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 ß-C-telopeptide of type I collagen (ß-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.

[PHASIC CHANGES OF BONE MASS, BONE TURNOVER MARKERS, AND ESTROGEN LEVELS AT DIFFERENT TIME POINTS AFTER GLUCOCORTICOID INTERVENTION AND THEIR CORRELATION IN RATS].

OBJECTIVE: To analyze the phasic changes of bone mass, bone turnover markers, and estrogen levels at different time points after glucocorticoid (GC) intervention in rat and their correlation. METHODS: Thirty-four female 3-month-old Sprague Dawley rats were randomly divided into the following 3 groups: baseline group (n = 6), dexamethasone (DXM) group (n = 14), and control group (n = 14). Rats were injected with DXM at the dose of 0.75 mg/kg, twice a week for 12 weeks in DXM group, with salt solution lavage in control group, and no treatment was given in baseline group. The body mass, adrenal weight, and uterus weight were measured. Bone mineral density (BMD), bone mineral content (BMC), and bone area (BA) of lumbar vertebral and femurs were detected by dual energy X-ray absorptiometry. Meanwhile, the serum levels of N-terminal propeptide of type I procollagen (PINP), C-terminal cross-linking telopeptide of type I collagen (ß-CTX), and estrogen levels were determined by ELISA before experiment in baseline group and at 4, 8, and 12 weeks after experiment in control and DXM groups. At last, the correlation was analyzed among body weight, BMD, PINP, ß-CTX, estrogen levels, and GC intervention duration of DXM group. RESULTS: The body mass, adrenal weight, and uterus weight in DXM group were signiflcantly lower than those in baseline group and control group at all the time points (P < 0.05). The levels of PINP and ß-CTX elevated slowly in DXM group, significant difference was found at 12 weeks (P < 0.05), but no significant difference at the 4 and 8 weeks (P > 0.05) when compared with those in baseline group and control group. The estrogen level in DXM group was significantly lower than that in baseline group and control group at all the time points (P < 0.05). BMD, BMC, and BA of lumbar vertebral and femurs in DXM group were significantly lower than those in control group at all the time points after GC intervention (P < 0.05). Loss of bone mass of L2 and femoral trochanteric region in DXM group was the lowest of all ranges of interest (ROIs). BMC and BA of lumbar vertebrae and BA of femoral shaft in DXM group at 4 weeks were significantly lower than those in baseline group (P < 0.05). But there was no significant difference in BMD, BMC, and BA of other lumbar vertebrae and femurs' ROIs between DXM group and baseline group at all the time points (P > 0.05). After GC intervention, BMD of lumbar vertebrae and femurs had negative correlation with PINP and ß-CTX (P < 0.05) and positive correlation with estrogen level (P < 0.05). CONCLUSION: The bone mass decreases rapidly at the early stage after GC intervention and then maintains a low level with time, the levels of bone turnover markers show a progressive increase, and the estrogen levels show a decrease trend. In addition, body weight, the levels of bone turnover markers and estrogen are associated with the change of bone mass.

[COMPARISON OF EFFECTIVENESS AND RADIOLOGICAL FEATURES BETWEEN SINGLE AND DOUBLE CAGE IMPLANTING THROUGH UNILATERAL TRANSFORAMINAL LUMBAR INTERBODY FUSION].

OBJECTIVE: To compare the effectiveness and imaging features between implanting single and double Cage into intervertebral body through unilateral transforaminal lumbar interbody fusion (TLIF). METHODS: The clinical data were collected and analyzed from 104 patients who underwent unilateral TLIF between January 2013 and October 2014, who were divided into 2 groups: single Cage was implanted into intervertebral body in 64 cases (76 segments) in traditional group, and double Cage was implanted into intervertebral body in 56 cases (70 segments) in reformative group. There was no significant difference in age, gender, bone mineral density, operation segments between 2 groups (P > 0.05). The visual analogue scale (VAS), Oswestry disability index (ODI), and Japanese Orthopedic Association (JOA) scores were used to evaluate the effectiveness; the area of intervertebral bone-graft, fusion rate, height of intervertebral space, and the number of Cage subsidence were measured by CT scan. RESULTS: All the patients were followed up 12.85 months on average (range, 9-15 months). The VAS, ODI, and JOA scores were significantly improved at each time point after operation when compared with preoperative values (P < 0.05), and no significant difference was found between 2 groups (P > 0.05) except VAS and ODI at 12 months after operation (P < 0.05). However, the area of intervertebral bone-graft in reformative group [(5.94 ± 1.17) cm2] was significantly larger than that in traditional group [(4.81± 0.97) cm2] at 7 days after operation (t = -6.365, P = 0.000). At 3 and 12 months after operation, the fusion rate was respectively 84.2% and 92.1% in traditional group and was respectively 88.6% and 94.3% in reformative group. Although the height of intervertebral space were increased when compared with preoperative height, the incidence rates of Cages subsidence in traditional group were 44.74% and 47.37% respectively at 3 and 12 months after operation and were significantly higher those that in reformative group (11.43% and 14.29% respectively) (P < 0.05). In addition, the height difference between affected side and normal side in traditional group was significantly larger than that in reformative group (P < 0.05). CONCLUSION: Both single and double Cage implanted into the intervertebral body through unilateral TLIF have good effectiveness. However, double Cage implanted into intervertebral body may hold the height of intervertebral space, reduce the incident rate of Cage subsidence, and prevent sagittal imbalance.