Aortic valve neocuspidization has shown satisfactory clinical outcomes; however, autologous pericardium durability is a concern for young patients. This study applied an autologous collagenous membrane (Biosheet^®), produced by in-body tissue architecture, to aortic valve neocuspidization and investigated its long-term outcome in a goat model. Moulds were embedded subcutaneously in 6 goats. After 2 months, Biosheets formed in the moulds. We performed aortic valve neocuspidization using a portion of the sheets with a thickness of 0.20–0.35 mm, measured by optical coherence tomography. Animals were subjected to echocardiography and histological evaluation at 6 months (n = 3) and 12 months (n = 3). As a control, the glutaraldehyde-treated autologous pericardium was used in 4 goats that were similarly evaluated at 12 months. All animals survived the scheduled period. At 6 months, Biosheets maintained valve function and showed a regeneration response: fusion to the annulus, cell infiltration to the leaflets and appearance of elastic fibres at the ventricular side. After 12 months, the regenerative structure had changed little without regression, and there was negligible calcification in the 1/9 leaflets. However, all cases had one leaflet tear, resulting in moderate-to-severe aortic regurgitation. In the pericardium group, three-fourths of the animals experienced moderate-to-severe aortic regurgitation with a high rate of calcification (9/12 leaflets). Biosheets may have regeneration potential and anti-calcification properties in contrast to autologous pericardium. However, in order to obtain reliable outcome, further improvements are required to strictly control and optimize its thickness, density and homogeneity.

Blood access is a lifeline for dialysis patients. However, serious problems such as stenosis or obstruction of access blood vessels, which are life-threatening conditions in daily clinical practice, still remain. One of the most promising candidates for solving these problems may be Biotube blood vessels. More than 20 years have passed since the development of in-body tissue architecture (iBTA), a technology for preparing tissues for autologous implantation in patients. The tissues obtained by iBTA do not elicit immunological rejection, which is one of the ultimate goals of regenerative medical engineering; however, their practical applications were quite challenging. The seemingly unorthodox iBTA concepts that do not follow the current pre-established medical system may not be readily accepted in general medicine. In contrast, there are many diseases that cannot be adequately addressed even with the latest and most advanced medical technology. However, iBTA may be able to save patients with serious diseases. It is natural that the development of high-risk medical devices that do not fit the corporate logic would be avoided. In order to actively treat such largely unattached diseases, we started Biotube Co., Ltd. with an aim to contribute to society. Biotubes induced by iBTA are collagenous tubular tissues prepared in the patient’s body for autologous implantation. The application of Biotubes as tissues for vascular implantation has been studied for many years. Biotubes may have excellent potential as small-diameter artificial blood vessels, one of the most difficult to clinically achieve. Their possibility is currently being confirmed in preclinical tests. Biotubes may save hundreds of thousands of patients worldwide annually from amputation. In addition, we aim to eliminate the recuring access vascular problems in millions of dialysis patients. This study provides an update on the current development status and future possibilities of Biotubes and their preparation molds, Biotube Makers.

Biotubes are autologous tubular tissues developed within a patient’s body through in-body tissue architecture, and they demonstrate high potential for early clinical application as a vascular replacement. In this pilot study, we used large animals to perform implantation experiments in preparation for preclinical testing of Biotube. The biological response after Biotube implantation was histologically evaluated. The designed Biotubes (length: 50 cm, internal diameter: 4 mm, and wall thickness: 0.85 mm) were obtained by embedding molds on the backs of six goats for a predetermined period (1–5 months). The same goats underwent bypass surgery on the carotid arteries using Biotubes (average length: 12 cm). After implantation, echocardiography was used to periodically monitor patency and blood flow velocity. The maximum observation period was 6 months, and tissue analysis was conducted after graft removal, including the anastomosis. All molds generated Biotubes that exceeded the tensile strength of normal goat carotid arteries, and eight randomly selected Biotubes were implanted. Thrombotic occlusion occurred immediately postoperatively (1 tube) if anticoagulation was insufficient, and two tubes, with insufficient Biotube strength (2 months without aneurysm formation. The spots far from the anastomosis became stenosed within 3 months (3 tubes) when Biotubes had a wide intensity distribution, but the shape of the remaining two tubes remained unchanged for 6 months. The entire length of the bypass region was walled with an αSMA-positive cell layer, and an endothelial cell layer covered most of the lumen at 2 months. Complete endothelial laying of the luminal surface was obtained at 3 months after implantation, and a vascular wall structure similar to that of native blood vessels was formed, which was maintained even at 6 months. The stenosis was indicated to be caused by fibrin adhesion on the luminal surface, migration of repair macrophages, and granulation formation due to the overproliferation of αSMA-positive fibroblasts. We revealed the importance of Biotubes that are homogeneous, demonstrate a tensile strength > 5 N, and are implanted under appropriate antithrombotic conditions to achieve long-term patency of Biotube. Further, we clarified the Biotube regeneration process and the mechanism of stenosis. Finally, we obtained the necessary conditions for a confirmatory implant study planned shortly.

This study investigated six-month outcomes of first models of ascending aortic replacement. The molds used to produce the Biotube were implanted subcutaneously in goats. After 2–3 months, the molds were explanted to obtain the Biotubes (inner diameter, 12 mm; wall thickness, 1.5 mm). Next, we performed ascending aortic replacement using the Biotube in five allogenic goats. At 6 months, the animals underwent computed tomography (CT) and histologic evaluation. As a comparison, we performed similar surgeries using glutaraldehyde-fixed autologous pericardial rolls or pig-derived heterogenous Biotubes. At 6 months, CT revealed no aneurysmalization of the Biotube or pseudoaneurysm formation. The histologic evaluation showed development of endothelial cells, smooth muscle cells, and elastic fibers along the Biotube. In the autologous pericardium group, there was no evidence of new cell development, but there was calcification. The histologic changes observed in the heterologous Biotube group were similar to those in the allogenic Biotube group. However, there was inflammatory cell infiltration in some heterologous Biotubes. Based on the above, we could successfully create the world’s first Biotube-based ascending aortic replacement models. The present results indicate that the Biotube may serve as a scaffold for aortic tissue regeneration.

We describe a 54-year-old man with neurofibromatosis type 1 who presented with a left-sided neck mass. Computed tomography demonstrated a left common carotid artery aneurysm (51 × 33 mm). Surgery was performed because of the risk of rupture. The left common carotid artery was found to be a huge aneurysmal dilatation, and the arterial wall partially collapsed and extensively adherent to the surrounding tissues. Left common carotid artery to internal carotid artery bypass grafting was performed with a reversed saphenous vein graft. Histopathological examination revealed vascular fragility of the left carotid arterial wall.

This study investigated the long-term patency of regenerative Biotube grafts and discusses their feasibility as an alternative to autologous vein grafts for peripheral artery disease. Six Biotubes with a diameter of 4 mm were autologously fabricated in recipients using in vivo tissue engineering (in-body tissue architecture) technology and implanted as carotid artery bypass grafts in a goat model. All six grafts remained patent at 6 months despite exceeding 10 cm in length, demonstrating their biocompatibility and durability. Histological analysis revealed neointima formation, endothelialization, and minimal inflammation. However, in one goat, a graft developed stenosis, while another showed dilatation. These findings demonstrate the use of Biotubes as a viable option for peripheral vascular reconstruction as tissue-engineered vascular grafts. However, further optimization is needed to address emerging issues with their use, such as stenosis and aneurysm formation, to improve long-term patency.