Possible application of glassy carbon composite scaffolds in bone tissue engineering

Introduction Bone defect management remains one of the challenging problems of regenerative medicine, for the solution of which the most promising trend is the use of tissue-engineered implants based on composite scaffolds that stimulate osteogenesis. One of the main tasks of tissue engineering is the development of a scaffold that mimics three-dimensional architecture for osteogenic progenitor cells inside the scaffold, with the possibility of cell interaction with appropriate chemical and physical stimuli of natural bone. The purpose of the work is to evaluate the possibility of using composite scaffolds based on glassy carbon in tissue engineering. Materials and Methods This study describes a reproducible method of obtaining three-dimensional porous glass-carbon-based scaffolds with surfaces modified with pyrocarbon (CF-C) and pyrocarbon and hydroxyapatite (CF-C-HAP) and investigates the porosity, strength characteristics, cytotoxicity, and osteoinductivity of the composite scaffolds obtained. Osteogenic differentiation of cultured human mesenchymal stem cells (MSCs) was evaluated on CF-C and CF-C-HAP scaffolds using common osteogenic markers such as: alkaline phosphatase (ALP) activity, alizarin red staining and quantitative real-time PCR (qPCR). Results In vitro studies showed the biocompatibility of the developed scaffolds. The ability of CF-C-HAP to induce MSC differentiation in osteogenic direction and to produce calcium-containing matrix was established. Discussion The scaffolds based on glassy carbon foam with pyrocarbon and hydroxyapatite coatings have a three-dimensional structure with open porosity, along with the strength comparable to the strength of the replaced tissue, and imitate the structure of trabecular bone. However, the strength of glassy carbon foam without coating is characterized by low compressive strength. All the studied materials demonstrated adhesive and proliferative activity of MSCs, high cell adhesion and absence of cytotoxicity. Determination of the mRNA expression level by real-time PCR showed that after 14 days, cells cultured on CS-C-HAP showed expression of the VDR, BMP7, IGFR1, SPP1 genes, what demonstrates osteogenic potential. The results of our studies on phosphatase activity and alizarin red staining demonstrated that the CF-C‑HAP scaffold stimulates osteoblast differentiation in vitro in the osteogenic direction, as well as intracellular mineralization processes. Conclusion Composite CF-C-HAP scaffolds based on glassy carbon foam support cell proliferation and differentiation and may be promising for use in bone tissue engineering.