The Mechanism Of Mechanical Strain Induced VSMC Phenotypic Differentiation In Aortic Dissection

Aortic dissection(AD)is an extremely dangerous disease with high mortality but without effective drug therapy.Its pathogenesis is the research focus at present.we used both ?-Aminopropionitrile(BAPN)and angiotensin ?(Ang ?)to establish SD rat aortic dissection(AD)model,with high success rate.The pathological process is similar to human's aortic dissection process.We stretched the rats' and human's aortic dissection vessels and found that mechanical strain induced aortic dissection vessel smooth muscle cell(VSMCs)phenotypic change in vitro.The conversion of VSMCs phenotype was related to the strength to a certain extent but is independent of the stretch time.When we used the stretch-activated ion channel(SAC)inhibitor and AKT2 inhibitor,the relationship between phenotype changing and stretch was abolished.We assumed that mechanical strain opens the SAC and then leads to VSMCs phenotypic change via AKT2 signal pathway.Part ?Use both BAPN and Ang ? to establish SD rat aortic dissection(AD)modelObjective To establish the SD rat aortic dissection(AD)model by using both BAPN and Ang ?,in order to investigate AD's pathogenesis.Methods 90 three weeks old SD rats were equally divided into three groups randomly: control group?medicine in water group and medicine gavage group.Rats in control group were fed on a regular diet;Rats in medicine in water group administered drinking water with BAPN dissolved in(1g/Kg/day);BAPN(1g/Kg/day)were forced into rats' stomaches in the medicine gavage group.4 weeks later,when the rats were 7 weeks old,we stop giving them BAPN,but to implant an omicro-osmotic pump subcutaneously in the abdomen.The pumps in control group were filled with 0.9% saline,the other two groups' pumps were filled with Ang ? solution(1ug/Kg/min).1 week later,all the survivals were dissected after anesthesia and the aortic vessels were acquired.All the acquired aortic vessels were proceed pathological examination.All the rats dead during the process of the experiment were dissected immediately to get the aortic vessels and proceed pathological examination.Results All 30 rats in control group were survival,there were no aortic dissection or death,their weight increased from 53.4±3.6(g)to 171.3±5.9(g);In medicine in water group,5 rats developped aortic dissection,3 among them were died of aortic dissection rupture,the aortic dissection formation rate was 16.7%,their weight increased from 53.2±4.4(g)to62.7±3.6(g);In medicine gavage group,15 rats developped aortic dissection,12 among them were died of aortic dissection rupture,the aortic dissection formation rate was 50%,their weight increased from 53.1±4.0(g)to 103.6±3.2(g).Conclusion Using both BAPN and Ang ? to establish the SD rat aortic dissection(AD)model is feasible,it is simple and practicable,mean while,it has high aortic dissection formation rate.The process is similar with human's aortic dissection process.Part ?Mechanical strain induce VSMCs phenotypic differentiation via SACObjective To investigate whether mechanical strain opens the SAC and then induces VSMCs phenotypic differentiation.Methods 95 three weeks old SD rats(weight 50.8 ± 3.2g)were used to establish AD model.Rats AD vessels were harvested when rat AD model was ready.At the same time,we collected 16 AD patients' AD vessels when they were underwent AD opertation.Both rats and human AD vessels were devided into two groups: the control group in which we didn't use SAC inhibitor and the experimental group in which we used SAC inhibitor.In the control group,the vessles were stretched by 0g,1g,3g and 5g four different stretches,and were strained by 30 minutes,1hour and 2 hours respectively.The vessels were then collected.The diffrence between control group and experimental group was that before strain experiment,the vessels in exprimental group were dealed with SAC inhibitor for 1 hour.Western blot and immunohistochemical method were used to detect VSMCs phenotypic correlation proteins: contractile phenotypic correlation protein ?-SMA,Calponin and SM-MHC;synthetic phenotypic correlation protein OPN,Smemb and Epiregulin.Results In vitro,expression of rats AD vessels VSMCs contractile phenotypic correlation protein decreased with the increase of strectch,and reduced to minimum when the stretch was 3g but rose again when the stretch was 5g while human's contractile phenotypic correlation protein reduced to minimum after 5g stretch.Expression of rats AD vessels VSMCs synthetic phenotypic correlation protein increased with the increase of strectch,and rose to the top when the stretch was 3g but fell when the stretch was 5g while human's synthetic phenotypic correlation protein rised to the top after 5g stretch.SAC inhibitor can abolish the phenomenon.Conclusion In vitro,mechanical strain opens the SAC and then leads to VSMCs phenotypic change in rats and human AD vessles.The conversion of VSMCs phenotype was related to the strength to a certain extent: the apex of rats AD vessels was 3g while human AD vessels was 5g.The conversion of VSMCs phenotype was independent of the stretch time.Part ?Mechanical strain opens the SAC and then leads to VSMCs phenotypic differentiation via AKT2 signal pathway.Objective To investigate whether mechanical strain opens the SAC and then induces VSMCs phenotypic differentiation via AKT2 signal pathway.Methods 90 three weeks old SD rats(weight 50.2±4.2g)were used to establish AD model.Rats AD vessels were harvested when rat AD model was ready.At the same time,we collected 15 AD patients' AD vessels when they were underwent AD opertation.Both rats and human AD vessels were devided into two groups: control group in which we didn't use AKT2 inhibitor and experimental group in which we used AKT2 inhibitor.In the control group,the vessles were stretched by 0g,1g,3g and 5g four different stretches,and were strained by 30 minutes,1hour and 2 hours respectively.The vessels were then collected.The diffrence between control group and experimental group was that before strain experiment,the vessels in exprimental group were dealed with AKT2 inhibitor for 1 hour.Western blot and immunohistochemical method were used to detect AKT2 protein,P-AKT protein and VSMCs phenotypic correlation proteins.Results In vitro,expression of rats AD vessels AKT2 protein,P-AKT protein and VSMCs contractile phenotypic correlation protein decreased with the increase of strectch,and reduced to minimum when the stretch was 3g but rose again when the stretch was 5g while human's contractile phenotypic correlation protein reduced to minimum after 5g stretch.Expression of rats AD vessels VSMCs synthetic phenotypic correlation protein increased with the increase of strectch,and rose to the top when the stretch was 3g but fell when the stretch was 5g while human's synthetic phenotypic correlation protein rose to the top after 5g stretch.AKT2 inhibitor can abolish the phenomenon.Conclusion In vitro,mechanical strain affected AKT2 protein and P-AKT protein expression,induced VSMCs phenotypic change in rats and human AD vessles via AKT2 signal pathway.The expression of AKT2 protein,P-AKT protein and the conversion of VSMCs phenotype were related to the strength to a certain extent: the apex of rats AD vessels was 3g while human AD vessels was5 g.The conversion of VSMCs phenotype was independent of the stretch time.The result was the same as part ?(mechanical strain open the SAC and then induces VSMCs phenotypic differentiation).We assumed that mechanical strain opens the SAC and then leads to VSMCs phenotypic change via AKT2 signal pathway.