Effects of Bisphosphonate on Osteogenesis in Osteoporosis Rats

Objectives: We investigated the effects of Bisphosphonate on osteogenesis for the healing of extracted wounds employing osteoporosis rats.

Methods: Female Wistar rats (8-weeks-old) were used, and all animals were divided into the following three groups: (1) sham operated (S-group) (2) ovariectomized (O-group) and (3) Bisphosphonate (Risedronate) injected (sc, dose: 50 µg/kg; three times/week from 14-weeks-old) after ovariectomy (R-group). The animals in the O- and R-groups were given low calcium feed. The bilateral maxillary first molars of all of the rats were extracted at 18-weeks-old, and all animals were euthanized at 3, 7, 14 or 28 days after extraction. To visualize the osteoid (OS), Hematoxylin-eosin staining combined with the Goland-Yoshiki method was performed, and observed under a light microscope. Using digital images of the specimens, the following three ratios were calculated; the ratios of the amount of new bone (NB)/extracted wound area (WA), OS/NB and mature bone (MB)/NB. All data were evaluated using standard statistical procedures.

Results: After 3 days, no osteogenesis was observed in any group. After 7 days NB/WA revealed no significant differences in the O-group, but there was a significant decrease in the R-group compared to the S-group (30%). OS/NB was 94~98%, and MB/NB was 2~6%. Compared to NB/WA and OS/NB of the S-group at 14 days (NB/WA: 60%; OS/NB: 35%) and 28 days (NB/WA: 80%; OS/NB: 5%), no significant differences were detected in NB/WA or OS/NB of the R-group. However, there were significant decrease in NB/WA and significant increase in OS/NB in the O-group compared to the S-group. In the healing of extracted wounds of the O-group, NB/WA was low, and bone maturation was delayed compared to the S-group.

Conclusions: We concluded that the Bisphosphonate injection contributed to delay osteogenesis at 7 days, and to promote osteogenesis and bone maturation after 14 days.