BACKGROUND:The imbalance between bone resorption and bone formation in microgravity environments leads to significant bone loss in astronauts.Current research indicates that bone loss under microgravity conditions is the result of the combined effects of various cells,tissues,and systems. OBJECTIVE:To review different biological effects of microgravity on various cells,tissues,or systems,and summarize the mechanisms by which microgravity leads to the development of osteoporosis. METHODS:Databases such as PubMed,Web of Science,and the Cochrane Database were searched for relevant literature from 2000 to 2023.The inclusion criteria were all articles related to tissue engineering studies and basic research on osteoporosis caused by microgravity.Ultimately,85 articles were included for review. RESULTS AND CONCLUSION:(1)In microgravity environment,bone marrow mesenchymal stem cells tend to differentiate more into adipocytes rather than osteoblasts,and hematopoietic stem cells in this environment are more inclined to differentiate into osteoclasts,reducing differentiation into the erythroid lineage.At the same time,microgravity inhibits the proliferation and differentiation of osteoblasts,promotes apoptosis of osteoblasts,alters cell morphology,and reduces the mineralization capacity of osteoblasts.Microgravity significantly increases the number and activity of osteoclasts.Microgravity also hinders the differentiation of osteoblasts into osteocytes and promotes the apoptosis of osteocytes.(2)In a microgravity environment,the body experiences changes such as skeletal muscle atrophy,microvascular remodeling,bone microcirculation disorders,and endocrine disruption.These changes lead to mechanical unloading in the bone microenvironment,insufficient blood perfusion,and calcium cycle disorders,which significantly impact the development of osteoporosis.(3)At present,the mechanism by which microgravity causes osteoporosis is relatively complex.A deeper study of these physiological mechanisms is crucial to ensuring the health of astronauts during long-term space missions,and provides a theoretical basis for the prevention and treatment of osteoporosis.

Objective To deveplope construct and validate a novel multiplex PCR system comprised of 30 Y-STR markers only with low and moderate mutation rates. Methods 30 Y-STRs characterized by low/moderate mutation rate and middle/high polymorphic was amplified simultaneously in a multiplex PCR system using the six color labeling fluorescence. PCR product was analyzed in a ABI 3500XL Genetic Analyzer. The accuracy, specifity, sensitivity and stability of the system and its validation on the mixtures were evaluated. Results The validation studies demonstrated that the system is a stable, accurate, and sensitive multiplex PCR system. The sensitivity was 0.0625ng DNA. Y-STR could be detection in a male/female DNA mixture ratio of 1:4. Conclusion The primary study demonstrates that this multiplex PCR system is effective and reliable for forensic routine DNA analysis. It will be very helpful for constructing Chinese forensic Y-STR database and population genetic research.

The main function of anterior cruciate ligament (ACL) is to maintain stability of the knee joint and prevent anterior displacement of the tibial plateau. ACL injury accounts for more than 50% of the knee joint injuries. If not timely handled, it will increase the risk of secondary injuries to structures such as the meniscus and cartilage, causing chronic pain and degeneration of the knee joint. Although most ACL injuries can be determined by their direct signs on MRI, the identification of complex situations and partial tears of ACL are still not satisfactory, which subsequently affects treatment strategies. After ACL injury, changes in anatomical relationship of the knee joint can also lead to morphological changes in other structures such as the posterior cruciate ligament (PCL) on MRI, and these indirect signs can assist in the diagnosis of ACL injury. The authors reviewed the application of MRI-related indicators of PCL in diagnosing ACL injury, hoping to provide references and new ideas for clinical decision-making.

Objective:To compare the efficacy of medial patellofemoral ligament (MPFL) reconstruction using single half tunnel, double half curved tunnel and suture anchor fixation in the treatment of patellar dislocation.Methods:A retrospective cohort study was used to analyze the clinical data of 58 patients with patellar dislocation treated in Second Hospital of Lanzhou University from June 2018 to February 2021, including 22 males and 36 females, aged 12-34 years [(19.6±5.5)years]. MPFL reconstruction was performed arthroscopically using single half tunnel fixation in 20 patients (single half tunnel group), double half curved tunnel fixation in 18 (double half curved tunnel group) and suture anchor fixation in 20 (suture anchor group). The Lysholm score, International Knee Documentation Committee (IKDC) score and Tegner activity score were compared among groups before operation, at 3 months after operation and at the last follow-up. The knee range of motion was compared among the three groups at 3 months after operation and at the last follow-up. The postoperative complications of the three groups were observed at the last follow-up.Results:All patients were followed up for 9-39 months [(26.5±9.1)months]. In single half tunnel group, double half curved tunnel group and suture anchor group, the Lysholm score was (78.4±12.0)points, (88.7±7.5)points and (81.1±9.8)points at 3 months after operation, and (80.4±14.2)points, (90.9±9.0)points and (83.3±9.1)points at the last follow-up. The postoperative Lysholm score in all groups was significantly increased from that preoperatively (all P<0.01). The Lysholm score in double half curved tunnel group was significantly higher than that in other two groups at 3 months after operation and at last follow-up (all P<0.05), but there was no significant difference between other groups (all P>0.05). In single half tunnel group, double half curved tunnel group and suture anchor group, the IKDC score was (76.7±12.2)points, (78.4±8.9)points and (81.0±8.1)points at 3 months after operation, and (77.6±15.8)points, (83.2±7.8)points and (82.4±12.4)points at the last follow-up. The postoperative IKDC score in all groups was significantly increased from that preoperatively (all P<0.01), but there was no significant difference among the three groups (all P>0.05). In single half tunnel group, double half curved tunnel group and suture anchor group, the Tegner score was (4.0±1.2)points, (5.4±1.7)points and (5.3±1.7)points at 3 months after operation, and (4.1±1.4)points, (5.8±1.8)points and (5.3±2.2)points at the last follow-up. The postoperative Tegner score in all groups was significantly improved from that preoperatively (all P<0.01). The Tegner score in single half tunnel group was significantly lower than that in other two groups at 3 months after operation and at last follow-up (all P<0.05), but there was no significant difference between other groups (all P>0.05). In single half tunnel group, double half curved tunnel group and suture anchor group, the knee range of motion was (122.3±6.4)°, (121.7±7.1)° and (123.3±5.7)° at the last follow-up, which were significantly increased from (117.3±8.0)°, (115.3±7.9)° and (116.8±8.3)° at 3 months after operation (all P<0.05), with no significant difference among the three groups (all P>0.05). The postoperative complication rate was 10.0% (2/20) in single half tunnel group, 5.6% (1/18) in double half curved tunnel group, and 25.0% (5/20) in suture anchor group ( P>0.05). Conclusions:For patellar dislocation, MPFL reconstruction using single half tunnel, double half curve tunnel and suture anchor fixation have achieved satisfactory improvement of knee range of motion, but knee functional recovery is much better after double half curved tunnel fixation.

BACKGROUND:Fluid shear stress plays an important role in osteoblast proliferation and apoptosis.However,whether Caveolin-1 is involved in the process of fluid shear stress-induced proliferation and apoptosis in osteoblasts is unknown. OBJECTIVE:To explore the role of Caveolin-1 in fluid shear stress-regulated osteoblast proliferation and apoptosis. METHODS:The MC3T3-E1 osteoblasts in good growth status were selected and loaded with fluid shear stress at an intensity of 1.2 Pa for different times(0,30,60,90 minutes).The expression of Caveolin-1 protein was observed and conditions with a time of 60 minutes were screened for the experiment.MC3T3-E1 cells were divided into control group,fluid shear stress group,fluid shear stress+pcDNA 3.1 group(control),fluid shear stress+pcDNA Cav-1 group(plasmid overexpression),and intervened with fluid shear stress and overexpression of Cav-1,respectively.The expression of molecules related to proliferation and apoptosis in MC3T3-E1 cells was detected by qRT-PCR and western blot.In addition,the proliferative activity of MC3T3-E1 cells was detected by cell counting kit-8 and EdU assay;and cell apoptosis was detected by Hoechst 33258 and flow cytometry. RESULTS AND CONCLUSION:The expression of Caveolin-1 in MC3T3-E1 cells was significantly down-regulated after loading fluid shear stress,and the expression level was lowest after 60 minutes.Overexpression of Caveolin-1 attenuated the proliferation-promoting and apoptosis-suppressing effects of fluid shear stress in MC3T3-E1 cells.In conclusion,Caveolin-1 has a vital role in fluid shear stress-regulated osteoblast proliferation and apoptosis,which may offer a potential therapeutic strategy for osteoporosis.

BACKGROUND:The extracellular-regulated protein kinase 5(ERK5)signaling protein is essential for the survival of organisms,and resveratrol can promote osteoblast proliferation through various pathways.However,whether resveratrol can regulate osteoblast function through the ERK5 signaling protein needs further verification. OBJECTIVE:To explore the regulatory effect of ERK5 on the proliferation of MC3T3-E1 cells and related secreted proteins,and to further verify whether resveratrol can complete the above process by activating ERK5. METHODS:Mouse MC3T3-E1 preosteoblasts were treated with complete culture medium,XMD8-92(an ERK5 inhibitor),epidermal growth factor(an ERK5 activator),resveratrol alone,XMD8-92+EGF,and resveratrol+XMD8-92,respectively.Western blot assay was used to detect the expression of ERK5 and p-ERK5 proteins,proliferation-related proteins Cyclin D1,CDK4 and PCNA,and osteoblast-secreted proteins osteoprotegerin and receptor activator of nuclear factor-κB ligand in MC3T3-E1 cells of each group.The fluorescence intensity of ERK5,osteoprotegerin and receptor activator of nuclear factor-κB ligand in each group was detected by cell immunofluorescence staining,and cell proliferation was detected by EdU staining,respectively.The appropriate concentration and time of resveratrol intervention in MC3T3-E1 cells were determined by cell morphology observation and cell counting kit-8 assay. RESULTS AND CONCLUSION:The activation of ERK5 signaling protein could effectively promote the proliferation of MC3T3-E1 cells,up-regulate the osteoprotegerin/receptor activator of nuclear factor-κB ligand ratio.The appropriate concentration and time for resveratrol intervention in MC3T3-E1 cells was 5 μmol/L and 24 hours,respectively.Resveratrol could activate ERK5 signaling protein,thereby promoting osteoblast proliferation and up-regulating the osteoprotegerin/RANKL ratio.All these results indicate that resveratrol can promote the proliferation of MC3T3-E1 cells and up-regulate the osteoprotegerin/RANKL ratio by activating the ERK5 signaling protein.