Objective To establish two osteoarthritis models of destabilization of the medial meniscus(DMM)and chronic ankle instability(CAI)in mice,and compare the effects of knee osteoarthritis with varus deformity on ipsilateral ankle cartilage degeneration.Methods Thirty 6-week-old C57BL/6J male mice were randomly divided into a control group and two surgical groups(DMM group and CAI group),respectively.The progression of ankle joint degeneration was quantitatively evaluated through behavioral observation,imaging techniques and histopathology analysis in each group of mice over a 12-week period.Results A decline in gait stability and balance was observed in two surgical groups.Compared to the control group,the time required to cross the balance beam was increased by 23.20％,and the number of slips was increased by 43.26％at 12th week postoperatively in the DMM group.The bone volume fraction and bone mineral density of ankle joints also increased.Meanwhile,wear and tear of the ankle cartilage were found,with the formation of osteophytes,and OARSI score was increased by 88.89％.These changes in ankle joint were more pronounced in the CAI group.Conclusions This mouse model-based study revealed a coupling relationship between the knee and ankle motion.Knee osteoarthritis with varus deformity could lead to a significant ankle joint degeneration,while the damage was less severe than that observed in CAI.

Objective To study the characteristics of gait behavior in a mouse model of chronic ankle instability and provide a reference for the study of the mechanism of chronic ankle instability as well as drug screening and evaluation.Methods Thirty C57BL/6J male mice were randomly divided into a control group(n=15)and an injury group(n=15).In the control group,the ankle joint underwent sham operation,and in the injury group,the anterior talofibular ligament and calcaneofibular ligament of the left ankle joint were transected.Gait parameters were analyzed in each group using TreadScan passive gait analysis system.Results Compared with the control group,the injury group showed a 28.43％increase(P＜0.05)in average standing time and a 23.07％increase(P＜0.05)in the percentage of standing time,whereas the average swing time and the percentage of swing time were shortened by 50.63％(P＜0.001)and 19.75％(P＜0.01),respectively.The average braking time and average stride time in the injury group were also shortened by 18.37％(P＜0.01)and 37.86％(P＜0.001),respectively.The injury group exhibited a decrease in step length,anterior-posterior step width,and mediolateral step width by 36.96％,13.66％,and 8.10％,respectively.The total movement speed and instantaneous speed decreased by 8.05％and 11.12％,respectively,while the stride frequency increased by 51.41％.The average footprint area and average maximum standing area decreased by 8.8％and 13.24％,respectively,and foot pressure decreased by only 3％.The plantar pressure distribution in the injury group was uneven,with a more obvious decrease in plantar pressure in the hindfoot,especially a 13.92％decrease in plantar pressure in the right posterior quadrant.Conclusions Mice with chronic ankle instability adopt a more conservative walking pattern during the motion,reducing movement volume and amplitude to improve coordination and stability during walking.

Objective To study the characteristics of gait behavior in a mouse model of chronic ankle instability and provide a reference for the study of the mechanism of chronic ankle instability as well as drug screening and evaluation.Methods Thirty C57BL/6J male mice were randomly divided into a control group(n=15)and an injury group(n=15).In the control group,the ankle joint underwent sham operation,and in the injury group,the anterior talofibular ligament and calcaneofibular ligament of the left ankle joint were transected.Gait parameters were analyzed in each group using TreadScan passive gait analysis system.Results Compared with the control group,the injury group showed a 28.43％increase(P＜0.05)in average standing time and a 23.07％increase(P＜0.05)in the percentage of standing time,whereas the average swing time and the percentage of swing time were shortened by 50.63％(P＜0.001)and 19.75％(P＜0.01),respectively.The average braking time and average stride time in the injury group were also shortened by 18.37％(P＜0.01)and 37.86％(P＜0.001),respectively.The injury group exhibited a decrease in step length,anterior-posterior step width,and mediolateral step width by 36.96％,13.66％,and 8.10％,respectively.The total movement speed and instantaneous speed decreased by 8.05％and 11.12％,respectively,while the stride frequency increased by 51.41％.The average footprint area and average maximum standing area decreased by 8.8％and 13.24％,respectively,and foot pressure decreased by only 3％.The plantar pressure distribution in the injury group was uneven,with a more obvious decrease in plantar pressure in the hindfoot,especially a 13.92％decrease in plantar pressure in the right posterior quadrant.Conclusions Mice with chronic ankle instability adopt a more conservative walking pattern during the motion,reducing movement volume and amplitude to improve coordination and stability during walking.

BACKGROUND:Numerous studies have shown that mechanical stimulation is essential for the lineage-specific differentiation of bone marrow mesenchymal stem cells.However,osteogenic differentiation of bone marrow mesenchymal stem cells on surfaces with different roughnesses under mechanical stretching conditions is unknown. OBJECTIVE:To investigate the effects and action mechanisms of different roughness surfaces of polydimethylsiloxane(PDMS)on osteogenic differentiation of bone marrow mesenchymal stem cells under stretching conditions. METHODS:Three morphologies with different roughnesses(PDMS-120M,PDMS-1000M,and PDMS-10000M)were constructed on PDMS surfaces by means of different grits of sandpaper(120 grits,1 000 grits and 10 000 grits),and PDMS surfaces in contact with air served as a control group.With different amplitudes of 0%,2%,4%,and 6%,osteogenesis-related gene expression of bone marrow mesenchymal stem cells on different PDMS surfaces under static and stretching conditions was detected by RT-qPCR.RT-qPCR and western blot assay were used to detect the expression of SIRT1 gene and protein as well as osteogenesis-related genes and proteins in bone marrow mesenchymal stem cells on different roughness surfaces under 2%stretching conditions.Alkaline phosphatase staining and alizarin red staining were further used to observe the osteogenic differentiation ability of bone marrow mesenchymal stem cells on different PDMS surfaces under 2%stretching conditions. RESULTS AND CONCLUSION:(1)Bone marrow mesenchymal stem cells on the PDMS-1000M surface with a roughness of(13.51±2.11)μm had better osteogenic gene expression under static conditions.(2)Bone marrow mesenchymal stem cells on the PDMS surface in contact with air had better osteogenic differentiation under 4%stretching conditions,while bone marrow mesenchymal stem cells on the PDMS-1000M surface had better osteogenic differentiation under 2%stretching conditions.(3)Bone marrow mesenchymal stem cells on the PDMS-1000M surface with a roughness of(13.51±2.11)μm had better osteogenic differentiation under 2%stretching conditions,which may be related to activation of SIRT1 signaling pathway.

Objective To establish two osteoarthritis models of destabilization of the medial meniscus(DMM)and chronic ankle instability(CAI)in mice,and compare the effects of knee osteoarthritis with varus deformity on ipsilateral ankle cartilage degeneration.Methods Thirty 6-week-old C57BL/6J male mice were randomly divided into a control group and two surgical groups(DMM group and CAI group),respectively.The progression of ankle joint degeneration was quantitatively evaluated through behavioral observation,imaging techniques and histopathology analysis in each group of mice over a 12-week period.Results A decline in gait stability and balance was observed in two surgical groups.Compared to the control group,the time required to cross the balance beam was increased by 23.20％,and the number of slips was increased by 43.26％at 12th week postoperatively in the DMM group.The bone volume fraction and bone mineral density of ankle joints also increased.Meanwhile,wear and tear of the ankle cartilage were found,with the formation of osteophytes,and OARSI score was increased by 88.89％.These changes in ankle joint were more pronounced in the CAI group.Conclusions This mouse model-based study revealed a coupling relationship between the knee and ankle motion.Knee osteoarthritis with varus deformity could lead to a significant ankle joint degeneration,while the damage was less severe than that observed in CAI.