Zhensong Yao

Variance of spinal osteoporosis induced by dexamethasone and methylprednisolone and its associated mechanism

BACKGROUND Glucocorticoid (GC) administration is the most common cause of secondary osteoporosis. Previous studies investigated GCs dose and frequency correlated positively with the side effects of glucocorticoid on bone health, however the impaired effect of various types of GCs on bone has not yet been reported. PURPOSE The aim is to compare the effect of long-acting (dexamethasone) and relatively short-acting glucocorticoid (methylprednisolone) on rat lumbar spine and try to explore the associated mechanism. METHOD Sprague Dawley rats (N=48) were randomly divided into four groups: baseline group (BL), control group (CON), methylprednisolone group (MP) and dexamethasone group (DEXA). BL rats were euthanized to remain as baseline (M0) at the beginning of experiment. CON group were injected daily with vehicle, while the other groups were given a daily subcutaneous injection of 1mg/kg methylprednisolone and were given a subcutaneous injection of 0.6mg/kg dexamethasone per 3days, respectively. CON, MP and DEXA groups were monitored at 4th week (M1), 8th week (M2) and 12th week (M3) after intervention. Dual-energy X-ray, micro-computed tomography, compressive test, enzyme-linked immunosorbent assay have been used for bone mineral density, microarchitecture, biomechanical property of vertebrae and levels of estrogen, PINP and β-CTX, respectively. mRNA expression analysis of Biglycan, Col1a1, MMP9, Cathepsin K, Runx2, OPG, LRP5, Sclerostin were performed. RESULT We found that the bone mineral density (BMD) was significantly lower in DEXA rats at M3 compared with MP rats. The relative surface and trabecular number were significantly lower in DEXA group than that in MP group at M2, while trabecular separation was significantly higher in DEXA group than that in MP group at the same point. The compressive strength was significantly lower in L4 of DEXA than that in MP rats at M2 and M3. The levels of both PINP and estradiol in DEXA group were lower than MP group at M3, even though without statistical significance. The expression of bone formation marker Runx2 was significantly down-regulated at M3 in DEXA group compared with MP, CON and BL groups, while the expression of Col1a1 was significantly up-regulated and biglycan, LRP-5, OPG were significantly down-regulated in GCs intervention groups compared with CON and BL groups. There were no statistical differences in MMP9, Cathepsin K, Sclerostin among CON, MP and DEXA groups. CONCLUSION These results indicate that dexamethasone, the long-acting glucocorticoid, generates more serious osteoporosis of rat lumbar spine than methylprednisolone, which is relatively short-acting glucocorticoid. The discrepancy between the two GCs inducing osteoporosis may be mainly caused by a decrease in bone formation. RUNX2 and Col1a1 may be the two of critical genes inducing the discrepant impairment.

Effects of combined ovariectomy with dexamethasone on rat lumbar vertebrae.

Objective:This study investigated the effects of combined ovariectomy with dexamethasone treatment on rat lumbar vertebrae in comparison with osteoporosis induced via ovariectomy or dexamethasone alone, and analysis of the associated molecular mechanism. Methods:Sixty-two female Sprague–Dawley rats (3 months’ old) were randomly divided into five treatment groups: an untreated baseline (BL) group; those receiving a sham operation (SHAM); those receiving a dexamethasone injection alone (DEXA); those undergoing bilateral ovariectomy (OVX); and those subjected to both ovariectomy and dexamethasone injection (OVX-DEXA). Animals in the BL group were euthanized at the beginning of the experiment, whereas animals in the remaining groups were euthanized at the end of the first month (M1), second month (M2), or third month (M3). Bone mineral density, bone microarchitecture, biomechanical properties of vertebrae, and serum levels of estrogen, amino-terminal propeptide of type I collagen (PINP), and &bgr;-C-telopeptide of type I collagen (&bgr;-CTX) were measured. In addition, we examined biglycan, runt-related transcription factor 2 (RUNX2), osteoprotegerin (OPG), lipoprotein receptor-related protein-5 (LRP-5), cathepsin K (CTSK), and sclerostin mRNA expression. Results:Bone mineral content and bone mineral density were markedly lower in the OVX-DEXA group compared with the OVX group at all time points examined. The relative bone surface (BS/TV, mm–1), relative bone volume (BV/TV,%), and trabecular number (Tb.N, 1/mm) were markedly lower in the OVX-DEXA group compared with the remaining groups, whereas trabecular separation (Tb.Sp, mm) was markedly higher in the OVX-DEXA group compared with the remaining groups at M2 or M3. The OVX-DEXA group showed lower compressive strength and lower stiffness compared with the other groups at M2 and M3. Compressive displacement and energy absorption capacity were also markedly lower in the OVX-DEXA group compared with the OVX group at M3. Estradiol levels were markedly lower in the OVX-DEXA group compared with the other groups. Biglycan, runt-related transcription factor 2, osteoprotegerin, and lipoprotein receptor-related protein-5 were down-regulated in the DEXA, OVX, and OVX-DEXA groups compared with the BL and SHAM groups, whereas cathepsin K and sclerostin were up-regulated in the OVX-DEXA group compared with the DEXA and OVX groups. Conclusions:Ovariectomy combined with dexamethasone induced more serious osteoporosis in the rat lumbar spine than either ovariectomy or dexamethasone alone. The combined effect may be due to a combination of suppressed bone formation and increased bone resorption related to an estradiol deficit.

Animal models for glucocorticoid-induced postmenopausal osteoporosis: An updated review

Glucocorticoid-induced postmenopausal osteoporosis is a severe osteoporosis, with high risk of major osteoporotic fractures. This severe osteoporosis urges more extensive and deeper basic study, in which suitable animal models are indispensable. However, no relevant review is available introducing this model systematically. Based on the recent studies on GI-PMOP, this brief review introduces the GI-PMOP animal model in terms of its establishment, evaluation of bone mass and discuss its molecular mechanism. Rat, rabbit and sheep with their respective merits were chosen. Both direct and indirect evaluation of bone mass help to understand the bone metabolism under different intervention. The crucial signaling pathways, miRNAs, osteogenic- or adipogenic- related factors and estrogen level may be the predominant contributors to the development of glucocorticoid-induced postmenopausal osteoporosis.

Biomechanical effects of cement distribution in the fractured area on osteoporotic vertebral compression fractures: a three-dimensional finite element analysis

BACKGROUND According to some clinical studies, insufficient cement distribution (ID) in the fractured area and asymmetrical cement distribution around the fractured area were thought to be the reasons for unrelieved pain and recollapse after percutaneous vertebral augmentation (PVA) in the treatment of symptomatic osteoporotic vertebral compression fractures. METHODS Finite element methods were used to investigate the biomechanical variance among three patterns of cement distribution (ID and sufficient cement distribution in the fractured area and asymmetrical cement distribution around the fractured area including upward [BU] and downward [BD] cement distribution). RESULTS Compared with fractured vertebra before PVA, distribution of von Mises stress in the cancellous bone was transferred to be concentrated at the cancellous bone surrounding cement after PVA, whereas it was not changed in the cortical bone. Compared with sufficient cement distribution group, maximum von Mises stress in the cancellous bone and cortical bone and maximum displacement of augmented vertebra increased significantly in the ID group, whereas asymmetrical cement distribution around the fractured area in BU and BD groups mainly increased maximum von Mises stress in the cancellous bone significantly. Similar results could be seen in all loading conditions. CONCLUSIONS ID in the fractured area may lead to unrelieved pain after PVA in the treatment of symptomatic osteoporotic vertebral compression fractures as maximum displacement of augmented vertebral body increased significantly. Both ID in the fractured area and asymmetrical cement distribution around the fractured area are more likely to induce recollapse of augmented vertebra because they increased maximum von Mises stress in the cancellous bone and cortical bone of augmented vertebra significantly.

Risk factors for recollapse of the augmented vertebrae after percutaneous vertebroplasty for osteoporotic vertebral fractures with intravertebral vacuum cleft.

Abstract To determine risk factors related to recollapse of the augmented vertebrae after percutaneous vertebroplasty (PVP) for osteoporotic vertebral compression fractures (OVCFs) with intravertebral vacuum cleft (IVC). Fifty-two patients treated with PVP for single OVCFs with the IVC were retrospectively reviewed. The follow-up period was at least 2 years. Vertebral height loss ≥15% or kyphotic angle ≥10° at the final follow-up in relation to the immediately postoperative values were adopted as a definition of recollapse of the augmented vertebrae. Correlation analysis and multiple logistic regression analyses were performed to elucidate the related clinical or radiological factors for recollapse of the augmented vertebrae including age, gender, bone mineral density, preoperative fracture severity, locations of IVC sign, distribution patterns of polymethylmethacrylate (PMMA), reduction rate, and reduction angle. Assuming the increase of height loss more than 15% as a criterion of recollapse, only cleft filling pattern of PMMA in the IVC area was a significant risk factor for recollapse of the augmented vertebrae (P < 0.01). Assuming ≥10° progression of kyphotic angle as a criterion, cleft filling pattern of PMMA and higher values of reduction angle was as 2 significant risk factors for recollapse of the augmented vertebrae (P < 0.01). No significant difference was found in other clinical and radiological factors (P > 0.05). Cleft filling pattern of PMMA and higher values of reduction angle may play an important role in inducing recollapse of the augmented vertebrae after PVP for OVCFs with the IVC. Careful observation of patients with these conditions is necessary to prevent deterioration of their clinical course.

Implications of the Interaction Between miRNAs and Autophagy in Osteoporosis

Abstract Imbalances between bone formation and resorption are the primary cause of osteoporosis. However, currently, a detailed molecular mechanism of osteoporosis is not available. Autophagy is the conserved process characterized by degrading and recycling aggregated proteins, intracellular pathogens, and damaged organelles. MicroRNAs (miRNAs) are novel regulatory factors that play important roles in numerous cellular processes, including autophagy, through the posttranscriptional regulation of gene expression. Conversely, autophagy plays a role in the regulation of miRNA homeostasis. Recent advances have revealed that both autophagy and miRNAs are involved in the maintenance of bone homoeostasis, whereas the role of the interaction of miRNAs with autophagy in osteoporosis remains unclear. In this paper, we review previous reports on autophagy, miRNAs, and their interaction in osteoporosis.

Mammalian Target of Rapamycin As a Therapeutic Target in Osteoporosis.

The mechanistic target of rapamycin (mTOR) plays a key role in sensing and integrating large amounts of environmental cues to regulate organismal growth, homeostasis, and many major cellular processes. Recently, mounting evidences highlight its roles in regulating bone homeostasis, which sheds light on the pathogenesis of osteoporosis. The activation/inhibition of mTOR signaling is reported to positively/negatively regulate bone marrow mesenchymal stem cells (BMSCs)/osteoblasts‐mediated bone formation, adipogenic differentiation, osteocytes homeostasis, and osteoclasts‐mediated bone resorption, which result in the changes of bone homeostasis, thereby resulting in or protect against osteoporosis. Given the likely importance of mTOR signaling in the pathogenesis of osteoporosis, here we discuss the detailed mechanisms in mTOR machinery and its association with osteoporosis therapy.

Promotion effect of extracts from plastrum testudinis on alendronate against glucocorticoid-induced osteoporosis in rat spine

Alendronate (ALN) is a key therapeutic used to treat glucocorticoid-induced osteoporosis (GIOP), but may induce severe side effects. We showed earlier that plastrum testudinis extracts (PTE) prevented and treated GIOP in vivo. However, clinically, PTE is seldom used alone. Herein, we reveal the synergistic effect of ALN and PTE can treat GIOP of the rat spine and define the mechanism. Sprague-Dawley rats were randomly assigned to four groups: a vehicle group, a GIOP group, an ALN group, and an ALN+PTE group. Each group was further divided into two experimental phases, including dexamethasone (DXM) intervention and withdrawal. Bone mass, microarchitecture, biomechanics, bone-turnover markers, and histomorphology were evaluated. The mRNA and protein expression levels of CTSK and Runx2 were detemined. We found that ALN+PTE improved bone quantity and quality, bone strength, bone turnover; and mitigated histological damage during glucocorticoid intervention and withdrawal. The therapeutic effect was better than that afforded by ALN alone. ALN+PTE reduced CTSK protein expression, promoted Runx2 mRNA and protein expression to varying extents, and more strongly inhibited bone resorption than did ALN alone. Overall, the synergistic effect mediated by ALN+PTE reversed GIOP during DXM intervention and withdrawal via affecting CTSK and Runx2 expression at mRNA and protein levels.

Efficacy and safety of the target puncture technique for treatment of osteoporotic vertebral compression fractures with intravertebral clefts

Objective To compare the efficacy and safety of our target puncture technique with the traditional technique during percutaneous kyphoplasty (PKP) for osteoporotic vertebral compression fractures (OVCFs) with intravertebral clefts (IVCs). Methods 104 patients treated with PKP for single OVCFs with IVCs were retrospectively reviewed. All patients were divided into three groups: cleft filling by the traditional technique (Group A, n=18); interdigitated filling (Group B, n=50); and overfilling by the target technique (Group C, n=36). Oswestry disability index (ODI) and visual analog scale (VAS) scores and radiological evidence of vertebral body height and kyphotic angle, cement leakage, and adjacent vertebral fractures were studied before and after surgery (immediate, 1 and 2 years). Results The ODI and VAS scores decreased for all patients and no significant difference was found between the three groups after treatment. However, 1 and 2 years after surgery a greater increase in ODI and VAS scores was observed in Group A compared with the other two groups. The initial correction of vertebral body height and kyphotic angle was not significant among the three groups. However, loss of correction was greater in Group A. No significant difference was found in cement leakage. The incidence of adjacent vertebral fractures in Group C was higher than in the other two groups. Conclusions Different puncture techniques were initially effective for all patients with IVCs. However, cement cleft filling by the traditional technique was found to have less stability causing higher VAS/ODI scores and greater loss of correction. Hence, our target puncture technique was recommended in this study.

Extracts from plastrum testudinis reverse glucocorticoid-induced spinal osteoporosis of rats via targeting osteoblastic and osteoclastic markers

Extracts from plastrum testudinis (PTE), an important traditional Chinese medicine, have been demonstrated promotion of osteoblastic function in vitro. This study aims to investigate the protective effect of PTE on glucocorticoid-induced osteoporosis(GIOP) in vivo and analyze therapeutic targets of PTE on GIOP. SD rats were randomly assigned to two experiments: preventive and therapeutic experiments, in which rats respectively received oral PTE at the same time of glucocorticoid injection or after glucocorticoid injection inducing osteoporosis. BMD, microarchitecture, biomechanics, bone metabolism markers and histomorphology were evaluated. mRNA and protein expression of OPG, Runx2, CTSK and MMP9 were examined.Results showed bone quality and bone quantity were significantly elevated by PTE. Histomorphometry showed thicker and denser bone trabecularsand more osteoblasts and less osteoclasts in group of PTE intervention. The mRNA expression of OPG was significantly upregulated whereas expression of CTSK was significantly downregulatedin different groups of PTE intervention. Stronger immunostaining for Runx2 and weaker immunostaining for CTSK were observed in groups of PTE intervention. This demonstrated that PTE may reverse GIOP in prevention and management via targeting OPG, Runx2 and CTSK in mRNA and protein levels.