The Influence Of Different Ways Of Exercises On BMD And Notch Signaling Pathways Related Gene Expression Of Mice During Growing Period

Research Basics:Exercises can promote bone health and influence the bone metabolism. The influences to the Bone Mineral Density and the mechanism of the osteoblasts of different ways of exercises are always one of the research foucses. As the key signaling pathway in participating and affecting the multiplication and differentiation of osteoblasts in the course of bone metabolism, Notch signaling pathway has attracted much attention, but most of the researches concentrate on the field of medical science, while the studies on the mechanism of Notch signaling pathway in bone tissue can be activated and regulate the bone metabolism under the intervention of exercise are very few. According to medical researches, Notch signaling pathway plays an important regulating role in the osteogenic differentiation process of BMP9 mesenchymal stem cells; it can increase the factor gene expression and activate Notch signaling pathway. Meanwhile, according to the researches on the relationship of exercises and Notch signaling pathway in muscular tissue and brain tissue, exercises can activate the Notch signaling pathway in muscular tissue and brain tissue of nerve cells and muscle cells and thus influence the expression of target genes by exerting fluid shear stress stimuli on osteoblasts. So it can provide new proof to the theory of exercises regulating bone metabolism and theoretical foundation to teenagers’ bone-invigorating by studying the regulation and control mechanism of Notch signaling pathway in different ways of exercises.Objectives:Through different ways of exercise intervention, which is through researching the influences on th Bone Mineral Density, Bone Mineral Content and expression of bone metabolism key factor of downhill running, flat slope running and swimming to the mice during growing period,by using many techniques, for example, RT-PCR, undecalcificated bones slicing, immunohistochemistry, the proliferation and differentiation of MSCs, from the aspects of cells, protein, mRNA and bone mass, this essay aims to study the biological mechanism of how different ways of exercises influence the osteoblast multiplication, differentiation and the metabolism of the skeletal system, key factor expression in Notch signal transduction pathway and in order to provide new proofs to different ways of exercises can regulate bone metabolism and scientific proofs to exercises can promote teenagers’ bone growth and enrich exercise bone-invigorating theory.Methods:24 four weeks old mice (C57 BL/6) which is during growing period were raised 7 days under rest state and then randomly divided into 4 groups:control downhill running group(DT, n=6), flat slope treadmill group(T, n=6), swimming group(S, n=6),control group(C, n=6). Training programs:the mice of DT group were implemented downhill running training with the speed of 0.8km/h, the slop was-9°; the mice of flat slope treadmill group were implemented flat slope running training with the speed of 0.8km/h, the slope was flat; the mice of swimming group were implemented under the condition as follows:the depth of water is 40cm while the temperature of water is 2℃ higher or lower than 30℃, and stir the motionless mice swim with tools. The training time was fixed at 18 o’clock and the training duration is 40 minutes.The mice were trained 8 weeks and 5 times every week. After 8 weeks, we tested the tibia bone mineral content by atomic absorption method, distal humerus bone mineral density by dual energy x ray method, the mRNA expression of BMP9 Notch1、Notch2、Jagged1、Deltal、PS1、APH1、HES1 etc in tibia by RT-PCR. the osteoblast ALP activity by ALP staining method and osteoblast mineralization ability by Von Kossa staining method. Moreover, we also tested the expression of NICD protein in Notch signaling pathway by related immunohistochemical technologies.Results:1. Weight:There are no significant differences between all the 4 groups mice (P>0.05).2. The result of distal humerus bone mineral density by dual energy x ray is that exercises can strengthen the bone mineral density and the effect of downhill running group is the most significant. Compared with C group, the bone mineral densityof other 3 groups have significantly increased in different extents (P<0.05). The DT group has markedly increased (P<0.01).3. The result of the tibia bone mineral content by atomic absorption method is that exercises can increase the content of calcium and phosphonium in bone tissue and the effect of downhill running group is the most significant.Bone mineral content: Compared with C group, the bone mineral content of other 3 groups have increased. The DT group has markedly increased (P<0.01).4. The result of mRNA expression of BMP9 Notch1、Notch2、Jagged1、Delta1、 PS1、APH1、HES1 etc in tibia is that different ways of exercises can increase the expression level of mRNA of BMP9, Jagged1, Notch1, PS1, APH1, HES1 mRNA in bone tissue.5. The result of expression of NICD protein in Notch signaling pathway by related immunohistochemical technologies is that the number of NICD protein in bones of DT and T group are markedly higher than C and S group.(P<0.05).6. The result of proliferation and differentiation in vitro of MSCs is that the ALP activity of osteoblast of T and S groups are higer than DT group; the C group is the lowest; as to the capability of osteoblast osteogenetic, the DT group is the highest, the following is T group and the lowest is C group.Conclusions:1.The treadmill exercise can significantly increase the expression of ligand Jaggedl, receptor Notchl, γ-secretase and its effector molecules-Hes1 of Notch signaling pathway. Meanwhile, it can also activitie the Jagged1/Notch1-Hes1 signal pathway of bone tissue.2. The exercise can promote mesenchymal stem cells inducing differentiate into osteoblasts, increasing the number of osteoblasts and enhance the osteogenetic ability of osteoblasts; swimming can promote mesenchymal stem cells inducing osteoblasts proliferate, but it is not obvious on the effect of the differentiation and maturity of osteoblasts and the enhancement of osteogenesis ability.3. The exercises can significantly increase the bone mineral content and bone mineral density, in which the effect of downhill running is the best.4. One of the mechanism of exercises promoting bone growth is probably that exercises increase the expression of bone tissue and the expression level of Notch1、Jaggedl、PS1 and APH1, activate the signaling pathway of Jaggedl/Notchl-Hesl,act on target genes,induce the proliferation and differentiation of osteoblasts,increase the content of bone mineral and strengthen the bone density,and then influence the growth of bones.