Osteogenic Response to Polysaccharide Nanogel Sheets of Human Fibroblasts After Conversion Into Functional Osteoblasts by Direct Phenotypic Cell Reprogramming.

Kei Nakai,Elia Marin,Francesco Boschetto,Tsunao Kishida,Hironaka Yamanobe,Kenta Yamamoto,Toshiro Yamamoto,Satoshi Horiguchi,Kazunari Akiyoshi,Wenliang Zhu,Yoshiki Sato,Shin-Ichiro Kotani,Narisato Kanamura,Tetsuya Adachi,Osam Mazda,Giuseppe Pezzotti

doi:10.3389/fbioe.2021.713932

Abstract

Human dermal fibroblasts (HDFs) were converted into osteoblasts using a ALK inhibitor II (inhibitor of transforming growth factor-β signal) on freeze-dried nanogel-cross-linked porous (FD-NanoClip) polysaccharide sheets or fibers. Then, the ability of these directly converted osteoblasts (dOBs) to produce calcified substrates and the expression of osteoblast genes were analyzed in comparison with osteoblasts converted by exactly the same procedure but seeded onto a conventional atelocollagen scaffold. dOBs exposed to FD-NanoClip in both sheet and fiber morphologies produced a significantly higher concentration of calcium deposits as compared to a control cell sample (i.e., unconverted fibroblasts), while there was no statistically significant difference in calcification level between dOBs exposed to atelocollagen sheets and the control group. The observed differences in osteogenic behaviors were interpreted according to Raman spectroscopic analyses comparing different polysaccharide scaffolds and Fourier transform infrared spectroscopy analyses of dOB cultures. This study substantiates a possible new path to repair large bone defects through a simplified transplantation procedure using FD-NanoClip sheets with better osteogenic outputs as compared to the existing atelocollagen scaffolding material.

Highlights

Modern challenges toward a super active aging society require diversification of the available options for bone regeneration therapies, which include large-scale bone defects caused by bone diseases (Gibon et al, 2016)
This study reported the osteogenic performance of two FDNanoClip polysaccharide scaffolds with the same pore structure but different morphologies in comparison with a sheet-type atelocollagen scaffold with a similar pore structure
All scaffolds were tested against the same directly converted osteoblasts (dOBs), a cell line directly converted from Human dermal fibroblasts (HDFs), and proved capable of biologically active effects

Summary

Introduction

Modern challenges toward a super active aging society require diversification of the available options for bone regeneration therapies, which include large-scale bone defects caused by bone diseases (Gibon et al, 2016). The successful direct conversion was reported from human fibroblasts to functional osteoblasts, brown adipocytes, Schwann cells, urothelial cells, and so on (Kishida et al, 2015; Yamamoto et al, 2015; Yamamoto et al, 2016; Sowa et al, 2017; Wakao et al, 2017; Sato et al, 2018; Yamamoto et al, 2018). In both bone transplantation and bone regeneration treatment, the direct conversion method could potentially be useful when applied with autologous osteoblasts. This study attempted to satisfy the requirements of a dense cell population of human fibroblasts to be directly converted into osteoblasts on engineered freeze-dried nanogelcross-linked porous (FD-NanoClip) polysaccharide scaffolds with different morphologies

Results

Discussion

Conclusion