Platelet lysate hydrogel-coated suture threads for tendon tissue engineering

Tendon injuries constitute significant clinical problems ascribable both to the limit natural healing capacity of this tissue and to the inefficiency of the current repair treatments. Tendon tissue engineering (TTE) represents an alternative approach that, through highly multidisciplinary strategies and techniques, aims to promote the generation of adequate tissue engineered tendons. Particularly, the development of biomimetic and micro-engineered hydrogels has been broadly investigated as a potential strategy, due to their ability to provide physiological support for cells mimicking the cellular instructive microenvironment. Based on this concept, herein, it is explored the use of platelet lysate (PL) to create a hydrogel layer as a depot of therapeutic factors to induce tenogenic differentiation of encapsulated human adipose-derived stem cells (hASCs). Thus, commercially available silk suture threads were first immersed into a thrombin/calcium chloride (CaCl2) solution and then incubated in PL, containing hASCs, to allow the hydrogel formation. Interestingly, cells were found viable and able to sense the presence of chemotactic factors, being aligned within and at the surface of the thread core. Furthermore, the presence of an ordered newly synthesized extracellular matrix (ECM) together with the expression of tendon-related markers demonstrate the potential use of this method for the generation of a tendon-specific microenvironment. Finally, the impressive silk sutures mechanical properties discovered, suggest the perspective clinical applications of these constructs to bridge injured tendons or as starting blocks in the development of more complex constructs for tendon repair approaches.