Biomedical subjects

Yuji Narita

Publications and source records attributed to Yuji Narita.

7 recordsLinked to original sources

PubMed2006

Evaluation of decellularized esophagus as a scaffold for cultured esophageal epithelial cells.

Recently, decellularized tissue has been reported to have the potential to regenerate a variety of tissues. However, the optimal protocol for a decellularized esophagus has not been studied. Here, we investigated the effect of different decellularization protocols on the histology and biocompatibility of decellularized esophagi in view of future applications to tissue engineering. The esophageal mucosal epithelium (EP) from 4-week-old Wistar rats was enzymatically dissociated and cultured with growth-arrested feeder cells. Two methods for decellularization using deoxycholic acid (DEOX) or Triton X-100 (TRITON) were compared on esophagi from adult Wistar rats. Those treated with DEOX showed superior mechanical properties, maintenance of extracellular matrix, and lower DNA content than those treated with TRITON. To evaluate the biocompatibility of the scaffold, cultured (passage 3) esophageal epithelial cells were seeded inside the decellularized esophagus and cultured for 7 days. The cells seeded onto the decellularized esophagus were examined histologically and immunocytochemically. Esophageal epithelial cells were stratified into three to four cellular layers in vitro inside the decellularized esophagus, to show polarity. The results from immunocytochemistry indicated that the seeded epithelial cells expressed characteristic marker proteins for native esophageal EP. Decellularized esophagus showed suitable compatibility as a scaffold material for esophageal tissue engineering.

Animals↗

PubMed2006

Surgical treatment for thoracic aortic aneurysm with aberrant right subclavian artery.

We present two operative cases of thoracic aortic aneurysm combined with aberrant right subclavian artery (ARSA). Case 1 was a 71-year-old man with a fusiform-type arch aneurysm. He underwent total aortic arch replacement to reconstruct all 4 arch branches. Case 2 was a 39-year-old man suffering from chronic DeBakey type IIIb dissection. He underwent total descending thoracic aortic replacement for the remaining ARSA. In both cases ARSA was diagnosed preoperatively by reconstructed three-dimensional computed tomography (3D-CT). Both patients followed uneventful postoperative courses with excellent results. 3D-CT is helpful for precise planning of surgical strategy in such cases.

Adult↗

PubMed2006

Development of a novel temporary epicardial pacing wire with biodegradable film.

PURPOSE: A temporary epicardial pacing wire (TEPW) has been routinely placed in patients undergoing cardiac surgery. However, its fixation or removal occasionally causes troublesome complications. The aim of this study is to develop a novel TEPW using biodegradable film to fix the electrode to the epicardium without needle stabbing. DESCRIPTION: A biodegradable film was prepared with poly(L-lactide-co-epsilon-caprolactone). The film has a honeycomb-patterned structure that serves as a temporary adhesive for the myocardial surface, and the electrode was incorporated within the film. The novel TEPW was placed on the ventricular epicardium of dogs (group A, n = 5). As a control, conventional TEPW was inserted (group B, n = 6). The pacing threshold, R wave amplitude, impedance, and slew rate were measured at postoperative days 0, 1, 3, 5, 7, and 14, and complications after removal were checked. EVALUATION: All measurements in both groups were identified and differences were not observed. In addition, the novel TEPWs could be easily removed without related complications. CONCLUSIONS: This novel TEPW is safe and feasible for postoperative management of cardiac surgeries.

Absorbable Implants↗

PubMed2006

Constructing a tissue-engineered ureter using a decellularized matrix with cultured uroepithelial cells and bone marrow-derived mononuclear cells.

This study investigated the efficacy of the ureteral decellularized matrix (UDM) as a scaffold material for a tissue-engineered ureter, and the effect of bone marrow-derived mononuclear cells (BM-MNC) on the neovascularization of the scaffold. Canine ureters were treated with deoxycholic acid to remove all cells. Uroepithelial cells (UEC) were obtained from canine bladders, cultured, and then seeded onto the inner surface of the UDM before transplantation into the subcutaneous space of nude mice or the omentum of nude rats. The cultured UECs began showing vacuolar degeneration 3 days after transplantation and gradually disappeared thereafter. To facilitate neovascularization in the implant, BM-MNCs were seeded around the UDM before transplantation. This facilitated the survival of the UECs, which formed three to five cellular layers after 14 days. The mean microvessel density was significantly increased in tissues seeded with BM-MNCs. However, cell-tracking experiments revealed that the increased number of capillaries in the experimental group was not due to the direct differentiation of transplanted endothelial progenitor cells. Our results demonstrate that the UDM is a useful scaffold for a tissue-engineered ureter, especially when seeded with BM-MNCs to enhance angiogenesis.

Animals↗

PubMed2002

Optimal size of prostheses for functioning of the aortic prosthetic valve in aortic and mitral valve replacement with annular enlargement through Manouguian's technique.

There is not yet agreement about the optimal size of the prostheses in aortic and mitral valve replacement with Manouguian's technique. In this technique, the aortic prosthetic valve can be pushed upon the mitral prosthesis which may cause dysfunction of the aortic prosthetic valve. The aim of this study was to clarify the size of the prostheses needed to avoid dysfunction of the aortic prosthetic valve. Three patients underwent aortic and mitral valve replacement through this procedure. Two of them had active aortic and mitral valve endocarditis. Aortomitral continuity involved with abscesses could be approached and completely excised using this technique. All patients survived the operation, but 1 of them suffered aortic mechanical valve dysfunction for the reason stated. Anatomical analysis of the geometrical relation of the 2 prosthetic valves suggests that the mitral annulus should be enlarged less than 25 mm to avoid dysfunction of the aortic prosthetic valve.

Adult↗

PubMedDate not supplied

Novel pulse duplicating bioreactor system for tissue-engineered vascular construct.

Cell culture in a biomimetic environment is known to improve the mechanical endurance of tissue-engineered cardiovascular components. Our goal was to generate a bioreactor that can reproduce a wide range of pulsatile flows with a completely physiological pressure profile. The morphology and biochemical properties of tissue-engineered products were also studied to test the usefulness of this novel bioreactor. The combination of an outflow valve, compliance chamber, and resistant clamps together with a balloon pumping system was able to successfully reproduce both physiological systolic and diastolic pressures. The compliance chamber was especially effective in transforming the original peaky pressure waveform into a physiological pressure profile. The tissues, cultured under a physiological pressure waveform with pulsatile flow, presented widely distributed cells in close contact with each other. They also showed significantly higher cell numbers, total protein content, and proteoglycan-glycosaminoglycan content than cultured tissues under a peaky pressure wave or under static conditions. This new bioreactor system is suitable for evaluating a favorable environment for tissue-engineered cardiovascular components.

Animals↗

PubMedDate not supplied

Evaluation of compliance and stiffness of decellularized tissues as scaffolds for tissue-engineered small caliber vascular grafts using intravascular ultrasound.

This study evaluated the compliance and stiffness of decellularized canine common carotid artery as well as decellularized canine ureter and compared it with that of polytetrafluoroethylene, elastin gel combined with polylactic acid tube, and canine common carotid artery. To calculate the compliance and stiffness, internal diameters and cross-sectional areas were measured according to changes in the intraluminal pressures using intravascular ultrasound in a closed circuit system equipped with a syringe pump. The pressure-area curve, stiffness parameter beta, and diameter compliance were evaluated. Canine common carotid artery and decellularized canine common carotid artery, as well as decellularized canine ureter, showed a compliant response, a J-shaped curve. However, the latter evidenced different characteristics in the low pressure range. Although the cross-sectional area of the elastin gel combined with polylactic acid tube showed some changes, it did not present a J-shape curve. Polytetrafluoroethylene exhibited a noncompliant response.The results in this study have shown that the compliance in the decellularized matrices was maintained after cell extraction, which demonstrated the importance of the remaining matrix structure in the mechanical properties of decellularized tissue. A clear difference between the decellularized matrices and synthetic materials was noted in terms of the compliance, even in materials composed of relatively elastic materials.

Animals↗