In vitro Chondrocyte Responses in Mg-doped Wollastonite/Hydrogel Composite Scaffolds for Osteochondral Interface Regeneration

Xinning Yu,Xianyan Yang,Xiaonan Liu,Quanming Yang,Zhongru Gou,Xuesong Dai,Yiying Qi,Tengfei Zhao,Tengjing Xu,Jianyang Luo,Jinghua Fang

doi:10.1038/s41598-018-36200-x

Abstract

The zone of calcified cartilage (ZCC) is the mineralized region between the hyaline cartilage and subchondral bone and is critical in cartilage repair. A new non-stoichiometric calcium silicate (10% Ca substituted by Mg; CSi-Mg10) has been demonstrated to be highly bioactive in an osteogenic environment in vivo. This study is aimed to systematically evaluate the potential to regenerate osteochondral interface with different amount of Ca-Mg silicate in hydrogel-based scaffolds, and to compare with the scaffolds containing conventional Ca-phosphate biomaterials. Hydrogel-based porous scaffolds combined with 0–6% CSi-Mg10, 6% β-tricalcium phosphate (β-TCP) or 6% nanohydroxyapatite (nHAp) were made with three-dimensional (3D) printing. An increase in CSi-Mg10 content is desirable for promoting the hypertrophy and mineralization of chondrocytes, as well as cell proliferation and matrix deposition. Osteogenic and chondrogenic induction were both up-regulated in a dose-dependent manner. In comparison with the scaffolds containing 6% β-TCP or nHAp, human deep zone chondrocytes (hDZCs) seeded on CSi-Mg10 scaffold of equivalent concentration exhibited higher mineralization. It is noteworthy that the hDZCs in the 6% CSi-Mg10 scaffolds maintained a higher expression of the calcified cartilage zone specific extracellular matrix marker and hypertrophic marker, collagen type X. Immunohistochemical and Alizarin Red staining reconfirmed these findings. The study demonstrated that hydrogel-based hybrid scaffolds containing 6% CSi-Mg10 are particularly desirable for inducing the formation of calcified cartilage.

Highlights

An osteochondral defect is common, especially in athletes, and this defect is often concomitant with subchondral bone injury[1]
The objective of this study is to evaluate the potential effects of the novel 3D-printed hydrogel/ CSi-Mg10 hybrid scaffolds on zone of calcified cartilage (ZCC) formation via a human deep zone chondrocyte culture experiment in vitro
The X-ray diffraction (XRD) patterns of bioceramic powders (CSi-Mg10, β-tricalcium phosphate (β-TCP), nHAp) presented in Fig. 1D confirmed that the β-TCP and nHAp powders were highly crystalline Ca-phosphates, while the CSi-Mg10 powders exhibited the pure wollastonite phase

Summary

Introduction

An osteochondral defect is common, especially in athletes, and this defect is often concomitant with subchondral bone injury[1]. The zone of calcified cartilage (ZCC) is a mineralized region in between the hyaline cartilage and subchondral bone. Is made resemble the tissue it replaces[6] Due to their compositional similarity to natural bone minerals, the synthesized calcium phosphates (CaPs), such as hydroxyapatite (HAp) and β-tricalcium phosphate (β-TCP), have been applied in clinic and osteochondral interface tissue engineering[7,8]. Compared with the clinically used bone CaPs implants, wollastonite exhibits higher bioactivity and osteogenesis due to the release of Ca2+ and SiO32− ions[11,12]. The mechanically strong CSi-Mg porous scaffolds were successfully fabricated via a bioceramic ink-writing technique for the highly efficient regeneration and repair of femoral or calvarial defects in situ in rabbit models. It was demonstrated that the surface bioactivity of CSi-Mg benefited osteogenic cell proliferation and osteogenic gene expression in comparison with the clinically available β-TCP material[15,16]

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Conclusion