Small intestinal submucosa covered expandable Z stents for treatment of tracheal injury: an experimental pilot study in swine

Biocompatibility and cellular compatibility of decellularized tracheal matrix derived from rabbits

Objective:

To study the different concentrations of Triton X-100 and nuclease needed to remove cells from the tracheal matrix of rabbits and analyse their biocompatibility and cellular compatibility.

Methods:

Fifty tracheas were harvested from donor New Zealand rabbits. Thirty tracheas were randomly divided into five groups (n = 6 each). The tracheas in group A were untreated and served as a control group, and those in groups B, C, D and E were treated with different concentrations of Triton X-100 (1%, 2%, 3% and 4%), respectively. The tracheas of the five groups were assessed by histological observation, scanning electron microscopy and mechanical evaluation. The remaining 20 donor tracheas, which were divided into a control group and an optimally decellularized group, were used for xenogeneic transplantation and cell seeding.

Results:

Many epithelial cells and cartilage cells were observed in the tracheas of group A. There were fewer cartilage cells in the tracheas of groups C, D and E than in the tracheas of groups A and B under histological observation. In scanning electron microscopy, there were many ciliated epithelial cells in the tracheas of group A; in groups B and C, the ciliated epithelial cells disappeared, but the basement membrane was intact. The basement membranes were broken in the tracheas of groups D and E. Implanted decellularized tracheas showed good biocompatibility. Bone marrow mesenchymal stem cells grown in the decellularized tracheal matrix grew well.

Conclusion:

Decellularized tracheal matrix obtained from rabbits by 2% Triton X-100 may be suitable for the construction of tissue-engineered trachea because of its favourable morphological and biomechanical properties as well as its biocompatibility and cellular compatibly.

Regeneration of Tracheal Tissue in Partial Defects Using Porcine Small Intestinal Submucosa

Background

Surgical correction of tracheal defects is a complex procedure when the gold standard treatment with primary end-to-end anastomosis is not possible. An alternative treatment may be the use of porcine small intestinal submucosa (SIS). It has been used as graft material for bioengineering applications and to promote tissue regeneration. The aim of this study was to evaluate whether SIS grafts improved tracheal tissue regeneration in a rabbit model of experimental tracheostomy.

Methods

Sixteen rabbits were randomized into two groups. Animals in the control group underwent only surgical tracheostomy, while animals in the SIS group underwent surgical tracheostomy with an SIS graft covering the defect. We examined tissues at the site of tracheostomy 60 days after surgery using histological analysis with hematoxylin and eosin (H&E) staining and analyzed the perimeter and area of the defect with Image-Pro® PLUS 4.5 (Media Cybernetics).

Results

The average perimeter and area of the defects were smaller by 15.3% (p = 0.034) and 21.8% (p = 0.151), respectively, in the SIS group than in the control group. Histological analysis revealed immature cartilage, pseudostratified ciliated epithelium, and connective tissue in 54.5% (p = 0.018) of the SIS group, while no cartilaginous regeneration was observed in the control group.

Conclusions

Although tracheal SIS engraftment could not prevent stenosis in a rabbit model of tracheal injury, it produced some remarkable changes, efficiently facilitating neovascularization, reepithelialization, and neoformation of immature cartilage.

Techniques and principles of endoscopic treatment of benign gastrointestinal strictures

PURPOSE OF REVIEW

The fundamental goal of treating any stenosis is luminal enlargement to ameliorate the underlying obstructive symptoms. Symptoms depend on the etiology and the site of the stricture and may include dysphagia, nausea and vomiting, abdominal pain, obstipation, or frank bowel obstruction. This article compares the various current technologies available for the treatment of gastrointestinal stenoses with regard to ease and site of application, patient tolerance, safety and efficacy data, and cost-benefit ratio.

RECENT FINDINGS

Recent studies indicate that gastrointestinal dilation and stenting have evolved to a point at which in many if not most situations they can be the first line therapy and potentially the final therapy needed to treat the underlying condition.

SUMMARY

Following techniques and principles in the management of gastrointestinal strictures would allow for the well tolerated and effective treatment of most patients with the tools currently available today.

Organ bioengineering for the newborn

Regenerative medicine has recently been established as an emerging interdisciplinary field focused on the repair; replacement or regeneration of cells, tissues and organs. It involves various disciplines, which are focused on different aspects of the regeneration process such as cell biology, gene therapy, bioengineering, material science and pharmacology. In this article, we will outline progress on tissue engineering of specific tissues and organs relevant to paediatric surgery.

Tissue engineered scaffolds for an effective healing and regeneration: reviewing orthotopic studies

It is commonly stated that tissue engineering is the most promising approach to treat or replace failing tissues/organs. For this aim, a specific strategy should be planned including proper selection of biomaterials, fabrication techniques, cell lines, and signaling cues. A great effort has been pursued to develop suitable scaffolds for the restoration of a variety of tissues and a huge number of protocols ranging from in vitro to in vivo studies, the latter further differentiating into several procedures depending on the type of implantation (i.e., subcutaneous or orthotopic) and the model adopted (i.e., animal or human), have been developed. All together, the published reports demonstrate that the proposed tissue engineering approaches spread toward multiple directions. The critical review of this scenario might suggest, at the same time, that a limited number of studies gave a real improvement to the field, especially referring to in vivo investigations. In this regard, the present paper aims to review the results of in vivo tissue engineering experimentations, focusing on the role of the scaffold and its specificity with respect to the tissue to be regenerated, in order to verify whether an extracellular matrix-like device, as usually stated, could promote an expected positive outcome.

Tissue engineered human tracheas for in vivo implantation

Two years ago we performed the first clinical successful transplantation of a fully tissue engineered trachea. Despite the clinically positive outcome, the graft production took almost 3 months, a not feasible period of time for patients with the need of an urgent transplantation. We have then improved decellularization process and herein, for the first time, we completely describe and characterize the obtainment of human tracheal bioactive supports. Histological and molecular biology analysis demonstrated that all cellular components and nuclear material were removed and quantitative PCR confirmed it. SEM analysis revealed that the decellularized matrices retained the hierarchical structures of native trachea, and biomechanical tests showed that decellularization approach did not led to any influence on tracheal morphological and mechanical properties. Moreover immunohistological staining showed the preservation of angiogenic factors and angiogenic assays demonstrated that acellular human tracheal scaffolds exert an in vitro chemo-active action and induce strong in vivo angiogenic response (CAM analysis). We are now able to obtained, in a short and clinically useful time (approximately 3 weeks), a bioengineered trachea that is structurally and mechanically similar to native trachea, which exert chemotactive and pro-angiogenic properties and which could be successfully used for clinical tissue engineered airway clinical replacements.

Moving towards in situ tracheal regeneration: the bionic tissue engineered transplantation approach

In June 2008, the world's first whole tissue-engineered organ - the windpipe - was successfully transplanted into a 31-year-old lady, and about 18 months following surgery she is leading a near normal life without immunosuppression. This outcome has been achieved by employing three groundbreaking technologies of regenerative medicine: (i) a donor trachea first decellularized using a detergent (without denaturing the collagenous matrix), (ii) the two main autologous tracheal cells, namely mesenchymal stem cell derived cartilage-like cells and epithelial respiratory cells and (iii) a specifically designed bioreactor that reseed, before implantation, the in vitro pre-expanded and pre-differentiated autologous cells on the desired surfaces of the decellularized matrix. Given the long-term safety, efficacy and efforts using such a conventional approach and the potential advantages of regenerative implants to make them available for anyone, we have investigated a novel alternative concept how to fully avoid in vitro cell replication, expansion and differentiation, use the human native site as micro-niche, potentiate the human body's site-specific response by adding boosting, permissive and recruitment impulses in full respect of sociological and regulatory prerequisites. This tissue-engineered approach and ongoing research in airway transplantation is reviewed and presented here.

Rabbit Ear Cartilage Regeneration With a Small Intestinal Submucosa Graft

OBJECTIVES/HYPOTHESIS

The objective was to demonstrate that interpositional grafting with porcine small intestinal submucosa promotes cartilage regeneration following excision of rabbit auricular cartilage.

STUDY DESIGN

Blinded, controlled study.

METHODS

Eight New Zealand white rabbits underwent excision of auricular cartilage on two sites with and two sites without preservation of perichondrium. Porcine small intestinal submucosa was implanted into one site with and one site without intact perichondrium. Remaining sites served as control sites. Histological assessment was performed at 3 (n = 4) and 6 (n = 3) months and at 1 year (n = 1) after grafting.

RESULTS

Histological evaluation showed cartilage regeneration accompanied by chronic inflammation in areas in which porcine small intestinal submucosa was implanted between layers of intact perichondrium. Other sites failed to show significant cartilage regeneration.

CONCLUSION

The results of the study using porcine small intestinal submucosa as a bioscaffold for cartilage regeneration are promising and justify further animal and human studies.

Physical and histopathological assessment of the effects of metallic stents on radiation therapy

To evaluate whether simultaneous metallic stent (MS) placement and radiotherapy are feasible, phantom and animal experiments were performed. The interface dose by external irradiation (EI) or intracavity irradiation (II) to 5 kinds of MS was measured using the charge-coupled device (CCD) camera with a thermoluminescent (TL) sheet, and backscatter and absorption were evaluated using composite method. Lineac 10 MV X-ray irradiated the MS in close contact with the TL sheet. II was performed using (192)Ir, and the irradiation dose transmitted through the MS was measured using the TL sheet. The ratio of the CCD value of the MS wire region to that of the MS non-wire region was defined as the dose perturbation factor (DPF). Furthermore, the effects of a combination of (60)Co gamma-ray EI and MS placement in the normal common bile duct were histopathologically evaluated in dogs. In the phantom experiments of EI, in backscatter by the MS, the DPF was 1.09 for CZ, and 1.03 for Pal, but no backscatter was detected in the remaining 3 MS. In absorption by the MS, the DPF was 0.92, 0.97, 0.97, and 0.98 for CZ, Wall, Pal, and Vel, respectively, but no absorption was detected in U. Flex. In those of II, the DPF of absorption was 0.91, 0.98, and 0.98 for CZ, U. Flex, and Wall, respectively, but no absorption was detected in Pal and Vel. The animal experiments showed infiltration of inflammatory cells and fibrosis in the case of both MS placement and EI. These changes were marked in EI treating after MS placement, but neither severe ulcer nor perforation was found. In conclusion, these results suggested that the effect of MS should be considered carefully when simultaneous MS placement and EI is performed clinically.

SIS with tissue-cultured allogenic cartilages patch tracheoplasty in a rabbit model for tracheal defect

CONCLUSIONS

In the rabbit model, small intestinal submucosa (SIS) compounded with tissue-cultured allogenic cartilages appeared to be an efficacious method for the patch repair of partial circumferential tracheal defects instead of autologous grafts. SIS appears to be a safe and promising means of facilitating neovascularization and tissue regeneration. The long-term use of SIS and tissue-cultured allogenic cartilages warrants further investigation.

BACKGROUND

Tracheal defect reparation remains a challenging surgical problem that can require reconstruction using autologous grafts or artificial stents. This study was performed to evaluate the efficacy of SIS, a biocompatible, acellular matrix, compounded with different tissue-cultured allogenic cartilages, in the repair of a critical-size tracheal defect.

MATERIALS AND METHODS

A full-thickness defect (4 x 8 mm) was created in tracheal rings four to six in adult rabbits. A piece of 8-ply SIS sandwiched in thyroid cartilage, auricular cartilage, or without cartilage, respectively (designated experiment 1, 2, or 3, respectively), was sutured to the edges of the defect with interrupted 4-0 polypropylene sutures. In control animals, the defect was closed with lamina praetrachealis. All animals were followed until signs of dyspnea became apparent or for 4 or 12 weeks. After follow-up and euthanasia, the trachea was harvested and prepared for histologic evaluation using conventional techniques.

RESULTS

All animals tolerated the procedure well but two animals in group 1 (n=5), three in group 2 (n=5), and one in group 3 (n=5) had stridor after operation and expired within <1 month with different degrees of obstruction. The other animals in these groups and the control animals (n =3) all survived >1 month. Histologically, neovascularization of the patch was noted with moderate inflammation. The surface of the SIS patch was covered with a lining of ciliated epithelial cells. The tissue-cultured allogenic cartilages degraded to some extent.

Remodeling of suspended small intestinal submucosa venous valve: an experimental study in sheep to assess the host cells' origin

PURPOSE

To investigate the origin of host cells during remodeling of small intestinal submucosa (SIS) square stent-based bicuspid venous valves (VVs).

MATERIALS AND METHODS

Suspended VVs (SVVs) were developed by suspending VVs within bare square stents so the valve elements would not contact the vein wall after deployment. Eight SVVs were placed within the intrahepatic and infrahepatic inferior venae cavae (IVCs) of four adult female sheep. Eight standard VVs were implanted in the external jugular veins of these animals for comparison. At 5 weeks after placement, the devices were examined for stability and patency and the animals were killed. Gross, histologic, and scanning electron microscopic (SEM) examinations were performed.

RESULTS

Follow-up spot radiographs and venography showed no migration of the devices, venous occlusion, or thrombus formation. All SVVs were intact without contact with the IVC wall. Six VVs were competent and two were slightly tilted with some reflux. Histologic study showed remodeling of SVVs and VVs with newly formed collagen fibers; fibroblasts and inflammatory cells were found penetrating the SIS leaflets and endothelial cells on the surface. SIS neovascularization was also present. There was no difference regarding SIS remodeling between SVVs and the free part of VV leaflets. The VV leaflets' bases were thicker compared to their free parts (P <.01). SEM examination showed endothelial cells on both sides of the SVVs and VVs. Endothelialization of the SVV central leaflet surfaces and both surfaces of the VV leaflets was more complete than that of the peripheral surfaces of the SVV leaflets.

CONCLUSION

SIS-based valve remodeling occurs independently of vessel wall contact by recruitment of cells directly from the circulation.