Smoking Increases The Risk Of Osteoporosis In Spontaneously Hypertensive Rats

Objective: To investigate whether cigarette smoking increases the risk of osteoporosis in spontaneously hypertensive rats and possible mechanism.Methods: 12 WKY(11 weeks age)and 12 SH rats(11 weeks age)were selected,both WKY and SHR divided into 4 groups,each group of 6 rats.A: control group(WKY+filtered air);B: smoking group(WKY+smoke exposure);C: hypertension group(SHR+filtered air);D: smoking combined with hypertension group(SHR+smoke exposure)which were exposed to filtered air and tobacco smoke.The BMD,BV/TV,Ct.Th,Tb.Th and Tb.Sp were measured by Micro-CT scan.The morphological changes of lumbar vertebrae such as trabecular bone structure,osteocytes and adipocytes were observed by HE staining.The expression of HIF-1α and VEGF in lumbar vertebrae was analyzed by immunohistochemistry.The average optical density of HIF-1α and VEGF and trabecular bone area were analyzed by Image-Pro Plus6.0 software.SPSS17.0 statistical software was used to analyze the experimental data,P<0.05 indicates that the statistically difference.Results: 1.The lumbar vertebrae of rats were detected by Micro-CT scan showed that:The BMD,BV/TV,Ct.Th,Tb.Th of B,C,D groups were lower than those of A group,and the Tb.Sp was higher than that of A group,and the difference was statistically significant(P<0.05).Compared to B and C groups,the BMD,BV/TV,Ct.Th and Tb.Th were decreased in D group and the Tb.Sp were increased in D group,and the difference was statistically significant(P<0.05).There was no significant difference in BMD,BV/TV,Ct.Th,Ct.Th,Tb.Sp between B and C groups(P>0.05).2.Observation morphology of lunmer under HE staining by the microscope: the trabecular bone of A group was tidy,uniform,tightly connected,and no fracture occurred.The trabecular space was small.The osteocytes arranged neatly,uniform size,nuclei were stained,no nuclear pyknosis.In B and C groups,the trabecular bone structure wasirregular arranged,the trabecular space was widened,the pore space was increased,and the osteocytes were arranged in disorder and osteocytes size was different,nuclear pyknosis,and a small amount of adipocytes could seen.The trabecular bone structure of D group was damaged,the trabecular bone was sparse,the arrangement of osteocytes was disordered,and the thrombosis was seen in the Haffle tube;Bone marrow was filled with a lot of adipocyteswhich were different,fusion.IPP6.0 software showed that: Compared with A group,the percentage of Tb.Ar in B,C,D groups were decreased and the number of adipocytes in B,C,D groups were increased,and the difference was statistically significant(P<0.05).Compared to B and C groups,the percentage of Tb.Ar in D groups was decreased and the number of adipocytes in D groups was increased,and the difference was statistically significant(P<0.05).3.The expression of HIF-1α and VEGF in the lumbar: Immunohistochemical staining showed expression of HIF-1α with different level in the osteocyte and bone marrow cavity of each group.VEGF was expressed in the bone marrow cavity in different level.IPP6.0software showed that: Compare to A group,the AOD of HIF-1α and VEGF in D group were decreased,and the difference was statistically significant(P<0.05);Compared to C group,the AOD of HIF-1α and VEGF in D group were decreased,and the difference was statistically significant(P<0.05);The AOD of HIF-1α and VEGF between A and C groups were not significant difference(P>0.05);The AOD of HIF-1α and VEGF between B and C groups were not significant difference(P>0.05).Conclusion: 1.Smoking or hypertetion can reduce the bone mass and damage bone microstructure of rats.2.Smoking can accelerate the decline of bone mineral density and bone microstructure in hypertensive rats,and increase the risk of osteoporosis.3.Cigarette smoking can cause the low expression of HIF-1α and VEGF in hypertensive rats,inhibit the bone formation,and limited the local blood supply,thus accelerate the bone loss and increasing the risk of osteoporosis.