Regeneration of pulp-dentine complex-like tissue in a rat experimental model under an inflammatory microenvironment using high phosphorous-containing bioactive glasses.

AIM

To investigate the effects of a bioactive glass with a high proportion of phosphorus (BG-hP) on the repair and regeneration of dental pulps in rats under an inflammatory microenvironment.

METHODOLOGY

Human dental pulp cells (hDPCs) stimulated with 1 μg mL lipopolysaccharide (LPS) were co-cultured with 0.1 mg mL BG-hP. Cell proliferation was detected by 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyltetrazolium bromide (MTT) assays. The expression of inflammation-related genes and odontogenic differentiation-related genes was determined by real-time PCR. Alizarin red staining was used to detect the formation of mineralized nodules. Coronal pulp tissues of rat molars were stimulated with 10 mg mL LPS and then treated with BG-hP. The expression of inflammation-related genes in pulp tissue was determined by real-time PCR. Haematoxylin-eosin staining and Masson staining were performed to observe the inflammatory response and mineralized matrix formation, after subcutaneous implantation in nude mice, at 3 days and 4 weeks, respectively. Analysis of variance was performed to measure statistical significance (P < 0.05).

RESULTS

BG-hP significantly reduced expression of interleukin-6 (IL-6) and IL-8 and significantly upregulated the expression of IL-10, IL-4 and transforming growth factor-β1 of the LPS-stimulated hDPCs (P < 0.05). BG-hP significantly inhibited the initial cell number (P < 0.05), but the hDPCs stimulated by LPS and co-cultured with BG-hP maintained the same proliferation rate as the untreated hDPCs. BG-hP significantly promoted the expression of dentine matrix protein-1 and dentine sialophosphoprotein and the mineralization capacity of the LPS-stimulated hDPCs (P < 0.05). Furthermore, BG-hP significantly downregulated the expression of Il-6 and reduced the inflammatory response of the LPS-stimulated pulp tissue 3 days after subcutaneous implantation (P < 0.05). Four weeks after subcutaneous implantation, BG-hP induced the formation of a continuous layer of dentine-like structure with dentinal tubules and polarizing odontoblast-like cells aligned along it in the LPS-stimulated pulp tissue.

CONCLUSION

The present preliminarily results demonstrated that the bioactive glass with a high proportion of phosphorus inhibited the inflammatory response and promoted the formation of a pulp-dentine complex in a rat experimental model. This study provides a foundation for the construction of materials with the dual functions of exerting anti-inflammatory effects and promoting tissue regeneration to meet the needs of dental pulp repair and regeneration.