The effects of prophylactic tadalafil use on VEGF expression in the rabbit model of steroid-induced femoral head avascular necrosis

Objective: The purpose of this study was to examine the effect of prophylactic tadalafil use on a steroid-induced femoral head avascular necrosis model in terms of microscopic, imaging, and molecular biological changes.Methods: Twenty-four New Zealand rabbits were divided into 3 equal groups. Eight rabbits were designated as the control group and did not receive treatment. Rabbits in group 1 (G1) received 0.1 mg/kg Escherichia coli lipopolysaccharide (LPS) intravenously and 40 mg/ kg methylprednisolone sodium succinate (MP) was administered intramuscularly for 3 days consecutively. Rabbits in group 2 (G2) were given 5 mg/kg tadalafil orally for 10 consecutive days. Starting on the eighth day, 0.1 mg/kg LPS was given, and following this 40 mg/kg MP injections were administered for 3 days. All animals were sacrificed 3 weeks after the final MP injection. Magnetic resonance imaging was performed, and bilateral femora were harvested. Half of the femoral head was stored for Vascular Endothelial Growth Factor (VEGF) examination with Western blot analysis. The other half was examined microscopically for the presence of osteonecrosis.Results: In G1, 15 out of 16 hips (93%) of the 8 rabbits had osteonecrosis compared to 8 out of 12 hips (67%) of 6 rabbits in G2 (P > .05). The VEGF expression in G2 was significantly higher than in the control group and G1 (P < .05 and P < .001, respectively). There was no significant difference in VEGF expression between the control group and G1 (P > .05).Conclusion: This study has shown us that femoral head osteonecrosis can be reliably induced with LPS and corticosteroid, as described in the literature. Prophylactic tadalafil use did not decrease the occurrence of osteonecrosis significantly. However, it significantly increased VEGF expression in the femoral head independent of the effects of steroids and LPS.