Histone acetylation promotes FKBP5 to increase reparative dentin formation in pulp repair

A well-formed dentin bridge isolates irritants and prevents bacterial penetration into the remaining pulp tissue, which is essential for pulp regeneration. The existing literature on promoting reparative dentin formation mostly focuses on the effects of pulp-capping materials but lacks investigations into the underlying mechanisms.

To identify potential targets for enhancing reparative dentin formation as well as the epigenetic mechanisms underlying these effects.

Laboratory-based study combining multi-omics sequencing, epigenetic assays, in vitro FK506-binding protein 51 (FKBP5) knockdown or overexpression experiments, and in vivo validation using rat pulp injury models and nude mouse subcutaneous transplantation models.

Laboratory-based in vitro and in vivo study.

N/A.

Dental pulp stem cells (DPSCs) were exposed to odontogenic differentiation induction or Lipopolysaccharide (LPS) stimulation. FKBP5 knockdown and overexpression were conducted using lentiviral vectors. In vivo validation was performed using a rat dental pulp injury model and a nude mouse subcutaneous transplantation model combining FKBP5 knockdown or overexpressed DPSCs with treated dentin matrix. Histone acetylation was modulated using dCas9-p300 targeting or pharmacological treatment with suberoylanilide hydroxamic acid (SAHA) or C646.

FKBP5 expression, mineralized nodule formation, alkaline phosphatase (ALP) activity, odontogenic marker expression, inflammatory cytokine expression, FKBP5 promoter chromatin accessibility, promoter methylation, H3K9ac/H3K27ac enrichment, reparative dentin formation and collagen formation were assessed.

FKBP5 was upregulated during odontogenic differentiation induction and highly expressed in human pulpitis tissues and injured rat pulps. Overexpression of FKBP5 promoting reparative dentin formation, collagen synthesis and mineralization (dentin sialophosphoprotein and dentin matrix protein 1 expressions). Down-regulation of inflammatory factors Interleukin-1β and Interleukin-8 also contributed to the process of pulp repair. H3K9ac and H3K27ac, rather than DNA methylation, were enriched at the FKBP5 promoter, enhancing chromatin accessibility and FKBP5 transcription. SAHA enhanced H3K9ac and H3K27ac and the expression of FKBP5 near the injury site. The newly-formed reparative dentin was upregulated and pulp inflammation was suppressed with the application of SAHA.

FKBP5 facilitated reparative dentin and neoplastic collagen synthesis at the injury site while mitigating inflammation. Histone acetylation H3K9 and H3K27 were the mechanism that modulated differentiation effects of FKBP5.