An optimized non-destructive protocol for testing mechanical properties in decellularized rabbit trachea.

Successful tissue-engineered tracheal transplantation relies on the use of non-immunogenic constructs, which can vascularize rapidly, support epithelial growth, and retain mechanical properties to that of native trachea. Current strategies to assess mechanical properties fail to evaluate the trachea to its physiological limits, and lead to irreversible destruction of the construct. Our aim was to develop and evaluate a novel non-destructive method for biomechanical testing of tracheae in a rabbit decellularization model. To validate the performance of this method, we simultaneously analyzed quantitative and qualitative graft changes in response to decellularization, as well as in vivo biocompatibility of implanted scaffolds. Rabbit tracheae underwent two, four and eight cycles of detergent-enzymatic decellularization. Biomechanical properties were analyzed by calculating luminal volume of progressively inflated and deflated tracheae with microCT. DNA, glycosaminoglycan and collagen contents were compared to native trachea. Scaffolds were prelaminated in vivo. Native, two- and four-cycle tracheae showed equal mechanical properties. Collapsibility of eight-cycle tracheae was significantly increased from -40cm H2O (-3.9kPa). Implantation of two- and four-cycle decellularized scaffolds resulted in favorable flap-ingrowth; eight-cycle tracheae showed inadequate integration. We showed a more limited detergent-enzymatic decellularization successfully removing non-cartilaginous immunogenic matter without compromising extracellular matrix content or mechanical stability. With progressive cycles of decellularization, important loss of functional integrity was detected upon mechanical testing and in vivo implantation. This instability was not revealed by conventional quantitative nor qualitative architectural analyses. These experiments suggest that non-destructive, functional evaluation, e.g. by microCT, may serve as an important tool for mechanical screening of scaffolds before clinical implementation. STATEMENT OF SIGNIFICANCE: Decellularization is a front-running strategy to generate scaffolds for tracheal tissue-engineering. Preservation of biomechanical properties of the trachea during this process is paramount to successful clinical transplantation. In this paper, we evaluated a novel method for biomechanical testing of decellularized trachea. We detected important loss of functional integrity with progressive cycles of decellularization. This instability was not revealed by our quantitative nor qualitative analyses. These experiments suggest that the technique might serve as a performant, non-destructive tool for mechanical screening of scaffolds before clinical implementation.

Prefabrication and prelamination strategies for the reconstruction of complex defects of trachea and larynx.

Complex tracheal and laryngeal defects can be reconstructed using prelamination and prefabrication techniques. Three clinical situations are described in detail in the article. In short segment restenosis defects within scarred surroundings, we restore the fibrocartilaginous defect with a radial forearm fascia flap prelaminated with buccal mucosa or cartilage. This provides a newly vascularized inner lining to the tracheal defect and restores the tubular convexity. For long segment defects we need a technique that can withstand respiratory forces. We use a heterotopic prefabrication strategy to vascularize a tracheal allograft wrapped in forearm fascia. Chimerism is created by replacing donor respiratory epithelium with buccal mucosa of the recipient. After orthotopic transfer, this chimerism allows immunosuppression to be tapered and stopped when bronchoscopy shows mucosal integrity of the new trachea, since the recipient epithelium replaces the allogeneic inner tracheal lining by means of a chronic rejection process. A distinct situation occurs after resection of a unilateral larynx tumor, which usually results in a total laryngectomy with loss of both vocal cords, since reconstruction of the hemilarynx is considered too complex. First, we prefabricate a nearby four-ring autologous tracheal segment using radial forearm fascia. In a second stage, this orthotopically vascularized trachea restores the laryngeal structure with the aim to conserve one vocal cord and thus speech. Orthotopic and heterotopic prelamination and prefabrication strategies offer efficient and reproducible solutions for the restoration of challenging short and long segment tracheal defects, as well as unilateral laryngeal defects. The series in this review article are based on previous studies and case reports. The level of evidence is III-"Study of nonconsecutive patients, without a universally applied gold standard: case-control study".

Retrospective analysis of umbilical, epigastric, and small incisional hernia repair using the Ventralex™ hernia patch.

OBJECTIVE: The aim of this retrospective study was to determine the long-term recurrence and complication rates following small abdominal wall hernia repair with the Ventralex hernia patch. The study also aimed to identify risk factors for hernia recurrence in patients undergoing such repair and to examine the relationship between quality of life and hernia recurrence. BACKGROUND: Hernia repair using prosthetic mesh materials has become the preferred method of repair, as the recurrence rates are much lower than with conventional repair techniques. The prevention of long-term complications and improvements in the quality of life should also be considered as important features of successful repair. The Ventralex patch is a bilayer prosthesis, designed for retromuscular or intraperitoneal placement. Currently, seven studies have evaluated the device for small ventral hernia repair, and all have shown low short- and long-term recurrence rates. MATERIALS AND METHODS: The medical records of 176 patients who underwent abdominal wall hernia repair using the Ventralex patch between May 2004 and February 2009 were reviewed. All patients were followed up after 1 month and later in 2010. The rate of recurrence, immediate postoperative and long-term complications, and quality of life were evaluated. RESULTS: Long-term follow-up data were available for 135 patients. The mean follow-up was 49 months (range 13-70 months). There were 12 hernia recurrences (8.9%) during this time. Postoperative (1-month) complications included seroma (4%), superficial surgical site infections (3%), and an abscess (1.5%). At the mean long-term follow-up, complications included infection (1.5%) and subobstruction (1.5%). The only risk factor for hernia recurrence was female gender (unadjusted odds ratio 0.19, 95% confidence interval [CI] 0.05-0.72, P = 0.02). Patients with hernia recurrence reported significantly lower quality of life scores than patients without recurrence. CONCLUSIONS: The Ventralex hernia patch offers a simple and quick means of repairing small abdominal wall hernias. A relatively high recurrence rate was observed in this study. Reviewing the available literature, a critical appraisal is needed, attention should be paid to follow the correct implantation technique, proper deployment technology should be used, and a lightweight version would be welcome.