A novel semisynthesized small molecule icaritin reduces incidence of steroid-associated osteonecrosis with inhibition of both thrombosis and lipid-deposition in a dose-dependent manner.

Abstract

BACKGROUND:

Intravascular-thrombosis and extravascular-lipid-deposition are the two key pathogenic events considered to interrupt intraosseous blood supply during steroid-associated osteonecrosis (ON) development. However, there are no reported candidate agents capable of simultaneously targeting these two key pathogenic events. The authors' published experimental studies have shown that Epimedium-derived flavonoids possess an anti-ON effect. Further, the authors have recently identified a small molecule Icaritin as an intestinal metabolite of Epimedium-derived flavonoids.

OBJECTIVE:

The present study was to evaluate the prevention effect of the available semisynthesized small molecule Icaritin on steroid-associated ON development in a rabbit model.

METHODS:

After receiving an established inductive protocol for inducing steroid-associated ON, eighty-four male 28-week-old New-Zealand white rabbits were divided into the following three daily oral administration groups, including low dose Icaritin group (L-ICT; n=28; 5 mg x kg(-1) x day(-1)), high dose Icaritin group (H-ICT; n=28; 10 mg x kg(-1) x day(-1)), and control vehicle group (CON; n=28). Before and after induction, dynamic contrast-enhanced MRI was performed on proximal femur for intra-osseous perfusion function index. Meanwhile, blood samples were examined for coagulation, fibrinolysis, lipid-transportation, endothelium injury, oxidative stress, and hepatocyte injury index, while marrow samples were quantified for adipogenic potential index of mesenchymal stem cell by in vitro culture and proliferator-activated receptor-gamma (PPARgamma) protein expression by western blot. At baseline, week 1 and 2 post-induction, 4, 8 and 16 rabbits in each group were sacrificed, respectively. After sacrifice, femora were dissected for micro-CT-based micro-angiography, followed by histological examination of ON lesion, intravascular thrombosis, extravascular fat-cell and vascular endothelial growth factor (VEGF) localized expression.

RESULTS:

The ON incidence in the L-ICT and H-ICT groups was both significantly lower than that in the CON group (p<0.05 for both). The ON incidence in the H-ICT group was significantly lower than that in the L-ICT group (p<0.05). A significant decrease in the vascularization index and a significant increase in the permeability index seen in the CON group was attenuated in the L-ICT group and almost prevented in the H-ICT group at week 1 post-induction. Reduced perfusion to vessel-like structural units was more rarely found in the H-ICT group than in the L-ICT group. Regarding intravascular thrombosis, a significant increase in the thrombotic vessel count, endothelium injury index, coagulation index, and a significant decrease in both the fibrinolysis and oxidative stress index in the CON group were attenuated in the L-ICT group and prevented in the H-ICT group. For extravascular lipid-deposition, a significant increase in the fat cell area fraction, adipogenic potential index, PPARgamma expression and lipid-transportation index in the CON group was attenuated in the L-ICT group and prevented in the H-ICT group. Increased immunoreactivity of VEGF in the CON group was attenuated in the L-ICT group and prevented in the H-ICT group. Regarding safety, the hepatocyte injury index did not show significant change from baseline in any group.

CONCLUSION:

Icaritin, a novel semisynthesized small molecule with osteoprotective potential, exerts dose-dependent effect on reducing incidence of steroid-associated ON with inhibition of both intravascular thrombosis and extravascular lipid-deposition. Suppression of the up-regulated PPARgamma expression for extravascular adipogenesis of mesenchymal stem cells and protection from activated oxidative stress for intravascular endothelium injury were found to be involved in the underlying mechanisms.

• Authors: Ge Zhang, Ling Qin, Hui Sheng, Xin-Luan Wang, Yi-Xiang Wang, David Ka-Wai Yeung, James F Griffith, Xin-Sheng Yao, Xin-Hui Xie, Zi-Rong Li, Kwong-Man Lee, Kwok-Sui Leung
• Journal: Bone (Bone) Vol. 44 Issue 2 Pg. 345-56 (Feb 2009) ISSN: 1873-2763 [Electronic] United States
• PMID: 19015051 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Flavonoids
• Steroids
• Vascular Endothelial Growth Factor A
• icaritin

Topics

• Angiography
• Animals
• Blood Vessels (drug effects, pathology)
• Dose-Response Relationship, Drug
• Flavonoids (administration & dosage, chemistry, pharmacology, therapeutic use)
• Lipid Metabolism (drug effects)
• Magnetic Resonance Imaging
• Male
• Osteonecrosis (drug therapy, etiology, pathology, prevention & control)
• Particle Size
• Perfusion
• Rabbits
• Steroids (adverse effects)
• Thrombosis (drug therapy, prevention & control)
• Treatment Outcome
• Vascular Endothelial Growth Factor A (metabolism)
• X-Ray Microtomography