The Research For Possible Mechanism For Rachioscoliosis Model Vertebral-body’s Bone-ultrastructure And Medicine Intervention

Objective:By inducing rachioscoliosis animal model amongbipedal rats through tying by asymmetric force, compare the differences among all groups of animal models, analysis the happening cause and mechanism, and discuss the effect of medicine on rat rachioscoliosis model vertebral body’s bone ultrastructure and possible mechanism of action.Lay the experimental basis for further research of IS etiology, and prophylaxis and treatment.Method:This experiment adopts60Sprague-Dawley (SD) rats with half males and half females, which were divided randomly into3groups. Biped rat group20; a group of20tethered-bipedal-rat-group;20rats for recombined parathyroid hormone (PTH) intervention group receive a subcutaneous injection of PTH the second day after surgery. Examine the rachis plainfilm and bone density of the SD rats for4times successively, observing the change of the Cobb angle and the density of bone. Killed rats12weeks after operation, took intervertebral disc tissues of T11, T12and T11-T12, fixed by methanal, dewatering, decalcification, paraffin embedding for HE dyeing, TUNEL dyeing, to observe change of histology.Take L170%ethanol to be fixed, and do Micro-CT scanning, to observe the transformation of microstructure of bone. Draw blood for the detection of the transformation index of bone when killing the SD rats, to see the metabolic condition of bone.Result:①General situation of rats:three groups of rats’bodyweight demonstrated a trend of gradual increase with the change of week old. There is a significant difference in bodyweight among three groups4,8and12weeks after operation (P<0.05). Weight growing curves of the three groups go basically the same way, existing no statistical difference.②Change of Cobb angle:no rachioscoliosis occurred in bipedal rats group; rachioscoliosis occurred in both tethered-bipedal-rat-group and PTH intervention group.Beginning to inject PTH from the4th week, the Cobb angle, rotation angle of apical vertebrae for intervention group is smaller than those for tethered-bipedal-rat-group, there is some statistics difference (P<0.05).③DXA examination of rats:during difference periods of bipedal rats group and tethered-bipedal-rat-group, the BMD, BMC and AREA of each position of bones of these rats increased gradually. The BMD, BMC and AREA of both body and spine between the two groups of rats in the same period have no significant difference. For PTH intervention group, BMD and BMC increased rapidly (especially for spine and whole-body) after injecting PTH from the4th week, representing a more remarkable difference than other groups (P<0.05).④Change of microstructure of bone:comparing between convex side and concave side for bipedal rats group, there is no significant difference in BMD, BV/TV, Tb.Th, Tb.N and Tb.Sp (P>0.05). comparing between convex side and concave side for tethered-bipedal-rat-group, there is a significant difference in BMD, BV/TV, Tb.Th, Tb.N and Tb.Sp (P<0.05). Compared with other two groups, BMD, Tb.Th and BV/TV of PTH treatment group increase while Tb. Sp decreases.⑤Change of histopathology:for HE dyeing tethered-bipedal-rat-group and PTH intervention group, there is wedging in apex vertebral body, intervertebral disc, nucleus pulposusside rachioscoliosis, obvious reduction of cartilage cells in concave side and their volume is smaller than normal cells; the hyperplasia for cells of growth plate cartilage on convex side is active, with more cells existing.The apoptosis index of cells of growth plate cartilage on concave side.for TUNEL dyeing tethered-bipedal-rat-group and PTH intervention group increases obviously and higher than that of bipedal rats group.⑥Inspecting bone conversion index:comparing with bipedal rats group and tethered-bipedal-rat-group, serum alkaline phosphatase (ALP-B), bone gla protein,(CTX-I)of PTH intervention group rise remarkably, representing a more remarkable difference than other groups (P<0.05). Conclusion:1.Posterior asymmetric force tying system can build a animal model of rachioscoliosis in bipedal rats.2.Both posterior asymmetric force tying system and PTH have no effect on the bodyweight of rats during their growing.3.The apoptotic cells on concave side of apical vertebrae of rachioscoliosis animal model increase more obviously than those on convex side of apical vertebrae. The apoptosis of such model cells may be related to the vicious cycle" induced by asymmetric-force-tying system.4.A11occurring rachioscoliosisin tethered-bipedal-rat-group, PTH intervention group by asymmetric-force-tying system, and the Cobb angle, rotation angle of apical vertebrae for PTH intervention group are smaller than those of tethered-bipedal-rat-group; PTH may have the function for preventing or delaying the developing rachioscoliosis.5. PTH can increase bone density, improve microscopic structure of bone, and enhance bone strength.6. The biomechanics plays an important role in generating and worsening process of rachioscoliosis, and PTH can restore the mechanical equilibrium of spine by increasing bone density, improving the microstructure of bone and enhancing strength of bone, break vicious cycle", prevent or delay the development of rachioscoliosis.