Stent implantation plays a more and more important role in the treatment of benign esophageal stenosis. Metal stents are most commonly used in the clinical practice, which can be classified into permanent stents and temporary retrieval stents. Permanent implantation of metal stents is easy to cause complications such as inflammatory hyperplasia, in-stent restenosis, perforation, bleeding, etc. Temporary retrieval stents should be removed with one week after it is implanted in order to avoid esophageal scar tissue repair and in-stent tissue hyperplasia, which can cause difficulty in its removing and produce higher recurrence rate of esophageal restenosis. Clinically, drug-eluting stents have already been used in cardiovascular system procedures, but at present the gastrointestinal drug-eluting stents are still in development and animal experiment stage. Biodegradable magnesium alloy stents have been widely employed in cardiovascular system procedures. With the rapid development of biological engineering materials, drug-eluting magnesium alloy stent has become a hot spot and the frontier in research field. This paper aims to make a comprehensive review about the current research status and prospect of the drug-eluting magnesium alloy stents, focusing on the stent technology, stent molding, coating modification, and the treatment of drug-eluting.

Stent implantation plays an significant role in the interventional therapy, mainly with permanent stent, possessing many disadvantages such as restenosis and inflammatory hyperplasia and can thus hardly be used in children and nonmalignant stenosis. Biodegradable stent has theoretical capability to solve these problems and acquires a bright future. Nowadays, with the development of material industry and manufacture craft, biodegradable stent technique has turned up to be mature in last decades. Through the strict animal experiments and prophase of clinic application, satisfactory result has been acquired. We believe that bioabsorbable stent will be widely used in many benign diseases which would be a good supplement for permanent stent in the near future.

Objective To assess the clinical value of batroxobin plus aspirin therapy in reducing the incidence of arterial re-stenosis or re-occlusion in diabetic patients with lower-limb ischemia after receiving angioplasty. Methods A total of 110 diabetic patients with symptomatic arterial obstructions were randomly divided into study group (n=50) and control group (n=60). Aspirin 100 mg/d plus batroxobin 5 IU every other day for six times was used in patients of the study group, while only aspirin 100 mg/d was used in patients of the control group. The follow-up finishing point was the end of 12 months. The arterial re-stenosis or re-occlusion was evaluated with magnetic resonance angiography (MRA) and/or vascular sonography. Amputation above the ankle, death, and the cumulative rate of amputation or death were determined, and the limb salvage and survival rates were assessed by using Kaplan-Meier analysis method. Results Twelve months after the treatment, the occurrence of restenosis in the study group and the control groups was 42.8%and 28.9% respectively (P = 0.002). MR angiography and color- duplex sonography revealed that the restenosis occurrence was much higher in infrapopliteal artery (P = 0.003) and in longer (length > 10 cm) diseased artery (P = 0.001). Twelve months after angioplasty Kaplan-Meier analysis showed that the limb salvage-survival rates of the study group and the control group were 78.2%and 93.5%respectively (log-rank test, P = 0.032 4). Conclusion Combination use of batroxobin and aspirin can effectively reduce the occurrence of restenosis after arterial angioplasty, and the clinical effect is particularly better for the artery distal to the knee and the artery with longer lesion (length > 10 cm), besides this treatment can also improve limb salvage rate.

Objective To investigate the feasibility of establishing aneurysm model at the carotid artery bifurcation in experimental dogs. Methods New aneurysm model at the common carotid artery (CCA) bifurcation was established in 18 experimental dogs, which were randomly and equally divided into study group (n =9) and control group (n=9). In the dogs of the study group, the bifurcation top was treated with elastase, while in the dogs of the control group the bifurcation top was treated with saline. Angiography was separately performed immediately after, and at 12 and 24 weeks after the operation to observe the changes of the aneurysm top. Pathological examination was separately carried out at 12 and 24 weeks after the operation. Results Angiography showed that nascent aneurysm formation (mean diameter of 3.2 ± 0.4 mm) was demonstrated at the arterial bifurcation top in 5 dogs of the study group; while no nascent aneurysm at the arterial bifurcation top was observed in the control group. During the follow-up period, no rupture of the nascent aneurysm occurred in the study group. Pathological examination revealed that discontinued internal elastic membrane, elastic fiber fracture, thinning muscle layer and reduction of smooth muscle cells were detected in the aneurysm at bifurcation top in the study group; when compared with those in the control group, the difference was statistically significant (P< 0.001). Conclusion The elastase-induced digestive degeneration of artery wall can cause new aneurysm formation in the newly-established aneurysm located at carotid artery bifurcation in experimental dogs.

Objective To assess the efficacy and safety of a newly-designed temporary covered cardia stent for the treatment of achalasia in canine models and to investigate the histopathological changes at different points of follow-up time after the stent was removed. Methods The canine achalasia model was created by injecting benzyl-dimethyl-tetradecyl ammonium chloride (BAC) circumferentially into the lower esophageal sphincter (LES) of the dogs. Twenty-four dogs with achalasia were randomly and equally divided into two groups with 12 dogs in each group:control group (using routine esophageal stents) and study group (using newly-designed temporary covered cardia stents). Under fluoroscopic guidance stents were implanted in the esophagus and were taken away from the esophagus 4 days after stent insertion in experimental dogs of both groups. LES pressures and timed barium esophagography (TBE) were performed in all dogs before and immediately after the stenting procedure,as well as at one week,3 and 6 months after the stent was removed. Every three dogs were sacrificed each time at one week,3 and 6 months after the stent was removed. The esophageal cardia was excised and sent for pathological examination. Results All animals well tolerated the stent insertion / removal and the follow-up procedures. No severe complications such as esophageal perforation occurred. Comparison between two groups showed that stent migration occurrence was much lower in study group (n = 1) than that in control group (n = 5). The reduction of LES pressures in study group was more significant in comparison with control group (at 6-month follow-up,P = 0.027). The difference in barium column product (height ? width) between 0-min and 5-min TBE was statistically significant in study group (at 3-month follow-up,P = 0.009). Integrated analysis of multi-comparison for LES pressures among subgroups of each group revealed that the dogs in study group exhibited better outcomes than the dogs in control group. Both proliferating cell nuclear antigen (PCNA) and ?-smooth muscle actin (?-SMA) immuno-staining revealed that the inflammatory reaction reached its peak at 1-month follow-up. Trichrome staining indicated that the collagenous fiber proliferating index inclined to be stable at 3-month follow-up. Conclusion In treating achalasia in canine models the newly-designed temporary covered cardia stent is superior to the routine esophageal stent in respect of safety and efficacy.

Objective To compare the clinical efficacy of transdorsal-to-plantar (TDP) or transplantar-to-dorsal (TPD) retrograde endovascular angioplasty in treating below-the-knee arterial occlusion diseases, and to compare it with conventional anterograde endovascular angioplasty. Methods A total of 96 patients with below-the-knee arterial occlusion diseases (112 diseased lower extremities in total), who were admitted to authors’ hospital during the period from Oct. 2009 to July 2011 to receive conventional anterograde endovascular angioplasty, were enrolled in this study. The clinical data were retrospectively analyzed. Among the 112 diseased lower extremities, conventional anterograde endovascular angioplasty failed in 27, and TDP or TPD retrograde endovascular angioplasty had to be carried out. A total of 71 patients (85 diseased lower limbs) were successfully treated with conventional anterograde endovascular angioplasty (routine group), while 20 patients (22 diseased lower limbs) were successfully treated with retrograde endovascular angioplasty (retrograde group). The preoperative ankle-brachial index(ABI), the coronary angiography-based thrombolysis in myocardial infarction (TIMI) flow score, the dorsal or plantar arterial pulse score, the postoperative limb salvage rate and target vessel patency rate were calculated, and the results were compared between the two groups. Results The technical success rate in the retrograde group and the routine group was 75.9% and 74.0%respectively (P>0.05). Preoperative ABI value of the retrograde group and the routine group was 0.55± 0.21 and 0.56±0.14 respectively, after the treatment which increased to 0.93±0.19 and 0.89±0.18 respectively (P>0.05). Preoperative TIMI score of the retrograde group and the routine group was 0.1 ±0.5 and 0.8 ±0.8 respectively, which significantly increased to 2.5±0.6 and 1.8±0.8 respectively (P<0.000 1). In the retrograde group, the blood flow perfusion of the distal foot tissue was improved. The primary target vessel patency rate at 12 months and 24 months after the treatment in the retrograde group and the routine group were 63.6%(14/22), 45.5%(10/22) and 52.9%(45/85), 37.6%(32/85) respectively (P>0.05). Twenty-four months after endovascular angioplasty Kaplan-Meier analysis indicated that the limb salvage rate of the retrograde group and the routine group was 95.5%and 96.5%respectively (P>0.05). Conclusion Compared with conventional anterograde endovascular angioplasty for the treatment of below-the-knee arterial occlusion diseases, retrograde endovascular angioplasty via TDP or TPD path can immediately improve the blood flow with obvious improvement of ABI score, primary target vessel patency rate as well as the limb salvage rate. Therefore, retrograde endovascular angioplasty should be regarded as an effective supplementary technique when anterograde angioplasty fails.

Objective The aim of the experiment is to make an intracranial aneurysm model in canine.Methods A digital tube was made based on raw magnetic resonance images of the human intracraaial carotid artery.Then 6 tubes were made in the 3 D rapid prototyping machine and coated with silicone.Finally we isolated the common carotid arteries of 6 canines and made them go through the tubes and anastomosed them end-to-side to get the aneurysm model.Six stents were implanted after one week.Results Six aneurysm models were successfully made in canines.The parent artery had similar geometrv of the human carotid siphon.All the aneurysms and parent arteries were patent in one week's follow-up.One canine died of excessive anesthesia after stentingr Two vaseular models kept patent in one month without stenosis.The other 3 had some stenosis on the bends of the vessel.Conclusions The aneurysm model in tIle experiment has high flexibility and reliability.The model provides an effective tool for research and testing neurovascular devices.It's also a useful device to train the neuroradiologists and interventional physicians.

Objective To establish a carotid siphon aneurysm model in dogs in order to test the mechanical features of a newly-designed Willis covered stent-graft and to investigate the histological reaction of the stent-implanted vessel during a follow-up period of 12 months.Methods Twenty-four saccular sidewall aneurysms were surgically created in twelve dogs(group A)and 12 carotid siphon aneurysms in another twelve dogs(group B).A Willis stent-graft was implanted in each aneurysm.Angiography was performed immediately after the procedure and 1,3,6 and 12 months after the implantation to investigate the aneurysm isolation,endoleak,stent angulation,and the patency or restenosis of the parent artery.Light and scanning electronic microscopy were used to identify aneurysmai sac thrombi,intima hyperplasia and endothelial progress of the stent-loaded arterial segment.Results In group B,postoperative immediate angiography demonstrated that two aneurysms had mild endoleak and three stents became angulated.Follow-up exam 12 months after the procedure revealed that all previous endoleaks disappeared,one parent artery became occluded and three parent arteries developed mild stenosis(＜50%).In group A.occlusion of parent artery was seen in one and mild stenosis(＜50%)in 2 cases.Electronic microscopy revealed new intima formation in all stents,and all aneurysmal sacs were filled with thrombi.In group B.the endothelialization process was not completed until 12 months after the stent implantation,and a marked correlation existed between endothelial cell arrangement and the hemodynamic orientation.Conclusion It is feasible to treat carotid-siphon aneurysm in dog with a Willis stent-graft.The complete endothelialization of the covered stent in tortuous vessel takes longer time than that in rather straight vessel.

Objective Complicated aneurysms located in the cisternal segment of the internal carotid artery(ICA-CSA)present unique therapeutic difficulties.This study is to discuss the feasibility of the Willis stent-graft in treating complicated ICA-CSA by comparing its effect with that of coiling therapy.Methods Willis covered stents were employed in 19 complicated ICA-CSAs(group A),while coils were used in 17 complicated ICA-CSAs(group B).Follow-up angiography was performed to investigate aneurysm recurrence,endoleak and parent artery(PA)stenosis.Kaplan-Meier curves were constructed to compare the recurrencefree and PA stenosis-free rate in both groups.Results Total exclusion was immediately achieved in 13 ICACSAs and minor endoleaks presented in 5 cases in group A.Total or near-total occlusion was achieved in 7 ICA-CSAs.subtotal occlusion in 8 and partial occlusion in 2 cases in group B after coiling.Acute thrombosis occurred in 1 patient in either group and re-hemorrhage happened in 1 patient after coiling.Follow-up angiography in group A revealed that 16 ICA-CSAs were completely isolated,with two parent arteries showing mild in-stent stenosis.Eighteen months after the procedure,Kaplan-Meier analysis showed that the recurrence-free rate was 93.3%and 50%,while the stenosis-free rate of parent artery was 87.5%and 100% in group A and in Group B,respectively.In group A and group B the clinical neurological symptoms were fully recovered in 9 and 9,obviously improved in 3 and 5,unchanged in 2 and 2,and aggravated in one and 0 patients,respectively.Conclusion The implantation of Willis stent-graft is a feasible endovascular therapy for complicated ICA-CSAs.When the parent artery is very tortuous or when the risk that a main collateral branch may be wrongly covered and occluded is present,the implantation of Willis covered stent can not be taken as the treatment of first choice.

Objective To study the defects of bone marrow-derived endothelial progenitor cells (EPCs) in number ratio and biological abilities (proliferation, adhesion and migration) in diabetic rats. Methods (1) Establishment of diabetic rat model:1%STZ solution was quickly injected into the abdominal cavity of the male SD rats with the dose of 60 mg/kg. (2). Isolation, culture and identification of bone marrow-derived EPCs in diabetic and normal rats. Bone marrow mononuclear cells were isolated from diabetic and normal rats by density gradient centrifugation methods and cultured by EGM-2 MV medium. The cells were identified by morphological observation, FITC-UEA-1 binding and Dil-Ac-LDL uptake assay, and fluorescent immunocytochemistry was used for detection of CD34 , CD133 and VEGFR-2 expression. CCK-8 method and Transwell kit method were used to determine biological activities of EPCs. Results (1) When cultured in vitro, both bone marrow-derived EPCs in diabetic and normal rats were fusiform in shape, the cells snuggled up to the wall. The expression of CD34, CDl33, VEGFR-2 could be detected in these cells, and the cells could uptake Dil-Ac-LDL and bind FITC-UEA-1, which proved that these cells were EPCs. (2) No significant difference in the number of EPCs derived from bone marrow existed between diabetic rats and normal rats, but the proliferation ability, migration ability and adhesion ability of bone marrow-derived EPCs in diabetic rats were obviously lower than those in normal rats. Conclusion The number of bone marrow-derived EPCs in diabetic rats is not obviously different from that in normal rats, but the biologic activity of EPCs derived from bone marrow in diabetic rats is degraded, which is manifested as weakened abilities of the proliferation, adhesion and migration.