SCAFFOLD-FREE TISSUE ENGINEERING USING DENTAL PULP CELLS TO ENHANCE FACIAL NERVE REGENERATION

Introduction: Peripheral nerve damage is a commonly encountered clinical problem caused by trauma, disease, or surgical injury. The current gold standard treatment utilizes autologous nerve grafts; however, this requires a prolonged repair time and full functional recovery is not achieved. Neurotrophic factors (NTF) are proteins known to enhance axon regeneration and growth. Dental pulp tissue contains a population of stem/progenitor cells (DPC) that secrete NTFs a characteristic likely due to their neural crest origin. Furthermore, these cells are easily accessible from autologous sources. Basic fibroblast growth factor / FGF2 is a growth factor considered as a potent mitogen and help mesenchymal stem cells maintain their stemness. The goal of this study was to develop and characterize scaffold-free DPC sheets as a NTF delivery system. We hypothesize that DPC sheets will express NTFs including brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factors (GDNF) and neurotrophin-3 (NT-3), and will accelerate repair of damaged nerves and improve functional recovery. Materials & Methods: In this study, we fabricated scaffold-free cell sheets by culturing DPCs to super confluence with and without fibroblast growth factor 2 (FGF2). NTF gene and protein expression of DPC sheets was assessed using qRT-PCR and ELISA, respectively. DPC sheets secretome was used to culture SH-SY5Y neurons to test the functional effect of the secretome and validated its effect by using NTF inhibitors on neurite extension in vitro. Results: DPC sheets were formed that are robust and can be easily handled. DPC sheets expressed BDNF, GDNF, NT3 at the gene and protein level and the expressions increased with the addition of FGF2 to the culture medium. NTF present in DPC sheet secretome enhanced neurite extension in SH-SY5Y neurons indicating that DPC sheets have a positive functional effect on neurons and the addition of NTF inhibitors reversed this effect confirming the effect of NTF on neurons. Conclusion: DPC sheets can be formed which secrete neurotrophic factors and enhance neurite extension in neurons. Scaffold-free DPC sheets show great promise as a new therapy to accelerate the regeneration of damaged peripheral nerves and improve functional recovery