Histopathologic and Immunohistochemical Investigation of the Effects of Vitamin C on Bone Healing in Rats Exposed to Nicotine.

Purpose: The aim of the present study was to perform a histopathologic and immunohistochemical investigation of the effects of vitamin C on bone healing in rats exposed to nicotine.

Materials And Methods: A total of 52 male Sprague-Dawley rats were assigned to 4 main groups: control, vitamin C, nicotine, and nicotine plus vitamin C. The rats in the nicotine groups were injected with nicotine at 12-hour intervals for 4 weeks. At the end of 4 weeks, a tibial defect was created in all the rats. Subcutaneous injections were administered at the same intervals postoperatively, and the vitamin C groups received intraperitoneal vitamin C injections every day for the first 3 days and then every other day postoperatively. The rats were sacrificed on postoperative days 7 and 21. The blood samples collected during sacrifice were tested to determine the blood cotinine levels, and histopathological and immunohistochemical analyses were performed on tibia samples.

Results: The histopathologic evaluation revealed that nicotine significantly increased the amount of necrosis and significantly decreased new bone formation and the bone healing score. The presence of necrosis in the nicotine plus vitamin C group was significantly lower on day 21 (P = .005). A statistically significant difference was observed among the new bone formation of the control, nicotine, vitamin C, and nicotine plus vitamin C groups on day 21 (P = .001). The new bone healing score of the nicotine group was significantly lower than that of the control, vitamin C, and nicotine plus vitamin C groups (P = .003, P = .001, and P = .001). The immunohistochemical evaluation showed that nicotine increased the hypoxia-inducible factor-1α and vascular endothelial growth factor levels and decreased the bone morphogenetic protein-2 levels, especially in the groups sacrificed on day 21.

Conclusions: Vitamin C did not have a significant effect on bone healing. However, vitamin C administered with nicotine decreased the metabolism of nicotine and, thus, increased nicotine excretion.