Histological assessment of the local effect of different concentrations of aminoguanidine hydrochloride on bone healing in rats

Background: Nitric oxide (NO) plays a key role in bone metabolism and the healing process. Selective inhibition of inducible nitric oxide synthase (iNOS) provides a useful approach for evaluating NO’s impact on bone repair. This study aimed to examine the local effects of varying concentrations of aminoguanidine hydrochloride (AG), a selective iNOS inhibitor, on bone defect healing in rats.
Materials and Methods: In this experimental animal study, 72 rats were randomly assigned to six groups: control, placebo, and four treatment groups receiving 5%, 10%, 15%, or 20% AG. A standardized bone defect (5 mm × 5 mm) was created in the femur of each rat. The control group received no treatment, while the placebo group was treated with a neutral gel. The remaining groups received the respective concentrations of AG applied directly to the defect site. Bone healing was evaluated histologically, and healing scores were analyzed using the Kruskal-Wallis test, with statistical significance set at P < 0.05.
Results: The healing scores in all AG-treated groups (5%, 10%, 15%, and 20%) were significantly higher than those in the control and placebo groups (P < 0.01). Among the AG groups, the 20% concentration produced the highest healing scores, although the difference compared to other AG concentrations was not statistically significant.
Conclusion: All tested concentrations of AG significantly enhanced bone healing compared to the control and placebo treatments. These findings suggest that selective iNOS inhibitors like AG may be beneficial for promoting local bone regeneration.