In-body tissue architecture (iBTA), a cell-free, in vivo tissue engineering technology that can produce autologous implantable tissues of the desired shape by subcutaneously embedding specially designed molds, was used to develop long tubular collagenous tissues called Biotubes. Spiral molds for long Biotubes were designed with an outer pipe-shaped spiral shell and an inner spiral mandrel, and embedded into subcutaneous pouches of beagle dogs or goats for 1 or 2 months. Tubular collagenous tissues were formed at the space between the shell and the mandrel of the mold. Depending on the spiral turn number in the mold, Biotubes of 25 cm or 50 cm (internal diameter 4 mm or 5 mm) were prepared with nearly homogeneous mechanical and histological properties over their entire length. Biotubes stored in 70% ethanol were allogenically implanted into beagle dogs or goats to evaluate their in vivo performance. The 25-cm Biotubes functioned as arterial grafts with no need for luminal modification or mechanical support, and demonstrated vascular reconstruction within 3 months after implantation into dogs. The 50-cm Biotubes functioned as arteriovenous shunt grafts in the neck region of goats without thrombus formation and vascular deformation for 1 month. Thus, the world’s longest tissue-engineered vascular grafts with small diameter could be developed using iBTA.

体内组织架构（iBTA），无细胞，体内组织工程技术可通过皮下植入专门设计的模具来生产所需形状的自体可植入组织，被用于开发长管状胶原组织，称为Biotubes。用于长型生物管的螺旋模具的设计采用外部管状螺旋壳和内部螺旋芯棒，然后将其埋入比格犬或山羊的皮下袋中放置1或2个月。在模具的壳和心轴之间的空间处形成管状胶原组织。根据模具中的螺旋圈数，制备25 cm或50 cm（内径4 mm或5 mm）的生物管，在其整个长度上具有几乎均一的机械和组织学特性。将储存在70％乙醇中的生物管同种异体植入比格犬或山羊，以评估它们的生物管。体内表现。25厘米长的生物管可充当动脉移植物，而无需进行管腔修饰或机械支撑，并且在植入狗后3个月内显示出血管重建。50厘米长的生物管在山羊的颈部区域用作动静脉分流移植物，在1个月内没有血栓形成和血管变形。因此，可以使用iBTA开发世界上最长的小直径组织工程化血管移植物。