Evaluating the oxysterol combination of 22(S)-hydroxycholesterol and 20(S)-hydroxycholesterol in periodontal regeneration using periodontal ligament stem cells and alveolar bone healing models

Stem Cell Res Ther. 2017 Dec 6;8(1):276. doi: 10.1186/s13287-017-0725-9.

Abstract

Background: Oxysterols, oxygenated by-products of cholesterol biosynthesis, play roles in various physiological and pathological systems. However, the effects of oxysterols on periodontal regeneration are unknown. This study investigated the effects of the specific oxysterol combination of 22(S)-hydroxycholesterol and 20(S)-hydroxycholesterol (SS) on the regeneration of periodontal tissues using in-vitro periodontal ligament stem cells (PDLSCs) and in-vivo models of alveolar bone defect.

Methods: To evaluate the effects of the combined oxysterols on PDLSC biology, we studied the SS-induced osteogenic differentiation of PDLSCs by assessing alkaline phosphatase activity, intracellular calcium levels [Ca2+]i, matrix mineralization, and osteogenic marker mRNA expression and protein levels. To verify the effect of oxysterols on alveolar bone regeneration, we employed tooth extraction bone defect models.

Results: Oxysterols increased the osteogenic activity of PDLSCs compared with the control group. The expression of liver X receptor (LXR) α and β, the nuclear receptors for oxysterols, and their target gene, ATP-binding cassette transporter A1 (ABCA1), increased significantly during osteogenesis. Oxysterols also increased protein levels of the hedgehog (Hh) receptor Smo and the transcription factor Gli1. We further confirmed the reciprocal reaction between the LXRs and Hh signaling. Transfection of both LXRα and LXRβ siRNAs decreased Smo and Gli1 protein levels. In contrast, the inhibition of Hh signaling attenuated the LXRα and LXRβ protein levels. Subsequently, SS-induced osteogenic activity of PDLSCs was suppressed by the inhibition of LXRs or Hh signaling. The application of SS also enhanced bone formation in the defect sites of in-vivo models, showing equivalent efficacy to recombinant human bone morphogenetic protein-2.

Conclusions: These findings suggest that a specific combination of oxysterols promoted periodontal regeneration by regulating PDLSC activity and alveolar bone regeneration.

Keywords: Alveolar bone defect; Bone regeneration; Osteogenic differentiation; Oxysterol; Periodontal ligament stem cells.

MeSH terms

  • ATP Binding Cassette Transporter 1 / genetics
  • ATP Binding Cassette Transporter 1 / metabolism
  • Alkaline Phosphatase / genetics
  • Alkaline Phosphatase / metabolism
  • Animals
  • Bone Morphogenetic Protein 2 / pharmacology
  • Bone Regeneration / drug effects*
  • Bone Regeneration / genetics
  • Cell Differentiation / drug effects
  • Gene Expression Regulation / drug effects*
  • Humans
  • Hydroxycholesterols / chemistry
  • Hydroxycholesterols / pharmacology*
  • Liver X Receptors / genetics
  • Liver X Receptors / metabolism
  • Male
  • Molar / cytology
  • Molar / metabolism
  • Molar / surgery
  • Osteogenesis / drug effects*
  • Osteogenesis / genetics
  • Periodontal Ligament / cytology*
  • Periodontal Ligament / metabolism
  • Periodontal Ligament / surgery
  • Primary Cell Culture
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Signal Transduction
  • Smoothened Receptor / genetics
  • Smoothened Receptor / metabolism
  • Stem Cells / cytology
  • Stem Cells / drug effects*
  • Stem Cells / metabolism
  • Stereoisomerism
  • Tooth Extraction
  • Zinc Finger Protein GLI1 / genetics
  • Zinc Finger Protein GLI1 / metabolism

Substances

  • ABCA1 protein, human
  • ATP Binding Cassette Transporter 1
  • BMP2 protein, human
  • Bone Morphogenetic Protein 2
  • GLI1 protein, human
  • Hydroxycholesterols
  • Liver X Receptors
  • Protein Isoforms
  • SMO protein, human
  • Smoothened Receptor
  • Zinc Finger Protein GLI1
  • Alkaline Phosphatase