Multilayered fibroblasts constructed by accelerated cellular self-assembly and applications for regenerative medicine.

Regenerative medicine research requires animal experiments to evaluate the treatment effects. According to the 3Rs principles, alternative models have been developed and utilized to evaluate the efficacy and safety of new products. Three-dimensional (3D) cell cultures have been recognized for their relevant structures and biological functions akin to native tissues. They can better represent in vivo conditions than two-dimensional (2D) cell cultures. Herein, we present a fast and simple technique for the construction of 3D dermal fibroblasts (3D-DFs) without exogenous scaffolds. The 3D-DFs can be obtained within 3 days by seeding DFs at a level that exceeds their confluent density and culturing in the presence of ascorbic acid. The 3D-DFs had a compact multilayer structure, as revealed from their histology. The collagen content of the resulting 3D-DFs drastically increased compared to in a monolayer. The 3D-DF-derived extracellular matrix can serve for the 3D culturing of other cells. A gap closure assay was performed with the 3D-DFs to represent a 3D-wounded dermal model. Interestingly, the multilayered structure of the 3D-DFs could be regenerated after wounding even when cultured in the absence of ascorbic acid. Moreover, skin grafting of the 3D-DFs was demonstrated in vitro using wounded full-thickness skin models as an alternative to animal experiments. The 3D-DFs will potentially be useful for regenerative medicine or as tissue models for in vitro studies.