Biphasic Hydrogels Integrating Mineralized and Anisotropic Features for Interfacial Tissue Engineering

The innate graded structural and compositional profile of musculoskeletal tissue interfaces is disrupted and replaced by fibrotic tissue in the context of disease and degeneration. Tissue engineering strategies focused on the restoration of the transitional complexity found in those junctions present special relevance for regenerative medicine. Herein, we developed a gelatin-based multiphasic hydrogel system, where sections with distinct composition and microstructure were integrated in a single unit. In each phase, hydroxyapatite particles or cellulose nanocrystals (CNC) were incorporated into an enzymatically cross-linked gelatin network to mimic bone or tendon tissue, respectively. Stiffer hydrogels were produced with the incorporation of mineralized particles, and magnetic alignment of CNC resulted in anisotropic structure formation. The evaluation of the biological commitment with human adipose-derived stem cells toward the tendon-to-bone interface revealed an aligned cell growth and higher synthesis and deposition of tenascin in the anisotropic phase, while the activity of the secreted alkaline phosphatase and the expression of osteopontin were induced in the mineralized phase. These results highlight the potential versatility offered by gelatin-transglutaminase enzyme tandem for the development of strategies that mimic the graded, composite, and complex intersections of the connective tissues.