Role of basic fibroblast growth factor in revascularization of rabbit tracheal autografts.

Despite omentopexy of the bronchial anastomosis, donor airway ischemia remains a problem after lung transplantation. This study examined the hypothesis that surface abrasion and topical application of basic fibroblast growth factor (bFGF) would enhance omental revascularization of trachea in a rabbit heterotopic autograft model. Tracheal segments were excised, primary tracheal anastomoses performed, and the segments placed in the peritoneal cavity wrapped in omentum. Animals were randomized to one of six groups according to tracheal segment treatment: control, surgical abrasion, Surgicel wrap with topical bFGF, Surgicel wrap with bFGF vehicle, Gelfoam wrap with bFGF, and topical bFGF alone. One week later, animals were heparinized, perfused with Aquablak dye, and killed. Tracheal segments were excised and sectioned for light microscopic quantitative assessment of viability and dye perfusion. There was no significant improvement in viability or perfusion between abraded tracheal segments or segments treated with bFGF/Gelfoam or bFGF alone when compared with control segments. Airways wrapped in Surgicel had significantly greater ischemic injury compared with the control group, regardless of bFGF application. Neither surgical abrasion nor topical bFGF increased omental revascularization of transplanted tracheal segments after 7 days.     

Effects of basic fibroblast growth factor on early revascularization and epithelial regeneration in rabbit tracheal orthotopic transplantation.

OBJECTIVES: Donor airway ischemia is a significant problem after tracheal replacement with homograft or lung transplantation. Omentopexy is the usual countermeasure to prevent or overcome the ischemia of the airway but this is frequently not sufficient. This study was designed to investigate whether basic fibroblast growth factor (bFGF) can augment tracheal revascularization and its epithelial regeneration in rabbit tracheal autograft. METHODS: About half the length (44-45%) of the trachea of New Zealand white rabbit were autotransplanted in the original position immediately after harvest. In group I (n=15, control group), cervical tracheal autotransplantation was done only. In group II (n=15, omentopexy group), the cervical tracheal autograft was wrapped with subcutaneously advanced omentum. In group III (n=15, bFGF group), 1 microg of bFGF was applied evenly on the graft after the completion of anastomosis. Five animals in each group were examined on the 3rd, 7th and 14th postoperative days. Three rings of trachea were taken at the mid portion of the graft and the supra-carinal untouched normal trachea in each. The effect of revascularization was assessed by measuring the uptake of human serum albumin labeled with 99m technetium, which was injected into the left atrium just before sacrifice. The epithelial regeneration was assessed by means of light microscopic examination. RESULTS: The proportion of perfusion of the graft to normal trachea was much higher in group III (P<0.05) on day 3 (25.4, 27.8 and 54.7% in groups I, II and III, respectively), but there was no difference on the 7th and 14th days. The epithelial regeneration was better in group III (P<0.05) than in the other groups on day 3, and was better in groups II and III than group I on day 7. CONCLUSION: we concluded that bFGF enhances the revascularization and epithelial regeneration of the tracheal autograft, especially during their early phases.     

Improved airway healing using basic fibroblast growth factor in a canine tracheal autotransplantation model.

OBJECTIVE: We studied 22 dogs to examine the effect of basic fibroblast growth factor (bFGF) alone, in comparison with omental or muscular wrapping on airway healing in a tracheal autotransplantation model. SUMMARY BACKGROUND DATA: Basic fibroblast growth factor is one of the most potent promoters of angiogenesis and has an ability to enhance blood supply to the ischemic airway. Topical administration of a fibrin glue enriched with 5 microg/cm2 bFGF, determined as a proportion of surface area of the tracheal grafts, improved revascularization of orthotopic canine tracheal autografts in a previous study. METHODS: All animals received orthotopic tracheal transplantation using 6-ring autografts that occupied a distal part of the thoracic trachea. Twenty-two animals were classified randomly into the following four groups: no treatment (Group G1, n = 4), muscular wrapping (Group G2, n = 4), omental wrapping (Group G3, n = 4), and topical administration of fibrin glue enriched with 5 microg/cm2 bFGF (Group G4, n = 10). Autografts were harvested 60 days after transplantation and assessed by the percent patency and histology. RESULTS: Devascularized tracheal autografts could not maintain their structural integrity without other treatments (Group G1). In contrast, more than half of all autografts receiving treatments remained viable, as demonstrated by gross and histologic findings (Groups G2, G3, and G4). Treatments with bFGF and omentum showed significantly better graft viability than no treatment. However, there was no statistical difference in the viability of tracheal autografts among the three treatment groups. In terms of the time performance ratio, bFGF was the best treatment for the devascularized autografts. CONCLUSIONS: Topical administration of bFGF was superior to the omental or muscular wrapping in terms of the time performance ratio. Clinical trials will be necessary to determine whether these findings are applicable to humans.     

The possibilities of greater omentum usage in thoracic surgery.

OBJECTIVE: To illustrate the wider role of an omental pedicle flap in surgical treatment for diverse thoracic organ disorders we have, retrospectively, reviewed our experience over the last 8 years. METHODS: We used the greater omental pedicle flap in 68 patients. Bronchial stump omentopexy was performed in 35 patients with a high risk of impaired bronchial healing after right pneumonectomy as a preventive method and in two patients with an acute bronchial fistula. In 13 patients after circular tracheal or carinal resections and in four after esophago-respiratory disjoints of fistulas we applied anastomoses or circular omentopexy of the fistula zone. The omental coverage was performed in four patients with chronic empyema, in seven patients after extensive chest wall resection and in two patients with post-sternotomy mediastinites. In one patient with idiopathic fibrosing mediastinitis, one-stage allotransplantation of tracheal thoracic segment was conducted and greater omentum (GO) was used to wrap the allograft. RESULTS: Three patients developed major complications. The first, bronchial fistula after bronchial stump omentoplasty. In two patients circular wide tracheal resection (11-12 rings) was complicated by a tracheal divergence of anastomoses. These complications were cured in a conservative way since a displaced omental flap substituted the tracheal wall and, therefore, the trachea remained hermetically sealed. In other cases, the perfect adhesive properties of the omental tissue promoted perfect adhesive properties promoted prevention of incompetence and inflammatory complications. Immunological and bacteriological examinations showed that pediculated omental flap is a lymphocyte source and promotes a decrease in bacterial quantity and activity. CONCLUSION: We think the series demonstrates the value of the omental method, which offers excellent therapeutic results following an easy surgical procedure. This method extends indications for surgical treatment and decreases the postoperative complications.     

Successful revascularization of large isolated tracheal segments.

The omentum has been shown to be of use in clinical and experimental revascularization of tracheobronchial anastomoses. We have evaluated the possibility of revascularizing large and completely isolated tracheal segments while preserving the main tracheal characteristics. Ten experiments were performed in dogs, introducing 10-14 cartilage ring tracheal segments enveloped in omentum into the abdomen. Revascularization resulted in all cases with preservation of tracheal consistency. In only two cases were small mucosal necrotic zones observed. The experimental model thus appears to be of use in the revascularization of large tracheal segments, with excellent preservation of both cartilage and mucosa.     

Experimental tracheal reconstruction by allotransplantation

Reconstruction using allotransplantation was successfully performed for large defects of the trachea. The defects of ten tracheal rings were surgically created in 28 mongrel dogs and they were repaired with allografts of 5 rings, using over-and-over continuous suture technique with 4-0 Prolene. After the completion of anastomosis, omental pedicle was used to wrap the allograft including both the ends of the graft. Immunosuppressant FR900506 (FK506) was daily administered with a dose of 0.1 mg/kg body weight intramuscularly. When the dogs were sacrificed or succumbed, all the grafts were excised and were examined microscopically and scanning electron microscopically. In some of them, the revascularization from the omental pedicle was examined by infusion of Indian ink from the feeding artery. Eleven dogs survived for more than 30 days and 3 of them did over 120 days. The longest survival is 202 days and the dog is now alive. Twenty out of the 28 allografts were proved to be viable with normal tracheal structure and also free of granulation or stricture. One dog died of perforation of the graft due to rejection. Another dog succumbed from other disease, but the graft was necrotized without the sign of rejection. The viability of the grafts of the remaining 6 dogs were not determined, because the survival time were not long enough, although the grafts were intact macroscopically and microscopically. Three or four weeks after transplantation, the surface of the graft was covered with ciliated epithelium and the tracheal architects were almost normalized. It was proved that revascularization of the tracheal graft from the omental pedicle was established within 7 days following the operation.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of early and delayed immunosuppression in experimental tracheal transplantation with omentopexy.

BACKGROUND/PURPOSE: Best results in experimental tracheal allotransplantation are obtained when metachronous revascularization by omentopexy and immunosuppression are used. Nevertheless, this method of revascularization implies in a 4-day period of ischemia to the graft. The aim of this study was to assess the influence of the 4-day period of ischemia on host sensitization as well as the effect of early or delayed immunosuppression on the outcome of the grafts. METHODS: Thirty rabbits were submitted to tracheal allotransplantation and divided according to position of the graft (orthotopic or heterotopic transplants) and the initiation of immunosuppression (early or delayed). The quality of the revascularization was evaluated by the identification of Indian ink, perfused through the abdominal aorta, inside the submucosal vessels. The outcome of the grafts was evaluated by histological analysis according to a semiquantitative scale of alterations. RESULTS: Grafts were better revascularized in heterotopic position. Grafts with late immunosuppression presented good outcome only when heterotopically positioned. No significant differences were observed in grafts placed heterotopically or orthotopically when immunosuppression was initiated early after the transplant. CONCLUSIONS: Transient ischemia produced by metachronous revascularization is not the single factor responsible for the histological alterations observed in tracheal allografts. These alterations probably also are produced by the activation of immune responses. This activation is more intense in more ischemic grafts, but can be suppressed by early administration of immunosuppression.     

Revascularization of trachea in lung and tracheal transplantation

Ischemia is the primary risk factor for airway complications in double lung transplantation using tracheal anastomosis and in tracheal transplantation. Many treatment options as to revascularization for the trachea were herein described and reviewed. They include direct revascularization (using a conduit such as artery or vein), revascularization with tissue wrapping (using omentum, muscle, internal thoracic artery pedicle, pleura, or pericardial fat pad), and with drug administration (using corticosteroid hormone, prostaglandin, or angiogenic factor). As there are few organized reports including new information on revascularization for the trachea these days, this review article would help thoracic surgeons who get engaged transplantation.     

Development of biologic coronary artery bypass grafting in a rabbit model: revival of a classic concept with modern biotechnology

OBJECTIVE: We have developed a technique for biologic coronary artery bypass grafting, which is a revival of a classic concept with modern biotechnology. METHODS: Acute myocardial infarction was created by ligating the major branch of the circumflex artery in rabbits. Animals were divided into four groups: a nontreated group (group N), a group in which omentum was used to wrap the infarcted area (group G), a group in which a gelatin hydrogel sheet incorporating 100 microg basic fibroblast growth factor was placed over the infarcted area (group F), and a group in which the infarcted area was similarly treated with basic fibroblast growth factor followed by omental wrapping (group FG). Cardiac function was subsequently assessed by echocardiography. Postmortem angiography through the gastroepiploic artery was done in groups G and FG. Infarct size and arteriolar density were evaluated. RESULTS: Group FG showed a better fractional area change than did the other groups (group N P <.001, group G P =.002, group F P <.001). Angiography revealed that communication from the gastroepiploic artery to the coronary artery was created through a rich bed of neovascularization in all 7 animals of group FG, whereas poor collaterals were recognized in only 2 of 7 animals in group G. Infarct size was reduced to a greater extent in group FG than in groups F, G, and N (10% +/- 3%, 16% +/- 5%, 19% +/- 7%, 23% +/- 2%, respectively, group F P =.04, groups G and N P <.01). The number of arterioles 20 to 100 microm in diameter was increased to a greater extent in group FG than in groups F, G, and N (23 +/- 5 arterioles/mm(2), 14 +/- 3 arterioles/mm(2), 10 +/- 1 arterioles/mm(2), 4 +/- 2 arterioles/mm(2), respectively), with the differences being significant. CONCLUSIONS: These results show that bypass from the gastroepiploic artery to coronary arteries can be achieved without surgical anastomosis through slow release of basic fibroblast growth factor in this rabbit acute myocardial infarction model. This new revascularization concept, biologic coronary artery bypass grafting, could be applicable for revascularizing many tiny coronary vessels in patients who are difficult to treat with conventional surgery or catheter intervention.     

异体气管移植再血管化与再上皮细胞化研究进展

目的探讨同种异体气管移植再血管化与再上皮细胞化的研究进展.方法广泛查阅近期相关文献,介绍一种先将同种异体移植段气管大网膜包裹,血管化后再种植自体上皮细胞后原位移植的方法.结果与一期原位移植加大网膜包裹相比,增加上皮细胞覆盖率,使之最接近自体生理条件.结论这一方法若能成功,可进一步减少移植段气管免疫排斥反应,防止其塌陷,延长患者生存时间.     

Heterotopic transplantation of cryopreserved tracheae in a rat model.

INTRODUCTION: The successful use of cryopreserved tracheal allografts in canine models suggests their use in humans. The grade of genetic difference, the mechanism of revascularisation and the method of cryopreservation are not clearly defined. The purpose of our study was to investigate the rejection of tracheal transplants in a standardised heterotopic rat model using different forms of cryopreservation. METHODS: Tracheae from Brown Norway rats were implanted into the omentum from Brown Norway rats or Lewis rats. We transplanted fresh isografts or allografts and pretreated isografts or allografts. Cryopreservation was performed in a medium containing 10% dimethyl sulphoxide at -80 degrees C for 28 days (I) or -196 degrees C for 84 days (II) or without medium at -80 degrees C for 28 days (III). The transplants were excised after 7 and 21 days, respectively. RESULTS: Histological examinations revealed normal structure and function of isografts after 21 days. In the cryopreserved isograft, the epithelium had disappeared and the tracheal lumen was partially obstructed by a non-compact fibrous tissue. In the fresh allografts, the epithelium was replaced by aggressive fibrous tissue, infiltrating the membranous part of the trachea and occluding the tracheal lumen. The cartilage was vital without any sign of rejection. In the cryopreserved allografts, the tracheal lumen was obstructed by dense fibrous tissue with an inflammatory reaction. The cartilage of cryopreserved allografts (II) and (III) had lost the nuclei corresponding to non-vital tissue. Only in the cryopreserved allografts (I) did we find nodular regeneration at the edges of the cartilaginous bow. CONCLUSIONS: The heterotopic transplantation model allows the study of the mechanisms leading to tracheal obstruction. Cryopreservation was found to have no clear advantage in reducing transplant immunogenicity. Cryopreservation leads to significant damage to the cartilage, the intensity of which is dependent on the mode of cryopreservation.     

Usefulness of the pedicled omental graft in thoracic surgery.

A retrospective evaluation on the usefulness of the pedicled omental graft (POG) in treating problems associated with thoracic surgery is reported. The omentum has been long used to manage numerous intra-abdominal problems because of its excellent blood supply that could limit the spread of infection. The POG finds even greater application in extraperitoneal use because it is able to extend to all areas of the thorax. In this study, we reviewed 25 patients with omentopexy cases in our thoracic surgery unit over the last 19 years. Indications and usage of the POG were divided into two categories. As a preventive measure, the POGs were used to wrap tracheal and bronchial anastomoses. As a corrective treatment, the POGs were used to wrap perforated esophageal lesions and bronchial stumps and cover postoperative bronchial and pulmonary fistulas, repair chest walls, fill empyema cavities, and control osteomyelitis in the sternum and ribs. Uneventful and successful treatments were obtained in 22 cases (88%). Two patients died due to multiple organ failure followed by sepsis, and another due to respiratory failure. The POG was considered to be effective and useful in treating both potential and existing conditions often encountered in thoracic surgery.     

Long-term results of ventricular assist pumping in postcardiotomy cardiogenic shock

A series of experiments were conducted to assess the possibility of revascularizing tracheal homografts with an omental pedicle flap. Three different experiments were performed. In Group I (N = 4) a ten-ring tracheal allograft was embedded into the greater omentum of a recipient animal for 30 days. At reexploration these four allografts were found to have been transformed into a tube consisting mainly of connective tissue. To provide more collateral circulation, we immediately reanastomosed an eight-ring tracheal autograft in Group II animals (N = 7). Collateral blood supply was possibly available from the surrounding mediastinal tissues, the recipient trachea, and the transposed omental graft. Tracheal malacia and loss of rings 4,5, and 6 was a consistent finding and cause of death. A third group of animals (Group III) underwent a similar operation with the addition of free bone grafts being applied to the external surface of the autograft to impede significant tracheal stenosis. The long-term results and the findings when the animals were put to death were the same as in Group II. We conclude that the omental pedicle graft cannot sustain chondrocyte viability. Thus a reliable method for revascularization of a tracheal transplant remains to be found.     

Treatment of postoperative osteomyelitis using an omental pedicle flap

We described two patients with postoperative sternal osteomyelitis with mediastinal abscess who were successfully treated by omentopexy. One was a 15-year-old boy. Five days after accessory pathway division for Wolff-Parkinson-White syndrome, he was diagnosed as having sternal osteomyelitis. Cultures of the exudate yielded staphylococcus epidermidis. Closed continuous irrigation with diluted povidone-iodine was not effective. After open drainage, omentopexy with an omental pedicle flap was performed. Postoperatively, computed tomography showed no abnormal findings in the omental flap and surrounding tissue. The second patient was a 33-year-old man. Re-aortic valve replacement for aortic regurgitation was performed. Eleven days after the operation, he was diagnosed as having postoperative sternal osteomyelitis. Cultures of the drainage fluid yielded staphylococcus epidermidis. Continuous closed irrigation with povidone-iodine was ineffective. Thus, the wound was opened and omentopexy with an omental pedicle flap was performed. The postoperative course was uneventful. Computed tomography showed no residual abscess or recurrent inflammation. We conclude that the omentopexy is useful in the treatment of postoperative sternal osteomyelitis.     

Importance of the omentum in the development of intra-abdominal metastases

Areas of trauma are preferred sites for metastatic tumour growth. In extensive intra-abdominal tumour recurrence the omentum is invariably involved. The importance of the omentum in the development of tumours at sites of intra-abdominal trauma has been investigated. Colonic anastomoses were performed in Hooded-Lister rats with and without omentectomy. Animals received intraluminal or intraperitoneal injections of a syngeneic tumour. With intraluminal injection, tumour occurred at the anastomosis and in the omentum in 38 and 43 per cent of animals respectively but following omentectomy the values were 14 and 9 per cent (omental remnant). With intraperitoneal administration tumour occurred in 53 per cent at the anastomosis and in 79 per cent in the omentum compared with 16 and 29 per cent (in omental remnant) following omentectomy. In this model a reduced ability of an anastomosis to support 'seeded' tumour following removal of the omentum is demonstrated and the development of local recurrence from spilled tumour cells during operation may be enhanced by, or be dependent on, the proximity of the omentum.     

Successful tracheal autotransplantation with a vascularized omental flap.

A major problem in tracheal transplantation is the restoration of an adequate vascular supply to the transplanted trachea. In 12 piglets, a segment (6 rings) of thoracic trachea was removed and the excised segment was then sutured back in place. In 9 animals (group A), a vascularized omental flap was wrapped around the autotransplanted trachea. In the other 3 pigs (group B), the omentum was not used. Eight of 9 group A pigs were killed, 1 or 2 months later, having had no signs of airway obstruction; the 9th pig was killed after 14 days because of airway obstruction. The 3 pigs in group B were killed after 11 to 13 days because of progressive respiratory obstruction. In the 8 asymptomatic pigs in group A, the omental flap was viable and tracheal growth was normal with no differences in diameter between normal and autotransplanted trachea. Histologically intact cartilage was lined with respiratory epithelium. In the one group A pig who was killed early, the omental flap was necrotic. In this pig and in the 3 group B animals, extensive tracheal necrosis and nonviable cartilage were observed. These findings indicate that in the pig, a 6-ring segment of trachea can be transplanted with vascularization provided by an omental flap.     

Effect of omental, intercostal, and internal mammary artery pedicle wraps on bronchial healing

Bronchial transection and devascularization is necessary in the course of sleeve resection or lung transplantation, leaving distal bronchial segments ischemic and subject to stricture or dehiscence. Thirty mongrel dogs underwent left lung autotransplantation. The bronchial anastomosis was wrapped with omentum (n = 9), intercostal muscle pedicle (n = 9), or internal mammary artery pedicle grafts (n = 6). Six control animals underwent bronchial anastomosis without an external wrap. Bronchial revascularization by capillary ingrowth from the pedicle to the bronchial submucosal plexus was demonstrated with all three types of vascular pedicle grafts; however, more consistent and confluent vascular ingrowth was provided by internal mammary artery pedicle grafts. Additionally, the bronchial anastomotic cross-sectional area was significantly better in the internal mammary artery group (84.5 +/- 3.3) as compared with that of the omental (68.4 +/- 8.3), intercostal muscle (66.9 +/- 10.9), or control groups (70.2 +/- 7.6). An internal mammary artery pedicle graft and the presence of dense confluent submucosal vascular ingrowth from any pedicle graft were independently predictive (p less than 0.05) of minimizing bronchial anastomotic narrowing. These data are consistent with previous findings suggesting that omental and intercostal muscle pedicle grafts promote early bronchial revascularization; moreover, the data demonstrate the superiority of an internal mammary artery pedicle graft to provide submucosal vascular ingrowth and to minimize anastomotic stenosis.     

Experimental tracheal transplantation using a cryopreserved aortic allograft

BACKGROUND: The tracheal reconstruction after wide resections remains a critical surgical problem. Our aim was to replace trachea with a tissue easy to vascularize, which allows a simple reconstruction and does not require an immunosuppressive regimen. MATERIALS AND METHODS: A segment of cryopreserved aorta was used in order to verify its adequacy as tracheal substitute. In phase 1, the thoracic aorta of 10 rabbits was excised, obtaining 20 segments that were cryopreserved. Ten segments were implanted in the omentum of 10 rabbits that were sacrificed on postoperative days 7, 14 and 21, and the grafts were examined histologically. In phase 2, a segment of cryopreserved aorta arranged with a silicone prosthesis was transplanted in 10 rabbits and wrapped with omentum. The animals were sacrificed on postoperative days 7, 14 and 21. RESULTS: In phase 1, the neovascularization of the grafts was present after 7 days, and after 14 days the fibroblasts invaded the lumen of the aorta. In phase 2, 8 rabbits survived and the histologic examination after 7, 14 and 21 days showed neovascularization, the absence of rejection and the proliferation of fibroblasts inside the lumen of the aorta; this growth has been restrained by an endoluminal prosthesis. CONCLUSIONS: Our study demonstrated that replacing the trachea with cryopreserved aorta is technically feasible and does not evoke immunologic reactions. It requires, however, a silicone tube inside the allograft to limit the colonization of fibroblasts.     

Failure of airway healing in an ovine autotransplantation model that includes basic fibroblast growth factor

OBJECTIVE: Basic fibroblast growth factor is among the most potent promoters of angiogenesis. Its ability to enhance the blood supply to ischemic airways or nonvascularized tracheal autograft has been demonstrated. Its cumulative effect with muscular wrapping and its efficacy in a noncanine large animal model remain unknown. Treatment with basic fibroblast growth factor and muscular wrapping were compared with no special treatment and with muscular wrapping alone in an ovine tracheal autotransplantation model. METHODS: All sheep underwent orthotopic tracheal transplantation with 5 to 8 ring autografts in the cervical trachea. Fifteen sheep were classified randomly into the following three groups: no treatment (group A, n = 5), muscular wrapping with the right sternomastoid muscle (group B, n = 5), and topical administration of fibrin glue enriched with 2 microg/cm(2) basic fibroblast growth factor (group C, n = 5). RESULTS: Devascularized tracheal autografts were unable to maintain their structural integrity without other treatment (group A). However, the grafts were surrounded by well-vascularized connective tissue. In the muscular wrapping group (group B), infections occurred around the grafts, and the muscular wrapping was subject to necrosis. No neovascularization of the grafts occurred. Therapy with basic fibroblast growth factor (group C) led to improved muscular wrapping circulation and to adherence to the tracheal stumps. However, no success was achieved in validating the circulation in the grafts. CONCLUSIONS: In contrast to the results achieved by other authors with canine models, the neovascularization of tracheal autografts was not achieved in sheep with the topical administration of basic fibroblast growth factor. Cranially pediculated muscular wrapping led to poorer circulation in the tissue around the graft than did no therapy at all.