The Experimental Study Of Inflammatory Factors And Adventitial Inflammation In Early Pathogenesis Of Allograft Arteriosclerosis

Objective: Recently, Heart Transplantation has been involved the most effective method for all kinds of end stage heart diseases. With the introduction of progressed immunosupressive drug, organ preservation and surgical technique, the short-term and long-term effects of heart transplantation have been improved obviously. Allograft arteriosclerosis is the main cause of death in long-term surviving population and also the reason of all kinds of transplanted organ failure. Serious and diffuse intimal proliferation leading to arterial stenosis and transplanted organ ischemic function failure is the main expression. Therefore, allograft arteriosclerosis has been kept the focus of study in recent years. There are several animal models for allograft arteriosclerosis study, but most of which was made by the method of microsurgery techniques. Technical problems and high risks of complication such as anastomotic stenosis and bleeding have limited its widespread use. The general pathologic changes of allograft arteriosclerosis begins with distal small artery, ends with diffuse and endocentric intimal thickness involved the entire intramyocardial and epicardial arteries, and leads to arterial atresia ultimately. The exact pathogenesis of allograft arteriosclerosis remains unclear. It is probably a disease involved immune and nonimmune factors. With the increasing attention paid for the role of adventitial inflammation in pathogenesis of arteriosclerosis, some studies showed that adventitial inflammation took part in the genesis of arteriosclerosis. For this reason, the objective of this study was 1) to establish rat chronic rejection model of abdominal thoracic aorta transplantation with cuff technique, 2) to study the role of serum inflammatory factors and allograft adventitial inflammation in early pathogenesis of allograft arteriosclerosis in rats. Methods: Sprague-Dawley rats and Wistar rats were randomly divided into two groups: allograft (SD-Wistar) group and within-strain control (Wistar-Wistar) group. The body weight of the donor rats was 130-150 g. The body weight of receipts was 250-350 g. The rat chronic rejection model of abdominal thoracic aorta transplantation was established with cuff technique. The pathological and immuohistochemical changes of transplant aorta was evaluated at 1,2,3,4,8 and 12 weeks after transplantation. Thirty-six allograft rats and 16 within-strain control rats were randomly divided into 4 groups (9 rats in experimental subgroup and 4 rats in control subgroup): Group A. sacrificed at the first postoperative week; Group B. sacrificed at the second postoperative week; Group C. sacrificed at the third postoperative week; Group D. sacrificed at the fourth postoperative week. Blood sample were collected before the transplantation and at the time point of sacrifice. Enzyme Linked Immunosorbent Assay was used for testing serum inflammatory factors (CRP, IL-6, TNF-a), HE staining for evaluating pathologic changes of aortic allograft and immunohistochemical staining for evaluating adventitial inflammatory cell infiltration, a-actin, CDK1 and PCNA. The inflammatory factors and other variables between groups and preoperative value were compared.Results: The abdominal thoracic aorta transplantation was performed in 60 rats through cuff technique and five died. One rat died on the third postoperative day because of lumbar artery damage. Two deaths occurred on the second and third postoperative day, respectively, and necroscopy showed bleeding of intercostal artery stump. Pneumonia and peritoneal abscess lead to the other two deaths at the 7th and 14th postoperative day and anastomotic stoma was well. Fifty-five rats (91.7%) survived, and the long-term patency rate of the transplanted thoracic aorta was 100%. The mean operative time was 50 min. The cold ischemia time and warm ischemia time of the donor was 15-20 min and 3-8 min, respectively. The pathological change of transplanted aorta in allograft group was as follows: Adventitial inflammatory cell infiltration was found at the first postoperative week; mild adventitial collagen fiber proliferation accompanied by inflammatory infiltration was found at second postoperative week ; significant adventitial proliferation with smooth muscle cells, collagen fiber and inflammatory cells, intimal fibrous degeneration and smooth muscle cell proliferation were found at fourth postoperative week; significant intimal thickening, smooth muscle cell proliferation and adventitial inflammation were found at 12th postoperative week. While there were no obvious changes in the within-strain control group. Compared with preoperative basal level, the serum inflammatory factors value increased significantly in group A, B, C and D. The changes of plasma inflammatory factor values were as follows: CRP level, compared to preoperative level, all control subgroups and experimental subgroups increased significantly (P < 0.01), and the experimental subgroup B, C, D were much higher than corresponding control subgroups (P < 0.01); IL-6 level, compared to preoperative value, the experimental subgroup B as well as the control subgroup A, B, C increased (P < 0.05), and the experimental subgroup A, C, D increased significantly (P < 0.01), when compared to control subgroups, the experimental subgroup A, C, D presented a significant increase (P < 0.01); TNF-a level, there was no difference between control subgroups and preoperative basal level, all experimental subgroups had higher level than preoperative and controls (P < 0.01). In allograft adventitial smooth muscle cell, the expression of a-actin, PCNA and CDK1 presented higher and higher (P < 0.05) and appeared before intimal SMCs.Conclusions: The cuff technique was feasible to establish chronic rejection model of abdominal thoracic aorta transplantation in rats. This technique would be ideal because it is simple and easier with higher successful rate. The increased inflammatory factors, allograft adventitial inflammation resulted from immune or nonimmune factors and adventitial SMC proliferation were both involved in the pathogenesis of early allograft arteriosclerosis.