Xufeng Wei

RGD-modified acellular bovine pericardium as a bioprosthetic scaffold for tissue engineering

Acellular biological tissues, including bovine pericardia (BP), have been proposed as natural biomaterials for tissue engineering. However, small pore size, low porosity and lack of extra cellular matrix (ECM) after native cell extraction directly restrict the seed cell adhesion, migration and proliferation and which is a vital problem for ABP’s application in the tissue engineered heart valve (TEHV). In the present study, we treated acellular BP with acetic acid, which increased the scaffold pore size and porosity and conjugated RGD polypeptides to ABP scaffolds. After 10 days of culture in vitro, the human mesenchymal stem cells (hMSCs) attached the best and proliferated the fastest on RGD-modified acellular scaffolds, and the cell has grown deep into the scaffold. In contrast, a low density of cells attached to the unmodified scaffolds, with few infiltrating into the acellular tissues. These findings support the potential use of modified acellular BP as a scaffold for tissue engineered heart valves.

Reduced Cardioprotective Action of Adiponectin in High-Fat Diet–Induced Type II Diabetic Mice and Its Underlying Mechanisms

Diabetes exacerbates ischemic heart disease morbidity and mortality via incompletely understood mechanisms. Although adiponectin (APN) reduces myocardial ischemia/reperfusion (MI/R) injury in nondiabetic animals, whether APNs cardioprotective actions are altered in diabetes, a pathologic condition with endogenously reduced APN, has never been investigated. High-fat diet (HD)-induced diabetic mice and normal diet (ND) controls were subjected to MI via coronary artery ligation, and given vehicle or APN globular domain (gAPN, 2 μg/g) 10 min before reperfusion. Compared to ND mice (where gAPN exerted pronounced cardioprotection), HD mice manifested greater MI/R injury, and a tripled gAPN dose was requisite to achieve cardioprotective extent seen in ND mice (i.e., infarct size, apoptosis, and cardiac function). APN reduces MI/R injury via AMP-activated protein kinase (AMPK)-dependent metabolic regulation and AMPK-independent antioxidative/antinitrative pathways. Compared to ND, HD mice manifested significantly blunted gAPN-induced AMPK activation, basally and after MI/R (p<0.05). Although both low- and high-dose gAPN equally attenuated MI/R-induced oxidative stress (i.e., NADPH oxidase expression and superoxide production) and nitrative stress (i.e., inducible nitric oxide synthase expression, nitric oxide production, and peroxynitrite formation) in ND mice, only high-dose gAPN efficaciously did so in HD mice. We demonstrate for the first time that HD-induced diabetes diminished both AMPK-dependent and AMPK-independent APN cardioprotection, suggesting an unreported diabetic heart APN resistance.

Increased expression of pigment epithelium-derived factor in aged mesenchymal stem cells impairs their therapeutic efficacy for attenuating myocardial infarction injury.

Aims Mesenchymal stem cells (MSCs) can ameliorate myocardial infarction (MI) injury. However, older-donor MSCs seem less efficacious than those from younger donors, and the contributing underlying mechanisms remain unknown. Here, we determine how age-related expression of pigment epithelium-derived factor (PEDF) affects MSC therapeutic efficacy for MI. Methods and results Reverse transcriptase–polymerized chain reaction and enzyme-linked immunosorbent assay analyses revealed dramatically increased PEDF expression in MSCs from old mice compared to young mice. Morphological and functional experiments demonstrated significantly impaired old MSC therapeutic efficacy compared with young MSCs in treatment of mice subjected to MI. Immunofluorescent staining demonstrated that administration of old MSCs compared with young MSCs resulted in an infarct region containing fewer endothelial cells, vascular smooth muscle cells, and macrophages, but more fibroblasts. Pigment epithelium-derived factor overexpression in young MSCs impaired the beneficial effects against MI injury, and induced cellular profile changes in the infarct region similar to administration of old MSCs. Knocking down PEDF expression in old MSCs improved MSC therapeutic efficacy, and induced a cellular profile similar to young MSCs administration. Studies in vitro showed that PEDF secreted by MSCs regulated the proliferation and migration of cardiac fibroblasts. Conclusions This is the first evidence that paracrine factor PEDF plays critical role in the regulatory effects of MSCs against MI injury. Furthermore, the impaired therapeutic ability of aged MSCs is predominantly caused by increased PEDF secretion. These findings indicate PEDF as a promising novel genetic modification target for improving aged MSC therapeutic efficacy.

Downregulation of adiponectin induced by tumor necrosis factor α is involved in the aggravation of posttraumatic myocardial ischemia/reperfusion injury*

Objective:Recent clinical observations have indicated that nonlethal mechanical trauma significantly increases myocardial infarction risk even in the presence of completely normal coronary arteries. We investigated the molecular mechanisms responsible for exacerbation of ischemic myocardial injury after nonlethal mechanical trauma with a special focus on the role of tumor necrosis factor &agr; and its potential downstream effector adiponectin, a novel adipokine with anti-inflammatory and cardioprotective properties. Design:Laboratory study. Setting:University research unit. Subjects:Male adult adiponectin knockout mice and wild-type mice. Interventions:The animals were subjected to nonlethal mechanical trauma using the Noble-Collip drum (40 rpm ± 5 mins) followed by myocardial ischemia/reperfusion injury 7 days posttrauma. We also investigated the effects of neutralizing tumor necrosis factor &agr; with etanercept and exogenous adiponectin supplementation on ischemic myocardial injury after trauma. Measurements and Main Results:Trauma significantly sensitized myocardium to ischemia/reperfusion injury as evidenced by increased apoptosis, enlarged infarct size, and decreased cardiac function. Plasma adiponectin concentrations were reduced after traumatic injury (the nadir occurring 3 days posttrauma), an effect abrogated by etanercept-mediated tumor necrosis factor &agr; blockade. The downregulation of adiponectin was accompanied by increased myocardial superoxide and nitric oxide generation and peroxynitrite formation. Both etanercept and exogenous adiponectin supplementation (on day 3 posttrauma or 10 mins before reperfusion on day 7 posttrauma) markedly inhibited oxidative/nitrative stress and ischemia/reperfusion injury in posttraumatic ischemic/reperfused hearts of wild-type mice, whereas only adiponectin supplementation (but not tumor necrosis factor &agr; inhibition) substantially attenuated posttraumatic ischemia/reperfusion injury in adiponectin knockout mice. Conclusions:Tumor necrosis factor &agr;-induced downregulation of adiponectin and the resultant enhanced oxidative/nitrative stress are involved in exacerbated posttraumatic ischemic myocardial injury. Therapeutic approaches blocking tumor necrosis factor &agr; production or restoring adiponectin might have prophylactic value against secondary myocardial ischemic injury after a primary nonlethal mechanical trauma.

Combined interventional and surgical treatment for acute aortic type a dissection

BACKGROUND Surgical repair and endovascular stent-graft placement are both therapies for thoracic aortic dissection. A combination of these two approaches may be effective in patients with type A dissection. In this study, we evaluated the prognosis of this combined technique. METHODS From December 2003 to December 2006, 15 patients with type A dissection were admitted to our institute; clinical data were retrospectively reviewed. Follow-up was performed at discharge and approximately 12 months after operation. RESULTS Endovascular stent-graft placement by interventional radiology and surgical repair for reconstruction of aortic arch was performed in all patients. Total arch replacement for distal arch aneurysm was carried out under deep hypothermia with circulatory arrest; antegrade-selected cerebral perfusion was used for brain protection. Four patients concomitantly received a coronary artery bypass graft. Hospital mortality rate was 6.7%; the patient died of cerebral infarction. Neural complications developed in two patients. Multi-detector-row computed tomography scans performed before discharge revealed complete thrombosis of the false lumen in six patients and partial thrombosis in eight patients. At the follow-up examination, complete thrombosis was found in another three patients, aortic rupture, endoleaks or migration of the stent-graft was not observed and injuries of peripheral organs or anastomotic endoleaks did not occur. CONCLUSIONS For patients with aortic type A dissection, combining intervention and surgical procedures is feasible, and complete or at least partial thrombosis of the false lumen in the descending aorta can be achieved. This combined approach simplified the surgical procedures and shortened the circulatory arrest time, minimizing the necessity for further aortic operation.

No infection with porcine endogenous retrovirus in recipients of acellular porcine aortic valves: a two-year study

Abstract:  Background:  Engineered tissue heart valves may become a promising therapeutics for heart valve disease. Compared with synthetic materials, acellular porcine scaffolds are considered as suitable matrices for tissue‐engineered heart valves for the mechanical and structural properties of native tissue. Whether acellular porcine scaffolds can cause infection in recipients with porcine endogenous retrovirus (PERV) is critical for evaluating the safety of transplantation of tissue‐engineered heart valves based on acellular porcine scaffolds. This study was completed to evaluate the risk of PERV transmission for application of acellular porcine aortic valves (PAVs).

cIAP1 attenuates shear stress-induced hBMSC apoptosis for tissue-engineered blood vessels through the inhibition of the mitochondrial apoptosis pathway.

AIMS Shear stress-induced apoptosis is one of the leading problems in seeding cells of tissue-engineered blood vessels (TEBVs). We aim to determine the human bone mesenchymal stem cell (hBMSC) apoptosis under shear stress and its possible mechanism. MAIN METHODS hBMSCs were subjected to 3-, 10-, and 30-dyn/cm(2) shear stress in vitro. Cell multiplication and apoptosis were analyzed by flow cytometry. Apoptosis-related genes were screened by a microarray and evidenced by real-time polymerase chain reaction (RT-PCR). hBMSCs were treated with the human recombinant cell inhibitor of apoptosis protein 1 (cIAP1) and its inhibitor, direct IAP-binding protein with low pl (DIABLO), and then cell apoptosis was analyzed. KEY FINDINGS Exposure to shear stress (3dyn/cm(2) for >6h) activated apoptosis progress of hBMSCs. However, the same degree of shear stress (3dyn/cm(2) for 6h) did not induce apoptosis. Microarray screening and RT-PCR revealed that Bcl-2-related ovarian killer (BOK) and apoptotic protease-activating factor 1 (APAF1), key molecules of the mitochondrial apoptosis pathway, were markedly upregulated under 3-dyn/cm(2) shear stress. Then, we observed that cIAP1, a Caspase 9 inhibitor, was elevated under 3dyn/cm(2) at short-time exposure (2 or 6h), and it was reduced at long-time exposure (24h). When treated with human recombinant cIAP1, Caspase 3 activity and LDH release of hBMSCs were decreased, and vice versa when treated with DIABLO. SIGNIFICANCE cIAP1 attenuates hBMSC apoptosis when cells were exposed to shear stress through the regulation of the BOK-APAF1-Caspase 9-Caspase 3 pathway. It may present a pharmacological target to enhance hBMSC biological function in the application of TEBVs.

Transthoracic occlusion for secundum atrial septal defects unsuitable for transcatheter occlusion approach

OBJECTIVE Transcatheter occlusion of secundum atrial septal defects is a safe and effective alternative to traditional surgical closure; however, it is associated with serious occasional complications and inapplicable to more than 20% of atrial septal defects. In 2000, transthoracic occlusion was pioneered at Xijing Hospital as a novel method of atrial septal defect closure. The purpose of this study is to report the early and mid-term results of the transthoracic occlusion procedure and to evaluate its safety and efficacy. METHODS From April 2000 to April 2006, 268 patients with atrial septal defects were classified into 2 groups: group A (unsuitable for transcatheter occlusion, n = 126) and group B (n = 142). The transthoracic occlusion method used transesophageal echocardiographic-guided atrial septal defects occluder deployment via a right minithoracotomy without cardiopulmonary bypass or fluoroscopy. RESULTS Device implantation was successful in 265 patients (98.9%), including 9 elliptical devices in group A. The average size of circular occluders in group A was 38.2 ± 4.2 mm, which was larger than in group B (24.0 ± 4.5 mm) (P < .001). The average procedure time was 37.2 ± 9.2 minutes, the average intracardiac manipulation time was 5.8 ± 3.0 minutes, and the average inpatient stay was 3.2 ± 0.8 days. Twenty-five complications (9.3%) occurred in patients during the follow-up period. No large residual shunting, device embolization, or other severe complications resulted from transthoracic occlusion. CONCLUSIONS Transthoracic occlusion is a new safe and effective method for atrial septal defect treatment, even for patients with partial atrial septal defects unsuitable for transcatheter occlusion. This hybrid method broadens the indications of atrial septal defect treatment with device occlusion.

Clinical outcomes with the epicholorohydrin-modified porcine aortic heart valve: a 15-year follow-up.

BACKGROUND The epichlorohydrin (ECH) modified porcine aortic heart valve, first clinically utilized in 1989, obtained 2006 approval from the State Food and Drug Administration in China. This study analyzes the 15-year follow-up data of patient recipients of the ECH-modified valve. METHODS From 1989 to 2002, 227 patients underwent ECH valve replacement at Xijing Hospital, consisting of mitral (129), aortic (57), tricuspid (26), and double (mitral and aortic[15]) valvular replacements. The mean age of patients was 42 +/- 7.9 years, and 50% were in New York Heart Association class III or IV. Follow-up included 8,885 patient-years, and was 96.5% complete. RESULTS At 15 years, actuarial survival and freedom from valve-related death were, respectively, 58.1% +/- 13.7% and 90.0% +/- 6.8% (aortic group), 49.0% +/- 15.4% and 89.2% +/- 5.7% (mitral group), 65.3% +/- 12.4% and 83.6% +/- 10.8% (tricuspid group), and 40.7% +/- 16.0% and 83.3% +/- 15.2% (double-valve replacement group). Actuarial freedom from structural valve deterioration was 91.1% +/- 6.2%, 88.3% +/- 8.1%, 100%, and 66.7% +/- 27.2% in the aortic, mitral, tricuspid, and double-valve groups, respectively. Actuarial freedom from reoperation necessity was 95.7% +/- 4.3%, 85.8% +/- 10.4%, 80.4% +/- 13.4%, and 55.6% +/- 24.8% in the aortic, mitral, tricuspid, and double-valve groups, respectively. Actuarial freedom from incidence of prosthetic valve endocarditis was 97.5% +/- 2.5%, 93.4% +/- 4.9%, 90.0% +/- 9.5%, and 83.3 +/- 15.2% in the aortic, mitral, tricuspid, and double-valve groups, respectively. Actuarial freedom from thromboembolism was 89.4% +/- 7.7%, 92.1% +/- 4.7%, 77.9% +/- 14.1%, and 50.0% +/- 25.0% in the aortic, mitral, tricuspid, and double-valve groups, respectively. CONCLUSIONS The epichlorohydrin-modified porcine valve has excellent durability and clinical performance in long-term follow-up.

Calcification Resistance of Procyanidin-Treated Decellularized Porcine Aortic Valves In Vivo

OBJECTIVES Conventional glutaraldehyde fixation is conducive to calcification of bioprosthetic tissues. The aim of this study was to test calcification resistance of procyanidin-treated decellularized porcine aortic valve in a rat model. MATERIALS AND METHODS We performed cross-linking of the decellularized porcine aortic heart valves by procyanidins and observed morphologic performance and examined the tensile strength and cross-linking index. Then we implanted subcutaneous samples of procyanidin cross-linking decellularized valves, glutaraldehyde cross-linking decellularized valves, and decellularized valves in rats. The retrieved grafts were stained with hematoxylin-eosin and von Kossa and were analyzed with scanning electron microscopy and x-ray energy dispersive spectroscopy (EDS) after 21 and 63 days. RESULTS After decellularized and cross-linking pretreatment, the procyanidin cross-linked leaflets were soft and stretchable. In addition, the cellular components of the porcine aortic heart valve leaflets were completely removed, and the extracelluar matrix was maintained completely. Examination of tensile strength revealed a significantly higher tissue resistance to tension in procyanidin cross-linked tissue than in other tissues, including the glutaraldehyde group (P< .05), even though the extents of cross-linking of each group were roughly the same at approximately 90%. Histopathologic examination showed that the procyanidin cross-linked valve matrix had no significant calcification, and there were no calcium peaks in the EDS profile of procyanidin cross-linked samples in the 21-day and 63-day rat studies. CONCLUSION This study demonstrated that procyanidin cross-linked decellularized heart valves can resist calcification to some extent.