Tendon ECM modified bioactive electrospun fibers promote MSC tenogenic differentiation and tendon regeneration

Proper niche environment is the key factor for mesenchymal stem cells (MSCs) involved tendon-lineage differentiation and regeneration. In the present study, soluble tendon derived extracellular matrix (sTECM) was used to modify aligned electrospun fibers with acid neutralizing effect in order to create an optimal niche environment for tendon regeneration, and its efficacy was evaluated using mouse MSC tenogenic differentiation in vitro and rat Achilles tendon regeneration in vivo. The results showed that sTECM modified ultrafine fibers were more cytocompatible and capable of inducing a predominant tenogenic phenotype of mouse MSCs with the enhanced expression of tendon markers including scleraxis, tenomodulin, collagen III, mohawk homeobox, decorin, fibromodulin and biglycan. By contrast, pure sTECM components led to enhanced multi-lineage differentiation of mouse MSCs including tenogenic lineage. This inductive effect was further enhanced when unilateral mechanical loading was applied in vivo. Moreover, the implantation of sTECM modified scaffold created an ideal niche environment including bioactive sTECM components, topological and mechanical signals, upon in vivo implantation for in situ tendon regeneration. As the results, sTECM modified scaffold in comparison with the non-modified one regenerated higher quality tendon tissue with the features of more mature tissue structure, better tissue organization, cell density and alignment as well as better collagen ultrastructure. Quantitative analysis demonstrated significantly bigger collagen fibril diameter, stronger mechanical property and better tissue grading score and higher expression levels of tenogenic markers when compared to those of control scaffold (p < 0.05). This study demonstrated that sTECM modified pH-neutral ultrafine fibers may represent a novel bioactive scaffold for in situ tendon regeneration, which deserves further investigation in large animals.