Systemic and local zoledronic acid treatment with hydroxyapatite bone graft: A histological and histomorphometric experimental study

Abstract

In this study, the aim was to compare the relative efficacy of systemic and local zoledronic acid (ZA) on a hydroxyapatite (HA) bone graft in a rat critical-size calvarial bone defect. In total, 84 female rats were divided into four groups: Empty control (EC) group with no treatment applied; HA group, in which only HA bone graft material was used in the calvarium; and HA plus local ZA (HA+LZA) and HA plus systemic ZA (HA+SZA) groups, in which animals received ZA locally or systemically, respectively, with HA bone graft material in the calvarium. A 5-mm standardised critical-size calvarial bone defect was created with a standard trephine drill and the respective treatment was applied. Rats were sacrificed 7, 14 and 28 days later. The numbers of osteoclasts and osteoblasts, and degree of bone formation were evaluated histopathologically and histomorphometrically. Statistically significant differences were detected between the HA, HA+LZA and HA+SZA groups and the EC group for new bone formation (P<0.05). Osteoblast numbers in the HA+LZA and HA+SZA groups were significantly higher compared with those in the EC and HA groups (P<0.05). No statistically significant difference was detected between the HA+LZA and HA+SZA groups in new bone formation or osteoblast number (P>0.05). Bone formation was significantly higher in the HA group than in the EC group (P<0.05). The numbers of osteoclasts in the HA+LZA and HA+SZA groups were significantly higher than those in the groups EC and HA (P<0.05); however, there was no significant difference between groups HA+LZA and HA+SZA (P>0.05). Within the limitations of this study, systemic or local administration of ZA enhanced new bone formation with a HA bone graft in a rat critical-size calvarial defect model.

Keywords: critical-sized defect; hydroxyapatite bone graft; rat calvarium; zoledronic acid.

Figure 1.

Histopathological findings of the (A) EC group, (B) HA group, (C) HA+LZA group and (D) HA+SZA group on days 7, 14 and 28. Haematoxylin and eosin staining; magnification ×2 and ×4 for left and right images at each time point, respectively. In the EC group, healing was characterised by thin fibrous connective tissue filling the defects, and no regenerative bone formation was detected at any time point. By day 28, new bone formation was visible in all three treatment groups. ZA administration, either systemically or locally, resulted in increased bone formation and greater numbers of osteoclasts and osteoblasts in comparison with those in the HA group. EC, empty control; HA, hydroxyapatit LZA, local zoledronic acid; SZA, systemic zoledronic acid.

Figure 2.

Bone formation of the groups on days 7, 14 and 28. Bone formation was scored as follows: No bone formation, 0; mild visible bone formation, 1; moderate visible bone formation, 2; dense visible bone formation, 3. Data are presented as mean ± standard deviation (n=7 at each time point). ^aP<0.05 vs. the EC group; ^bP<0.05 vs. the HA group. EC, empty control; HA, hydroxyapatit LZA, local zoledronic acid; SZA, systemic local zoledronic acid.

Figure 3.

Osteoclast number of the groups on days 7, 14 and 28. Osteoclast numbers were scored as follows: No osteoclasts, 0; low-density osteoclasts, 1; dense osteoclasts, 2. Data are presented as mean ± standard deviation (n=7 at each time point). ^aP<0.05 vs. the EC group; ^bP<0.05 vs. the HA group. EC, empty control; HA, hydroxyapatit LZA, local zoledronic acid; SZA, systemic local zoledronic acid.

Figure 4.

Osteoblast number of the groups on days 7, 14 and 28. Osteoblast numbers were scored as follows: No osteoblasts, 0; low-density osteoblasts, 1; and dense osteoblasts, 2. Data are presented as mean ± standard deviation (n=7 at each time point). ^aP<0.05 vs. the EC group; ^bP<0.05 vs. the HA group; ^cP<0.05 vs. the HA+LZA group. EC, empty control; HA, hydroxyapatit LZA, local zoledronic acid; SZA, systemic local zoledronic acid.