Diabetes enhances periodontal bone loss through enhanced resorption and diminished bone formation

Abstract

Using a ligature-induced model in type-2 Zucker diabetic fatty (ZDF) rat and normoglycemic littermates, we investigated whether diabetes primarily affects periodontitis by enhancing bone loss or by limiting osseous repair. Diabetes increased the intensity and duration of the inflammatory infiltrate (P < 0.05). The formation of osteoclasts and percent eroded bone after 7 days of ligature placement was similar, while four days after removal of ligatures, the type 2 diabetic group had significantly higher osteoclast numbers and activity (P < 0.05). The amount of new bone formation following resorption was 2.4- to 2.9-fold higher in normoglycemic vs. diabetic rats (P < 0.05). Diabetes also increased apoptosis and decreased the number of bone-lining cells, osteoblasts, and periodontal ligament fibroblasts (P < 0.05). Thus, diabetes caused a more persistent inflammatory response, greater loss of attachment and more alveolar bone resorption, and impaired new bone formation. The latter may be affected by increased apoptosis of bone-lining and PDL cells.

Figure 1

Diabetes prolongs osteoclast formation and activity. Ligatures were placed around the molar teeth of ZDF type 2 diabetic and normoglycemic control rats and left in place for 7 days. Rats were killed prior to the placement of ligatures (no ligatures), immediately after removal (0 day), or 4 or 9 days later. Histologic TRAP-stained sections, original magnification 200x. Large open arrows indicate osteoclasts, large closed arrows indicate Howship’s lacunae, small closed arrows point to a reversal line, and small open arrows point to the extent of new bone formation (A). Osteoclasts were counted (B), and the percent eroded bone surface (C) was measured in TRAP-stained sections. Each value in B and C is the mean of 5 to 7 rats ± SE. *Significant difference between diabetics and normoglycemic control rats (P < 0.05). Bar in far left panel represents 0.05 mm.

Figure 2

Diabetes impaired new bone formation and increased osteoblastic apoptosis. The area of new bone formation (A) was measured in TRAP-stained sections as described in MATERIALS & METHODS. The area of alveolar bone between the cemento-enamel junction (CEJ) and a line 1 mm apical to the CEJ was measured in H&E-stained sections (B). Rats described in Fig. 1 were examined for the percent of apoptotic bone-lining cells by the TUNEL assay (C) and the number of bone-lining cells per mm bone length in H&E-stained sections (D). Each value is the mean of 5 to 7 rats ± SE. *Significant difference between diabetics and normoglycemic control rats (P < 0.05).

Figure 3

Diabetes increases the loss of attachment, increases apoptosis of PDL fibroblasts, and decreases PDL fibroblast numbers. Rats described in Fig. 1 were examined for loss of attachment in H&E-stained sections (A) and for the number of fibroblasts in the coronal aspect of the PDL space (C). Apoptosis of PDL fibroblasts was determined by the TUNEL assay and expressed as the percent of apoptotic fibroblasts (B). Each value is the mean of 5 to 7 rats ± SE. *Significant difference between diabetics and normoglycemic control rats (P < 0.05).