Development of biological assays for disruptive cellular therapy pathways for burn and wound care

Severe burns exceed the skin’s natural repair capacity, requiring rapid and multidisciplinary intervention. Standard treatment typically begins with debridement of necrotic tissue, followed by the application of temporary wound dressings such as allogeneic biological bandages, xenografts, or synthetic substitutes. These dressings help maintain hydration, protect against infection, and reduce fluid loss, but they do not provide definitive closure. For permanent coverage, autologous split-thickness skin grafts remain the gold standard. However, their use is often limited in patients with extensive burns, and harvesting donor skin introduces additional morbidity. To overcome these limitations, cultured epidermal autografts (CEA) and cultured dermo-epidermal autografts (CDEA) have been developed as a major advancement in regenerative burn care. CEA are produced by isolating and expanding keratinocytes from a skin biopsy to generate multiple epidermal sheets; however, the lack of a dermal component often yields suboptimal take and mechanical stability. CDEA address this by combining expanded dermal fibroblasts with keratinocytes to form a bilayer autograft that better mimics native skin. While effective, their production requires 6-8 weeks, primarily due to the slow expansion of autologous fibroblasts. The aim of this work was therefore to identify strategies to shorten the manufacturing process of CDEA. Progenitor fetal fibroblasts FE002-SK2, derived from a clinical-grade cell bank and used in burn patients for more than 10 years at CHUV, were investigated as an alternative. Since they are safe and available “off the freezer,” FE002-SK2 cells represent an immediate substitute for autologous fibroblasts in CDEA manufacturing. Moreover, our analyses have demonstrated that these cells exhibit rapid proliferation, elevated collagen synthesis, and phenotypic stability without unwanted differentiation. For comparative analyses, the experiments in this work were conducted using an optimized de-epidermized dermis (DED) model, which closely mimics the structure of burn- injured skin and provides an alternative to direct animal experimentation. This model allows the evaluation of multiple parameters when cells or skin grafts are applied, including cell adhesion, migration, and epidermal regeneration. The use of the DED model, supported with published data, confirmed that bicomponent constructs combining fibroblasts and keratinocytes outperform keratinocyte-only cultures, with optimal outcomes obtained at a 1:5 fibroblast-to-keratinocyte ratio, leading to the formation of structures that closely resemble those of native human skin. Based on these findings and under the hypothesis that FE002-SK2 cells possess intrinsic scarless healing properties, the development of novel cell therapy formulations appears particularly promising. These could include ready-to-use suspensions, sprays, or collagen-based matrices designed to enable the direct and homogeneous application of cells onto large wound areas. Such approaches hold great potential not only for the treatment of acute burns but also for broader applications in regenerative and aesthetic medicine.