Study Of Intraosseous Blood Vessels Of The Rabbit Femoral Head After High-dose Glucocorticoid Treatment

Objective To observe the pathological changes of blood vessels and tissue cells in articular cartilage of the femoral head in rabbits after injecting high-dose glucocorticoid,so as to investigate the pathogenesis of early steroid-induced avascular necrosis of the femoral head(SANFH).Methods Twenty-four Japanese rabbits(male or female is unconditional; weighting 3.0～4.2 kg) were randomly divided into three groups,group A:9 animals were injected with Methylprednisolone 30 mg/kg as an initial bolus,followed 5.4 mg/kg/h for further 23 h by ear vein;group B:9 animals were injected with Methylprednisolone 8 mg/kg,which lasted for 10 days;and group C:6 animals as the control were not given any treatment.The experiment lasted for 6 weeks.All of the femoral head of rabbits were obtained at a survival of 2 weeks,4 weeks and 6 weeks. The changes of tissue cells and vascular morphous,distribution,number and diameter in articular cartilage were observed with optical microscope after perfusing gelatin-ink,HE stain,and immunohistochemical stain.And the Mi-crovascular density and diameter were measured by image analysis.Results①Ink-gelatin perfusion showed:In normal control group,the micr-ovascular was filled with black ink in articular cartilage of the femoral head, trabecular bone around the edge of the structure.The end blood vessels and the network of capillaries connected in the articular cartilage.The intact morphous of intraosseous capillary vessels of the femoral head were observed clearly.Some small branches can be seen,which was coral-like.In group A and B,some fringes of vessels were unclear differently after 6 weeks.The number of perfused vessels had significantly decreased,and some were point-like distribution in the articular cartilage, which was perfused defectively and no significant ink lack of regional perfusion.The perfused vessels were no significant difference in the right or left femoral head.②HE staining showed:In normal control group,chondrocytes arranged neatly, trabecular bone was integrity and regulation.Empty bone lacunaes were rare; trabecular bone cells were clearly visible with nuclear larger central.Small vessels were integrity.There was no obvious endovascular embolization or bleeding and the hematopoietic cells were rich in medullary cavity.In group A and B,some trabecular bones becomed minute and irregularity partly and even fractured,some bone cells were karyopyknosis,margination or disappeared.Empty bone lacunaes increaseed evidently,the vessels decreased significantly and some were crack-like.The vascular walls damage,blood vessel occlusion or hemorrhage was seen;hematopoietic cells decreased significantly in medullary cavity.③Immunohistochemistry showed:The vascular endothelial cells(VEC) were marked by CD34 monoclonal antibody in articular cartilage of the femoral head, which were positive brown staining.In normal control group,the distribution of vessels was even,the vascular lumina were broadly consistent,vascular wall was integrity and endothelial cells were rich.In experimental group A and B,the vessels distributed sparsely in the articular cartilage,with no significant lumina stenosis.Part structure of the vascular walls was irregular,and vascular wall thickened slightly. Image analysis showed that the lumina of vessels were not constrictive apparentely in each group,but the microvessel density decreased significantly in the experimental group.Conclusions①The method which capillary vessels of bone were marked by gelatin-ink,showing the microvascular integrity,is simple and is one of the effective ways of morphologic study on blood vessel of bone.②Glucocorticoid could damage vascular endothelial,and inhibit capillary growth and regeneration in the femoral head,resulting in lower MVD of the femoral head.③High-dose glucocorticoid could cause the bone cell degeneration and necrosis, the fat cells hypertrophy,the hematopoietic cells diminish,reduction of number and density of vessels,vascular wall structural damage and intravascular thrombosis, which may be one of the reasons in early steroid-induced avascular necrosis of the femoral head.