Large full-thickness wounded skin regeneration using 3D-printed elastic scaffold with minimal functional unit of skin.

Traditional tissue engineering skin are composed of living cells and natural or synthetic scaffold. Besize the time delay and the risk of contamination involved with cell culture, the lack of autologous cell source and the persistence of allogeneic cells in heterologous grafts have limited its application. This study shows a novel tissue engineering functional skin by carrying minimal functional unit of skin (MFUS) in 3D-printed polylactide-co-caprolactone (PLCL) scaffold and collagen gel (PLCL + Col + MFUS). MFUS is full-layer micro skin harvested from rat autologous tail skin. 3D-printed PLCL elastic scaffold has the similar mechanical properties with rat skin which provides a suitable environment for MFUS growing and enhances the skin wound healing. Four large full-thickness skin defects with 30 mm diameter of each wound are created in rat dorsal skin, and treated either with tissue engineering functional skin (PLCL + Col + MFUS), or with 3D-printed PLCL scaffold and collagen gel (PLCL + Col), or with micro skin islands only (Micro skin), or without treatment (Normal healing). The wound treated with PLCL + Col + MFUS heales much faster than the other three groups as evidenced by the fibroblasts migration from fascia to the gap between the MFUS dermis layer, and functional skin with hair follicles and sebaceous gland has been regenerated. The PLCL + Col treated wound heals faster than normal healing wound, but no skin appendages formed in PLCL + Col-treated wound. The wound treated with micro skin islands heals slower than the wounds treated either with tissue engineering skin (PLCL + Col + MFUS) or with PLCL + Col gel. Our results provide a new strategy to use autologous MFUS instead "seed cells" as the bio-resource of engineering skin for large full-thickness skin wound healing.

Fully Reduced HMGB1-Containing Peptide-Based Polyurethane Scaffold with Minimal Functional Unit of Skin (MFUS) Enhances Large and Deep Wounded Skin Healing.

A novel peptide-based polymer is developed by lysine-diisocyanate (LDI), glycerol (Gly), and fully reduced HMGB1 (frHMGB1). This frHMGB1-LDI-Gly polymer either forms sponge-like foam (scaffold) or a hydrogel or a film under different reaction conditions. It degrades into nontoxic lysine, glycerol, and frHMGB1. The hydrogel glues tissues together and the glued tissues have strong mechanical properties. The film and scaffold provide the suitable environment for enhancing cell proliferation by releasing frHMGB1. The scaffold carries 1 mm diameter of full-thickness rat skin-island as a minimal functional unit of skin (MFUS) to treat large full thickness skin wounds, and the hydrogel glues the MFUS and scaffold with skin edges together (MFUS+Scaffold group). The scaffold treated wounds (Scaffold group) heal much faster than the wounds either treated with MFUS (MFUS group) or without treatment (Wound group). The MFUS+Scaffold treated wound regenerates more functional full-thickness skin with more hair follicles and sweat glands, higher CD146 and α-smooth muscle actin levels, more blood vessels and collagen productions, and less scar tissues when compared to the other three groups. The results demonstrate that the combination of frHMGB1-LDI-Gly polymer with MFUS provides a new tissue engineering approach for large full-thickness skin wound healing.

Density Regulation and Localization of Cell Clusters by Self-Assembled Femtosecond-Laser-Fabricated Micropillar Arrays.

Tumor cell clusters of varying sizes and densities have different metastatic potentials. Three-dimensional (3D) patterned structures with rational topographical and mechanical properties are capable of guiding the 3D clustering of tumor cells. In this study, single femtosecond laser pulses were used to fabricate individual high-aspect-ratio micropillars via two-photon polymerization (TPP). By combining this approach with capillary-force self-assembly, complex 3D microstructure patterns were constructed with a high efficiency. The microstructures were able to regulate the formation of cell clusters at different cell seeding densities and direct self-guided 3D assembly of cell clusters of various sizes and densities. Localization of cell clusters was achieved using grid-indexed samples to address individual cell clusters, which holds great promise for in situ cell cluster culture and monitoring and for applications such as RNA sequencing of cell clusters.