Production of injectable marine collagen-based hydrogel for the maintenance of differentiated chondrocytes in tissue engineering applications

Cartilage is an avascular tissue with limited ability of self-repair. The use of autologous chondrocyte transplants represent an effective strategy for cell regeneration; however, preserving the differentiated state, which ensures the ability to regenerate damaged cartilage, represents the main challenge during in vitro culturing. For this purpose, we produced an injectable marine collagen-based hydrogel, by mixing native collagen from the jellyfish Rhizostoma pulmo with hydroxy-phenyl-propionic acid (HPA)-functionalized marine gelatin. This biocompatible hydrogel formulation, due to the ability of enzymatically reticulate using horseradish peroxidase (HPR) and HO, gives the possibility of trap cells inside, in the absence of cytotoxic effects, during the crosslinking process. Moreover, it enables the modulation of the hydrogel stiffness merely varying the concentration of HO without changes in the concentration of polymer precursors. The maintenance of differentiated chondrocytes in culture was then evaluated via morphological analysis of cell phenotype, GAG production and cytoskeleton organization. Additionally, gene expression profiling of differentiation/dedifferentiation markers provided evidence for the promotion of the chondrogenic gene expression program. This, combined with the biochemical properties of marine collagen, represents a promising strategy for maintaining in vitro the cellular phenotype in the aim of the use of autologous chondrocytes in regenerative medicine practices.