Nanogel tectonic porous 3D scaffold for direct reprogramming fibroblasts into osteoblasts and bone regeneration.

Transplantation of engineered three-dimensional (3D) bone tissue may provide therapeutic benefits to patients with various bone diseases. To achieve this goal, appropriate 3D scaffolds and cells are required. In the present study, we devised a novel nanogel tectonic material for artificial 3D scaffold, namely the nanogel-cross-linked porous (NanoCliP)-freeze-dried (FD) gel, and estimated its potential as a 3D scaffold for bone tissue engineering. As the osteoblasts, directly converted osteoblasts (dOBs) were used, because a large number of highly functional osteoblasts could be induced from fibroblasts that can be collected from patients with a minimally invasive procedure. The NanoCliP-FD gel was highly porous, and fibronectin coating of the gel allowed efficient adhesion of the dOBs, so that the cells occupied the almost entire surface of the walls of the pores after culturing for 7 days. The dOBs massively produced calcified bone matrix, and the culture could be continued for at least 28 days. The NanoCliP-FD gel with dOBs remarkably promoted bone regeneration in vivo after having been grafted to bone defect lesions that were artificially created in mice. The present findings suggest that the combination of the NanoCliP-FD gel and dOBs may provide a feasible therapeutic modality for bone diseases.