Evaluation of phosphodiesterase inhibitors in neural cell models for the development of functionalized chitosan microstructured films as scaffolds for peripheral nerve regeneration.

Following severe peripheral nerve injuries, effective repair requires both surgical strategies, based on scaffolds that provide structural guidance for regeneration, and biomolecular stimuli, able to enhance the coordinated interaction between regenerating axons and Schwann cells. In this context, an integrated approach that combines physical and biochemical cues could be promising. We here investigated the use of phosphodiesterase inhibitors (PDEIs), as pro-regenerative agents, and biomaterial guidance, with the aim to enhance regenerative outcomes. In particular, sildenafil (PDE5-I) and rolipram (PDE4-I) were evaluated on neuronal and glial cell models, revealing complementary and temporally distinct effects. Sildenafil promoted motor neuron neurite outgrowth and enhanced a pro-regenerative signaling, including BDNF upregulation, whereas rolipram induced Krox20 in a model of glial Schwann cells and supported a later stage of regeneration associated with myelination. Based on these findings, glycerol-blended chitosan plasticized films, micro-patterned with directional geometries and functionalized with sildenafil, as a bioactive component, were developed through a solvent casting process. The sildenafil-functionalized glycerol-chitosan films demonstrated effective drug loading and sustained release in biomimicking conditions, without compromising their softness and ability to guide cell alignment. In vitro studies with Schwann cells confirmed that the combined presence of biochemical stimulation, nerve mechanical compliance and anisotropic topography promoted cell polarization and directional migration. Overall, these results support an integrated approach combining microtopographical and pharmacological stimuli and identify sildenafil-loaded scaffolds as a promising strategy for peripheral nerve regeneration.