Association between the baseline gene expression profile in periapical granuloma and periapical wound healing after surgical endodontic treatment

Abstract

In this study, we have investigated the association between the baseline gene expression profile in periapical granuloma and periapical wound healing after surgical endodontic treatment. Twenty-seven patients aged between 15 and 57 years underwent periapical surgery. The retrieved periapical tissue sample was used for mRNA expression analysis of COL1A1, VTN, ITGA5, IL-4, TNF, ANGPT, VEGFA, and CTGF. All patients were recalled after 6 and 12 months for periapical healing evaluation. Healing was then correlated with baseline gene expression. Healing was observed in 15 patients at the end of 6 months, which increased to 21 patients after 12 months. Six patients showed no healing even after 12 months. Analysis of baseline expression levels of the tested genes with healing status showed the mean relative expression of VTN, VEGFA, ANGPT, TNF, and CTGF to be significantly different (p < 0.05) between the healing group (6 and 12 months) (72.99%) and the non-healing (94.42%) group. Periapical Index scores 3-5 exhibited a positive correlation with ITGA-5 expression. Overexpression of ANGPT and a strong positive correlation between ITGA5 and PAI scores in the non-healing group of patients may suggest these genes to be a potential prognostic biomarker for periapical wound non-healing after surgical endodontic treatment.

Figure 1

(A) Immediate postoperative periapical radiograph showing periapical radiolucency around the apex of Tooth 11 and 21. (B) Periapical radiolucency decreased in 6 months. (C) Complete resolution of periapical radiolucency in 1 year.

Figure 2

(A) Immediate postoperative periapical radiograph showing periapical radiolucency around the apex of Tooth 31 and 32. (B) Periapical radiolucency slightly decreased in 6 months. (C) No resolution of periapical radiolucency in 1 year.

Figure 3

Baseline expression of COL1A1, VTN, ITGA5, IL-4, TNF, ANGPT, VEGFA, and CTGF in healing at 6- and 12-months versus non-healing group: The baseline expression of COL1A1, VTN, ITGA5, IL-4, TNF, ANGPT, VEGFA, and CTGF was measured in the healing at 6 months (circles), healing at 12 months (squares) and non-healing (triangles) groups. The Y-axis shows the relative expression (ΔCt) of each gene tested, symbols (circles, squares and triangles) represent each data point, and the error bars show the standard error of the mean. The lines with the asterisk sign show a significant difference (**p < 0.001, *p < 0.05) in the expression of tested genes between the healing (6–12 months) and non-healing groups.

Figure 4

Baseline expression of COL1A1, VTN, ITGA5, IL-4, TNF, ANGPT, VEGFA, and CTGF in (A) periapical abscess, and (B) periapical periodontitis groups in healing at 6- and 12-months versus non-healing group: The baseline expression of COL1A1, VTN, ITGA5, IL-4, TNF, ANGPT, VEGFA, and CTGF was measured for (A) periapical abscess, and (B) periapical periodontitis lesions at 6 months (circles), 12 months (squares) and non-healing (triangles) groups. The Y-axis shows the relative expression (ΔCt) of each gene tested, symbols (circles, squares and triangles) represent each data point, and the error bars show the standard error of the mean. The lines with the asterisk sign show a significant difference (***p < 0.0001, **p < 0.001, *p < 0.05) in the expression of tested genes between the healing (6–12 months) and non-healing groups.

Figure 5

Graphical representation of the pathways of genes involved in periapical wound healing. It shows the baseline expression of wound healing marker genes viz. COL1A1, VTN, ITGA5, IL-4, TNF, ANGPT1, VEGFA, and CTGF in periapical granuloma after surgical endodontic treatment. In this study, we found the downregulation of ANGPT1, TNF, and CTGF genes in the healing group and upregulation of ANGPT1, TNF, and CTGF genes in the non-healing group. It also shows that periapical wound healing is associated with a decrease in the gene expression of the mediators of the inflammatory phase of wound healing (TNF), a decrease in mediators of angiogenesis (ANGPT1), and a decrease in the mediators of the remodeling phase of wound healing. Arrows directed upwards show the upregulation and arrows directed downwards show the downregulation of the gene expression on the analysis between the healing and non-healing groups. Green solid lines indicate that statistically significant positive correlations have been found in these pairs of genes in the healing group, whereas red solid lines indicate the statistically significant positive correlations association of a pair of genes in the non-healing group.