1H—MRS评价激素性骨质疏松模型兔：与病理对照

MR Spectroscopy in Evaluation of Glucocorticoid-Induced Osteoporosis in Rabbits:Comparison with Histopathology

目的采用3.0 T磁共振波谱(1H-MRS)动态评估糖皮质激素诱导的兔骨质疏松模型骨髓脂质变化规律。方法将20只(5个月)雌性新西兰大白兔随机分为对照组及肌肉注射甲泼尼龙琥珀酸钠组(MPS组),每组10只。分别于0、4、8、12周行L3～L4及股骨近端MRS扫描及骨密度测定,获取骨髓脂质分数(LF)。第8周及12周各处死实验兔10只行病理组织学检查。结果第4、12周时,MPS组LF较基线时分别增高35.9%和75.2%(P值均<0.001)。第4周始,组间LF有显著性差异,而组间骨密度至第8周时差异有统计学意义(P<0.05)。第8、12周MPS组骨髓脂肪细胞密度较对照组分别增高57.1%和35.4%,而骨髓脂肪细胞直径分别降低13.3%、增高22.7%,骨髓脂肪细胞面积分别增高30.8%和53.8%。结论 MRS可以动态评估骨髓脂质变化规律。糖皮质激素诱导的骨质疏松初期骨髓脂肪以小尺寸脂肪细胞为主,后期以大尺寸脂肪细胞为主。

Objective To evaluate the temporal changes of marrow lipids content and adipocytes in rabbit model of glu- cocorticoid induced osteoporosis （GIOP） using 3 Tesla proton MR spectroscopy （ 1 H-MRS）. Methods Twenty 5 - month - old female rabbits were randomly divided into control group and methylprednisolone （MPS） group （ n = 10 in each group）. Marrow lipids fraction （LF） and bone mineral density at left proximal femur and L3 -L4 vertebrae were measured by MR spectroscopy and dual energy X-ray absorptiometry at 0, 4, 8, and 12 weeks. Marrow adipocyte density （Ad. D） , adipocyte mean diameter （ Ad. MD） , and percentage area of adipocyte （ Ad. V/Ma. V ） were quantitatively evaluated by histopathology. Results LF in MPS group showed a dramatic increase over time. Compared with baseline, LF increased by 35.9% and 75.2% at 4th week and 12th week. In MPS group, LF increased was detected at 4th week, while signifi- cant bone loss was detected at 8th week compared with control group （ P 〈 0.05 ）. In contrast to control group at 8th week and 12th week , Ad. D increased by 57.1% and 35.4% in MPS group respectively. A decrease （ - 13.3% ） at 8th week but a significant increase （ ＋ 22.7% ） at 12th week were found in Ad. Ad. V/Ma. V in MPS group was much larger than those of control rabbits at 8th week and 12th week （P 〈 O. 05 ）. Conclusion The GIOP development was characterized by a significant increase in the number of small size adipocytes at early stage and big size adipocytes at late stage. MRS ap- pears to be the most powerful tool to characterize the dynamical change process of the marrow fat.