The skin is the largest human organ, and defects in the skin with a diameter greater than 4 cm do not heal without treatment. Allogeneic skin transplantation has been used to allow wound healing, but many grafts do not survive after implantation, due to multiple complications in the procedure. In the present study, the vascularization of three-dimensional (3D) printed full-thickness skin grafts was investigated. Dermal-epithelial grafts were transplanted into a nude mouse model to evaluate integration with the host tissue and the extent of wound healing. To create microvessels in the skin grafts, a bilayer structure consisting of human dermal fibroblasts, keratinocytes, and microvascular endothelial cells was designed and fabricated using an extruded 3D printer. Human dermal fibroblasts and human microvascular endothelial cells were mixed with gelatin-sodium alginate composite hydrogel as the dermis, and human keratinocytes were mixed with gel as the epithelium. Confocal imaging allowed visualization of the location of the cells in the double-layer skin grafts. A full-thickness wound was created on the backs of nude mice and then covered with a double-layer skin graft. Various groups of mice were tested. Animals were euthanized and tissue samples collected after specified time points. Compared with the control group, wound contraction improved by approximately 10%. Histological analysis demonstrated that the new skin had an appearance similar to that of normal skin and with a significant degree of angiogenesis. The results of the immunohistochemical analysis demonstrated that the transplanted cells survived and participated in the healing process.

No abstract

No abstract

No abstract

Purpose Reconstructing multi-layer tissue structure using cell printing to repairing complex tissue defect is a challenging task, especially using in situ bioprinting. This study aims to propose a method of in situ bioprinting multi-tissue layering and path planning for complex skin and soft tissue defects. Design/methodology/approach The scanned three-dimensional (3D) point cloud of the skin and soft tissue defect is taken as the input data, the depth value of the defect is then calculated using a two-step grid division method, and the tissue layer is judged according to the depth value. Then, the surface layering and path planning in the normal direction are performed for different tissue layers to achieve precise tissue layering filling of complex skin soft tissue defects. Findings The two-step grid method can accurately calculate the depth of skin and soft tissue defects and judge the tissue layer accordingly. In the in situ bioprinting experiment of the defect model, the defect can be completely closed. The defect can be reconstructed in situ, and the reconstructed structure is basically the same as the original skin tissue structure, proving the feasibility of the proposed method. Originality/value This study proposes an in situ bioprinting multi-tissue layering and path planning method for complex skin and soft tissue defects, which can directly convert the scanned 3D point cloud into a multi-tissue in situ bioprinting path. The printed result has a similar structure to that of the original skin tissue, which can make cells or growth factors act on the corresponding tissue layer targets.

No abstract