In Vitro And In Vivo Investigation Of Engineered Tendon Using Dental Pulp Stem Cells

Tendon attaches muscles to the bones and transmits tensile loads. A damagedtendon never returns to its original biochemical properties and results to scar tissueformation. Tendon injuries are difficult to treat and often cause significant dysfunctionand disability, leading to instability, abnormal joint movement and pain. Traditionaltreatments can only reduce pain over a long healing phase, whereas a surgical methodmay be needed to repair or replace the damaged tendons. However, these therapieshave some inevitable complications, such as donor site morbidity, risk of diseasetransmission, poor graft integration, and high rates of recurrent tearing. Significantprogress has been made in tendon engineering research in the past 2 decades, whichreveals a promising prospect for engineered tendon repair and regeneration.Tissue engineering utilizes a combination of seed cells, bio-scaffolds, andbioactive molecules to replace or repair injured tissues. Previous tendon tissueengineering researchers also proved the efficacy of cell transplantation with scaffolds.However there are three challenges remained to be overcome before clinicaltranslation. One is how to get the enough seed cells? The second is how to design theteno-lineage inductive scaffold. The last one is the effect of mechanical stretchon tenogenic differentiation. However, none of the key components of thistechnique has not been optimized.The current study includes four parts: We firstly isolated human adult dental pulpstem cells(DPSCs), and showed that they possess several universal criteria of stemcells, including clonogenicity, self-renewal and multipotent differentiation capacity.Then we investigated the expression of tendon related markers in human native dentalpulp tissue and human tendon. Surprisingly, some markers were strongly expressed inodotoblastic layers, but weakly in cell-rich zone. Collagens I and VI were stronglyexpressed in the whole dental pulp tissue and DPSCs. In the third part, weinvestigated the molecular mechanisms underlying the synergistic effect of biologicalscaffold and mechanical stretch on tenogenic differentiation in DPSCs engineeredtendon in vitro. The activity of DPSCs on aligned fibers was investigated andcompared with randomly-oriented fibers. We found aligned fiber initiatedteno-lineage differentiation and is suitable for tendon tissue engineering. Thedifferentiation of dental pulp stem cell may be regulated by the alignment of fibersand mechanical stretch. Finally, we studied the effect of mechanical stimulus onfiber-like tissue remodeling in vivo. In vivo mouse model demonstrated that a maturetendon-like tissue could be formed using DPSCs in aligned PGA scaffolds withmechanical loading. In a word this study demonstrated that DPSCs could be analternative cell source for engineering functional tendons.