Cellular Kinetics in Plate of the Femoral Head of the Spontaneously Hypertensive Rats

Purpose:Although metaphyseal growth plates are assumed to be affected in the ischemic necrosis of the epiphysis in children´s femoral head, little is known about the pathologic changes occurring within the growth plate. The present study ws designed to investigate any histopathological changes in the growth plate using the spontaneously hypertensive rats (SHRs). Meterials and Methods: 60 SHRs and 30 Wister Kyoto rats (WKY) were sacrificed at each of 6,9,12,15 and 18 weeks of age. SHRs were divided into two groups, [SHR-n] and [SHR+n], according to the existence of histopathological changes of ischemic necrosis of the secondary ossification center of the existence of histopathological changes of ischemic necrosis of the secondary ossification center of the femoral gead and WKY were used as control. 5-bromo-2´-deoxyuridin (Brdu) was injected and BedU immunohistichemistry was performed for the cell kinetic analysis. TUNEL (reansferase-mediated deoxyuridine triphosphate-biotin nick end labeling) assay was done for the investigation of any apoptotic changes in the growth plate. In both TUNEL and BrdU staining, the positive cells were counted in each zones of the growth plate. The length of each zone of growth plate - resting, proloferative and hypertrophic zone was measured by histomorphometric analysis. All the data were analyzed by two way ANOVA. Results:Total length of growth plate was found to be decreased overtime. At earlier growth stages, the length of the growth plate of [SHR+n[ group was shorter than those of the [SHR-n] and WKY group. As again, hypertrophic zone of the growth plate in [SHR+n] was the mostly affected zone of the growth plate. The cell proliferation analysis of the growth plate in [SHR+n] showed lower activity than those of the [SHR-n]and WKY at earlier growth stages. Apoptosis occurring in the growth plate of [SHR+n] were observed mainly at earlier stages. and at the hypertrophic zone in later stages. Conclusion:The metaphyseal growth plate in the femoral gead of SHR was found to be affected by the disease process of ischemic necrosis of the epophysis of the femoral head, and this would explain the reason why round femoral head is frequently associated with relative overgrowth of the greater trovhanter in later stages of Legg-Perthes disease.ope