Collagens I and III in a porcine bronchial model of obliterative bronchiolitis.

The main extracellular matrix components of the lung, type I and III collagens, were studied in chronic allograft rejection developing in a porcine heterotopic bronchial transplantation model. Specific porcine complementary DNA probes were constructed for detection of the expression of type I and III procollagen messenger RNAs in the bronchial wall structures and in the obliterative plug by in situ hybridization. In autografts, and in allografts immunosuppressed with 40-O-(2-hydroxyethyl)-rapamycin, cyclosporine A, and methylprednisolone, no histological changes of obliterative bronchiolitis (OB) developed, and the number of fibroblast-like cells expressing type I and III procollagen mRNA remained low. In nontreated allografts obliterating within 21 d, a preponderance of fibroblast-like cells showing positivity for type III procollagen mRNA existed in the obliterative plug and bronchial wall. This study shows for the first time the temporal and spatial activation of type I and III procollagen genes during the course of obliterative bronchiolitis. The number of cells expressing procollagen III mRNA increased parallel to developing obliteration and fibrosis in nontreated allografts, whereas autografts and immunosuppressed allografts exhibited no such trend. This finding suggests a positive association between type III collagen mRNA expression in fibroblast-like cells and development of obliterative bronchiolitis.

Immune cells and immunosuppression in a porcine bronchial model of obliterative bronchiolitis.

BACKGROUND: To study obliterative bronchiolitis (OB), we have developed a porcine heterotopic bronchial model. Allografts obliterate within 3 weeks, the immunosuppression cyclosporine (CsA)-azathioprine (AZA)-methylprednisolone (MP) delays OB, but OB is prevented when AZA is switched to 40-0-(2-hydroxyethyl)-rapamycin (RAD). To characterize our model, we studied immune cells under various immunosuppressive conditions. METHODS: The groups studied were autografts (U), allografts (A), and allografts given either CsA-RAD-MP (R), or CsA-AZA-MP (C). The implants were harvested at 3, 7, 10, 14, 21, 30, 60, and 90 days after transplantation. Epithelial damage and obliteration were graded histologically, and the number of CD4, CD8, MHC class II expressing cells, macrophages, and B lymphocytes were counted (mean+SEM)/high-power visual field. RESULTS: In group U, normal epithelium was regained with no obliteration and only few immune cells. In group A, consistent with initially acute ejection, an influx of CD4 (105+23), CD8 (166+23), and class II (92+20) cells was seen up to day 21, when total obliteration preceded by epithelial destruction had already developed. Some macrophages were seen and B cells were scarce. In group R, epithelial damage and obliteration were insignificant, but moderate numbers of CD4, CD8, and class II cells were seen. In group C, epithelial damage and obliteration were only delayed, but the immune cell response was clearly blunted. CONCLUSIONS: In our model, rejection with significant immune cell influx was still active when obliteration was total in nontreated allografts. In immunosuppressed allografts, decrease in the number of immune cells alone did prevent OB. These results support OB being T-cell mediated. RAD may have additional important effects on growth factors and proliferation in prevention of OB.

Biodegradation of the copolymeric polylactide stent. Long-term follow-up in a rabbit aorta model.

The behavior of biodegradable polylactide as a stent material has not yet been fully established in small vessels such as arteries with a diameter <3 mm. The aim of this study was to investigate the long-term effect of a copolymeric polylactide (PLA96) stent. Appropriately sized spiral PLA96 stents were implanted into the infrarenal aortas of 20 rabbits. Intraoperative systemic heparinization (150 IU/kg), perioperative subcutaneous enoxaheparin sodium (10 mg), ticlopidine (250 mg/day) for 1 month, and acetosalicylic acid (12.5 mg/day) were continuously administered. Animals were euthanized according to a fixed timetable for up to 34 months for histologic and scanning-electron-microscopic assessment. Endothelialization was complete within 1 month. In 2 of the 3 aortas sampled 3 months after implantation, a mild inflammatory reaction was visible, with no sign of granulomatous or foreign-body reaction in the vessel wall. Instead, in 1 sample examined at the same time point, neointimal chondroid metaplasia was detected. After 6 months, inflammatory reaction declined in the vessel wall. Hydrolyzation of the stent was histologically evident at 12 months, with mild foreign-body reaction detectable in 2 of 5 aortas sampled at this time point. The stent disintegrated without fragmentation by 24 months, as it was gradually replaced by fibrosis. The vessel lumen remained patent at all time points. We conclude that the PLA96 stent degraded with minimal tissue response within 24 months. PLA96 may thus be a promising stent core material for small vessels in the future, although further investigation is needed to establish its final biocompatibility.

Obliterative lesions in a heterotopic bronchial xenograft model--a preliminary study.

BACKGROUND: We further developed our heterotopic pig model of obliterative bronchiolitis to study airway obliteration in xenografts. METHODS: Four domestic piglets each received 40 bronchial xenografts s.c. from a donor lamb. Piglet X was not immunosuppressed. The other animals received daily oral cyclosporine, 15 mg/kg (XC), or SDZ RAD, 1.5 mg/kg (XR), or both (XCR). Five implants at a time were serially removed from each animal during 17 days for histological assessment. RESULTS: In contrast to the grafts of the others, the xenografts of XCR recovered after initial ischemic damage. No epithelial damage (P<0.01) or mural necrosis occurred on day 7. Airway obliteration developed in all, but was significantly delayed in XCR. CONCLUSIONS: Invariably developing airway obliteration in nontreated xenografts was delayed by immunosuppression, making the model useful, especially in testing the efficacy of immunosuppressive drugs in a xenogeneic system.

Prevention of small airway obliteration in a swine heterotopic lung allograft model.

BACKGROUND: In our swine model of obliterative bronchiolitis preventing obliteration by the standard immunosuppression with cyclosporine, methylprednisolone, and azathioprine was not successful. The purpose of this study was to test the ability of a new immunosuppressive regimen to prevent alloimmune reaction and obliteration of the allografts. This regimen includes the novel macrolide SDZ RAD, i.e., 40-O-(2hydroxyethyl)-rapamycin. METHODS: Donor lung allografts of 1 cm3 were implanted sub-cutaneously into 11 random-bred non-related domestic pigs receiving daily oral cyclosporine (10 mg/kg) and methylprednisolone (20 mg). In addition, the animals received either oral azathioprine (2 mg/kg) (Group 1) or oral SDZ RAD (1.5 mg/kg) (Group 2). Histologic alterations were graded from 0 to 3 based on repeatedly removed implants during a follow-up period of 3 months. RESULTS: Total epithelial destruction and permanent luminal obliteration occurred within 37 days in Group 1. After an initial grade of 2.3+/-0.3 destruction, epithelial recovery was evident in Group 2 (P < 0.01), and the bronchi stayed patent. Cartilaginous destruction was milder in Group 2 (P < 0.05) than in Group 1, but chondrocytic proliferation was more intense (P < 0.05). Alveolar tissue and native structures of the bronchial wall were destroyed in Group 1, but preserved in Group 2 with total recovery after a mild-grade initial necrosis. CONCLUSIONS: Unlike the standard triple therapy, SDZ RAD combined with cyclosporine and methylprednisolone preserves the pulmonary allografts and prevents epithelial destruction and subsequent luminal obliteration. This suggests that this regimen might efficiently suppress obliterative bronchiolitis and improve long-term results in lung transplant recipients.

Alloimmune injury preceding airway obliteration in porcine heterotopic lung implants: a histologic and immunohistologic study.

BACKGROUND: Obliterative bronchiolitis (OB), the major long-term complication of lung transplantation, has thus far lacked a good large-animal model. Our goal was to develop such a model on the basis of previous rodent models with tracheal implants. METHODS: Fragments of pulmonary tissue with structures of terminal bronchi were subcutaneously transplanted to four random-bred domestic piglets. Each animal received 10 autograft and 10 allograft implants. The histologic findings were graded from 0 to 3 for implants harvested repeatedly over 2 months. RESULTS: In autografts, partial destruction of the respiratory epithelium and gradual luminal obliteration as well as mild damage to the cartilage and the bronchial wall underwent rapid reversal after initial ischemic injury. In the allografts, epithelial destruction and gradual obliteration were total within 14 days, the difference being statistically significant (P<0.05) in both. The histologic features of the obliterative plug were similar to those of human OB. In the allografts, cartilaginous destruction and pericartilaginous inflammation increased gradually to severe levels, significantly worse than in the autografts (P<0.05). Necrosis and inflammation of the bronchial wall were also more severe in the allografts (P<0.05). CONCLUSIONS: At the end of follow-up, all autografts were vital, whereas the allografts were almost totally rejected and were without native structures. All bronchi in the allografts exhibited accelerated obliteration with histologic features characteristic of human OB, thus providing a model for research into OB and its prevention.

Ceftriaxone versus vancomycin prophylaxis in cardiovascular surgery.

The efficacy of antibiotic prophylaxis in cardiac surgery was compared between 97 patients receiving a single 2 g dosage of ceftriaxone and 103 receiving 500 mg of vancomycin i.v. every 6 h for 48 h. The overall infection rate was 13.4% in the ceftriaxone and 10.7% in the vancomycin group. Four (4%) wound infections, including one mediastinitis, occurred in the ceftriaxone group and five (5%) in the vancomycin group, with no statistically significant difference. The findings of this study support the adequacy of a simple single dose of ceftriaxone prophylaxis in cardiac surgery, at least in hospitals with low incidence of vancomycin-resistant staphylococcal infections.

Small airway obliteration in a new swine heterotopic lung and bronchial allograft model.

BACKGROUND: We studied a heterotopic large-animal model with obliterative airway lesions caused by allograft rejection. METHODS: Lung fragments (1 cm3) with airways (LB), and 1 to 2 mm diameter bronchi alone (B) were implanted subcutaneously in 11 domestic piglets weighing 20 kg. Six animals each received 40 implants from nonrelated donors without immunosuppression (group A). Another 5 animals had autograft implants (group U). The implants were harvested consecutively for histologic analysis over 3 months in group A and 6 months in group U. RESULTS: In group U, the initial ischemia caused mild to moderate epithelial damage with moderate metaplasia but with a return to normal ciliary epithelium within 1 month. Transient mild luminal obliteration with granulation tissue and mononuclear cells was observed during the first weeks, but after 4 weeks the lumen was patent and filled with mucus. In the bronchial wall, moderate fibrosis developed in LB implants, whereas mild fibrosis was seen in B implants. In group A, the epithelium was totally absent by 2 weeks, and mild inflammation, fibrosis, and destruction of the cartilage with pericartilaginous mononuclear accumulation were observed in the bronchial wall. Small airways were gradually obliterated between days 7 and 21, initially by granulation tissue and mononuclear cells and later by progressive fibrosis. CONCLUSIONS: In this model, autografted airway implants stayed patent for at least 6 months, whereas total luminal obliteration histologically resembling obliterative bronchiolitis developed in allografts within 21 days. Because small airways, including bronchioli, can be transplanted with the use of this model, it may be useful for research into the causes of airway obliteration, which may be relevant to the pathogenesis of obliterative bronchiolitis in lung recipients.

Obliterative lesions in small airways in an immunosuppressed porcine heterotopic bronchial allograft model.

We have recently developed a heterotopic large-animal model for research into obliterative lesions in small airways caused by allograft rejection. In this model, the small airways of subcutaneously implanted allografts gradually obliterate, whereas autografts remain patient. Twenty lung fragments and 20 segments of bronchi were implanted in domestic pigs weighing 20 kg from non-related donors. The histology of five animals receiving daily cyclosporine A (CsA) (10 mg/kg), azathioprine (2 mg/kg) and methylprednisolone (20 mg), Group C, was compared with that of six animals without immunosuppression, Group A. Four animals received monotherapy with CsA (10 mg/kg) or methylprednisolone (3 mg/kg). The histological findings were graded from 0 to 3 on the basis of implants harvested repeatedly over 3 months. Epithelial destruction and bronchial obliteration was rapid and permanent in all the allografts. Inflammation and fibrosis of the bronchial wall was less prominent in Group C than in Group A and the onset of fibrosis was delayed. Cartilage degeneration and pericartilagineous inflammation were significantly less severe in Group C (P < 0.05). Monotherapy was less potent than triple therapy. This large-animal model is useful for studying the effects of immunosuppressive drugs on obliterative airway disease.

High-resolution CT in long-term follow-up after lung transplantation.

OBJECTIVE: Our aim was to evaluate the development of changes on high-resolution CT (HRCT) associated with chronic pulmonary rejection. MATERIALS AND METHODS: Repeated HRCT examinations were performed 140 times on 13 consecutive lung transplant recipients during a mean observation period of 26 months. The postoperative time interval to the first detection of each chronic change on CT was calculated and compared with the onset of chronic rejection. Bronchiolitis obliterans syndrome (BOS) or the histologic diagnosis of obliterative bronchiolitis was assessed by the published criteria of the International Society for Heart and Lung Transplantation. RESULTS: BOS developed in eight patients, on an average, within 11.6 (+/-5.0) months. Histologic diagnosis was available from five patients. On HRCT, among the first identifiable chronic changes were volume contraction, decreased peripheral vascular and bronchial markings, and thickening of septal lines, all of which appeared between 7 (+/-5.0) and 11 (+/-6.8) months postoperatively. The mean interval for appearance of bronchodilatation was 12.5 (+/-8.7) months. Hyperlucency and mosaic phenomenon were identified, on an average, 16 (+/-6.3) and 21 (+/-7.3) months after transplantation. CONCLUSION: On radiologic monitoring of lung recipients with HRCT, in addition to bronchodilatation. a special attention should be paid to the early chronic changes, including diminution of peripheral bronchovascular markings, thickening of septal lines, and volume reduction, which usually precede the establishment of the diagnosis of chronic rejection, whereas hyperlucency and mosaic phenomenon usually appear during more advanced BOS.

Acute rejection diagnosed with computed tomography in a porcine experimental lung transplantation model.

The role of computed tomography (CT) in the diagnosis of acute rejection was studied in an experimental lung transplantation model, with 15 left lung allotransplantations and six autotransplantations performed on piglets weighing 16-24 kg. There were 31 episodes of acute rejection. In the allotransplantation group the development of acute rejection was monitored 115 times with CT, transbronchial biopsy (TBB) and bronchoalveolar lavage (BAL). The stages of acute rejection were 1) ill-defined centrilobular micronodules or minimal patchy ground-glass opacities. 2) dense, small-nodular infiltration or extensive ground-glass opacities, and bronchial wall thickening. 3) lung volume loss and dense, patchy ground-glass opacities and 4) consolidation of the lung. In the autotransplantation group monitoring was done 42 times. After allotransplantation, TBB and BAL suggested rejection 60 times and infection 23 times. CT had 86.7% sensitivity and 85.6% specificity. During the first month these figures were, respectively, 71.4% and 84.2%. Rising histologic grade was associated with increasing stage of acute rejection on CT, which thus proved to be a sensitive and specific method for diagnosing acute rejection of lung transplant.

Detection of acute rejection by 133Xe radiospirometry after single lung transplantation in an experimental porcine model.

Aim of this experimental study was to evaluate acute rejection in a porcine single-lung transplantation model by using 133Xe radiospirometry. Left lung allotransplantation was performed on 11 and autotransplantation on 5 piglets. Postoperative monitoring consisted of 77 radiospirometric examinations with assessments of regional perfusion (Qtx), ventilation (V) and ventilation/perfusion ratio (V/Qtx). Results were compared with transbronchial biopsy. A significant decrease in Qtx (p < 0.01) and an increase in V/Qtx (p < 0.01) were observed during acute rejection, whereas V remained unaltered. These changes were significant already at minimal rejection (grade A1), and further increased at moderate rejection (grade A3). Sensitivity and specificity of Qtx were 82 and 74%, and those of V/Qtx, 87 and 65%. 133Xe radiospirometry detects even minimal acute rejection after single lung transplantation.

Value of high-resolution computed tomography in routine evaluation of lung transplantation recipients during development of bronchiolitis obliterans syndrome.

BACKGROUND: Chronic rejection is a major long-term complication after lung transplantation. The purpose of our study was to evaluate the role of repeated high-resolution computed tomographic examinations in monitoring the development of bronchiolitis obliterans syndrome after lung transplantation. METHODS: A total of 126 high-resolution computed tomographic examination in 13 lung transplant recipients was analyzed. During a mean follow-up period of 23 months, bronchiolitis obliterans syndrome developed in eight of the patients. A scoring system from 0 to 10 based on the number of chronic changes on high-resolution computed tomography was developed, and the score of each patient was compared with decline in the forced expiratory volume in 1 second and maximal forced expiratory flow rate of 50% of the forced vital capacity. RESULTS: The score of chronic changes, measured at 1 year after transplantation, correlated inversely with the values of forced expiratory volume in 1 second and maximal forced expiratory flow rate at 50% of the forced vital capacity (p < 0.05). Stage I bronchiolitis obliterans syndrome was associated with scores of 4 to 6 (mean 5.0), stage 2 with scores of 6 to 9 (mean 7.0), and stage 3 with scores of 6 to 9 (mean 7.7). The sensitivity of high-resolution computed tomography was 93% and its specificity was 92% when five chronic changes were used as a cutoff level. CONCLUSIONS: The progress of chronic changes on high-resolution computed tomography occurs concurrently with the development of bronchiolitis obliterans syndrome. High-resolution computed tomography may provide additional morphologic information for noninvasive evaluation of chronic lung rejection.

Selective assessment of single-lung graft function with 133Xe radiospirometry in acute rejection and infection.

In single-lung transplant recipients, the usefulness of spirometric indexes in detecting acute events involving the lung graft is limited due to the bias caused by the native lung. Selective functional monitoring is needed for the proper evaluation of complications after transplantation, but thus far, to our knowledge, no clinically feasible methods for selective graft-function assessment have been presented. In ten single-lung recipients, of whom six had a parenchymal lung disease and four had pulmonary hypertension, the relative ventilation (Vtx), perfusion (Qtx), and ventilation/perfusion ratio of the transplanted lung (V/Qtx) were determined with multidetector 133Xe radiospirometry. Additionally, the fractions of FEV1, FVC, and diffusing capacity for carbon monoxide (Dco) of the transplant (FEV1tx, FVCtx, Dcotx, respectively) were determined by using corresponding radiospirometric parameters for the calculation of their distribution between the lungs. The analysis included seven episodes of acute rejection and nine episodes of infection. The Qtx decreased during acute rejection but did not change during infection (p=0.001). Compared with the figures during infection, the V/Qtx increased during acute rejection significantly (p<0.05) in patients with underlying fibrosis or emphysema, but not in those with pulmonary hypertension. In detection of acute events, the sensitivity of the selective parameters, ie, FEV1tx (86%) and FVCtx (73%), was higher than that of the sum-function parameters, FEV1 (66%) and FVC (40%). Moreover, the sensitivity of Dcotx (80%) was higher than that of Dco (60%) in detecting acute rejection. The findings indicate that, in single-lung recipients with a parenchymal lung disease, the assessment of Qtx, V/Qtx, and Dcotx with a radioactive tracer can help to distinguish acute rejection from infection. The graft-selective parameters, ie, FEV1tx, FVCtx, and Dcotx, tended to be more sensitive than the corresponding sum-function parameters in detecting acute events, thus providing a more accurate functional profile of the single-lung graft.