Human Adipose-Derived Mesenchymal Stem Cells Differentiate Into Functional Schwann Cells And Promote Peripheral Facial Nerve Regeneration

Background Trauma, tumor resection and surgical manipulation can all cause peripheral facial nerve injury accompanied with facial paralysis which is a common but devastating condition producing functional, esthetic, mental and psychological deficits in patients. Although numerous modern microsurgical techniques are available for facial nerve repair, the resulting facial function sometimes remains unsatisfactory, together with inevitable post-paralytics syndrome (paresis, synkinesis and dysreflexia). SCs are the most important seed cells for nerve tissue-engineered grafts because of the pivotal role of such cells in the regeneration process of injured nerve tissues. However, cultured autogenic SCs have limited clinical application because of donor site morbidity and the inability to generate a large number of cells quickly. Adipose-derived mesenchymal stem cells have been reported to be a population of self-renewing and multipotent cells that might have clinical therapeutic potentials. Although rodent adipose-derived mesenchymal stem cells can differentiate into Schwann-like cells by a cocktail of growth factors, there is no report about the in vitro differentiated Human adipose-derived mesenchymal stem cells (hASCs) with SC properties and their function after transplantation into model of peripheral nerve injury. Froma clinical standpoint, SC-like cells transdifferented from hASCs rather than rodent cells must be investigated if such studies successfully lead to future translational studies in patients.Aims The main purpose of this study is to investigate the feasibility about the transdifferention of hASCs into SC-like cells and evaluate their roles on the lesioned buccal branch of the facial nerve in a rat model.Methods In the first part, hASCs were transdifferented by a cocktail of grow factors and chemical regents. As the control of human SC, d-hASCs were examed by immunocytochemistry, RT-PCR and western blotting for Schwann cell markers, such as S100, p75, glial fibrillary acidic protein (GFAP).In the second part, using enzyme-linked immunosorbent assay and qRT-PCR methodology, we compared the neurotrophic factors including nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3(NT-3) secreted and expressed by d-hASCs. The sprouting number per neurites, the percent of neurons bearing neuritis and neurite length were measured after indirect co-culture with dorsal root ganglia neurons (DRGN) and NG-108.In the third part, a6-mm segment of the buccal branch of facial nerve was removed and a silicon tube filled with hASCs> t-hASCs-. SC separately was sultured to the stumps of the nerve. At4weeks after surgery, a serious of examinations, such as vibrissae movement, electrophysiological assessment, morphological evaluation of regenerated nerve segments, were performed to evaluate the facial nerve regeneration.Results In the first part, hASCs change their morphology to resemble native SCs and express SC markers, such as S100, GFAP, p75in gene and protein level after induction.In the second part, neurotrophin production of d-hASCs was comparable to naive SC. The d-hASCs enhanced the sprouting number per neurites, the percent of neurons bearing neuritis and neurite length in DRGN and NG-108.In the third part, the transected nerves reconstructed with d-hASCs-seeded silicon conduits achieved satisfying regenerative outcomes associated with morphological and functional improvements which approached those achieved with SC-seeded silicon conduits, and superior to those achieved with silicon conduits alone or hASCs-seeded silicon conduits; Besides, numerous transplanted Dil-labeled dADSCs maintained their acquired SC-phenotype and myelin sheath-forming capacity inside silicon conduits and were involved in the process of axonal regeneration and remyelination.Conclusion Our findings indicated that cells with SC properities and with the ability to support axonal regeneration and reconstruct myelin can be successfully transdifferented from hASCs, and can promote functional recovery after facial nerve injury. This system may be applicable for development of cell-based therapies.