Abstract
Purpose: Ghrelin is an endogenous ligand for growth hormone secretagogue receptor. The current study was aimed at examining the effect of ghrelin on avascular necrosis of the femoral head (ANFH) induced by steroids in a rabbit model and also exploring the underlying mechanism.
 Methods: Experimental rabbits were separated into three groups: Control, Vehicle and Ghrelin. We established a steroid-induced ANFH model in rabbits. Then, MRI scanning and hematoxylin-eosin staining (HE) were conducted to see ANFH. The mRNA levels of Vascular Endothelial Growth Factor (VEGF) and Bone Morphogenetic Protein 2 (BMP-2) were evaluated using real-time qRT-PCR.
 Results: Rabbits in the Vehicle group showed increased empty bone lacunae, reduced bone trabecula in femoral head; the number of hematopoietic cells in the bone marrow was reduced, whereas number of adipocytes increased with evident fusion phenomenon in comparison with the Control group. All of the changes induced in Vehicle group were attenuated in Ghrelin group. MRI scanning showed obvious necrosis of femoral head in the Vehicle group and less in the Ghrelin group. The mRNA levels of VEGF and BMP-2 were raised in Vehicle group and further enhanced in Ghrelin group.
 Conclusion: Ghrelin attenuates steroid-induced avascular necrosis in femoral head in rabbit model. A possible mechanism may be through VEGF/BMP-2 axis.
 Keywords: ANFH, BMP-2, Ghrelin, VEGF
Highlights
Avascular necrosis of the femoral head (ANFH) is a progressive and disabling illness, which eventually results in femoral head collapse and hip arthroplasty [1]
MRI scanning was conducted to evaluate the avascular necrosis of the femoral head upon the establishment of ANFH model and after ghrelin treatment
Our results showed that ghrelin treatment significantly increased Bone Morphogenetic Protein 2 (BMP-2) and Vascular Endothelial Growth Factor (VEGF) expressions in the femoral head
Summary
Avascular necrosis of the femoral head (ANFH) is a progressive and disabling illness, which eventually results in femoral head collapse and hip arthroplasty [1]. We hypothesized that ghrelin may play a role in the avascular necrosis of the femoral head. We examined the effect of ghrelin on steroid-induced ANFH in a rabbit model, and explored the possible mechanism. To establish the model of ANFH, the rabbits were injected with horse serum (10ml/kg) at the first and third weeks via the ear vein. After 2 weeks, the rabbits were sacrificed by air embolism, and femoral heads were collected for analysis. MRI scanning was conducted 2 weeks after the last methylprednisolone injection at the end of the experiments before the rabbits were sacrificed. After the rabbits were sacrificed, the femoral heads were collected quickly and fixed by 10% formalin for 24 hours, followed by decalcification in nitric acid solution (5%) for 7 days. A p value less than 0.05 was considered statistically significant
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