In vivo implantation of a tissue engineered stem cell seeded hemi-laryngeal replacement maintains airway, phonation, and swallowing in pigs

Laryngeal functional impairment relating to swallowing, vocalisation, and respiration can be life changing and devastating for patients. A tissue engineering approach to regenerating vocal folds would represent a significant advantage over current clinical practice. Porcine hemi-larynx were de-cellularised under negative pressure. The resultant acellular scaffold was seeded with human bone marrow derived mesenchymal stem cells and primary human epithelial cells. Seeded scaffolds were implanted orthotopically into a defect created in the thyroid cartilage in 8 pigs and monitored in vivo for 2 months. In vivo assessments consisted of mucosal brushing and bronchoscopy at 1, 2, 4, and 8 weeks post implantation followed by histological evaluation post termination. The implanted graft had no adverse effect on respiratory function in 6 of the 8 pigs; none of the pigs had problems with swallowing or vocalisation. Six out of the 8 animals survived to the planned termination date; 2 animals were terminated due to mild stenosis and deep tissue abscess formation, respectively. Human epithelial cells from mucosal brushings could only be identified at Weeks 1 and 4. The explanted tissue showed complete epithelialisation of the mucosal surface and the development of rudimentary vocal folds. However, there was no evidence of cartilage remodelling at the relatively early censor point. Single stage partial laryngeal replacement is a safe surgical procedure. Replacement with a tissue engineered laryngeal graft as a single procedure is surgically feasible and results in appropriate mucosal coverage and rudimentary vocal fold development.

Full-thickness laparoendoscopic colonic excision in an experimental model

Background

Patients requiring surgery for complex colonic polyps traditionally undergo colectomy, with significant risks. Typically in excess of 10–30 cm of colon is removed at laparoscopic or open surgery lasting over 60 min. This study details the preclinical development of a rapid, minimally invasive, limited full-thickness colonic resection.

Methods

Both survival and non-survival procedures were performed in anaesthetized 70-kg pigs. A simulated colonic polyp was created by endoscopic ink injection with a clearance margin delineated by circumferential placement of mucosal argon plasma coagulation marks. Full-thickness eversion of the bowel was achieved using endoscopically placed anchors and the polyp was excised using a laparoscopic stapler. In survival procedures, pigs were killed under anaesthetic 8 days after surgery. All pigs underwent post-mortem examination.

Results

Five procedures were performed (5 pigs). The median (range) procedure duration was 26 (20–31) min, with a specimen diameter of 5·1 (4·5–6·3) cm. The postoperative recovery of survival animals (4 pigs) was uneventful. At post-mortem evaluation the resection sites were well healed with no evidence of stenosis, intra-abdominal infection or inadvertent organ damage. Histological assessment of anastomoses showed mucosal repair and restoration of submucosal continuity.

Conclusion

Full-thickness localized colonic excision with this technique provides a large specimen with adequate healing in a porcine model.

Presented to the Annual Meeting of the Association of Surgeons of Great Britain and Ireland, Glasgow, UK, May 2013; published in abstract form as Br J Surg 2013; 100(Suppl 7): 2

The role of human-derived fibrin sealant in the reduction of postoperative flexor tendon adhesion formation in rabbits

This study assessed the role of a novel fibrin sealant (Vivostat in adhesion reduction after flexor tendon surgery. The deep flexor tendons of the 2nd and 4th digits of the left paw of 20 rabbits were exposed and a standard partial injury was performed on each. The rabbits were randomized to either immediate post-injury treatment with Vivostat or no treatment. In each case active movement of the 2nd digit was prevented while the 4th digit was allowed to move normally. The two groups were assessed at 14 days for adhesion formation with a tensiometer. The right paw acted as the unoperated control. Results showed that there was no significant difference in the force needed to remove the tendon from its sheath when comparing the two Vivostat((R))-treated groups to the unoperated controls. There was, however, a highly significant difference in this force between the non-Vivostat-treated groups and the unoperated controls. This suggests a beneficial effect of Vivostat in reducing post surgical tendon adhesion formation.

The effect of benomyl on neurite outgrowth in mouse NB2A and human SH-SY5Y neuroblastoma cells in vitro

The commercial fungicide methyl 1-[(butylamino) carbonyl]-1H-benzimidazol-2-ylcarbamate (benomyl) is teratogenic in rats. Its mode of action is believed to be related to its ability to inhibit the polymerization of brain tubulin. In this study its effects were studied in cultured neuronal cells during differentiation and neurite outgrowth. Mouse NB2a and human SH-SY5Y neuroblastoma cells were induced to differentiate by addition of dibutyryl cyclic AMP and at the same time were exposed to various concentrations of benomyl. Benomyl significantly inhibited neurite outgrowth in both cell lines at concentrations of 10(-8) M and above with IC50 values of 5.9 x 10(-7) M and 1.0 x 10(-6) M in the NB2a and SH-SY5Y cells respectively. The results show that benomyl inhibits neuronal cell differentiation at concentrations likely to be achieved during the development of fetal abnormalities in rats in vivo.

Comparative and experimental pathology of fibrosing colonopathy

Although the occurrence of fibrosing colonopathy is temporally associated with the introduction of high-strength pancreatic enzyme supplements, its pathogenesis remains uncertain. The UK case-control study showed fibrosing colonopathy to be associated with high doses of high-strength pancreatic enzyme supplements and with a group of brands which occupy only 30% of the market. Two alternative hypotheses were proposed to explain the aetiology of fibrosing colonopathy: exposure to high levels of enzymes or to as yet unidentified components of the formulation. Comparison of the anatomical pathology of fibrosing colonopathy with that of previously encountered forms of obstructive gastrointestinal pathology, such as stricturing lesions due to potassium chloride preparations and nonsteroidal anti-inflammatory drugs, confirmed it to be a previously unencountered, long-segment lesion of the colon. Thus the use of the descriptive term 'stricture' is a misnomer leading to much clinical confusion when discussing obstructive bowel pathology in cystic fibrosis patients. Gavage studies in the rat with one of the two monomers (ethyl acrylate) forming the methacrylic acid copolymer (Eudragit L30D55) used for the enteric coating of the high-strength pancreatic enzyme supplements, have shown pathology comparable to fibrosing colonopathy. These findings prompted a series of exploratory studies in adolescent pigs. After seven days caecal gavage of Eudragit L30D55 at doses of 10, 50 or 500 mg/kg/day (comparable to human intake), extensive fibrosing colonopathy-like changes, inclusive of dense submucosal fibrosis, were noted at all dose levels in seven out of nine animals. Similar studies of the monomer components of the Eudragit L30D55 copolymer, at dose levels of 0.015 to 50 mg/kg/day, representing possible residues in Eudragit L30D55, did not produce comparable changes. The conclusion is that, although the precise mechanisms have not been elucidated, the role of enteric coatings containing Eudragit L30D55 in the pathogenesis of fibrosing colonopathy requires urgent further study.