Incorporation of capillary-like structures into dermal cell sheets constructed by magnetic force-based tissue engineering

One of the major challenges in tissue engineering remains the construction of vascularized 3D transplants in vitro. We recently proposed novel technologies, termed "magnetic force-based tissue engineering" (Mag-TE), to establish three-dimensional (3D) tissues without using scaffolds. Magnetite cationic liposomes (MCLs), which contain 10-nm magnetite nanoparticles in order to improve accumulation of magnetite nanoparticles in target cells, were used to magnetically label normal human dermal fibroblasts (NHDFs). Magnetically labeled NHDFs were seeded onto ultralow-attachment plates. When a magnet was placed under the plate, cells accumulate on the bottom of the well. After a 24-h-incubation period, the cells form a sheet-like structure, which contains the major dermal extracellular matrix (ECM) components (fibronectin and type I collagen) within the NHDF sheet. Human umbilical vein endothelial cells (HUVECs) were co-cultured with NHDF sheets by two methods: HUVECs and NHDFs were mixed and then allowed to form cell sheets by Mag-TE; or NHDF sheets were constructed by Mag-TE and HUVECs were subsequently seeded onto NHDF sheets. These methods gave tube-like formation of HAECs, resembling early capillaries, within or on the surface NHDF sheets after short-term 3D co-culture, thus suggesting that Mag-TE may be useful for constructing 3D-tissue involving capillaries.