BACKGROUND:Arthroscopic anchor repair has become the main treatment method for rotator cuff tears at present.Among them,the insertion status of the anchor is a key factor in the success or failure of the operation.However,currently,the impact of the insertion depth of the anchor on the stress of the bone tunnel and the anchor under different bone density conditions remains unclear.OBJECTIVE:To explore the stress distribution of the bone tunnel and the anchor when the insertion depth of the anchor varies under different bone density conditions by using three-dimensional finite element analysis technology.METHODS:The CT image data of the humerus of volunteers were collected,and the models of the humerus and the anchor were constructed by using Mimics,3-Matic,and Solidworks software.In 3-Matic,holes with distances of 0,2,4,6,and 8 mm from the surface of the humerus were respectively created at the same position of the humerus and assembled with the anchor.In Mimics,values were assigned based on the CT gray value to obtain a model with normal bone mass(T value ≥-1.0).The parameters were changed to construct models with reduced bone mass(-2.5＜T value＜-1.0)and osteoporosis(T value＜-2.5).In each model,a 70 N pulling force was applied to the anchor along the direction tangent to the inner edge of the bone tunnel.The stress distribution and magnitude of the bone tunnel and the anchor when inserted at different depths under different bone density conditions were observed.RESULTS AND CONCLUSION:(1)When the insertion depth was the same,as the bone density decreased,the maximum equivalent stress of the anchor increased,while the maximum equivalent stress of the bone tunnel decreased.(2)When the bone density was the same,as the insertion depth of the anchor increased,the maximum equivalent stress of the anchor decreased.When the insertion depth was 4 mm,the stress of the bone tunnel was the smallest and the distribution was relatively uniform.The stress of the anchor was mainly distributed around the lower anchor hole and the proximal thread,and the stress of the bone tunnel was mainly at the part in contact with the proximal thread.The increase in the insertion depth would change the uniformity and pattern of the stress distribution,while the bone density had a relatively small impact on the stress distribution pattern.(3)It is concluded that the bone density of the humerus is crucial for the anchor repair of rotator cuff tears.It is recommended that clinicians measure the bone density of the greater tuberosity of the humerus before the operation.Excessive insertion depth of the anchor does not significantly increase its stability.Clinicians can conduct personalized preoperative assessments by using the finite element analysis method in combination with the actual situation of patients to achieve the best surgical results.

BACKGROUND:Arthroscopic anchor repair has become the main treatment method for rotator cuff tears at present.Among them,the insertion status of the anchor is a key factor in the success or failure of the operation.However,currently,the impact of the insertion depth of the anchor on the stress of the bone tunnel and the anchor under different bone density conditions remains unclear.OBJECTIVE:To explore the stress distribution of the bone tunnel and the anchor when the insertion depth of the anchor varies under different bone density conditions by using three-dimensional finite element analysis technology.METHODS:The CT image data of the humerus of volunteers were collected,and the models of the humerus and the anchor were constructed by using Mimics,3-Matic,and Solidworks software.In 3-Matic,holes with distances of 0,2,4,6,and 8 mm from the surface of the humerus were respectively created at the same position of the humerus and assembled with the anchor.In Mimics,values were assigned based on the CT gray value to obtain a model with normal bone mass(T value ≥-1.0).The parameters were changed to construct models with reduced bone mass(-2.5＜T value＜-1.0)and osteoporosis(T value＜-2.5).In each model,a 70 N pulling force was applied to the anchor along the direction tangent to the inner edge of the bone tunnel.The stress distribution and magnitude of the bone tunnel and the anchor when inserted at different depths under different bone density conditions were observed.RESULTS AND CONCLUSION:(1)When the insertion depth was the same,as the bone density decreased,the maximum equivalent stress of the anchor increased,while the maximum equivalent stress of the bone tunnel decreased.(2)When the bone density was the same,as the insertion depth of the anchor increased,the maximum equivalent stress of the anchor decreased.When the insertion depth was 4 mm,the stress of the bone tunnel was the smallest and the distribution was relatively uniform.The stress of the anchor was mainly distributed around the lower anchor hole and the proximal thread,and the stress of the bone tunnel was mainly at the part in contact with the proximal thread.The increase in the insertion depth would change the uniformity and pattern of the stress distribution,while the bone density had a relatively small impact on the stress distribution pattern.(3)It is concluded that the bone density of the humerus is crucial for the anchor repair of rotator cuff tears.It is recommended that clinicians measure the bone density of the greater tuberosity of the humerus before the operation.Excessive insertion depth of the anchor does not significantly increase its stability.Clinicians can conduct personalized preoperative assessments by using the finite element analysis method in combination with the actual situation of patients to achieve the best surgical results.

Objective:To investigate the application value of risk prediction model for acute kidney injury (AKI) after donation of cardiac death (DCD) liver transplantation based on machine learning algorithm.Methods:The retrospective cohort study was conducted. The clinicopathological data of 1 001 pairs of DCD liver transplant donors and recipients at five hospitals, including The First Affiliated Hospital of Zhejiang University School of Medicine et al, in the Chinese Liver Transplan-tation Registry from January 2015 to December 2023 were collected. Of the donors, there were 825 males and 176 females. Of the recipients, there were 806 males and 195 females, aged 52 (range, 18-75)years. There were 281 recipients included using oversampling technique, and all 1 282 recipients were divided to the training set of 897 recipients and the validation set of 385 recipients by a ratio of 7∶3 using computer-generated random numbers. Seven prediction models, including Random Forest (RF), Extreme Gradient Boosting (XGBoost), Support Vector Machine (SVM), Logistic Regression (LR), Decision Tree (DT), K-Nearest Neighbors (KNN), and Categorical Boosting (CatBoost), were constructed for AKI after liver transplantation based on machine learning algorithm. Observation indicators: (1) comparison of clinicopathological characteristics between recipients with and without AKI and donors; (2) follow-up and survival of recipients with and without AKI; (3) construction and validation of nomogram prediction model of AKI after liver transplantation; (4) construction and validation of machine learning prediction model of AKI after liver transplantation. Comparison of measurement data with normal distribution between groups was conducted using the independent sample t test. Comparison of measurement data with skewed distribution between groups was conducted using the Mann-Whitney U test, and comparison among groups was conducted using the Kruskal-Wallis H test. Comparison of count data between groups was conducted using the chi-square test or corrected chi-square test. Kaplan-Meier method was used to calculate survival rates and plot survival curves. Logistic regression model was performed for univariate and multivariate analyses. The receiver operating characteristic (ROC) curve was plotted to calculate area under curve (AUC) and 95% confidence interval ( CI). The performance of prediction model was evaluated using DeLong test, accuracy, sensitivity, specificity. The calibration curve was plotted to evaluate the performance of predicted probability and actual probability. The interpretability analysis of machine learning algorithm and SHapley Additive exPlanations was used to explain the model decision separately. Results:(1) Comparison of clinicopathological characteristics between recipients with and without AKI and donors. Of 1 001 recipients, there were 360 cases with AKI and 641 cases without AKI after liver transplantation. There were significant differences in body mass index (BMI), hepatic encepha-lopathy, hepatitis B surfact antigen (HBsAg), hepatorenal syndrome (HRS) and donor diabetes, donor blood urea nitrogen, donor alanine aminotransferase, donor aspartate aminotransferase, mass of graft, volume of blood loss during liver transplantation, warm ischema time of donor liver, and operation time between recipients with and without AKI ( Z=-4.337, χ2=9.751, 9.088, H=11.142, χ2=5.286, Z=-3.360, -2.539, -3.084, -1.730, -3.497, -1.996, -2.644, P<0.05). (2) Follow-up and survival of recipients with and without AKI. All the 1 001 recipients received follow-up. The recipients with AKI after liver transplantation were followed up for 18.6(range, 0-102.3)months, and recipients without AKI after liver transplantation were followed up for 31.9(range, 0.1-105.5)months. The 1-, 3-, and 5-year overall survival rates were 72.1%, 63.5%, and 59.3% of recipients with AKI, versus 86.7%, 76.7%, and 72.5% of recipients without AKI, respectively, showing a significant difference in overall survival between them ( χ2=26.028, P<0.05). (3) Construction and validation of nomogram predic-tion model of AKI after liver transplantation. Results of multivariate analysis showed that recipient BMI, recipient creatinine, recipient HBsAg, recipient HRS, donor blood urea nitrogen, donor crea-tinine, anhepatic phase and volume of blood loss during liver transplantation were independent risk factors for AKI of recipients after liver transplantation ( odds ratio=1.113, 0.998, 0.605, 1.580, 1.047, 0.998, 1.006, 1.157, 95% CI as 1.070-1.157, 0.996-1.000, 0.450-0.812, 1.021-2.070, 1.021-1.074, 0.996-0.999, 1.000-1.012, 1.045-1.281, P<0.05). The nomogram prediction model of AKI after liver transplantation was constructed based on the results of multivariate analysis. Results of ROC curve showed that the AUC of 0.666 (95% CI as 0.637-0.696). (4) Construction and validation of machine learning prediction model of AKI after liver transplantation. Based on the Lasso regression analysis, seven machine learning algorithm prediction models, including RF, XGBoost, SVM, LR, DT, KNN, and CatBoost, were constructed, with ROC curves of the validation set plotted. The AUC of above models were 0.863, 0.841, 0.721, 0.637, 0.620, 0.708, 0.731, accuracies were 0.764, 0.782, 0.701, 0.592, 0.605, 0.605, 0.681, sensitivities were 0.764, 0.789, 0.719, 0.588, 0.694, 0.694, 0.704, specificities were 0.763, 0.774, 0.683, 0.597, 0.511, 0.511, 0.656, respectively. Delong test showed that the RF model with the highest AUC of 0.863(95% CI as 0.828-0.899). Calibration curve analysis showed the predicted probability closest to the actual probability of RF model, indicating the model with a good validation value. Further sorting of SHAP of different clinical factors based on RF model showed that recipient BMI, donor blood urea nitrogen, volume of blood loss during liver transplantation, donor age had large effects on the output outcomes. Conclusion:The nomogram prediction model and seven machine learning algorithm prediction models for AKI after DCD liver transplantation are constructed, and the RF model based on machine learning has a better predictive performance.

Objective:To explore the diagnostic value of a clinical-radiomics model based on the T 1 mapping and apparent diffusion coefficient (ADC)-based radiomics, and the clinical indicator for renal fibrosis (RF) caused by chronic kidney disease (CKD). Methods:This cross-sectional study prospectively and consecutively enrolled 122 patients with CKD at the Second Affiliated Hospital of Soochow University from September 2021 to December 2023 who were randomly allocated to a training set ( n=85) or a validation set ( n=37) in an approximate 7∶3 ratio using simple random sampling. Patients underwent T 1 mapping and diffusion-weighted imaging scans. Renal biopsy was performed within 3 days after the MRI scans. Patients were categorized into three groups based on the degree of RF: no RF ( n=25), mild RF ( n=55), and moderate to severe RF ( n=42). To differentiate the presence of RF (no RF vs. any RF) and the severity of RF (mild RF vs. moderate to severe RF), univariate and multivariate logistic regression were used to optimize the independent clinical predictor, which constituted the clinical model. Radiomics features were extracted from regions of interest delineated within the renal parenchyma of the right kidney on T 1 mapping and ADC maps. Features were selected using least absolute shrinkage and selection operator regression to build the radiomics model. A clinical-radiomics model was subsequently constructed by integrating the independent clinical predictors with the selected radiomics features. Model diagnostic performance was evaluated using the area under the receiver operating characteristic curve (AUC). Calibration curve was plotted to assess model calibration, and decision curve analysis was performed to evaluate clinical net benefit. Results:Univariate logistic regression analysis revealed that estimated glomerular filtration rate (eGFR), serum creatinine, and blood urea nitrogen exhibited statistically significant differences ( P0.05) in distinguishing both the presence and severity of RF. Multivariate analysis identified eGFR as an independent clinical predictor for both the presence of RF ( OR=0.939, 95% CI 0.898-0.982, P=0.006) and RF severity ( OR=0.956, 95% CI 0.917-0.997, P=0.037). From the MRI images, 7 radiomics features were selected to build the radiomics model for distinguishing the presence of RF, and 8 features were selected for the model assessing RF severity. These radiomics models were then combined with eGFR to construct the clinical-radiomics models. The clinical-radiomics models demonstrated the highest diagnostic performance, with an AUC of 0.935 (95% CI 0.859-0.977) for RF presence and 0.967 (95% CI 0.891-0.995) for RF severity in the training set, and 0.914 (95% CI 0.774-0.981) and 0.908 (95% CI 0.748-0.981) in the validation set. Calibration curves and decision curve analysis confirmed that the clinical-radiomics models exhibited excellent calibration and provided the highest clinical net benefit for assessing RF in CKD patients. Conclusion:The clinical-radiomics model integrating T 1 mapping and ADC-based radiomics and eGFR can effectively improve the diagnostic performance for RF in CKD patients.

BACKGROUND:Small intestinal submucosal acellular matrix has been proven by clinical and basic studies to be useful for urethral repair and reconstruction.However,when applied alone,it has problems such as slow growth of host cells,difficulty in survival due to insufficient stent vascularization,and obstruction of reconstructed urethral stricture,and is only suitable for short urethral stricture.OBJECTIVE:To investigate the feasibility of constructing tissue engineered urethra with acellular matrix combined with exosomes in small intestinal submucosa.METHODS:Exosomes were isolated from rabbit bone marrow mesenchymal stem cells.The porcine small intestinal submucosal acellular matrix was prepared,and exosomes were loaded on the porcine small intestinal submucosal acellular matrix.The extracellular stroma-exosome(PKH26 dye labeled)complex of small intestinal submucosa was co-cultured with umbilical vein endothelial cells for 12 hours to observe the uptake of exosomes.The umbilical vein endothelial cells with good growth status were selected and cultured in three groups:the blank group was cultured routinely.The control group was added with small intestinal submucosal acellular matrix,and the experimental group was added with small intestinal submucosal acellular stromat-exosome complex.The angiogenesis was evaluated by scratch test,tube formation test,and angiogenic factor secretion test.Thirty New Zealand white rabbits were selected to establish a long(3 cm)urethral defect model,and the intervention was divided into three groups by random number table method(n=10).The single material group was implanted with small intestinal submucosal acellular matrix.The control group was implanted with small intestinal submucosal acellular matrix-bone marrow mesenchymal stem cell complex.The experimental group was implanted with small intestinal submucosal acellular matrix-exosome complex.Urethrography,urodynamic examination,and pathological observation of reconstructed urethral sections were performed 12 weeks after implantation.RESULTS AND CONCLUSION:(1)Exosomes in the acellular matrix of small intestinal submucosa could be taken up by umbilical vein endothelial cells under the fluorescence microscope.(2)Compared with the blank group and the control group,the experimental group could promote the migration of umbilical vein endothelial cells,angiogenesis ability,and the secretion of angiogenic factors vascular endothelial growth factor,hepatocyte growth factor,and interleukin 8(P<0.05).(3)Urethrography results showed that all 10 rabbits in the single material group had urethral stenosis;2 out of 10 rabbits in the control group had urethral stenosis,and none of the 10 rabbits in the experimental group had urethral stenosis.The results of urodynamic examination showed that the maximum urethral pressure at 12 weeks after implantation was higher in the single material group than before surgery(P<0.05),and the maximum urethral pressure at 12 weeks after implantation was lower in the control group and the experimental group than in the blank group(P<0.05).Hematoxylin-eosin,Masson and immunohistochemical staining showed that in the single material group,there were obvious regenerated epidermis,a small amount of subcutaneous smooth muscle and blood vessels,mainly fibrous tissue hyperplasia,accompanied by obvious inflammatory cell infiltration.In the control group,there were more complete regenerated epithelium and a small amount of collagen,a large number of subcutaneous blood vessels and smooth muscle,accompanied by inflammatory cell infiltration.The experimental group showed complete regenerated epidermis,a large number of subcutaneous blood vessels and smooth muscle,and no obvious inflammatory cell infiltration.The positive expressions of AE1/AE3,alpha smooth muscle actin,and CD31 in the experimental group were higher than those in the single material group and the control group(P<0.05).(4)The results show that the small intestinal submucosal acellular matrix-exosome tissue engineered urethra can repair the urethral defect by promoting angiogenesis.

Objective This study aims to explore the efficacy and complication rates of the transcranial approach(TCA)and extended endoscopic endonasal approach(EEEA)for the treatment of craniopharyngiomas based on the QST classification,providing a scientific reference for clinical decision-making on surgical approach.Methods A total of 151 patients who underwent craniopharyngioma surgery at our center from January 2018 to December 2023 were enrolled.The patients were categorized into Q-CP(suprasellar type),S-CP(infundibular type),and T-CP(tuberal type)according to the QST classification.Systematic collection and analysis were performed on the outcomes of TCA and EEEA treatments,respectively.The differences in effectiveness between the two approaches were evaluated based on the QST classification.Results The improvement rate of visual symptoms was overall higher in the EEEA group than in the TCA group(59.1%vs.36.5%,P=0.006),and the visual deterioration rate was lower(3.0%vs.14.1%,P=0.006).However,the incidence of cerebrospinal fluid leakage was higher in the EEEA group(15.2%vs.3.5%,χ2=4.986,P=0.026).The incidence of postoperative seizures(8.2%vs.0,P=0.019),brain contusions(10.6%vs.0,P=0.005),and subdural hematoma(9.4%vs.0%,P=0.01)was higher in the TCA group.For patients with Q-CP type,the EEEA group had a higher rate of total tumor resection(92.9%vs.65.2%,P=0.025)and a lower recurrence rate(3.6%vs.21.7%,P=0.047),with shorter hospital stays and lower postoperative costs.The TCA group had higher intraoperative blood loss in this type(300 mL vs.200 mL,Z=-2.261,P=0.024).For S-CP type patients,the EEEA group showed a higher rate of total tumor resection(91.3%vs.74.2%)and a lower recurrence rate(0 vs.12.9%,P=0.031),with lower postoperative hospital costs.In T-CP type,due to the deeper location,EEEA showed limitations in protecting hypothalamic function and the TCA group had a better postoperative hypothalamic function score(P=0.035).Conclusion Based on QST classification,EEEA has advantages in Q-CP and S-CP types and is recommended as the preferred surgical procedure;In the T-CP type,TCA surgery is more helpful in protecting hypothalamic function.

Objective:To observe the therapeutic effects of electroacupuncture(EA)stimulation on chronic pain and associated negative emotions,and to investigate the activity changes of glutamatergic neurons in the primary motor cortex(M1)following EA stimulation.Methods:Male C57BL/6J mice were randomly divided into four groups:sham surgery(Sham),pure electroacupuncture stimulation(EA),nerve injury(SNI)and electroacupuncture treatment of nerve injury(SNI+EA).Thirty days after the SNI model establishment,EA stimulation was administered bilaterally to the Zusanli(ST36)acupoints in mice.von Frey filaments and Hargreaves heat sensitivity testing were used to detect mechanical and thermal hyperalgesia.The elevated plus maze test was conducted to assess the impact on anxiety-like behaviors in mice.Dual immunofluorescence staining was employed to observe changes in c-Fos expression in M1 gluta-matergic neurons.Results:As compared to Sham group,SNI-treated mice exhibited significant mechanical and thermal hyperalgesia in bilateral hindpaws at 30 days post-modeling(P＜0.01)and displayed obvious anxiety-like behaviors(P＜0.01).The SNI+EA group showed significant relief in pain and anxiety-like behaviors(P＜0.01).c-Fos expression in M1 glutamatergic neurons was significantly decreased in SNI mice.Conversely,after electroacupuncture(EA)treatment,compared to the SNI group,M1 glutamatergic neurons in the SNI+EA group showed significantly in-creased c-Fos expression(P＜0.01).Conclusion:Electroacupuncture significantly alleviated chronic pain and associ-ated anxiety-like behaviors induced by SNI,which might involve the activation of glutamatergic neurons in the M1 in this process.

Objective This study aims to explore the efficacy and complication rates of the transcranial approach(TCA)and extended endoscopic endonasal approach(EEEA)for the treatment of craniopharyngiomas based on the QST classification,providing a scientific reference for clinical decision-making on surgical approach.Methods A total of 151 patients who underwent craniopharyngioma surgery at our center from January 2018 to December 2023 were enrolled.The patients were categorized into Q-CP(suprasellar type),S-CP(infundibular type),and T-CP(tuberal type)according to the QST classification.Systematic collection and analysis were performed on the outcomes of TCA and EEEA treatments,respectively.The differences in effectiveness between the two approaches were evaluated based on the QST classification.Results The improvement rate of visual symptoms was overall higher in the EEEA group than in the TCA group(59.1%vs.36.5%,P=0.006),and the visual deterioration rate was lower(3.0%vs.14.1%,P=0.006).However,the incidence of cerebrospinal fluid leakage was higher in the EEEA group(15.2%vs.3.5%,χ2=4.986,P=0.026).The incidence of postoperative seizures(8.2%vs.0,P=0.019),brain contusions(10.6%vs.0,P=0.005),and subdural hematoma(9.4%vs.0%,P=0.01)was higher in the TCA group.For patients with Q-CP type,the EEEA group had a higher rate of total tumor resection(92.9%vs.65.2%,P=0.025)and a lower recurrence rate(3.6%vs.21.7%,P=0.047),with shorter hospital stays and lower postoperative costs.The TCA group had higher intraoperative blood loss in this type(300 mL vs.200 mL,Z=-2.261,P=0.024).For S-CP type patients,the EEEA group showed a higher rate of total tumor resection(91.3%vs.74.2%)and a lower recurrence rate(0 vs.12.9%,P=0.031),with lower postoperative hospital costs.In T-CP type,due to the deeper location,EEEA showed limitations in protecting hypothalamic function and the TCA group had a better postoperative hypothalamic function score(P=0.035).Conclusion Based on QST classification,EEEA has advantages in Q-CP and S-CP types and is recommended as the preferred surgical procedure;In the T-CP type,TCA surgery is more helpful in protecting hypothalamic function.

Objective:To observe the therapeutic effects of electroacupuncture(EA)stimulation on chronic pain and associated negative emotions,and to investigate the activity changes of glutamatergic neurons in the primary motor cortex(M1)following EA stimulation.Methods:Male C57BL/6J mice were randomly divided into four groups:sham surgery(Sham),pure electroacupuncture stimulation(EA),nerve injury(SNI)and electroacupuncture treatment of nerve injury(SNI+EA).Thirty days after the SNI model establishment,EA stimulation was administered bilaterally to the Zusanli(ST36)acupoints in mice.von Frey filaments and Hargreaves heat sensitivity testing were used to detect mechanical and thermal hyperalgesia.The elevated plus maze test was conducted to assess the impact on anxiety-like behaviors in mice.Dual immunofluorescence staining was employed to observe changes in c-Fos expression in M1 gluta-matergic neurons.Results:As compared to Sham group,SNI-treated mice exhibited significant mechanical and thermal hyperalgesia in bilateral hindpaws at 30 days post-modeling(P＜0.01)and displayed obvious anxiety-like behaviors(P＜0.01).The SNI+EA group showed significant relief in pain and anxiety-like behaviors(P＜0.01).c-Fos expression in M1 glutamatergic neurons was significantly decreased in SNI mice.Conversely,after electroacupuncture(EA)treatment,compared to the SNI group,M1 glutamatergic neurons in the SNI+EA group showed significantly in-creased c-Fos expression(P＜0.01).Conclusion:Electroacupuncture significantly alleviated chronic pain and associ-ated anxiety-like behaviors induced by SNI,which might involve the activation of glutamatergic neurons in the M1 in this process.

BACKGROUND:Small intestinal submucosal acellular matrix has been proven by clinical and basic studies to be useful for urethral repair and reconstruction.However,when applied alone,it has problems such as slow growth of host cells,difficulty in survival due to insufficient stent vascularization,and obstruction of reconstructed urethral stricture,and is only suitable for short urethral stricture.OBJECTIVE:To investigate the feasibility of constructing tissue engineered urethra with acellular matrix combined with exosomes in small intestinal submucosa.METHODS:Exosomes were isolated from rabbit bone marrow mesenchymal stem cells.The porcine small intestinal submucosal acellular matrix was prepared,and exosomes were loaded on the porcine small intestinal submucosal acellular matrix.The extracellular stroma-exosome(PKH26 dye labeled)complex of small intestinal submucosa was co-cultured with umbilical vein endothelial cells for 12 hours to observe the uptake of exosomes.The umbilical vein endothelial cells with good growth status were selected and cultured in three groups:the blank group was cultured routinely.The control group was added with small intestinal submucosal acellular matrix,and the experimental group was added with small intestinal submucosal acellular stromat-exosome complex.The angiogenesis was evaluated by scratch test,tube formation test,and angiogenic factor secretion test.Thirty New Zealand white rabbits were selected to establish a long(3 cm)urethral defect model,and the intervention was divided into three groups by random number table method(n=10).The single material group was implanted with small intestinal submucosal acellular matrix.The control group was implanted with small intestinal submucosal acellular matrix-bone marrow mesenchymal stem cell complex.The experimental group was implanted with small intestinal submucosal acellular matrix-exosome complex.Urethrography,urodynamic examination,and pathological observation of reconstructed urethral sections were performed 12 weeks after implantation.RESULTS AND CONCLUSION:(1)Exosomes in the acellular matrix of small intestinal submucosa could be taken up by umbilical vein endothelial cells under the fluorescence microscope.(2)Compared with the blank group and the control group,the experimental group could promote the migration of umbilical vein endothelial cells,angiogenesis ability,and the secretion of angiogenic factors vascular endothelial growth factor,hepatocyte growth factor,and interleukin 8(P<0.05).(3)Urethrography results showed that all 10 rabbits in the single material group had urethral stenosis;2 out of 10 rabbits in the control group had urethral stenosis,and none of the 10 rabbits in the experimental group had urethral stenosis.The results of urodynamic examination showed that the maximum urethral pressure at 12 weeks after implantation was higher in the single material group than before surgery(P<0.05),and the maximum urethral pressure at 12 weeks after implantation was lower in the control group and the experimental group than in the blank group(P<0.05).Hematoxylin-eosin,Masson and immunohistochemical staining showed that in the single material group,there were obvious regenerated epidermis,a small amount of subcutaneous smooth muscle and blood vessels,mainly fibrous tissue hyperplasia,accompanied by obvious inflammatory cell infiltration.In the control group,there were more complete regenerated epithelium and a small amount of collagen,a large number of subcutaneous blood vessels and smooth muscle,accompanied by inflammatory cell infiltration.The experimental group showed complete regenerated epidermis,a large number of subcutaneous blood vessels and smooth muscle,and no obvious inflammatory cell infiltration.The positive expressions of AE1/AE3,alpha smooth muscle actin,and CD31 in the experimental group were higher than those in the single material group and the control group(P<0.05).(4)The results show that the small intestinal submucosal acellular matrix-exosome tissue engineered urethra can repair the urethral defect by promoting angiogenesis.