BACKGROUND:Programmed cell death protein 1 belongs to the immunoglobulin gene superfamily and can regulate the differentiation of osteoblasts and affect bone homeostasis.However,there are few studies on the regulatory role and mechanism of programmed cell death protein 1 in diabetic osteoporosis.OBJECTIVE:To investigate the regulatory role and mechanism of programmed cell death protein 1 on osteogenic differentiation of rat bone marrow mesenchymal stem cells under high-glucose environment.METHODS:(1)Animal experiment:A total of 12 Sprageu-Dawley rats were randomized into a control group(n=6)and a model group(n=6).The control group was fed routinely,whereas the model group was injected intraperitoneally with streptozotocin to establish a model of type 1 diabetes mellitus,and the high-fat feed was fed for 8 weeks to establish a model of type 1 diabetic osteoporosis.After 8 weeks of feeding,the femurs of rats in the two groups were taken and subjected to hematoxylin-eosin staining and micro-CT assay.The mRNA expression of programmed cell death protein 1 and programmed death ligand 1 was detected.(2)Cell experiment:Passage 3 rat bone marrow mesenchymal stem cells were randomly divided into four groups:normal control group,high-glucose model group cultured in low glucose medium,programmed cell death protein 1-silenced group transfected with programmed cell death protein 1 siRNA,and programmed cell death protein 1-silenced null group transfected with siRNA-NC.After 48 hours of transfection,the normal control group was cultured in a new low-glucose medium,and the other three groups were cultured in a high-glucose medium for another 48 hours of culture followed by osteogenic induction.After 21 days of osteogenic induction,alizarin red staining,and qRT-PCR(programmed cell death protein 1 and RUNX2 mRNA expression)and western blot(β-catenin,GSK-3β,p-GSK-3β and Axin2 protein expression)were performed.RESULTS AND CONCLUSION:In the animal experiment,hematoxylin-eosin staining and micro-CT assay showed successful modeling of type 1 diabetic osteoporosis in the model group.qRT-PCR assay showed that the mRNA expression of programmed cell death protein 1 and programmed cell death ligand 1 was higher in the model group than the control group(P<0.05).In the cell experiment,the results of alizarin red staining showed that the ability of mineralized nodule formation was lower in the high-glucose model group and the programmed cell death protein 1-silenced null group than in the control group and the programmed cell death protein 1-silenced group.Compared with the normal control group,the programmed cell death protein 1 mRNA expression and GSK3β and Axin2 protein expression were elevated in the high-glucose model group and the programmed cell death protein 1-silenced null group(P<0.05),and the RUNX2 mRNA expression and p-GSK3β and β-catenin protein expression were decreased(P<0.05).Compared with the high-glucose model group and the programmed cell death protein 1-silenced null group,programmed cell death protein 1 mRNA expression and GSK3β and Axin2 protein expression were decreased in the programmed cell death protein 1-silenced group(P<0.05),and RUNX2 mRNA expression and p-GSK3β and β-catenin protein expression were elevated(P<0.05).To conclude,programmed cell death protein 1 silencing can activate the Wnt/β-catenin and improve the osteogenic differentiation of rat bone marrow mesenchymal stem cells under high-glucose conditions.

BACKGROUND:The mechanism of programmed death receptor-1(PD-1)effect on osteogenic differentiation of bone marrow mesenchymal stem cells in high glucose environment remains unclear. OBJECTIVE:To explore the effect of PD-1 on osteogenic differentiation of rat bone marrow mesenchymal stem cells in high glucose environment and its regulatory mechanism. METHODS:Rat bone marrow mesenchymal stem cells were randomly divided into normal glucose group(5.6 mmol/L),high glucose group(30 mmol/L),PD-1 overexpression group,PD-1 overexpression no-load group,PD-1 knockdown group,PD-1 knockdown no-load group,and PI3K/AKT pathway inhibitor group(PD-1 knockdown+5 μmol/L LY294002).Rat bone marrow mesenchymal stem cells were cultured in high glucose to simulate the diabetic environment in vitro.The mRNA expression of PD-1 and ligand PD-L1 and the mRNA expression of osteogenic markers Runx2 and OSX in rat bone marrow mesenchymal stem cells were detected by qRT-PCR.The osteogenic differentiation ability was observed by alkaline phosphatase staining and alizarin red staining.Cell proliferation was detected by CCK-8 assay.The protein expressions of PD-1,PD-L1,p-PI3K,and p-AKT were detected by western blot assay. RESULTS AND CONCLUSION:(1)The levels of PD-1 and PD-L1 were significantly increased in the high glucose environment in vitro,and the osteogenic differentiation ability of bone marrow mesenchymal stem cells was inhibited in the high glucose environment.(2)Knockdown of PD-1 expression could promote osteogenic differentiation of bone marrow mesenchymal stem cells,increase cell proliferation activity,and activate the PI3K/AKT pathway.(3)After addition of PI3K/AKT pathway inhibitor LY294002,the ability of bone marrow mesenchymal stem cells to differentiate into osteoblasts decreased.The results show that PD-1 is dependent on the PI3K/AKT signaling pathway to inhibit osteogenic differentiation of rat bone marrow mesenchymal stem cells under high glucose environment.

BACKGROUND:Programmed cell death protein 1 belongs to the immunoglobulin gene superfamily and can regulate the differentiation of osteoblasts and affect bone homeostasis.However,there are few studies on the regulatory role and mechanism of programmed cell death protein 1 in diabetic osteoporosis.OBJECTIVE:To investigate the regulatory role and mechanism of programmed cell death protein 1 on osteogenic differentiation of rat bone marrow mesenchymal stem cells under high-glucose environment.METHODS:(1)Animal experiment:A total of 12 Sprageu-Dawley rats were randomized into a control group(n=6)and a model group(n=6).The control group was fed routinely,whereas the model group was injected intraperitoneally with streptozotocin to establish a model of type 1 diabetes mellitus,and the high-fat feed was fed for 8 weeks to establish a model of type 1 diabetic osteoporosis.After 8 weeks of feeding,the femurs of rats in the two groups were taken and subjected to hematoxylin-eosin staining and micro-CT assay.The mRNA expression of programmed cell death protein 1 and programmed death ligand 1 was detected.(2)Cell experiment:Passage 3 rat bone marrow mesenchymal stem cells were randomly divided into four groups:normal control group,high-glucose model group cultured in low glucose medium,programmed cell death protein 1-silenced group transfected with programmed cell death protein 1 siRNA,and programmed cell death protein 1-silenced null group transfected with siRNA-NC.After 48 hours of transfection,the normal control group was cultured in a new low-glucose medium,and the other three groups were cultured in a high-glucose medium for another 48 hours of culture followed by osteogenic induction.After 21 days of osteogenic induction,alizarin red staining,and qRT-PCR(programmed cell death protein 1 and RUNX2 mRNA expression)and western blot(β-catenin,GSK-3β,p-GSK-3β and Axin2 protein expression)were performed.RESULTS AND CONCLUSION:In the animal experiment,hematoxylin-eosin staining and micro-CT assay showed successful modeling of type 1 diabetic osteoporosis in the model group.qRT-PCR assay showed that the mRNA expression of programmed cell death protein 1 and programmed cell death ligand 1 was higher in the model group than the control group(P<0.05).In the cell experiment,the results of alizarin red staining showed that the ability of mineralized nodule formation was lower in the high-glucose model group and the programmed cell death protein 1-silenced null group than in the control group and the programmed cell death protein 1-silenced group.Compared with the normal control group,the programmed cell death protein 1 mRNA expression and GSK3β and Axin2 protein expression were elevated in the high-glucose model group and the programmed cell death protein 1-silenced null group(P<0.05),and the RUNX2 mRNA expression and p-GSK3β and β-catenin protein expression were decreased(P<0.05).Compared with the high-glucose model group and the programmed cell death protein 1-silenced null group,programmed cell death protein 1 mRNA expression and GSK3β and Axin2 protein expression were decreased in the programmed cell death protein 1-silenced group(P<0.05),and RUNX2 mRNA expression and p-GSK3β and β-catenin protein expression were elevated(P<0.05).To conclude,programmed cell death protein 1 silencing can activate the Wnt/β-catenin and improve the osteogenic differentiation of rat bone marrow mesenchymal stem cells under high-glucose conditions.