Tracheal allotransplantation in beagle dogs without immunosuppressants

BACKGROUND: The antigenicity of tracheal grafts is still unclear. We investigated the possibility of performing tracheal allotransplantation without immunosuppressants. METHODS: Intrathoracic five-ring tracheal replacements were performed in beagle dogs without immunosuppressants (n = 18). The dogs were divided into 9 pairs, and grafts were exchanged within the pairs. In group 1 (n = 6), the paired dogs were blood relatives, whereas in group 2 (n = 12), the paired dogs were not related. Full-thickness skin transplantation was also performed in both groups. RESULTS: In group 1, 5 animals survived uneventfully for more than 3 months. No stenosis was observed in any of the dogs. In group 2, the grafts were incorporated by the host trachea in 2 dogs. Four animals died of airway obstruction within 3 months. Moderate or slight airway stenosis was observed in 6 dogs. Rejection was confirmed by histologic examination. In both groups, all of the skin allografts were destroyed within 2 weeks. CONCLUSIONS: After tracheal allotransplantation, long-term survival was achieved, especially in recipient dogs that were blood relatives of donors. We conclude that it is possible to perform tracheal allotransplantation using histocompatible matched grafts without immunosuppressants.     

Revascularization of canine cryopreserved tracheal allografts

Background. We examined the blood supply of a cryopreserved tracheal allograft and its morphohistologic changes after transplantation.

Methods. In each of 22 dogs, a five-ring tracheal segment was replaced by one of the following tracheal grafts: fresh autografts (n = 8), cryopreserved tracheal allografts (n = 8), or fresh allografts (n = 6). The cryopreserved tracheal allografts were preserved at −196°C for 60 days. No immunosuppressant was given to any of the animals. All grafts were retrieved at 1 and 12 weeks and assessed by microangiography and histology.

Results. The epithelial denudation and the revascularization of the transverse intercartilaginous arteries were recognized within 7 days as common to each of the three types of grafts. In the cryopreserved tracheal allografts, neither cartilage degradation nor graft shrinkage occurred at 7 days. However, the recanalized transverse intercartilaginous arteries completely disappeared at 12 weeks, and marked shrinkage occurred; the cartilage cells were accompanied by karyolysis and were significantly decreased in number (p < 0.05). Recanalization of the transverse intercartilaginous arteries was also demonstrated in the fresh allografts; however, necrosis abruptly occurred as a result of acute rejection responses.

Conclusions. Cryopreservation of a tracheal allograft provided sufficient reduction of the acute rejection responses, and blood supply to the cryopreserved tracheal allograft was established through the recanalized transverse intercartilaginous arteries within 7 days; however, subsequent chronic rejection responses resulted in occlusion of the transverse intercartilaginous arteries and atrophy.     

供体犬移植段气管的最佳获取时间

目的 探讨热缺血对移植体存活的影响，寻求获取供体气管的可靠时间。方法 选用杂种犬进行同种异体气管移植。供犬处死后经过不同热缺血时间取出气管，TUNEL法检测软骨细胞凋亡。各移植体植入受犬的气管原位及腹腔大网膜内，4周后处死取材。行病理学检查。并比较各组移植体软骨细胞存活率。结果 随着热缺血时间的延长，移植体软骨细胞凋亡数逐渐增加，移植后软骨结构破坏加重。并且相同热缺血期移植体，异位移植较原位移植结构保持好。结论 气管移植体对热缺血有较好的耐受，但是长时间的热缺血仍会给气管移植体带来损害。     

Obliterative airway disease and graft stenting in pig-to-dog tracheal xenotransplantation

OBJECTIVE: Obliterative airway disease occurring in concordant tracheal xenografts in rodent models is histologically similar to obliterative bronchiolitis in human lung allografts. We studied whether obliterative airway disease would occur in a large animal-discordant model. METHODS: Pig and dog tracheas were cryopreserved for 7 to 14 days, and 18 recipient dogs given splenectomy 7 days before transplantation, then seven tracheal rings were removed and a corresponding five-ring donor tracheal segment was transplanted to the excised site. Grafts were wrapped with pedicled omentum and inmmunosuppression was conducted with tacrolimus or deoxyspergualin. Graft status was observed by bronchoscopy. Dogs were classified into three groups. Group 1 consisted of dog-to-dog allotransplantation animals (control group, n = 5), Group 2 of pig-to-dog xenotransplantation animals (n = 8), and Group 3 of pig-dog xenotransplantation animals who also underwent graft stenting immediately after transplantation (n = 5). RESULTS: Grafts healed well in 4 of 5 Group 1 dogs. Tracheal stricture began on day 5 post transplantation and the lumen was obstructed by fibrosis by days 8 to 14 in all Group 2 dogs. All Group 3 dogs remained in good respiratory status until death. CONCLUSION: Obliterative airway disease developed quickly in pig-to-dog discordant tracheal xenografts. Graft stenting is a feasible treatment for managing of tracheal obstruction.     

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.     

Acceptable warm ischemia time of tracheal grafts from non-heart-beating donors in rats

Objectives

Warm ischemia (WI)-induced airway complications are common in clinical lung transplantation. However, the acceptable WI time of tracheal grafts from non–heart-beating donors (NHBDs) is unknown. The purpose of this study was to determine the acceptable WI time by observing tracheal epithelial regeneration among NHBD.

Method

Forty-eight rats were randomly divided into four groups (each with 12 rats): WI-0 minutes (group A), WI-30 minutes (group B), WI-45 minutes (group C), and WI-60 minutes (group D). In each group, the tracheas from 6 rats were imbedded in the greater omentum of 6 other rats. Fourteen days later, the transplanted trachea was obtained from the recipient to evaluate epithelial thickness and regeneration. Six tracheas were obtained from living donors as a control group.

Results

There were no significant differences in tracheal transplantation time (mean, 17.66 ± 1.21 minutes). There were no significant differences in epithelial thickness and regeneration between the controls and groups A, B, and C (P < .05). Group D showed no normal epithelial structure of the trachea only with monolayer cells.

Conclusions

The time limits of tolerance to WI of tracheal grafts from NHBDs may be 45 minutes.     

Tracheal allotransplantation maintaining cartilage viability with long-term cryopreserved allografts

BACKGROUND: Cartilage viability of a cryopreserved tracheal allograft seems to affect graft function and durability. We previously reported the influence of warm ischemia and cryopreservation on cartilage viability of tracheal allografts. For the clinical application of tracheal allotransplantation, it is essential to preserve grafts for a long time. In this study, we assessed cartilage viability of tracheal allografts after long-term cryopreservation in transplantation models. METHODS: The tracheas were harvested from Lewis rats. The grafts were frozen to -80 degrees C in a programmable freezer immediately after being harvested and were then stored in liquid nitrogen (-196 degrees C) for different lengths of preservation (1, 2, 6, 9, 12, 18, and 24 months; n for each group = 8). Cartilage viability was evaluated by estimating proteoglycan synthesis. After harvest or thawing of the tracheas, the cartilage was labeled with 4 muCi/mL of Na2 35SO4. Specimens were then hydrolyzed in 0.5 mol/L NaOH, and a solution of the extracts was then counted by a liquid scintillation counter. 35Sulfur incorporation before and after cryopreservation was examined in each group. Tracheal allotransplantation was performed using Lewis rats as donors and Brown Norway rats as recipients. RESULTS: The average 35S incorporation in the cartilage before cryopreservation was 224 +/- 17 disintegrations per minute per milligram of tissue protein. The average 35S incorporation in the cartilage after cryopreservation decreased to 67% to 76% compared with that before cryopreservation. There were no significant differences among the groups in 35S incorporations after cryopreservation. Histologic examination after transplantation revealed normal tracheal cartilage in all groups. CONCLUSIONS: The viability of tracheal cartilage after cryopreservation decreased to 67% to 76%. There were no significant differences in viability of cartilage among the tracheas after different lengths of cryopreservation. Tracheal allotransplantation after long-term cryopreservation can be safely performed in the rat model.     

Epithelial re-growth is associated with inhibition of obliterative airway disease in orthotopic tracheal allografts in non-immunosuppressed rats

BACKGROUND: Because epithelial cells are targets of alloimmune injury leading ultimately to airway obliteration, we tested whether epithelial re-growth could prevent obliterative airway disease (OAD) in orthotopic tracheal allografts. METHODS: Brown Norway tracheal segments were orthotopically transplanted into nonimmunosuppressed Lewis rats. Allografts were removed on days 2-10 (n=13), 30 (n=4), and 60 (n=5) for histology, computerized morphometry (obliteration), and immunohistochemical detection of mononuclear cells, smooth muscle alpha-actin, and tissue phenotype. Normal tracheas, host tracheas, and heterotopically transplanted allografts served as controls. RESULTS: Orthotopic allografts removed on days 2-10 exhibited epithelial damage and re-growth and mononuclear cell infiltration. On days 30 and 60, partially ciliated cuboidal or attenuated epithelium completely covered the lumen. Although mononuclear cells declined, numerous T cells with a high CD4/CD8 ratio were found in the epithelium till day 60. Orthotopic allograft epithelium expressed donor phenotype on day 7, but recipient phenotype on days 30 and 60. Despite subepithelial alpha-actin positive myofibroblast proliferation, obliteration did not progress from day 7 to 30 and 60 (35, 30, and 33%, respectively). Although more than in normal or host tracheas, the obliteration in orthotopic allografts on days 30 and 60 was significantly less (P<0.001) than in heterotopic allografts. CONCLUSIONS: We describe, for the first time, longterm patency of fully histoincompatible orthotopic tracheal allografts in nonimmunosuppressed rats. Despite acute alloimmune injury and induction of myofibroblast proliferation, epithelial re-growth from the host limited the progression of OAD, thus emphasizing the role of epithelium in the control of airway obliteration.     

异体气管移植去抗原性的实验研究

目的探讨移植段气管去除上皮细胞和腺体细胞后异体、异位移植排斥反应的强弱。方法25只雄性SD大鼠作为供体,制备新鲜移植段气管、冷冻移植段气管和去上皮细胞移植段气管。取制备的新鲜移植段气管40个平均分为4组,分别用0、0.1、0.3和0.5mg/ml的蛋白酶溶液,4℃浸泡12h,根据镜下移植段气管上皮细胞和腺体细胞脱落情况及软骨细胞破坏程度确定蛋白酶的最佳浓度。另取30只雄性SD大鼠作受体,均分成3组,分别为:新鲜气管移植组(A组)、冷冻气管移植组(B组)及去上皮细胞移植组(C组),n=10。行左上腹旁正中切口,提出大网膜包绕各移植段气管,于21d后取出移植段气管,行组织学观察及淋巴细胞浸润测定。结果0.3mg/ml蛋白酶能去除移植段气管上皮细胞及腺体细胞,而对软骨细胞无明显损坏。异体植入大鼠腹腔的3组气管软骨均成活,血运建立,其中A组管腔内有肉芽组织,出现坏死、实变;B组有少量肉芽组织;C组管腔内无肉芽组织。A、B、C3组淋巴细胞浸润分别为29.16±2.69、15.17±2.19和11.56±0.87个/Hp,A组与B、C组比较及B组与C组比较,差异均有统计学意义(P<0.05),排斥反应强弱为:A组>B组>C组。结论0.3mg/ml蛋白酶,4℃,浸泡12h的移植段气管,能完全脱上皮细胞和腺体,对软骨细胞基本无损伤,与冷冻法比较去抗原作用更好。一期异体大网膜包裹异位移植后,血运重建且移植段气管成活。     

Induction of Unresponsiveness to Major Transplantable Organs in Adult Mammals: A Recapitulation of Ontogeny by Irradiation and Bone Marrow Replacement

Transplantation of renal allografts obtained from prospectively selected genotypically DLA-identical donors into supralethally irradiated dogs reconstituted with their own stored bone marrow has produced a state of unresponsiveness to these kidneys in the recipients. Eleven of 18 kidneys transplanted at 12 hours after marrow replacement currently survive with normal function and maintain life in the recipients for 757, 800, 825, 978, 1062, 1092, 1136, 1282, 1373, 1380, and 1381 days, respectively. Similar results occurred in eight of 13 allografts transplanted at 28 hours after marrow replacement, which currently survive for 349, 363, 377, 407,436,470, 485, and 513 days, respectively, and in eight of 13 kidneys grafted at 36 hours after marrow replacement, which are surviving for 197, 247, 298, 324, 337, 396, 443, and 472 days, respectively. Achievement of optimal results is dependent on the specific timing and sequence of each procedure. Only four of 16 recipients of kidneys transplanted at the time of marrow replacement were unresponsive to their allografts. Similarly, only five of 19 recipients of kidneys placed in irradiated dogs at 40 hours before marrow replacement accepted such allografts. When kidney transplants were placed into the recipients 20 hours before removal of marrow, irradiation, and reconstitution with stored marrow, only three of 21 dogs became unresponsive to such ailografts. In five of 12 instances, the recipients were also unresponsive to skin allografts obtained from their respective kidney donors. Such skin grafts currently survive for 606, 673, 687, 701, and 708 days, respectively. The remaining seven skin grafts were rejected at 28, 39,42, 84, 90, 92, and 115 days, respectively. Second- and third-set skin grafts from the same kidney donor were rejected by six of these dogs at 19, 20, 21, 29, 29, and 30 days, and at 21, 22, 23, 24, 27, and 27 days, respectively. Rejection of these skin grafts had no detectable effect on the function and survival of kidney allografts from the same source. Seven of eight skin grafts obtained from other DLA-identical donors were rejected at 13,14,16,25,28,38, and 84 days, respectively; one allograft continues to survive for 708 days. Eleven DLA-incompatible skin allografts placed on the recipients at the same time were rejected within 11-20 days. Supralethal total body irradiation and bone marrow replacement can establish in the adult canine host a privileged phase of immunological reactivity during which exposure to alloantigens produces specific long-term unresponsiveness rather than sensitization. The use of stored autologous rather than allogeneic bone marrow for reconstitution of the irradiated recipient eliminates the hazards of GVH complication usually associated with this procedure. This consideration and the apparent capacity of the tolerant host to maintain a long-term state of unresponsiveness without any further immunosuppressive therapy point to the potential relevance of the results to human transplantation.     

Techniques for experimental heterotopic and orthotopic tracheal transplantations - When to use which model?

BACKGROUND: Different animal models have been developed to study the pathogenesis and treatment of obliterative airway disease (OAD). Here we describe the techniques of heterotopic and orthotopic tracheal transplantations in the rat, comparing the kinetics of systemic host immune response and of histopathologic OAD development. METHODS: Heterotopic and orthotopic tracheal transplantations were performed in both allogeneic (Brown Norway-to-Lewis) and syngeneic (Lewis-to-Lewis) models. Grafts were harvested after 7, 30, and 60 days post-transplant for histologic evaluation and analysis of host cellular and humoral response. RESULTS: Syngeneic tracheal grafts did not develop luminal obliteration and were morphologically indistinguishable from native tracheas. In heterotopic allografts, airway epithelium was rapidly destroyed and OAD progressed with complete luminal occlusion by 30 days. Orthotopic allografts showed enhanced early infiltration (1298+/-45 vs. 674+/-75 cells/high power field, p<0.001) with concomitant greater day 7 luminal narrowing (45+/-6% vs. 14+/-3%, p<0.001). In this model, donor-type BN epithelium (62+/-17%, 21+/-19%, and 1+/-1% on days 7, 30, and 60) was gradually replaced by recipient-type epithelial cells (2+/-4%, 70+/-22%, and 98+/-2%). OAD developed with circular orientation of cells and connective tissue fibers to 45+/-6% obliteration by day 60. Cellular host response, as determined by IFN-gamma-ELISPOT assay (548+/-132 vs. 402+/-197 spots, p=0.046) and anti-donor alloreactive IgM antibody production (2827+/-148 vs. 1565+/-393 mean channel fluorescence, p<0.001) were significantly stronger in rats bearing orthotopic vs. heterotopic allografts. CONCLUSIONS: The orthotopic tracheal transplantation model may be more representative of OAD found in human lung transplant recipients and we therefore encourage the wider use of this model.     

Cryopreserved, irradiated tracheal homograft transplantation for laryngotracheal reconstruction in human beings

Subglottic tracheal stenosis is a common clinical entity. Management in severe cases is often problematic. Various techniques for tracheal replacement have been used with varying degrees of success. In this study we used cryopreserved, irradiated tracheal homografts, the use of which in human beings has not been reported previously. In a sterile setup, the tracheas were harvested from donor cadavers within 24 hours of death. The grafts were initially kept at 57 degrees C for 20 minutes; they were then placed in a -70 degrees C chamber for another 2 to 3 days or more and were irradiated to 25 kGy (2.5 million rad). Finally, the grafts were stored at -70 degrees C until usage. Seven patients underwent the surgery, but only 4 are presented here. In the remaining 3 patients, the follow-up time was too short to be evaluated. Four patients, 2 male and 2 female (aged 2-40 years, mean 16 years), with severe subglottic tracheal stenosis underwent segmental tracheal graft reconstruction. Immunosuppressant medications were not given to any patient. Follow-up ranged from 18 to 20 months. Three patients successfully underwent decannulation, and 1 patient had local infection and dislodgment of the intraluminal stent with subsequent restenosis. The postoperative tracheal lumen appeared to be near normal, with histologic evidence of normal respiratory epithelium at the grafted site. In conclusion, cryopreserved, irradiated tracheal homograft transplantation is a valuable alternative for subglottic tracheal reconstruction.     

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)     

Late treatment with angiotensin-converting enzyme inhibitors plus endothelin receptor antagonists ameliorates rat tracheal allograft rejection.

Inhibition of the renin-angiotensin and endothelin (ET) systems prevents the development of obliterative airway disease (OAD) in rat tracheal allografts. In this study, we assessed whether these therapeutic approaches are effective even when the same were started after signs of OAD were already manifest. Rat tracheas were heterotopically transplanted from Brown-Norway donors into Brown-Norway or Lewis recipients. Allograft recipients received bosentan, ramipril, bosentan plus ramipril or vehicle from day 10 to 24. Untreated allografts and isografts were harvested at day 10 or 24. In tracheal grafts, morphometric studies together with molecular analysis by real-time PCR were performed. Fibroproliferative process in untreated tracheal allografts but not in isografts started already at day 10. Neither bosentan nor ramipril treatment alone as monotherapy could modify the development of OAD when administered only between day 10 and day 24. By contrast, the combination treatment of bosentan and ramipril ameliorated airway obstruction by day 24, which was accompanied by reduced mRNA expression of intragraft transforming growth factor-beta1 and platelet-derived growth factor-A and -B chains. Only the combined blockade with angiotensin-converting enzyme inhibitors and ET receptor antagonists can reduce the progression of OAD in this model if the treatment is initiated late in the disease course.     

供体犬移植段气管的最佳获取时间研究

目的 探讨尸体气管移植中热缺血对移植体存活的影响,寻求获取尸体气管的可靠时间。方法 选用杂种犬进行同种异体气管移植。供犬处死后经过不同热缺血时间取出气管,TUNEL法检测软骨细胞凋亡。各移植体植入受者犬的气管原位及腹腔大网膜内。4周后处死取材,行病理学检查,并比较各组移植体软骨细胞存活率。结果 随着热缺血时间的延长,移植体软骨细胞凋亡数逐渐增加,移植后软骨结构破坏加重,软骨细胞存活率逐渐降低。并且相同热缺血期移植体,异位移植较原位移植结构保持好。结论 气管移植体对热缺血有较好的耐受,但是长时间的热缺血仍会给气管移植体带来损害,二期手术可能更有利于尸体气管移植。     

Successful tracheal transplantation using cryopreserved allografts in a rat model.

OBJECTIVES: The purpose of this study was to determine the appropriate cryopreservation period of tracheal allografts based on morphological and immunological findings and to test the possibility of tracheal transplantation in rats using cryopreserved allografts without immunosuppression. METHODS: Morphological and immunological studies were performed to compare the differences between non-cryopreserved grafts and cryopreserved grafts. Orthotopic tracheal transplantation using cryopreserved allografts, non-cryopreserved allografts, and non-cryopreserved autografts was performed and the rejection score of each group was evaluated. RESULTS: Epithelial cells were lost when the grafts were cryopreserved for more than 20 days. Immunohistochemical staining of the trachea revealed that the MHC classII antigen was expressed on normal epithelium. These findings suggest that cryopreservation for more than 20 days decreased the antigeneicity of allografts because of epithelial desquamation. All rats that received allografts cryopreserved for more than 20 days survived until the scheduled sacrifice day. Microscopically, cryopreserved allografts that had been preserved for more than 20 days had a significantly lower rejection score than that of non-cryopreserved allografts (P < 0.05). CONCLUSIONS: We conclude that the appropriate period for cryopreservation of allografts would be 20 days or more, because cryopreservation for more than 20 days depleted epithelium, which possessed the MHC classII antigen. Therefore, a longer period of cryopreservation decreases the antigeneicity of allografts. Rat tracheal transplantations using cryopreserved allografts is possible without immunosuppression when the grafts have been cryopreserved for more than 20 days.     

Tracheal intubation with a camera embedded in the tube tip (Vivasight™)

We studied tracheal intubation in manikins and patients with a camera embedded in the tip of the tracheal tube (Vivasight^?). Four people in two teams and two individuals attempted intubation of a manikin through an i‐gel^? 10 times each. The tracheas of 12 patients with a Mallampati grade of 1 were intubated with a Vivasight tracheal tube through a Berman airway, passed over a Frova^? introducer. All 60 manikin intubations were successful, taking a mean (SD) time of 1.4 (0.5) s. The fastest intubation was performed in 0.5 s. All 12 participants’ tracheas were successfully intubated in a median (IQR [range]) time of 90 (70–120 [50–210]) s. Seven participants complained of a sore throat, comparable with earlier findings for standard laryngoscopy and intubation: five mild; one moderate; and one severe. Tracheal intubation with the Vivasight through the i‐gel or Berman airway is an alternative to existing techniques, against which it should be compared in randomised controlled trials in human participants. It has potential as a fast airway rescue technique.     

颈部肌肉联合瓣包裹自体气管游离移植的实验研究

目的 研究肌肉瓣在再植气管重建血运中的作用。方法 实验用犬32只,采用单侧胸头肌瓣和双侧胸骨舌骨肌－胸骨甲状肌联合瓣包裹不同长度的气管段,以及不同肌肉瓣包裹5个环的气管段,分别行自体气管游离移植。术后通过纤维支气管镜检查、粘膜血流量的测定、病理学检查、血管造影以及存活率和通畅度的计算,研究各组犬的存活情况。结果 有肌肉瓣包裹组中,短于4cm的再植气管术后第1周时粘膜充血水肿,易出血;激光多普勒血流仪测到粘膜下有血流存在,粘膜血流量达到正常的60％,其在近吻合口和中间部位无明显差别;造影显示有密集的血管从肌肉瓣长入再植气管;病理检查其结构完整,管腔内为假复层柱状纤毛上皮所覆盖,软骨无变性坏死;再植气管均能长期存活。但长于4cm的再植气管术后第1周时9只犬有6只的中间段粘膜呈苍白或灰黑色,近吻合口处粘膜充血水肿,易出血;中间部位的粘膜血流量明显低于近吻合口处;7只犬再植气管的中间段管塌陷或肉芽组织增生。无肌肉瓣包裹组再植气管的粘膜在术后第1周时即呈黑色,5只犬有4只无法检测到粘膜血流,实验只犬随后因再植气管坏死而死亡。结论 单侧胸头肌瓣和双侧胸骨舌骨肌－胸骨甲状肌联合瓣包裹可以维持短于4cm再植气管的长期存活。     

Evaluation of Antigenicity of Components of Tracheal Allotransplant and Effect of Immunosuppressant Regime in a Rodent Model

Background  Tracheal transplantation seems to be the logical step in the process of reconstruction of the trachea following a long-segment resection, which is usually done to treat malignant disease or benign stenosis of the airway caused by a traumatic, congenital, inflammatory, or iatrogenic lesion. Immunosuppression following transplant is essential but not ideal after oncoresection. Methods  The tracheal allografts, harvested from Sprague Dawley rats, were implanted in the Wistar strain rat. The harvested tracheal grafts were divided into groups and subgroups, based on the layers of trachea, method of decellularization, and immunosuppression. The antigenicity of different layers of trachea and the effect of various decellularization methods were studied within three time frames, that is, day 3, 9, and 15. Result  On structural analysis, the day 3 and day 15 samples showed no meaningful comparison could be made, due to extensive neutrophil infiltration in all three layers. The day 9 tracheal grafts showed loss of epithelium, with no signs of regeneration in most of the allografts. The subepithelial lymphoid infiltration was found to be severe in nonimmunosuppressed allografts. The group in which both inner and outer layers were removed showed moderate-to-severe infiltrate of lymphoid cells in all the allografts, but there was no cartilage loss, irrespective of the method of decellularization. The irradiated specimens retained the cartilage but showed extensive ischemic damage. Conclusion  Rat trachea is a good model for tracheal transplant research but not adequately sturdy to sustain mechanical debridement. Irradiation and chemical decellularization eliminates the immune response but causes intense ischemic damage. Out of the three time frames, day 9 seemed to be the best to study the immune response. To substantiate the results obtained in this study, the immunohistochemical study of the allografts is needed to be performed among a larger group of animals.     

A comparison of antibiotic-sterilized, stent-mounted pulmonary and aortic valve allografts in the mitral region of dogs

Monro, J. L., Gavin, J. B., and Barratt-Boyes, B. G. (1974).Thorax, 29, 323-328. A comparison of antibiotic-sterilized, stent-mounted pulmonary and aortic valve allografts in the mitral region of dogs. The mitral valves of 40 dogs were replaced with antibiotic-sterilized, stent-mounted semilunar valve allografts. Twenty grafts were pulmonary valves and 20 were aortic valves. Six dogs in each group died from causes related to the operation. All remaining dogs with pulmonary valve grafts died of causes related to the allograft itself (vegetative endocarditis (5), peripheral leak (1), cusp rupture (4), cusp shrinkage (4)). In the aortic valve group there were seven deaths from allograft endocarditis and one from a peripheral leak, but six dogs had competent allografts when sacrificed up to 12 months after surgery. It is concluded that the inherent strength and bulk of the aortic valve cusps make this valve a more suitable mitral valve replacement than the more delicate pulmonary valves.