Three-dimensional bioprinting of gelatin methacryloyl hydrogel with a tri-layered vascularized architecture for full-thickness skin regeneration

Abstract

The skin is the largest organ of the human body and is the primary barrier against external stressors. However, in cases of severe skin damage or pathological conditions, the body’s natural physiological repair mechanisms are often insufficient to support effective skin tissue repair and regeneration. Bioprinting, a form of three-dimensional (3D) printing technology, utilizes various biomaterials and cells to construct complex 3D structures, offering the potential to overcome the limitations of conventional tissue-engineered skin and to develop functional skin substitutes. In this study, we developed a 3D bioprinter with excellent printing performance to fabricate vascularized skin substitutes. Through methacrylic anhydride-mediated modification of gelatin, we synthesized gelatin methacryloyl (GelMA) with varying degrees of substitution. The resulting GelMA hydrogel exhibited excellent mechanical properties, swelling ratio, porosity, and rheological properties. To create a hydrogel-multicellular composite bio-ink, we adjusted the concentration of the GelMA solution and co-cultured human immortalized epidermal cells, human foreskin fibroblasts, and human umbilical vein endothelial cells to optimize biological function. Importantly, by fine-tuning the printing parameters, the 3D extrusion-printed lines successfully fused into a continuous membrane, enhancing interlayer bonding and mechanical integrity. This process enabled the construction of a vascularized skin substitute with distinct reticular and papillary layers. In addition, the 3D-printed vascularized skin was implanted into skin defect models established in BALB/c nude mice and New Zealand rabbits to investigate its regenerative capabilities. These findings hold significant implications for the utilization of 3D-printed vascularized skin for improving skin injury repair, thereby advancing the field of skin tissue engineering.

Keywords

Three-dimensional bioprinting / Gelatin methacryloyl / Skin injury / Vascularized skin