently being assessed in phase II and III trials. A primary challenge we are facing involves the incorporation of undulating epidermal extensions, known as rete ridges, into the dermis. This integration enhances mechanical stiffness at the dermal-epidermal junction and extend the capillary-epidermal interface, thereby facilitating wound healing. To address this challenge, we employed a refined version of our laboratory's established protocol, utilizing simpler technologies. We specifically used a hydrogel formulated from pure type I collagen mixed with fibroblasts, which was then subjected to plastic compression to ensure mechanical stability. To introduce dermal papillae, we modified the surface of the compression piston to create a 'wavy' texture, mimicking natural skin. This piston acts as a mould during both the gelation and plastic compression phases of the hydrogel. As a result, we successfully developed rete ridges with the expected dimensions, but their stability after keratinocyte seeding remains an issue. In summary, while operational simplicity and avoidance of potentially toxic crosslinkers, provides a safe and easily adoptable route to replicating the natural structure of the rete ridges, we still face challenges in controlling ridge dimensions and maintaining the integrity of the dermal-epidermal junction structure.