Kei Torikai

Tissue- and Plasma-Specific MicroRNA Signatures for Atherosclerotic Abdominal Aortic Aneurysm

Background Atherosclerotic abdominal aortic aneurysm (AAA) is a progressive, gradual aortic rupture that results in death in the absence of surgical intervention. Key factors that regulate initiation and progression of AAA are unknown, making targeted interventions difficult. MicroRNAs play a fundamental role in atherosclerosis, and atherosclerotic coronary artery disease is characterized by tissue- and plasma-specific microRNA signatures. However, little is known about microRNAs involved in AAA pathology. This study examined tissue and plasma microRNAs specifically associated with AAA. Methods and Results AAA and normal wall tissues were sampled from patients undergoing AAA repair (n=13; mean age, 68±6 years) and aortic valve replacement surgery (n=7; mean age, 66±4 years), respectively. MicroRNA expression was assessed by high-throughput microRNA arrays and validated by real-time polymerase chain reaction for individual microRNAs that showed significant expression differences in the initial screening. MicroRNAs related to fibrosis (miR-29b), inflammation (miR-124a, miR-146a, miR-155, and miR-223), and endothelium (miR-126, let-7 family members, and miR-21) were significantly upregulated in AAA tissue. Significant negative correlations were seen in expression levels of monocyte chemoattractant protein-1 and miR-124a, -146a, and -223; tumor necrosis factor-α and miR-126 and -223; and transforming growth factor-β and miR-146a. Expression of microRNAs, such as miR-29b, miR-124a, miR-155, and miR-223, that were upregulated in AAA tissue was significantly reduced in plasma of patients with AAA (n=23; mean age, 72±9 years) compared to healthy controls (n=12; mean age, 51±11 years) and patients with coronary artery disease (n=17; mean age, 71±9 years). Conclusions The expression of some microRNAs was specifically upregulated in AAA tissue, warranting further studies on the microRNA function in AAA pathogenesis and on the possibility of using a microRNA biomarker for AAA diagnosis.

In situ tissue regeneration using a novel tissue-engineered, small-caliber vascular graft without cell seeding

OBJECTIVE Various types of natural and synthetic scaffolds with arterial tissue cells or differentiated stem cells have recently attracted interest as potential small-caliber vascular grafts. It was thought that the synthetic graft with the potential to promote autologous tissue regeneration without any seeding would be more practical than a seeded graft. In this study, we investigated in situ tissue regeneration in small-diameter arteries using a novel tissue-engineered biodegradable vascular graft that did not require ex vivo cell seeding. METHODS Small-caliber vascular grafts (4 mm in diameter) were fabricated by compounding a collagen microsponge with a biodegradable woven polymer tube that was constructed in a plain weave pattern with a double layer of polyglycolic acid (core) and poly-L-lactic acid (sheath) fibers. We implanted these tissue-engineered vascular grafts bilaterally into the carotid arteries of mongrel dogs (body weight, 20-25 kg). No anticoagulation regimen was used after implantation. We sacrificed the dogs 2, 4, 6, and 12 months (n = 4 in each group) after implantation and evaluated the explants histologically and biochemically. RESULTS All of the tissue-engineered vascular grafts were patent with no signs of thrombosis or aneurysm at any time. Histologic and biochemical examinations showed excellent in situ tissue regeneration with an endothelial cell monolayer, smooth muscle cells, and a reconstructed vessel wall with elastin and collagen fibers. CONCLUSION Our study indicated that this novel tissue-engineered vascular graft promoted in situ tissue regeneration and did not require ex vivo cell seeding, thereby conferring better patency on small-caliber vascular prostheses.

A self-renewing, tissue-engineered vascular graft for arterial reconstruction

OBJECTIVE Various tissue-engineered vascular grafts have been studied to overcome the clinical disadvantages of conventional prostheses. Previous tissue-engineered vascular grafts have generally required preoperative cellular manipulation or use of bioreactors to improve performance, and their mechanical properties have been insufficient. We focused on the concept of in situ cellularization and developed a tissue-engineered vascular graft for arterial reconstruction that would facilitate renewal of autologous tissue without any pretreatment. METHODS The graft comprised an interior of knitted polyglycolic acid compounded with collagen to supply a scaffold for tissue growth and an exterior of woven poly-L-lactic acid for reinforcement. All components were biocompatible and biodegradable, with excellent cellular affinity. The grafts, measuring 10 mm in internal diameter and 30 mm in length, were implanted into porcine aortas, and their utility was evaluated to 12 months after grafting. RESULTS All explants were patent throughout the observation period, with no sign of thrombus formation or aneurysmal change. Presence in the neomedia of endothelialization with proper integrity and parallel accumulation of functioning smooth muscle cells, which responded to vasoreactive agents, was confirmed in an early phase after implantation. Sufficient collagen synthesis and lack of elastin were quantitatively demonstrated. Dynamic assessment and long-term results of the in vivo study indicated adequate durability of the implants. CONCLUSION The graft showed morphologic evidence of good in situ cellularization, satisfactory durability to withstand arterial pressure for 12 postoperative months, and the potential to acquire physiologic vasomotor responsiveness. These results suggest that our tissue-engineered vascular graft shows promise as an arterial conduit prosthesis.

Expression of Epstein-Barr virus latent infection genes and oncogenes in lymphoma cell lines derived from pyothorax-associated lymphoma

Malignant lymphomas frequently develop in the pleural cavity of patients with long‐standing pyothorax. The term pyothorax‐associated lymphoma (PAL) has been proposed for this type of tumor. Most PALs are diffuse lymphomas of the B‐cell type and contain Epstein‐Barr virus (EBV) DNA. We have established 2 lymphoma cell lines from biopsy specimens of PAL cases, OPL‐1 and OPL‐2, and examined their growth characteristics and the expression of EBV latent infection genes and oncogenes. OPL‐2 exhibited a more rapid growth and higher saturation density than OPL‐1, and only OPL‐2 exhibited colony‐forming activity in soft agar. OPL‐1 and ‐2 were positive for B‐cell differentiation markers and showed clonal surface immunoglobulins. Both lines contained a single predominant form of episomal EBV DNA, indicating clonal cellular proliferation of an EBV‐infected progenitor cell. OPL‐1 and ‐2 contained type B and A EBV genome, respectively. Expression of EBV nuclear antigen (EBNA)2 mRNA and protein was detected by Northern and Western blot analysis in OPL‐1, but not in OPL‐2. On the other hand, the expression of latent membrane protein (LMP) I mRNA in both OPL‐1 and ‐2 was extremely weak and detectable only by reverse transcription‐polymerase chain reaction. Protein expression of LMPI was not observed by Western blot analysis or immunocytochemistry. Both lines expressed c‐myc mRNA. Only OPL‐1 expressed mRNA of c‐fgr, an oncogene whose expression is upregulated by EBNA2. Both OPLs expressed bcl‐2 mRNA without detectable expression of LMPI protein.

New Self-Expanding Transcatheter Aortic Valve Device for Transfemoral Implantation – Early Results of the First-in-Asia Implantation of the ACURATE Neo/TF TM System –

BACKGROUND Feasibility and early results of transfemoral aortic valve implantation using the ACURATE neo/TF(TM)self-expanding stent are reported. METHODS AND RESULTS The study group of 15 patients (mean age 83.3±6.0) was enrolled with a mean EuroSCORE and STS score of 21.9±11.6% and 7.5±3.1%, respectively. Clinical and echocardiographic evaluations were performed at baseline, discharge, 30 days and 6 months. The primary endpoint was all-cause mortality at 30 days. Transcatheter aortic valve implantation (TAVI) using the ACURATE neo/TF device was successful in 14 patients; 1 patient underwent valve-in-valve implantation because the prosthetic valve embolized during withdrawal of the delivery system. Conversion to surgery, coronary obstruction, peri-operative stroke, and pacemaker implantation did not occur at 30 days. Mean transvalvular gradients at discharge significantly decreased from 44.2±10.5 mmHg (preprocedural) to 7.7±3.1 mmHg (P<0.0001) and effective orifice area significantly increased from 0.77±0.12 to 1.69±0.25 cm(2)(P<0.0001). None or trace paravalvular leak was revealed in 50.0%, and no patient exhibited moderate or higher paravalvular leak. The overall mortality at 30 days and 6 months was 0% and 6.7%, respectively. CONCLUSIONS A new self-expanding TF TAVI device, ACURATE neo/TF, is safe and effective in the treatment of severe aortic stenosis in elderly patients at high risk for surgery.

Newly Developed Tissue-Engineered Material for Reconstruction of Vascular Wall Without Cell Seeding

BACKGROUND We have developed a tissue-engineered patch for cardiovascular repair. Tissue-engineered patches facilitated site-specific in situ recellularization and required no pretreatment with cell seeding. This study evaluated the patches implanted into canine pulmonary arteries. METHODS Tissue-engineered patches are biodegradable sheets woven with double-layer fibers. The fiber is composed of polyglycolic acid and poly-L-lactic acid, and compounding collagen microsponges. The patches (20- x 25-mm) were implanted into the canine pulmonary arterial trunks. At 1, 2, and 6 months after implantation (n = 4), they were explanted and characterized by histologic and biochemical analyses. Commercially available patches served as the control. No anticoagulant therapy was administered postoperatively. RESULTS No aneurysm or thrombus was present within the patch area in all groups. The remodeled tissue predominantly consisted of elastic and collagen fibers, and the endoluminal surface was covered with a monolayer of endothelial cells and multilayers of smooth muscle cells beneath the endothelial layer. The elastic and collagen fibers and smooth muscle cells kept increasing with a maximum at 6 months, while a monolayer of endothelial cells was preserved. The expression levels of messenger RNA of several growth factors in the tissue-engineered patches were higher than those of native tissue at 1 and 2 months and decreased to normal level at 6 months. No regenerated tissue was found on the endoluminal surface in the control group. CONCLUSIONS The novel tissue-engineered patches showed in situ repopulation of host cells without prior ex vivo cell seeding. This is promising material for repair of the cardiovascular system.

Minimally immunogenic decellularized porcine valve provides in situ recellularization as a stentless bioprosthetic valve

Currently used bioprosthetic valves have several limitations such as calcification and functional deterioration, and revitalization through cellular ingrowth is impossible. To overcome these obstacles, we have developed a minimally immunogenic tissue-engineered valve that consists of an unfixed, decellularized porcine valve scaffold capable of being spontaneously revitalized in vivo after implantation. Porcine aortic root tissue was decellularized using detergents such as sodium lauryl sulfate and Triton X-100. The porcine valve was treated very gently and plenty of time was allowed for constituents to diffuse in and out of the matrix. In a preliminary study, a piece of decellularized porcine valve tissue was implanted into the rat subdermal space for 14 and 60 days and the structural integrity and calcification were evaluated. As an in vivo valve replacement model, the decellularized porcine valve was implanted in the pulmonary valve position in dogs and functional and histological evaluation was performed after 1, 2, and 6 months. Histological examination showed that the newly developed detergent treatment effectively removed cellular debris from the porcine aortic tissue. Decellularized porcine valve tissue implanted subdermally in rats showed minimal inflammatory cell infiltration and calcification. In the valve replacement model, spontaneous reendothelialization and repopulation of the medial cells were observed within 2 months, and good valve function without regurgitation was observed by echocardiography up to 6 months. The minimally immunogenic decellularized porcine valve proved effective in mitigating postimplant calcification and provided a suitable matrix for revitalizing prostheses through in situ recellularization, cellular ingrowth, and tissue remodeling.

The efficacy and short-term results of hybrid thoracic endovascular repair into the ascending aorta for aortic arch pathologies.

OBJECTIVES Conventional total aortic arch repair is a high-risk procedure, particularly for high-risk patients. Although endovascular treatment of aortic arch aneurysm is a recently induced procedure, only a few cases are indicated and outcomes are questionable. Here, we report on the early and short-term results of our surgical procedure, i.e. hybrid arch repair with supra-aortic debranching and endografting into the ascending aorta. METHODS Of the 514 patients who underwent arch repairs from 1997 to March 2012, 40 (28 males; mean age 74.4 years) were high-risk patients for whom hybrid arch repair of the ascending aortic landing zone was performed. Aortic pathologies included 31 degenerative aneurysms (including two ruptures), three type A dissections and four type B dissections. We performed supra-aortic debranching from the ascending aorta and endografting into the ascending aorta in 28 patients (including 10 patients with graft replacements and 3 patients with banding of the ascending aorta). For the 12 patients with an ascending aorta diameter of <36 mm, the chimney graft technique into the innominate artery was performed. RESULTS The 30-day mortality rate was 3%. Postoperative complications were as follows: stroke (0 patient), haemodialysis (1), prolonged mechanical ventilation (2) and spinal cord ischaemia (1). There were one early type I and two type II endoleaks. The mean follow-up duration was 15.5 months, during which freedom from aorta-related death and aortic events were 91 and 89% at 3 years. CONCLUSIONS We achieved satisfactory early and short-term results with hybrid arch repair into the ascending aorta. Our findings suggest that hybrid repair into the ascending aorta may be a viable option for high-risk patients with aortic arch pathologies.

Aortic Remodeling as a Prognostic Factor for Late Aortic Events After Thoracic Endovascular Aortic Repair in Type B Aortic Dissection With Patent False Lumen

Purpose: To assess the significance of aortic remodeling in the prevention of the late aortic events after thoracic endovascular aortic repair (TEVAR) for aortic dissection. Methods: The study involved 52 patients (41 men; mean age was 59.7±13.3 years) with type B aortic dissections and patent false lumens treated with TEVAR between 2004 and 2011. Of the 52 patients, 18 were treated in the acute phase for rupture (n=1), malperfusion (n=10), aortic diameter over 40 mm at onset (n=3), and rapid enlargement of the false lumen (n=4). In the chronic setting, the indications for TEVAR were rupture (n=1), malperfusion (n=2), aortic diameter >50 mm (n=18), and rapid enlargement of the false lumen (n=13). Aortic remodeling was evaluated at 6 months postoperatively, and risk factors for late aortic events were evaluated in multivariate analysis using aortic remodeling and other pre-, peri-, and postoperative factors. Results: Over a mean 36.0±18.9 months, 19 aortic events were documented: enlargement of the false lumen (n=4), type I endoleak (n=2), and erosion at the stent-graft edges (n=13). Multivariate analysis revealed that failure to achieve aortic remodeling at 6 months postoperatively was the only significant risk factor for late aortic events (hazard ratio 0.20, p=0.037). Patients with aortic remodeling had a higher rate of freedom from aortic events compared with those without aortic remodeling (100% vs. 81.5% at 1 year and 79.3% vs. 48.4% at 3 years, respectively). Conclusion: Aortic remodeling after TEVAR is a significant prognostic factor for better long-term results for type B aortic dissection.

Clinical Outcomes and Bioprosthetic Valve Function After Transcatheter Aortic Valve Implantation Under Dual Antiplatelet Therapy vs. Aspirin Alone

BACKGROUND Dual antiplatelet therapy (DAPT) is commonly used after transcatheter aortic valve implantation (TAVI); however, the supporting evidence is limited. To determine if aspirin alone is a better alternative to DAPT, we compared the outcomes of patients treated with DAPT or aspirin alone after TAVI.Methods and Results:We analyzed a total of 144 consecutive patients (92 females, mean age 83±6 years) who underwent implantation of a balloon-expandable transcatheter valve (SAPIEN or SAPIEN XT, Edwards Lifesciences). Patients were divided into DAPT (n=66) or aspirin-alone treatment groups (n=78). At 1 year after TAVI, the composite endpoint, which consisted of all-cause death, myocardial infarction, stroke, and major or life-threatening bleeding complications, occurred significantly less frequently (Kaplan-Meier analysis) in the aspirin-alone group (15.4%) than in the DAPT group (30.3%; P=0.031). Valve function assessed by echocardiography was similar between the 2 treatment groups with respect to effective orifice area (1.78±0.43 cm2in DAPT vs. 1.91±0.46 cm2in aspirin-alone group; P=0.13) and transvalvular pressure gradient (11.1±3.5 mmHg in DAPT vs. 10.3±4.1 mmHg in aspirin-alone group; P=0.31). CONCLUSIONS Treatment with aspirin alone after TAVI had greater safety benefits and was associated with similar valve function as DAPT. These results suggest that treatment with aspirin alone is an acceptable regimen for TAVI patients.