Management of severe tracheal anomalies remains a clinical challenge. Tissue engineering offers new hope in trachea reconstruction surgery. However to date no optimal technique achieved in the formation of human or animal trachea. The main problem lies on the biomaterial used and the complex city of forming trachea in vivo. This study was aimed at creating tissue-engineered trachea cartilage from easily accessible human and animal nasal septum cartilage using internal scaffold and biodegradable human and animal fibrin.
Absorbable Implants ; Chondrocytes/pathology ; Chondrocytes/*transplantation ; Mice, Nude ; Polyethylene ; *Tissue Engineering ; Trachea/pathology ; Trachea/*surgery

According to the numerous experimental studies but limited clinical applications, the tracheal replacement is still far to be applied maturely. This should be attribute to the poor biocompatibility of the substitute and insufficient vascularization, even with added prosthetic migration and dislocation, epithelial ischemia and necrosis, as well as local infections, and so on. Here we present a review in the attempts to summarize the progress and prospective advances in tracheal substitute.
Humans ; Prostheses and Implants ; Tissue Engineering ; Tissue Transplantation ; Trachea ; surgery

The major step toward successful tracheal transplantation is revascularization of the grafted trachea. There are many reports that although omentopexy is an effective method to facilitate neo-vascularization in tracheal transplantations, the procedure has not been accepted universally in the transplantation field. It remains unclear whether an omentopexy can successfully revascularize tracheal graft regardless of the length of graft. This study was undertaken to assess the usefulness of omentopexy for long-segment(more than 4 cm) tracheal allotransplantation. We have performed six tracheal transplantations with omentopexy (group A) and four tracheal transplantations without omentopexy (group B) in mongrel dogs from July 1993 to February 1995. Five mid-portion tracheal rings were removed from ten donor dogs and ten corresponding tracheal rings were removed from the ten recipient dogs. The excised tracheal rings from the donors were transplanted to the recipient tracheal-excised sites. All the recipients were given cyclosporine, azathioprine, and prednisolone for immunosuppression in the post-operative period. The histologic results of all the surviving members of group B were better than those of the group A. These findings indicate that omentopexy has a limitation, it is not a major method for graft revascularization. Therefore the length of the tracheal graft was greater than 4.0 cm, for its viability, a longer tracheal graft requires some other blood supply aside from the omentopexy.
Animal ; Dogs ; Omentum/*surgery ; Support, Non-U.S. Gov't ; Trachea/*transplantation ; Transplantation, Homologous

OBJECTIVETo detect the factors relevant to stenosis of tracheal graft and to find feasible methods to solve this problem.

METHODSSixteen mongrel dogs were divided into groups A and B randomly and equally. Five-ring-length tracheal segments were allotransplanted. All grafts and anastomotic sites were covered with omental pedicles. In group A, no immunosuppressant was given and in group B, the recipients were treated with cyclosporine. The animals were sacrificed 4 weeks after operation, and their postmortem specimens were examined grossly and histologically. All allografts were assessed by percent patency. Epithelial regeneration and morphology of the cartilage were semiquantitatively evaluated.

RESULTSStructural integrity of the allografts were maintained better in group B than in group A. Tracheal stenosis was found to be more serious in group A. The scores of epithelial regeneration and cartilage morphology were higher in group B than in group A, and in each group positive correlation was found between the percent patency and the score of epithelial regeneration or cartilage morphology.

CONCLUSIONSImmunosuppressive drugs are necessary to maintain the structure of allografts. Tracheal stenosis is correlated closely with epithelial regeneration and morphological maintenance of the cartilage.

Animals ; Dogs ; Immunosuppressive Agents ; pharmacology ; Male ; Trachea ; pathology ; transplantation ; Transplantation, Homologous

OBJECTIVETo investigate the immunological rejection mechanism of tracheal xenotransplantation and xenografts as potential sources of trachea.

METHODSOn SD rat model, a xenotransplanted tracheal from the guinea pig was established by wrapping it in the cervical muscles in situ. It was divided into cryopreserved group and uncryopreserved group. Under the examinations with histochemistry, immunofluorescence (IFL) and flow cytometry (FCM) techniques, the pathomorphological characteristics of the tracheal xenografts and the immunological rejection mechanism were evaluated.

RESULTSThe tracheal allotransplantation with cryopreserved grafts wrapped by neck muscles was survived for a longer period. Histological examination revealed normal appearance of the allografts. The tracheal grafts patency was above 80%. However, cryopreserved tracheal xenografts of the guinea pig-to-rat maintained vitality for 14 days in maximum and 13.2 days on average, while the fresh tracheal xenografts only for 9 days in maximum, and 8 days on average. Acute rejection occurred in the tracheal xenotransplantation. A marked mononuclear-macrophage cellular infiltration mixed with eosinophils and lymphocyte was seen in the xenografts. Antibody (IgM, IgG) and complement (C3) deposition were also obviously detected by IFL in the xenografts. CD4 T+ cells and CD8+ T cells increased significantly in the vascular circulation. In all of the xenografts, complete loss of tracheal epithelium was associated with cartilage necrosis. The grafts patency was below 50%. This performance deteriorated with extended time periods. The fresh xenografts performed significantly worse than the cryopreserved xenografts.

CONCLUSIONSAcute rejection, caused by humoral immune reaction mainly integrated with cellular immunity, is the most notable characteristics in the guinea pig-to-rat tracheal xenotransplantation in situ. Cryopreservation can potentially reduce the antigenicity. The low antigenicity may inhibit the immunologic reaction relatively, so that prolonged survival of discordant cryopreserved tracheal xenografts could be achieved.

Animals ; Graft Rejection ; Guinea Pigs ; Rats ; Rats, Sprague-Dawley ; Trachea ; transplantation ; Transplantation, Heterologous

BACKGROUND: There are no ideal substitutes for tracheal replacement. Therefore we investigated the possibility of clinical use of cryopreserved tracheal homograft with special interest in the viability and rejection of the epithelial cell and cartilage. MATERIAL AND METHOD: Rabbit's trachea was sected and stored in liquid nitrogen tank for 1 month. Tracheal replacement was done in 45 rabbits with autograft (n=15, Group 1), fresh allograft (n=15, Group 2) and cryopreserved homograft (n=15, Group 3). After 7, 14, and 30 days, 5 rabbits in each group were sacrificed and the regeneration of epithelium and cartilage and the degree of rejection were assessed by counting the monocellular infiltration. RESULT: Investigation at day 7, showed no difference in epithelial regeneration, however, at days 14 and 30, Group 1 showed better regeneration of epithelium than groups 2 and 3. There was no difference of epithelial regeneration between group 2 and 3. There was little rejection at day 7, but at days 14 and 30, there was significant rejection in group 2 and group 3. (p<0.05). Group 3 showed lesser rejection than group 2 at days 14 and 30, but it was not statistically significant. Cartilage showed no rejection and maintained its viability in groups 2 and 3. CONCLUSION: Cryopreserved tracheal homograft can maintain its viability, therefore it may represent a possibility of clinical application for tracheal replacement. However, cryopreservation can not eliminate the antigenicity of the trachea completely. Furthere studies for lowering the antigenicity and rejection should be performed for an ideal substitute for tracheal replacement.
Allografts* ; Autografts ; Cartilage ; Cryopreservation ; Epithelial Cells ; Epithelium ; Nitrogen ; Rabbits ; Regeneration ; Trachea ; Transplantation

Although several reports were presented recently about bronchial arterial revascularization in clinical lung transplantation, one factor peculiar to the lung transplantation is the ischemia of the donor bronchus. Poor bronchial healing occurs frequently following clinical lung transplantation and this has been major cause of mortality and morbidity. There have been many attempts to solve bronchial anastomotic complications. Telescoping technique, one of those attempts, was advocated by San Antonio Group recently. This experiment was performed to evaluate the effect of telescoping anastomotic technique upon the healing of the tracheo-bronchial anastomosis. We used rabbits(weighing about 800 g) as experimental animal. METHOD: Resection of middle one third of cervical trachea and reanastomosis was performed by simple interrupted anastomotic technique in Group 1(n=15) and by telescoping anastomotic technique in Group 2(n=15). RESULT: Anastomotic sites in the telescoping technique group showed significant increase of fibrosis in the early postoperative days(< 5days) and remarkable band-like fibrous union compared to the simple interrupted group.
Anastomosis, Surgical ; Animals ; Bronchi ; Fibrosis ; Humans ; Ischemia ; Lung Transplantation ; Mortality ; Tissue Donors ; Trachea

OBJECTIVECanine model established for tracheal defect reconstruction, to investigate the outcome of tracheal reconstruction with combination of polypropylene and flap.

METHODSAbout 3.5 to 4 centimeter cervical trachea was resected and replaced with artificial trachea made from monofilament knitted polypropylene and surgical flap. Covered stent was implanted postoperatively. Survival period and quality of life were recorded, bronchofibroscopy, X-ray films and HE sections were performed.

RESULTSSix dogs survived well and another two died. The causes of death were respiratory failure in 1 and infection in another. Stenosis of anastomosis in 1 was recorded during survival period. The dogs started drinking and eating on the second postoperative day, no dyspnea was found. The animals were sacrificed at 2, 4, 8 weeks and 6 months after surgery. Soft tissue growth was found in polypropylene net 2 weeks after surgery and more at 4 weeks. The polypropylene net was covered completely with soft tissue at 8 weeks and 6 months postoperatively, the hardness and sustentation degree were enhanced following the growth and fibrosis of soft tissue. The squamous epithelium and columnar epithelium were observed healing well by HE staining method.

CONCLUSIONSOne-stage operative artificial trachea made from monofilament knitted polypropylene which has good histocompatibility and surgical flap is the closer artificial trachea to native trachea. It has a promising prospect in clinical use.

Animals ; Dogs ; Polypropylenes ; Prostheses and Implants ; Reconstructive Surgical Procedures ; instrumentation ; methods ; Skin Transplantation ; Surgical Flaps ; Trachea ; surgery

OBJECTIVETo investigate the feasibility and efficacy of the cervical tracheal reconstruction using porous titanium rings and free skin flap.

METHODSTwelve adult mongrel dogs were divided randomly into group I and group lI. A segment of cervical trachea (25 mm, 4 rings, about 2/3 circumference) was resected and a rectangular free skin flap was harvested from abdomen. The flap was sutured to the defect part and supported with two porous titanium rings (group I) or without (group II ). X ray and fiberscopic examinations were performed at the end of the first and the sixth months postoperatively. After six months the dogs were sacrificed and the grafts were examined macroscopically and microscopically.

RESULTSIn group I, one dog was sacrificed for wound infection and skin flap necrosis with deflexion of titanium rings in the fifth day postoperatively. The other 5 of 6 survived until the end of six months. X-ray examination showed titanium rings were fastened well without displacement or deformity. Through fiberscopy, the trachea luminal patency was maintained well without stricture, shrinkage or necrosis. Histologic examination showed most of the inner surface of the flap was covered with ciliated columnar epithelium. In group II, 3 of 6 dogs died of suffocation within 24 hours postoperatively. The remaining 3 dogs survived from 7 to 16 days with dyspnea and fiberscopic examination showed narrowed trachea lumens.

CONCLUSIONSPorous titanium rings could recreate the framework for cervical tracheal reconstruction using free skin flap and would be one of the options for tracheal reconstruction.

Animals ; Dogs ; Female ; Male ; Reconstructive Surgical Procedures ; methods ; Skin Transplantation ; Stents ; Surgical Flaps ; Titanium ; Trachea ; surgery

OBJECTIVETo investigate the proper time of cryo-preserving tracheal allograft so as to minimize its antigenicity.

METHODSOn a dog model, this study was carried out by allografting a tracheal into a muscular flap formed with sternocephalic muscle and sternohyoid--sternothyroid muscle. The tracheal was treated with cryopreservation in defferent intervals. The viability of the graft was evaluated by the examination of fiberoptic bronchoscopy, histopathology and microangiography. The blood flow of the tracheal mucous was measured with a blood flowmeter and the survival area was decided in the calculation of the percentage.

RESULTSThere are no significant differences in the mucous membrane appearance and the mucosal blood flow one week after the surgery among the non-cryopreservation group and the groups treated with cryopreservation in 1 day, 2 weeks, 4 weeks, 6 weeks and 8 weeks. The graft was found to start necrosis 2 weeks after the transplantation with the infiltration of mononuclear cells examined under light microscope in almost all of the groups, especially in the non-cryopreservation group and the groups treated with cryopreservation in 1 day, 2 weeks. However, there was no significant difference among the autograft group and the allograft groups cryopreservated in 6 weeks and 8 weeks, and the infiltration of the mononuclear cells was not found in these groups either.

CONCLUSIONThe antigenicity of the tracheal allografts could be significantly decreased by the treatment of cryopreservation over 6 weeks.

Animals ; Bronchoscopes ; Cryopreservation ; methods ; Dogs ; Flowmeters ; Models, Animal ; Respiratory Mucosa ; blood supply ; pathology ; Trachea ; immunology ; pathology ; transplantation ; Transplantation, Homologous