Steroid-Associated Hip Joint Collapse in Bipedal Emus

In this study we established a bipedal animal model of steroid-associated hip joint collapse in emus for testing potential treatment protocols to be developed for prevention of steroid-associated joint collapse in preclinical settings. Five adult male emus were treated with a steroid-associated osteonecrosis (SAON) induction protocol using combination of pulsed lipopolysaccharide (LPS) and methylprednisolone (MPS). Additional three emus were used as normal control. Post-induction, emu gait was observed, magnetic resonance imaging (MRI) was performed, and blood was collected for routine examination, including testing blood coagulation and lipid metabolism. Emus were sacrificed at week 24 post-induction, bilateral femora were collected for micro-computed tomography (micro-CT) and histological analysis. Asymmetric limping gait and abnormal MRI signals were found in steroid-treated emus. SAON was found in all emus with a joint collapse incidence of 70%. The percentage of neutrophils (Neut %) and parameters on lipid metabolism significantly increased after induction. Micro-CT revealed structure deterioration of subchondral trabecular bone. Histomorphometry showed larger fat cell fraction and size, thinning of subchondral plate and cartilage layer, smaller osteoblast perimeter percentage and less blood vessels distributed at collapsed region in SAON group as compared with the normal controls. Scanning electron microscope (SEM) showed poor mineral matrix and more osteo-lacunae outline in the collapsed region in SAON group. The combination of pulsed LPS and MPS developed in the current study was safe and effective to induce SAON and deterioration of subchondral bone in bipedal emus with subsequent femoral head collapse, a typical clinical feature observed in patients under pulsed steroid treatment. In conclusion, bipedal emus could be used as an effective preclinical experimental model to evaluate potential treatment protocols to be developed for prevention of ON-induced hip joint collapse in patients.

本研究构建了类固醇相关性髋关节塌陷的双足动物模型，以鸸鹋（emu）为实验对象，用于临床前研究场景中测试旨在预防类固醇相关性关节塌陷的潜在治疗方案。5只成年雄性鸸鹋采用脉冲脂多糖（pulsed lipopolysaccharide, LPS）联合甲泼尼龙（methylprednisolone, MPS）的方案，进行类固醇相关性骨坏死（steroid-associated osteonecrosis, SAON）造模。另有3只鸸鹋作为正常对照组。造模后，研究人员观察鸸鹋步态，开展磁共振成像（magnetic resonance imaging, MRI）检测，并采集血液进行常规检查，涵盖凝血功能与脂质代谢相关指标检测。造模后第24周处死所有受试鸸鹋，采集双侧股骨用于显微计算机断层扫描（micro-computed tomography, micro-CT）与组织学分析。
类固醇处理组鸸鹋可见不对称跛行步态与异常磁共振信号。所有类固醇处理组鸸鹋均检出SAON，关节塌陷发生率为70%。造模后，中性粒细胞百分比（Neut %）与脂质代谢相关指标均显著升高。显微CT结果显示软骨下骨小梁结构出现退变。组织形态计量学分析显示，与正常对照组相比，SAON组的脂肪细胞占比与体积均更大，软骨下板与软骨层变薄，成骨细胞周缘占比更低，塌陷区域的血管分布更少。扫描电子显微镜（scanning electron microscope, SEM）结果显示，SAON组塌陷区域的矿化基质质量较差，且骨陷窝轮廓更为明显。
本研究开发的脉冲LPS联合MPS造模方案安全有效，可在双足鸸鹋体内诱导SAON与软骨下骨退变，并继发股骨头塌陷——这一特征与接受脉冲类固醇治疗的患者所出现的典型临床表现一致。综上，双足鸸鹋可作为一种有效的临床前实验模型，用于评估旨在预防患者骨坏死相关性髋关节塌陷的潜在治疗方案。