Fabrication of an anatomy-mimicking BIO-AIR-TUBE with engineered cartilage.

INTRODUCTION: We devised a strategy for the fabrication of an 'anatomy-mimicking' cylinder-type engineered trachea combined with cartilage engineering. The engineered BIOTUBEs are used to support the architecture of the body tissue, for long-segment trachea (>5 cm) with carinal reconstruction. The aim of the present study was to fabricate an anatomy-mimicking cylinder-type regenerative airway, and investigate its applicability in a rabbit model. METHODS: Collagen sponge rings (diameter: 6 mm) were arranged on a silicon tube (diameter: 6 mm) at 2-mm intervals. Chondrocytes from the auricular cartilage were seeded onto collagen sponges immediately prior to implantation in an autologous manner. These constructs were embedded in dorsal subcutaneous pouches of rabbits. One month after implantation, the constructs were retrieved for histological examination. In addition, cervical tracheal sleeve resection was performed, and these engineered constructs were implanted into defective airways through end-to-end anastomosis. RESULTS: One month after implantation, the engineered constructs exhibited similar rigidity and flexibility to those observed with the native trachea. Through histological examination, the constructs showed an anatomy-mimicking tracheal architecture. In addition, the engineered constructs could be anastomosed to the native trachea without air leakage. CONCLUSION: The present study provides the possibility of generating anatomy-mimicking cylinder-type airways, termed BIO-AIR-TUBEs, that engineer cartilage in an in-vivo culture system. This approach involves the use of BIOTUBEs formed via in-body tissue architecture technology. Therefore, the BIO-AIR-TUBE may be useful as the basic architecture of artificial airways.

Long-term follow-up of tracheal cartilage growth promotion by intratracheal injection of basic fibroblast growth factor.

BACKGROUND: Intratracheal injection of basic fibroblast growth factor (b-FGF) has been shown to enlarge the tracheal lumen 4 weeks after treatment. The objective of this study was to investigate the long-term effect of tracheal cartilage growth promotion by intratracheal injection of b-FGF. MATERIALS AND METHODS: New Zealand white rabbits were classified into four groups to receive either distilled water alone (Group 1; n = 16; control), 40 µg (Group 2; n = 10), 100 µg (Group 3; n = 13), or 200 µg (Group 4; n = 16) of b-FGF dissolved in water. The treatment was injected into the posterior wall of the cervical trachea using a tracheoscope. The animals were sacrificed 4 or 12 weeks later. RESULTS: Four weeks after treatment, the mean luminal areas of tracheas for Groups 1, 2, 3, and 4 were 27.2, 25.6, 32.2, and 36.2 mm2, respectively. At 12 weeks, these were 29.3, 37.9, 42.5, and 56.0 mm2, respectively. The levels of glycosaminoglycan at 12 weeks were 93.9, 152.5, 123.2, and 210.6 µg/mg, respectively. At 12 weeks, the levels of type II collagen were 77.2, 133.1, 99.2, and 148.9 µg/mg, respectively. CONCLUSION: Twelve weeks after a single injection of b-FGF, the mean luminal area of the trachea continued to increase.

Tracheal cartilage growth by intratracheal injection of basic fibroblast growth factor.

BACKGROUND/PURPOSE: We have previously shown that intratracheal injection of slowly released (in gelatin) basic fibroblast growth factor (bFGF) significantly enlarged the tracheal lumen by a slight margin. This study aimed to investigate differences in tracheal cartilage growth by the intratracheal injection of bFGF doses in a rabbit model. METHODS: Water (group 1; n=7; control) or 100µg (group 2; n=8) or 200µg (group 3; n=8) of bFGF dissolved in water was injected into the posterior wall of the cervical trachea of New Zealand white rabbits using a tracheoscope. All animals were sacrificed four weeks later. RESULTS: The mean circumferences of cervical tracheas for groups 1, 2, and 3 were 18.8±0.83, 21.1±2.0, and 22.1±1.3mm, respectively. A significant difference was found between groups 1 and 2 (P=0.034) and groups 1 and 3 (P=0.004). The mean luminal areas of cervical tracheas for groups 1, 2, and 3 were 27.0±2.1, 32.2±4.8, and 36.3±4.6mm2, respectively. A significant difference was found between groups 1 and 3 (P=0.001). CONCLUSION: Intratracheal injection of bFGF in the dose range used significantly promoted the growth of tracheal cartilage in a rabbit model. LEVELS OF EVIDENCE: Level II at treatment study (animal experiment).

Patch tracheoplasty in body tissue engineering using collagenous connective tissue membranes (biosheets).

BACKGROUND: Collagenous connective tissue membranes (biosheets) are useful for engineering cardiovascular tissue in tissue engineering. The aim was to evaluate the use of biosheets as a potential tracheal substitute material in vivo in a rabbit model. METHODS: Group 1: Rectangular-shaped Gore-Tex (4×7mm) was implanted into a 3×6mm defect created in the midventral portion of the cervical trachea. Group 2: Rectangular-shaped dermis was implanted into a tracheotomy of similar size. Group 3: Biosheets were prepared by embedding silicone moulds in dorsal subcutaneous pouches in rabbits for 1month. Rectangular-shaped biosheets were implanted into a tracheotomy of similar size in an autologous fashion. All groups (each containing 10 animals) were sacrificed 4weeks after implantation. MAIN RESULTS: All materials maintained airway structure for up to 4weeks after implantation. Regenerative cartilage in implanted Biosheets in group 3 was confirmed by histological analysis. Tracheal epithelial regeneration occurred in the internal lumen of group 3. There were significant differences in the amounts of collagen type II and glycosaminoglycan between group 3 and group 1 or 2. CONCLUSION: We confirm that cartilage can self-regenerate onto an airway patch using Biosheets.

Tracheoplasty with cartilage-engineered esophagus environments.

PURPOSE: Our objective was to investigate the feasibility of engineering cartilage on the esophagus layer and outside the esophagus. Moreover, we investigated the feasibility of tracheoplasty with cartilage engineered on the esophagus in rabbits. METHODS: Chondrocytes were isolated from auricular cartilages. 1. Engineered cartilage formation by histological findings on/into the esophageal layer was compared with that of injectable scaffold and preformed scaffold with chondrocytes. 2. Chondrocytes adhered to gelatin+vicryl mesh™ and b-FGF, were implanted on the outer esophageal surface. Four weeks after seeding, we found that cartilage was implanted in the midposterior portion of the cervical trachea (n=5), and it was retrieved 8weeks after seeding. RESULTS: 1. A gelatin sponge incorporating ß-TCP with vicryl mesh™ showed the best performance for fabricating engineered cartilage on the outer side of the esophagus. 2. Two of 5 rabbits died due to obstructed esophagus. Cartilage engineered outside the esophagus by a composite scaffold as the main material in the gelatin sponge, maintained the airway structure for up to 1month after implantation. Tracheal epithelial regeneration occurred in the internal lumen of this engineered cartilage. CONCLUSION: Tracheoplasty with cartilage engineered outside the esophagus may be useful for reconstructing airways.

Bile duct duplication as a cause of distal bowel gas in neonatal duodenal obstruction.

PURPOSE: The aim of this study is to investigate the clinical characteristics of cases of duodenal atresia (DA) which present with bowel gas distal to a typical double-bubble sign through an anomalous bile duct conduit. METHODS: Medical records of 57 neonates with duodenal obstruction (atresia or stenosis), presenting with a double-bubble sign and treated at our institute from 1978 to 2010, were retrospectively reviewed. RESULTS: Thirteen (23%) of 57 neonates presented with bowel gas distal to the double-bubble sign. Passage of gas through the duodenal stenosis may have occurred in 3 cases, whereas in 9 cases, gas may have bypassed the atresia through an anomalous bifurcated bile duct termination and through the pancreatic duct from the accessory to the main pancreatic duct in one case. A preoperative upper gastrointestinal series was performed in 9 cases, and an anomalous bifurcated bile duct conduit was demonstrated in 5 cases. Severe and prolonged cholestasis necessitating evaluation for biliary atresia was found in 2 patients with anomalous bile duct anatomy. CONCLUSIONS: Neonatal DA presenting with distal bowel gas via an anomalous bifurcated bile duct conduit is more common than initially thought and occurs more frequently than duodenal stenosis. These patients might be at risk for cholestasis, possibly owing to duodeno-biliary reflux through the ampulla.