The Changes Of Collagen In Aorta During Rabbit Atherosclerosis And The Effects Of PACAP

Objective:To investigate the changes of typeⅠand typeⅢcollagen during rabbit experimental AS development and the effects of pituitary adenylate cyclase activating polypeptide(PACAP),as well as the possible intervention mechanisms of PACAP by detecting the collagen content and composition in plaque of arteries.Methods:60 male New Zealand rabbits were equally randomly divided into three groups:control group(C group,fed on general diet) and atherosclerosis model group(AS group,treated with high cholesterol diet) and PACAP intervention group(P group,treated with high- cholesterol diet and PACAP by injection).At the 0^th,2^th,4^th,8^th and 12^th weekends of the experiment,the concentration of serum total cholesterol(TC) and triglyceride(TG) were measured.And at the 4^th,8^th,12^th weekends of the experiment,5～8 animals in each group were sacrificed,and arteries were harvested for paraffin.Sections were stained with hematoxylin-eosin,Masson and picrosirus red separately.The morphological changes of arteries and the changes of the collagen content were observed and these graphic results were analyzed with computer image analysis system calculated,the expressions of MMP-2 and TIMP-2 in aortic tissue were detected by immunohistochemisty staining.Results:1.Changes of serum lipid:TC and TG in both AS group and P group were increased,the increase of TC and TG in AS group was more obviously than in the P group.But those were significantly lower in P group than that in AS group since 4^th weekend.Compared with P group, TC and TG in group AS were higher at the 12^th weekend(P＜0.05).2.Results observed qualitatively:(1) Changes of histology:HE staining showed that there were no plaques formations in C group.Plaques in both P group and AS group were aggravated gradually accompanying the progression of lesion,but plaques in P group were smaller than those in AS group.(2) Changes of collagen:There was collagen accumulation in plaque in both P group and AS group,but collagen in P group was less than that in group.Observed with polarization microscopy showed that both the typeⅠand typeⅢcollagen increased(especially the typeⅠcollagen),but the increased degree of the typeⅢcollagen in P group was more distinct than that in AS group.(3) Changes of MMP-2 and TIMP-2:The expressions of MMP-2 and TIMP-2 were inferior in C group.They were intensified gradually as the pathology developed both in P group and AS group,but the masculine extent in P group was inferiorer than that in AS group.3.Results analysed quantitatively:(1) Percentage of plaque formation increased in P group and AS group with the experiment, but that was lower in P group.At the 12^th weekend,percentage of plaque formation in AS group was 100%,but that in P group was only 80%.(2) Collagen volume fraction(CVF) was increased in P group and AS group.Compared with AS group,the CVF in P group was significant lower since 8^th weekened(P＜0.01).At the 12^th weekend,CVF in group AS was(32.46±8.78),which was significantly lower than that in P group(48.15±5.74).(3) Both CVF of the typeⅠand ratio of typeⅠto typeⅢin P group and AS group were significantly increased,but the above parameters in P group were lower than those in AS group since 8^th weekened(P＜0.01).At the 12^th weekend,CVF of the typeⅠin AS group was (32.94±8.34),but that in P group was(19.44±6.06).At the same time,ratio of typeⅠto typeⅢin AS group was(3.21±1.56),which is higher than that in P group(6.06±3.21).CVF of typeⅢin P group was higher than that in AS group since 8^th weekened(P＜0.01),At the 12^th weekend, CVF of typeⅢin P group was(8.60±4.72),which is higher than that in AS group(6.56±2.74).Conclusions:The collagen content and the ratio of typeⅠto typeⅢin plaque increased,as well as the expressions of MMP-2 and TIMP-2 intensifyed gradually as the pathology developed.PACAP may have good benifit on AS development by decreaseing serum lipid and affecting the expression of MMP-2 and TIMP-2.