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 was designed to investigate any histopathological changes in the growth plate using the spontaneously hypertensive rats (SHRs).
Materials 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 femoral head and WKY were used as control. 5-Bromo-2'-deoxyuridin (BrdU) was injected and BrdU immunohistichemistry was performed for the cell kinetic analysis. TUNEL (transferase-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, proliferative, 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 aging, 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 of [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 head of SHR was found to be affected by the disease process of ischemic n
