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BACKGROUND: Exercise is an effective method for preventing and treating osteoporosis, but it is unclear whether its effect on postmenopausal osteoporosis is related to changes in bone autophagy levels. OBJECTIVE: To observe the effects of exercise via cellular autophagy on the morphology and mechanical properties of bone tissue in ovariectomized rats, and to explore the mechanism of exercise on bone mass in ovariectomized rats from the perspective of autophagy. METHODS: A rat model of postmenopausal osteoporosis was established, and a 24-week moderate-intensity exercise was used for intervention. After the experiment, serum estradiol levels were measured by ELISA, and bone mineral density and bone microstructure of the cortical and trabecular bone were detected by micro-CT. The biomechanical indicators of the tibia were tested by a three-point bending test. Autophagosomes were observed by transmission electron microscopy. The expression of LC3 and ATG7 proteins was analyzed by western blot. RESULTS AND CONCLUSION: The serum estradiol level in the ovariectomized group was significantly lower than that of the sham-operation group and ovariectomized+exercise group (P < 0.01). The body mass of rats in each group increased, and the order was the ovariectomized group > the ovariectomized+exercise group > the sham-operation group > the sham-operation+exercise group. The bone mineral density and bone mass of rats in all groups significantly increased (P < 0.01), but the increase in the ovariectomized group was significantly lower than that of the other groups, and the increase in the ovariectomized+exercise group was significantly higher than that of the ovariectomized group. Compared with the sham-operation group, the bone mineral density of the tibial cancellous bone in the sham-operation+exercise group was significantly increased (P < 0.01), while the bone mineral density in the ovariectomized and ovariectomized+exercise groups was significantly decreased (P < 0.01). Compared with the ovariectomized+exercise group, the ovariectomized group showed significantly lower bone volume fraction, number of trabeculae, and bone mineral density of cancellous bone (P < 0.05), extremely significantly lower trabecular thickness (P < 0.01), and significantly higher mean trabecular pattern factor, trabecular separation, and structural model index (P < 0.01). Compared with the ovariectomized group, the LC3-II/LC3-I ratio and the relative expression of ATG7 protein significantly increased in the ovariectomized+exercise group (P < 0.05). Compared with the sham-operation and ovariectomized groups, the number of autophagosomes increased in the sham-operation+exercise and ovariectomized+exercise groups, respectively. To conclude, moderate-intensity treadmill exercise can improve the bone microstructure and biomechanical properties of the tibial cancellous bone and increase bone mass in ovariectomized rats by increasing serum estradiol levels and bone autophagy levels. [ABSTRACT FROM AUTHOR]

BACKGROUND: Gutta-percha has low yield strength and shows hard and tough mechanical properties. On this basis, a sports protective gear that can be freely shaped according to the body shape has been developed, and it has been preliminarily confirmed that this performance can reduce the damage to athletes caused by external impact forces. OBJECTIVE: To evaluate the effect of gutta-percha splint on fracture fixation. METHODS: Thirty-five adult male New Zealand rabbits were used to establish closed fracture models of the left tibia by the modified three-point stress method. Totally 30 successful models were randomly divided into two groups (n=15) and fixed with gutta-percha splint and gypsum, respectively. The effects of the two external fixation methods were compared by X-ray imaging and fracture healing was observed at 2 hours, 4 and 6 weeks after fixation. After 6 weeks of fixation, the tibia specimens were observed for gross and histological morphology. RESULTS AND CONCLUSION: (1) X-ray films: Clear fracture line was seen 2 hours after fixation, without obvious periosteal reaction. After 4 weeks, the fracture line became blurred, and a large area of spindle low-density callus shadow was seen at the broken end. After 6 weeks, the fracture line nearly disappeared; the callus connected together to form a cortical bone bridge, and the bone marrow cavity was partially canalized, and partially close to recanalization. After 6 weeks, gray value at the fracture site was higher in the gutta-percha splint group than that in the gypsum group (P < 0.05). (2) General observation: In the gutta-percha splint group, except for three rabbits with malunion, the fracture line of the rest of the rabbits basically disappeared; part of the outer callus was absorbed, and the cortical bone density was close to the normal level. In the gypsum group, except for four rabbits with malunion, the fracture line of the rest of the rabbits disappeared, a small part of the outer callus was absorbed, and the cortical bone density was close to the normal level. (3) Histological morphology: In the gutta-percha splint group, new bone trabeculae were thick; the trabecular space was reduced and fused to form lamellar bone, and the medullary cavity had been partially recanalized. In the gypsum group, new bone trabeculae were reticular, forming a woven bone, and a large number of transected small arteries, veins and capillaries could be seen in the medullary cavity. (4) Complications: Within 6 weeks of fixation, the extremity swelling, purple darkening, displacement and malunion, and the number of local pressure ulcers in the gutta-percha splint group tended to be less than those in the gypsum group, but there was no significant difference in statistical analysis (P > 0.05). (5) The results showed that gutta-percha splint could play a similar fixation effect to plaster on the rabbit model of closed tibial fracture. [ABSTRACT FROM AUTHOR]