| Tendon is highly prone to injury,which often results in instability and abnormal joint movement.Due to its hypovascularity and limited cellular content,auto-repair of tendon is extremely inefficient and remains a clinical challenge.Currently,tendon therapy includes autografts,allografts,xenografts,tenorrhaphy,and physical therapy etc,while the results are unsatisfied,as the biochemical properties and functions of repaired tendon tissue never reach to those of intact tendon.Therefore,more effective therapeutic techniques for tendon repair are urgently required.In the last decade,tissue engineering became a promising approach for tendon repair and regeneration.However,there are still some critical problems to be solved.The first is to optimize physical environment for ex vivo tenocytes development.The second is to maintain the phenotype of ex vivo tenocytes.And the last is to create a 3D space to support tenogenesis for in vivo application.Based on our study,we successfully established a robust,stepwise topographic strategy to commit teno-lineage differentiation of hiPSCs by sequential culture on smooth plastic surface and well-aligned chitosan-based ultrafine fibers.Cells derived from hiPSCs cultured on smooth plastic surface possessed the same proliferative and multipotent properties as mesenchymal stem cells.After subsequential culture on the well-aligned fibers,these cells were differentiated into tenocytes which were confirmed by the expression of tendon-specific genes and proteins.However,we also found that the ex vivo tendon stem/progenitor cells(TSPCs)were prone to dedifferentiate and lose their functions.This phenotype change was a dynamic process associated with histone deacetylation.Suppression of HDACs(histone deacetylases)of TSPCs by TSA at early passage numbers could maintain their phenotype so as to generate greater numbers of functional TSPCs for tendon repair.Finally,based on the above results,we developed a novel well-aligned fiber scaffold combined with epigenetic bioactive TSA for tendon regeneration.The composite of TSA and topographical cue played a synergistic effect on teno-lineage differentiation and Achilles tendon defect repair.In summary,this study enriched our knowledge about the physical regulation on tenocyte development and the epigenetic regulation on TSPCs maintenance.The combination of epigenetic factors with well-aligned scaffold provided a novel and important strategy for the tendon regeneration. |
