Polymeric membranes modulate human keratinocyte differentiationin specific epidermal layers

In vitro models of human bioengineered skin substitutes are an alternative to animal experimentationfor testing the effects and toxicity of drugs, cosmetics and pollutants. For the first time specific and dis-tinct human epidermal strata were engineered by using membranes and keratinocytes. To this purpose,biodegradable membranes of chitosan (CHT), polycaprolactone (PCL) and a polymeric blend of CHT-PCLwere prepared by phase-inversion technique and characterized in order to evaluate their morphologi-cal, physico-chemical and mechanical properties. The capability of membranes to modulate keratinocytedifferentiation inducing specific interactions in epidermal membrane systems was investigated. The over-all results demonstrated that the membrane properties strongly influence the cell morpho-functionalbehaviour of human keratinocytes, modulating their terminal differentiation, with the creation of specificepidermal strata or a fully proliferative epidermal multilayer system. In particular, human keratinocytesadhered on CHT and CHT-PCL membranes, forming the structure of the epidermal top layers, such asthe corneum and granulosum strata, characterized by withdrawal or reduction from the cell cycle andcell proliferation. On the PCL membrane, keratinocytes developed an epidermal basal lamina, with highproliferating cells that stratified and migrated over time to form a complete differentiating epidermalmultilayer system.