Photocrosslinkable silk-based bioinks embedded with growth factor loaded microspheres towards cell-free 3D printing approach for biomimetic regeneration of meniscal tissue

Abstract

Fibrocartilaginous meniscal tear regeneration is a major challenge due to the large avascular regions which suffer several injuries among all age-groups. Mostly, meniscus implants are focused on the development of multi-layered meniscus constructs and scaffolds that mimic the macro-architecture, functionality and mechanical strength. The native human menisci consist of vascular and avascular regions that contain different cellular phenotypes and are hence composed of a gradient of extracellular matrix (ECM) components. The biochemical composition of the inner, middle and outer regions of the knee menisci plays a significant role in the mechanical behavior and its overall functionality. We have developed a photo-polymerizing mulberry and non-mulberry silk-based biomaterial ink which is laden with growth factor loaded gelMA microspheres for the zone-specific regeneration of full thickness meniscus tears using three-dimensional (3D) fabrication. We have fabricated growth factor loaded gelMA microspheres and encapsulated them within the biomaterial ink for controlled release of Connective Tissue Growth Factor (CTGF) and Transforming Growth Factor-beta3 (TGF-β3) from the different zones of the meniscus constructs. The growth factor releasing constructs demonstrate the requisite mechanical resilience, degradability and release behaviour for regeneration of meniscal tissue. The developed growth factor loaded constructs demonstrate zone specific phenotypic differentiation of adipose derived stem cells and extracellular matrix deposition by the differentiated stem cells in vitro. The microsphere loaded constructs were found to be immuno-compatible as well. Therefore, these bioactive microsphere-laden 3D printed meniscus constructs would potentially promote regeneration and integration of meniscal tissue in vivo.