Objective:To investigate and summarize the imaging and pathological features of non-acute occlusion following flow diverter (FD) implantation in animal models.Methods:Four experimental pigs (experimental group) that experienced non-acute occlusion (occlusion time exceeding 24 hours) within the FD stent implanted in the common carotid artery, and 19 pigs (control group) that did not experience stent occlusion during the same period were involved. Using an interventional approach under digital subtraction angiography (DSA), the 4 occluded FD lumens were mechanically opened. Optical coherence tomography (OCT), intravascular ultrasound (IVUS) and histopathological examinations were performed to evaluate the intraluminal composition and characteristics of the occlusive tissues. These findings were compared with non-occluded FD stents to summarize the imaging and pathological changes within the occluded FD lumen.Results:The occlusion times of the FD stents in the 4 experimental pigs were 16 weeks, 20 weeks, 20 weeks, and 24 weeks postoperatively. All occluded stents were successfully recanalized under DSA, with a technical success rate of 4/4. Among the 19 non-occluded FD stents, OCT and IVUS revealed uniform (16 stents) or non-uniform (3 stents) neointimal coverage of the stent struts, presenting as homogeneous high/slightly high signal intensity or medium echogenicity. Histopathological examination indicated that the neointima was primarily composed of smooth muscle cells and a small amount of fibrous connective tissues. In contrast, the 4 occluded FD stents demonstrated excessive neointimal proliferation and plaque formation, leading to luminal loss, as shown by OCT and IVUS. The occlusion tissues predominantly presented as homogeneous high signal intensity with weak attenuation (fibrous plaques) on OCT, with some regions showing blurred low signal intensity and strong attenuation (lipid plaques). IVUS presented homogeneous echogenicity (fibrous plaques) and hypoechogenic zones (lipid plaques). Histopathological examination showed that the occlusion tissues mainly consisted of smooth muscle cells, fibrous connective tissues, and lipids, accompanied by numerous foam cells and a minor presence of inflammatory cells.Conclusions:Histopathological examinations confirm that non-acute occlusion of FD is mainly caused by excessive hyperplasia of intima along with the formation of fibrous plaques and lipid plaques. OCT and IVUS have typical finding in imaging that can assist in determining the cause of stent occlusion as well as the lesion's nature, thereby providing crucial guidance for subsequent clinical treatment and drug selection.

Objective:To investigate and summarize the imaging and pathological features of non-acute occlusion following flow diverter (FD) implantation in animal models.Methods:Four experimental pigs (experimental group) that experienced non-acute occlusion (occlusion time exceeding 24 hours) within the FD stent implanted in the common carotid artery, and 19 pigs (control group) that did not experience stent occlusion during the same period were involved. Using an interventional approach under digital subtraction angiography (DSA), the 4 occluded FD lumens were mechanically opened. Optical coherence tomography (OCT), intravascular ultrasound (IVUS) and histopathological examinations were performed to evaluate the intraluminal composition and characteristics of the occlusive tissues. These findings were compared with non-occluded FD stents to summarize the imaging and pathological changes within the occluded FD lumen.Results:The occlusion times of the FD stents in the 4 experimental pigs were 16 weeks, 20 weeks, 20 weeks, and 24 weeks postoperatively. All occluded stents were successfully recanalized under DSA, with a technical success rate of 4/4. Among the 19 non-occluded FD stents, OCT and IVUS revealed uniform (16 stents) or non-uniform (3 stents) neointimal coverage of the stent struts, presenting as homogeneous high/slightly high signal intensity or medium echogenicity. Histopathological examination indicated that the neointima was primarily composed of smooth muscle cells and a small amount of fibrous connective tissues. In contrast, the 4 occluded FD stents demonstrated excessive neointimal proliferation and plaque formation, leading to luminal loss, as shown by OCT and IVUS. The occlusion tissues predominantly presented as homogeneous high signal intensity with weak attenuation (fibrous plaques) on OCT, with some regions showing blurred low signal intensity and strong attenuation (lipid plaques). IVUS presented homogeneous echogenicity (fibrous plaques) and hypoechogenic zones (lipid plaques). Histopathological examination showed that the occlusion tissues mainly consisted of smooth muscle cells, fibrous connective tissues, and lipids, accompanied by numerous foam cells and a minor presence of inflammatory cells.Conclusions:Histopathological examinations confirm that non-acute occlusion of FD is mainly caused by excessive hyperplasia of intima along with the formation of fibrous plaques and lipid plaques. OCT and IVUS have typical finding in imaging that can assist in determining the cause of stent occlusion as well as the lesion's nature, thereby providing crucial guidance for subsequent clinical treatment and drug selection.

In the course of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)infec-tion,to verify whether ursodeoxycholic acid(UDCA)can reduce angiotensin-converting enzyme 2(ACE2)receptor in BALB/c mice and reduce the risk of infection.UDCA was administered by in-tragastric administration to BALB/c mice for 7 d.During the treatment,the turbinate bones and lungs of mice were taken every day,and the changes of ACE2 content in the turbinate bones and lungs of mice were detected by ELISA.In addition,after 1,4 and 7 d of intragastric prophylaxis,BALB/c mice were infected with SARS-CoV-2 C57MA14 mouse adapted strain and SARS-CoV-2 Omicron DY1.1,respectively,after nasal inoculation,and viral load was detected on the turnings and lungs of mice 3 d after challenge to evaluate the preventive effect.In addition,UDCA was used to treat BALB/c mice infected with SARS-CoV-2 C57MA14 mouse adapted strain after nasal drops by gavage for 3 d,and the viral load of the mouse turbinate and lung was detected to evaluate the therapeutic effect.UDCA can decrease ACE2 content in turbinate and lung of BALB/c mice.How-ever,after 1,4 and 7 d of UDCA intragastric administration,there was no statistical difference in viral load in turbinate and lung of BALB/c mice between the prevention group and the virus con-trol group.There was no significant difference in the viral load of the turbinate and lung between the UDCA treatment group and the viral control group.UDCA could reduce the ACE2 content in the turnings and lungs of aged BALB/c mice,but the daily dose and duration of UDCA treatment had no significant effect on the mice infected with SARS-CoV-2 C57MA14 mouse adapted strain and SARS-CoV-2 Omicron DY1.1.

Objective To explore the mechanism of down-regulation of regulatory T cells (Treg) by immunization with attenuated activated autologous T cells. Methods Aulologous T cells were activated with ConA in vitro. Mice were immunized subcutaneously and inlraperitoneally every 5 days for 3 times (5 ×10~6 per time for each mouse), and the number and function of Treg were examined. PBS was subcutaneously injected for control group. Serum level of anti-mouse CD25 antibody was measured by ELISA. The number and function of Treg was detected by serum adoptive transfer and proliferation and inhibition assays. Results Compared with control group, there were less CD4~+ CD25~+ Foxp3~+ Treg in the mice after immunization (P < 0. 01), the immunosuppression ability decreased (P<0. 01), and the level of anti-CD25 antibody increased (P <0.01). Adoptive transfer of serum from immunized mice to naive mice led to a significant decrease in Treg population and function in recipient mice (P<0. 01). Conclusion Immunization with attenuated activated autologous T cells induces more anti-CD25 antibody, which may further down-regulate CD4~+CD25~+Foxp3~+ Treg expansion and function in vivo.