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Background. alpha 1,3-Galactosyltransferase gene knockout (GTKO) pigs reduced the significance of antibody to galactose alpha 1,3-galactose (Gal) antigens but did not eliminate delayed xenograft rejection (DXR). We hypothesize that DXR of GTKO organs results from an antibody response to a limited number of non-Gal endothelial cell (EC) membrane antigens. In this study, we screened a retrovirus expression library to identify EC membrane antigens detected after cardiac xenotransplantation.Methods. Expression libraries were made from GT(+):CD46 and GTKO porcine aortic ECs. Viral stocks were used to infect human embryonic kidney cells (HEK) that were selected by flow cytometry for IgG binding from sensitized cardiac heterotopic xenograft recipients. After three to seven rounds of selection, individual clones were assessed for non-Gal IgG binding. The porcine complementary DNA was recovered by polymerase chain reaction amplification, sequenced, and identified by homology comparisons.Results. A total of 199 and 317 clones were analyzed from GT(+):CD46 and GTKO porcine aortic EC complementary DNA libraries, respectively. Sequence analysis identified porcine CD9, CD46, CD59, and the EC protein C receptor. We also identified porcine annexin A2 and a glycosyltransferase with homology to the human beta 1,4 N-acetylgalactosaminyl transferase 2 gene.Conclusion. The identified proteins include key EC functions and suggest that non-Gal antibody responses may compromise EC functions and thereby contribute to DXR. Recovery of the porcine beta 1,4 N-acetylgalactosaminyl transferase 2 suggests that an antibody response to a SDa-like carbohydrate may represent a new carbohydrate moiety involved in xenotransplantation. The identification of these porcine gene products may lead to further donor modification to enhance resistance to DXR and further reduce the level of xenograft antigenicity.

Background. Left ventricular hypertrophy (LVH) and diastolic dysfunction occur after cardiac transplantation. We investigated sirolimus (SRL) as primary immunosuppression for the attenuation of LVH and diastolic dysfunction of the cardiac allograft. Methods. Seventy cardiac transplant recipients were converted to SRL, 5.79 ± 3.90 years after transplant, with complete calcineurin-inhibitor (CNI) withdrawal. Three consecutive echocardiographic studies, 1 year apart, were analyzed for changes in left ventricular (LV) mass and diastolic function during CNI and SRL treatment. Results. Changes in systolic (P=0.69) and diastolic blood pressures (BP) (P=0.32) did not differ between SRL and CNI treatment. LV mass and LV mass index increased (185.03 ± 41.59 -197.21±47.39 g, P=0.033 and 94.20 ± 18.64 -98.93 ± 20.08g/m 2 ; P=0.030) during CNI and decreased (197.21 ± 47.39 -187.59 ± 48.88 g, P= 0.025 and 98.93 ±20.08 -94.06 ± 20.31 g/m 2 P= 0.050) during SRL. The difference in ALV mass and ALV mass index was significant (P=0.011 and P= 0.017, respectively) and was not associated with changes in BP. Left atrium volume index increased during CNI (46.73 ± 16.3 5-54.20 ± 18.47 cm 3 /m 2 , P=0.006) and decreased during SRL (54.20±18.47- 49.75 ± 18.40 cm 3 /m 2 , P=0.0036). The difference in left atrium (ALA) volume index was significant (P=0.002) and was not associated with changes in BP. Conclusions. Withdrawal of CNI and replacement with SRL in cardiac transplant recipients results in a decrease in LV mass and improvement in diastolic function. SRL may be useful to attenuate LVH and improve cardiac allograft diastolic function.

BACKGROUND AND AIMS: The combination of CTLA-4Ig with sirolimus can promote indefinite survival in allograft models for which CTLA-4Ig monotherapy is ineffective. We sought to determine whether a limited course of CTLA-4Ig and sirolimus would alter survival of rat orthotopic single-lung transplantations. METHODS: Left lungs of Brown Norway rats were transplanted into four groups of Lewis recipients (n=6 per group): group 1, no treatment; group 2, mCTLA-4Ig (250 microg/day for 4 days); group 3, sirolimus (3 mg/kg per day for 14 days); group 4, combined therapy with sirolimus and mCTLA-4Ig. Graft survival was determined by daily radiologic examination. Histologic grading of rejection and immunohistochemical staining for T and B lymphocytes were carried out at the time of radiologic graft loss. RESULTS: Rejection of lung allografts in group 1 occurred at a median of 6.5 days. Neither sirolimus nor mCTLA-4Ig monotherapy resulted in significant prolongation of graft survival (median 9.5 and 8.0 days, respectively). Graft survival in group 4 was significantly prolonged compared with all other groups (median 29.5 days), and a significant reduction in histologic grade of rejection was observed following combination therapy compared with all other groups. Infiltration by CD8+ve T cells at the time of rejection was proportionately greater than CD4+ve T-cell infiltration for groups 1, 2, and 3 but not for the combined-therapy group. CONCLUSIONS: A brief course of combined mCTLA-4Ig and sirolimus prolongs graft survival, reduces severity of rejection, and attenuates CD8+ve T-cell infiltration of fully major histocompatibility complex mismatched lung allografts.

Background. Expression of human complement regulating factor (hCRF) in porcine organs prevents hyperacute rejection of these organs after xenotransplantation to nonhuman primates. Experiments were designed to characterize endothelial and smooth muscle function of arteries from pigs transgenic for hCD46. Methods. Arterial blood from outbred pigs transgenic for hCD46 expression and nontransgenic animals of the same lineage was analyzed for angiotensin-converting enzyme (ACE), C-type natriuretic peptide (CNP), and nitric oxide. Aortic endothelial cells were prepared for measurement of mRNA or activity for nitric oxide synthase (NOS). Rings cut from femoral and pulmonary arteries were suspended in organ chambers for measurement of isometric tension. Results. CNP was significantly greater, ACE was similar, and nitric oxide was significantly less in plasma from transgenic compared with nontransgenic pigs. Neither mRNA nor activity of NOS differed between the groups. Endothelium-dependent relaxations to bradykinin and acetylcholine but not the calcium ionophore were shifted significantly to the left in femoral and pulmonary arteries from hCD46 transgenic pigs compared with nontransgenic pigs. The ACE-inhibitor captopril augmented relaxations similarly in both groups, but N G -monomethyl-L-arginine (L-NMMA) did not inhibit relaxations in rings from transgenic pigs. Conclusions. Data suggest that expression of hCD46 on endothelium of pigs selectively augments endothelium-dependent relaxations to bradykinin by increased release of endothelium-derived factors other than nitric oxide. There does not seem to be any change in activity of ACE or NOS with expression of the human protein. Increased relaxations to bradykinin may be beneficial in lowering vascular resistance when transgenic organs are used for xenotransplantation.

Background. Blockade of T-cell costimulation by local delivery of an adenoviral vector encoding for CTLA-4Ig and systemic administration of the protein are compared in a rat lung allograft model. Methods. Left lungs of Brown Norway rats (RT1 n ) were transplanted into Lewis (RT1 1 ) recipients in four groups of six animals each: 1) no treatment; 2) intrabronchial transduction of donor lung with adenovirus encoding mCTLA-4Ig (adeno-mCTLA-4Ig); 3) intrabronchial transduction with empty adenovirus; and 4) intraperitoneal injection of mCTLA-4Ig. Grading of rejection, mCTLA-4Ig measurement in serum and bronchial washings, RT-PCR for virally encoded transcripts, and immunohistochemistry for mCTLA-4Ig were carried out 4 days later. Results. Intrabronchial transduction with adeno-mCTLA-4Ig resulted in detectable transgene expression in graft tissue and bronchial fluid but not in serum. Significant reduction in rejection grade (from grade 3 to 2) occurred after systemic mCTLA-4Ig but not adeno-mCTLA-4Ig transduction. Conclusion. Local expression of immunomodulatory proteins can be achieved within lung allografts by intrabronchial delivery of adenoviral vector but may not significantly modify acute rejection.

BACKGROUND: This study was designed to assess which cells in transplanted lungs express endothelin-1 (ET-1) and if expression of the peptide can be used to discriminate between rejection and infection in transplanted lungs. METHODS: Transbronchial biopsies (n=104) from 29 human lung transplant recipients were stained immunohistochemically for ET-1. Cells expressing ET-1 (pneumocytes, endothelial cells, airway epithelial cells, lymphocytes, and macrophages) were quantified and correlated with clinical histopathology findings. RESULTS: ET-1 was expressed in airway epithelial cells (93% of the biopsies), infiltrating macrophages (86%), and lymphocytes (19%) but not in endothelial cells or pneumocytes. ET-1 expression did not vary with rejection, obliterative bronchiolitis, or infection. ET-1 expression did not correlate with age, grade of rejection, pulmonary function, or time after transplantation. CONCLUSION: In transplanted human lungs, ET-1 is expressed in airway epithelial cells and infiltrating macrophages, and expression does not vary with pathological processes. Therefore, immunostaining for ET-1 probably cannot be used to discriminate between rejection and infection in transplanted lungs.

BACKGROUND: Experiments were designed to determine expression of type II (iNOS) and type III (ecNOS) nitric oxide synthase in lung parenchyma and systemic endothelial cells with rejection and/or infection of single lung allografts. METHODS: After single lung allotransplantation, dogs were maintained on standard triple immunosuppressive therapy for 5 days and then placed into one of three groups. Group I (n=4) was maintained on immunosuppressants, group II (n=7) immunosuppression was withdrawn to allow acute rejection of the allograft, and group III (n=6) infection was induced by bronchoscopic inoculation of Escherichia coli. RESULTS: At postoperative days 7-9, no histological evidence of rejection or infection was observed in transplanted lungs of group I. In lungs of group II, rejection ranged from mild to severe; in lungs of group III, infection was severe. Some animals had both rejection and infection (n=8) and were studied separately. Plasma levels of nitric oxide increased comparably with rejection and/or infection compared to preoperative values. Expression of mRNA for ecNOS decreased significantly in lung parenchyma but not in aortic endothelial cells from dogs of groups II and III. However, expression of mRNA for iNOS increased with both rejection and/or infection in both lung parenchyma and aortic endothelial cells. CONCLUSIONS: iNOS is induced locally within the graft and systemically in aortic endothelial cells with rejection and/or infection of lung allografts. Plasma levels of nitric oxide are elevated with both rejection and infection and may not be useful in the differential diagnosis of these processes after lung transplantation.

Background. Experiments were designed to evaluate the effect of treatment with an inhibitor of lipid peroxidation, H 290/51, on the interaction of lymphocytes and pulmonary arteries during acute lung rejection. It was hypothesized that inhibition of lipid peroxidation would reduce contractions of the pulmonary arteries to autogenous rejection-activated lymphocytes. Methods. Single-lung transplantation was performed in three groups of dogs: group 1 was maintained on immunosuppression for 8 days postoperatively; in group 2, immunosuppression was discontinued on postoperative day 5, so that rejection occurred on postoperative day 8; in group 3, immunosuppression was discontinued after 5 days, and the lipid peroxidation inhibitor H 290/51 was given orally for 3 days. The pulmonary arteries were removed, cut into rings, and suspended in organ chambers for measurement of isometric force. Results. Macrophage-depleted mononuclear cells (MNCs; lymphocytes) isolated from blood caused cell number-dependent contractions in rings of the pulmonary arteries from all dogs. In the rejecting dogs treated with H 290/51 (group 3), contractions to MNCs were significantly greater in rings without endothelium compared to rings with endothelium. Contractions to MNCs with or without endothelium were reduced by adding deteroxamine to the medium but not by adding superoxide dismutase and catalase. Conclusions. The results of this study show that treatment with a lipid peroxidation inhibitor, H 290/ 51, does not prevent acute rejection of transplanted lungs. The treatment with the peroxidation inhibitor modifies contractions of the pulmonary arteries in response to rejection-activated lymphocytes, indicating that reactive oxidative metabolites may be involved in the vasoactive response resulting from this interaction.

Experiments were designed to characterize endothelin receptors in bronchi and parenchyma of transplanted lungs during acute rejection. Third-order bronchi from autografted or allografted lungs were either cut into rings and suspended in organ chambers for the measurement of isometric force or frozen for isolation of membrane proteins. Lung parenchyma was prepared for histology or isolation of membrane protein. The grade of rejection was 2.74±0.17 (n=19) in allotransplanted lungs; evidence of infection was present in 58% of the transplanted lungs. In organ chamber experiments, endothelin 1 (which stimulates endothelin A receptors) caused comparable contraction of bronchi from autotransplanted and allotransplanted rejecting lungs. Endothelin 3 (which stimulates endothelin A and B receptors) caused contractions of bronchi from autotransplanted lungs which were not different from those caused by endothelin 1. In contrast, contractions caused by endothelin 3 were reduced in bronchi from rejecting allotransplanted lungs. The magnitude of contractions caused by endothelin 3 was reduced further when infection was present with rejection. Competitive inhibition of 125 I-endothelin 1 by endothelin 3 was significant for a two-site binding model in membranes prepared from all bronchi and lung parenchyma. The total number of binding sites (B max ) was reduced significantly in bronchi and parenchyma from rejecting lungs with or without infection. The relative proportions of high-affinity and low-affinity binding sites did not change. Affinities of both high- and low-affinity receptors were not altered with rejection. These results indicate that at least two subtypes of endothelin receptors are present on canine bronchial smooth muscle and parenchyma. The number of endothelin receptors associated with bronchial contractions is reduced with rejection of lung allografts.

BACKGROUND: The current success of cardiac transplantation is in part attributable to the development of effective immunosuppressive agents such as cyclosporine. However, concern remains regarding the potential for cyclosporine-induced nephrotoxicity. Animal studies and early reports of renal protective effects of pentoxifylline in bone marrow transplant recipients prompted a randomized trial in cardiac transplant recipients. METHODS: Twenty-nine patients were randomized to receive pentoxifylline 400 mg p.o. t.i.d. or matching placebo for 1 year after cardiac transplantation. Renal function was assessed preoperatively and at 1, 6, and 12 months postoperatively. Glomerular filtration rate and renal plasma flow were measured with iothalamate and para-aminohippurate, respectively. Serum creatinine was also measured. Ambulatory blood pressure monitoring after withdrawal of antihypertensives for 3 days was performed 12 months postoperatively. RESULTS: Twenty-seven patients completed the study. Glomerular filtration rate rose between 1 and 6 months after transplantation, presumably due to the reduction in goal cyclosporine level in that period, and then fell modestly between 6 and 12 months, presumably due to ongoing nephrotoxic effects of cyclosporine. No difference in glomerular filtration rate or creatinine was seen between pentoxifylline and placebo groups at any interval. Renal plasma flow increased modestly between baseline and 6 months in the pentoxifylline group, but not in the placebo group, and then fell between 6 and 12 months. Serum creatinine increased between baseline and 6 months in both groups, apparently due to increased body weight. Results of 18-hr ambulatory blood pressure monitoring obtained 1 year after transplantation was not different between groups. CONCLUSIONS: Renal function declines only modestly in the first year after cardiac transplantation. Pentoxifylline did not attenuate this process and had no effect on blood pressure. The modest decline in renal function may be related to current immunosuppressive strategies.

Endothelin-1 (ET-1) is found in bronchoalveolar lavage fluid in patients following lung transplantation. ET-1 causes contraction of isolated pulmonary vessels and bronchi and stimulates proliferation of smooth muscle cells in culture. Therefore, ET-1 could contribute to the smooth muscle hyperplasia and stromal proliferation seen in chronic rejection of lung allografts. Experiments were designed to determine whether (1) ET-1 stimulates proliferation of pulmonary tissue, (2) proliferation is increased in rejecting allotransplanted lungs, (3) endothelin-A receptors mediate the proliferative response, and (4) ET-1 is produced by activated infiltrating immunocompetent cells. Lung organ cultures were prepared from unoperated dogs and dogs with rejecting single lung allografts. Incubation of organ cultures from unoperated dogs with ET-1 (10(-9) to 10(-7) M)) increased positive staining for proliferation cell nuclear antigen (PCNA) in lung parenchyma. PCNA staining was not decreased by the endothelin-A antagonist BQ123 (10(-6) M). In addition, immunostaining for endothelin-B receptors was present in sections of unoperated but not rejecting lungs. PCNA staining in lung cultures from rejecting allotransplanted dogs was significantly greater than that from unoperated dogs. Positive immunohistochemical staining for ET-1 was found in mononuclear cells infiltrating rejecting transplanted lungs. In conclusion, exogenous ET-1 is mitogenic in lung organ cultures through receptors other than endothelin-A. Proliferation in rejecting transplanted lungs is increased compared with unoperated lungs. Mononuclear cells may be a source of endothelin-1 in the rejecting lung. ET-1, therefore could, in synergism with other cytokines, contribute to acute and chronic pathological changes seen in pulmonary rejection.

Experiments were designed to evaluate function of the endothelium and smooth muscle of coronary arteries following storage of hearts in cardioplegia containing an inhibitor of lipid peroxidation (H 290/51, cis-7-methyl-9-methoxy-5,5a, 6,10b tetrahydroindeno [2,1-b] indole). Canine hearts were perfused with crystalloid cardioplegia (Plegisol, 15 ml/kg, 4 degrees C) and left circumflex arteries were isolated and studied either immediately (group I, n = 6), or after storage of the hearts at 4 degrees C for 10 (group II, n = 6) or 24 hr with (group III, n = 6) or without (group IV, n = 6) addition of H 290/51. The final concentration of H 290/51 was 1 mumol/L. Arteries were removed, cut into rings, and suspended in organ chambers for measurements of isometric force. In selected rings, the endothelium was removed in order to study the function of the smooth muscle. In order to discriminate effects of ischemia/reperfusion and protective properties on coronary endothelium or smooth muscle, drugs with different mechanisms were used. The function of the endothelium were studied with the alpha 2-adrenergic agonist UK 14,304, bradykinin and A 23187. The smooth muscle function were studied with isoproterenol and nitric oxide. Endothelium-dependent relaxations to the alpha 2-adrenergic agonist UK 14,304 and bradykinin, but not to A 23187, were reduced significantly in arteries from hearts stored for 24 hr in cardioplegic solution alone. Relaxations of arteries from hearts stored for 24 hr with H 290/51 were comparable to those arteries from hearts that were not stored. Endothelium-independent relaxations to isoproterenol and nitric oxide among the different groups were comparable. These results suggest that storage of canine hearts with crystalloid cardioplegia selectively inhibits endothelium-dependent relaxations mediated by receptor activation. Inhibition of lipid peroxidation with H 290/51 preserves these relaxations and may therefore represent a therapeutic alternative to preserve hearts used for transplantation.

Chronic pulmonary disease is associated with varying degrees of cardiac dysfunction. Because of the potentially predominant effect of severe lung disease on right ventricular (RV) size and function, a reliable method to assess RV mechanics before and after lung transplantation may provide information of long-term significance and/or prognosis. Conventional invasive and non-invasive imaging methods have a number of limitations in evaluating RV function. Ultrafast computed tomographic (ultrafast CT) scanning has been shown to provide quantitative assessment of RV and left ventricular (LV) function in individuals with and without cardiac disease. Twenty-two patients presenting during evaluation for possible lung transplantation with end-stage pulmonary disease formed the basis of this study. There were 14 patients with chronic obstructive pulmonary disease and 8 with pulmonary fibrosis. Conventional transthoracic echocardiography and ultrafast CT were used for the assessment of RV and LV function. All patients had invasive assessment of right-sided hemodynamics and pulmonary function studies performed within 7-10 days of cardiac imaging. A qualitative assessment of RV size or function was possible in all but two patients by echocardiogram, but in 45%, the echocardiographic examination was described as suboptimal. In contrast, a quantitative assessment of ventricular volumes and systolic function was obtained in all patients by ultrafast CT. Pulmonary function parameters or hemodynamic measurements obtained during cardiac catheterization did not correlate with any assessment of RV function. We concluded that (1) ultrafast CT provides measurement of the RV and LV cavity dimension and systolic function; (2) invasive right-sided hemodynamics or pulmonary function studies do not predict RV function; and (3) echocardiography does not uniformly provide assessment of RV function in patients with chronic pulmonary disease.

BACKGROUND: Simultaneous combined orthotopic heart and liver transplantation (CHLTx) remains a lifesaving procedure for the patients suffering from coincident end-stage heart and liver disease and several metabolic disorders. We analyze the long-term outcome of the patients undergoing CHLTx. METHODS: Between January 1992 and May 2007, 15 CHLTx were attempted at the Mayo Clinic including two combined heart, liver, and kidney transplantations and one combined heart, lung, and liver transplantations. Pretransplant cardiac diagnoses were familial amyloidosis (11), hemochromatosis (1), restrictive cardiomyopathy and cardiac cirrhosis (1), previously operated congenital heart disease and cardiac cirrhosis (1), and primary pulmonary hypertension with primary biliary cirrhosis (1). RESULTS: Heart and liver transplantation were performed as a single combined procedure in 13 (93%) hemodynamically stable patients, and there was no perioperative mortality. Survival rates for the CHLTx recipients at 1 year, 5 years, and 10 years were 100%, 75%, and 60%, respectively, and did not differ from survival after isolated heart transplantation (93%, 83%, and 65%, respectively, P=0.39). Freedom from cardiac allograft rejection (ISHLT > or =grade 2) for CHLTx was 83% at 1 month, did not change with time, and was lower than after isolated heart transplantation (P=0.02). At the mean follow-up of 61.6+/-53.6 months, normal left ventricular ejection fraction and good liver allograft function were demonstrated. Three patients developed end-stage renal failure secondary to calcineurin nephrotoxicity. CONCLUSION: Simultaneous heart and liver transplantation is feasible and achieved excellent results for selected patients.

BACKGROUND: We evaluated the feasibility of noninvasive micro-single photon emission computed tomography (SPECT)/computed tomography (CT) imaging and quantification of cardiac gene expression after sodium iodide symporter (hNIS) gene transfer in cardiac transplantation. METHODS: Donor rat hearts were perfused ex vivo with adenovirus expressing hNIS (Ad-hNIS), Ad-Null, or University of Wisconsin (UW) solution prior to heterotopic transplantation into syngeneic recipients. In the first group of recipients, imaging of the transplanted hearts with micro-SPECT/CT on day 5 was followed by immediate explant of the organs for ex vivo analyses. Radioactivity counts in the explanted hearts were obtained ex vivo and expressed as a percentage of the injected dose per gram of tissue (%ID/g). Intensities of the SPECT images of the transplanted hearts were quantified and converted to radioactive counts using a standard equation. The second group of recipients was imaged sequentially after injection of I on days 2 to 14 after transplantation. RESULTS: Higher ex vivo radioiodine counts were noted in the hearts perfused with Ad-hNIS (1.04+/-0.2) compared to either the UW group (0.31+/-0.11, P

BACKGROUND: The objective of the authors' study was to characterize the clinical and pathologic differences between patients who develop posttransplant lymphoproliferative disorders (PTLD) early or late after transplantation and to assess the overall survival in these two groups. METHODS: One hundred seven adult solid organ transplant patients were identified at the Mayo Clinic between December 1970 and May 2003. RESULTS: Forty-nine patients developed PTLD within the first year (early PTLD, 1-11.8 months) and 58 patients developed PTLD after 1 year (late PTLD, 14 months-17 years). Patients with early PTLD more commonly had the following characteristics: positive Epstein-Barr virus (EBV) in situ hybridization status (P < 0.0001), CD20-positive status (P = 0.002), and involvement of the grafted organ (P = 0.02). Overall survival did not differ between the two groups (P = 0.25). PTLD may occur in two different settings with different characteristics. CONCLUSIONS: Early PTLD is more commonly EBV in situ hybridization-positive and CD20-positive, and more commonly involves the grafted organ.

Background Animal organs could satisfy the demand for solid organ transplants, which currently exceeds the limited human donor supply. Hyperacute rejection, the initial immune barrier to successful xenotransplantation, has been overcome with pig donors transgenic for human complement regulatory proteins. Delayed xenograft rejection, thought to be mediated by anti-pig antibodies predominantly to Gal antigens, is currently regarded as the major barrier to successful xenotransplantation. A median graft survival of 90 days in the life-supporting position is considered a reasonable initial standard for consideration of entry to the clinic. Methods A series of 10 heterotopic heart transplants from CD46 transgenic pigs to baboons was completed. Immunosuppression consisted of splenectomy, Rituximab (Anti-CD20), tacrolimus, sirolimus, corticosteroids, and TPC. Thymoglobulin (Rabbit Anti-Thymocyte Globulin) was used to treat putative rejection episodes. Results Median graft survival was 76 days (range 56-113 days, n = 9). Only three grafts were lost to rejection. The remaining grafts lost were due to recipient mortality with baboon cytomegalovirus (BCMV) being the major cause (n = 4). No cellular infiltrates were present as a manifestation of rejection. Three hearts showed chronic graft vasculopathy. Conclusions The median survival of 76 days in this group of heterotopic porcine-to-baboon cardiac xenografts represents a major advance over the median 27-day survival reported in the literature. Cellular rejection may not constitute a direct major barrier to xenotransplantation. A median survival of 90 days may be achievable with better control of BCMV infection. If further studies in the orthotopic position replicate these outcomes, criteria considered appropriate for clinical application of cardiac xenotransplantation would be approached.

In a canine model of acute ischemic lung injury, a hypertonic citrate solution (HTC) widely used for renal preservation in the United Kingdom, was compared with modified Euro-Collins' solution (ECS) currently the most widely clinically used pulmonary perfusate. Ten beagle dogs underwent left thoracotomy and exclusion of the left lung in situ. The lung was flushed with 30 ml/kg of either HTC or ECS and subjected to 60 min of warm ischemia. The circulation to the lung was then restored, the contralateral lung excluded, and the animal ventilated at a fixed FiO2 of 0.4 for 4 hr. Lung function was assessed by arterial oxygenation and hemodynamic measurements and, following sacrifice, by lung weight gain, bronchoalveolar lavage, and ultrastructural studies. Flush perfusion with HTC was associated with significantly less severe reperfusion injury, as determined by superior arterial oxygenation (PaO2 at 1 hr: HTC--152 mmHg [(95% confidence interval) CI] [122-182], ECS--59 [47-70]; PaO2 at 4 hr: HTC--124 [100-149], ECS--51 [42-61]), lower pulmonary vascular resistance index (PVRI at 4 hrs: HTC--838 dynes sec cm-5m-2 [651-1075], ECS--1233 [963-1588]); and lower lung weight (HTC--85 g [66-107], ECS--146 [114-184]). Bronchoalveolar lavage studies demonstrated an influx of neutrophils following reperfusion that was significantly less marked in the HTC group (increase in % neutrophils: HTC 24 [19-29], ECS 77 [72-82]). Lung injury assessed by electron microscopy tended to be less severe in the HTC animals. We conclude that HTC may offer an alternative superior to ECS for lung preservation.

The single-flush technique of lung preservation is thought to be enhanced by prostaglandin treatment. In order to test this hypothesis, ten beagle dogs underwent thoracotomy and in situ flush perfusion of the excluded left lung with 30 ml/kg of cold, modified Euro-Collins' solution. Group 1 (n = 5) received pretreatment with 30 ng/kg/min of PGI2 by infusion and as an additive to the flush (20 micrograms/L). Group 2 (n = 5) received no PGI2 and served as controls. Following 60 min of warm ischemia, the left lung was reperfused, the contralateral lung excluded, and the animal ventilated at a fixed FiO2 of 0.4 for 4 hr. The severity of reperfusion injury was assessed by arterial oxygenation and hemodynamic measurements and, following sacrifice, by lung weight gain and bronchoalveolar lavage and ultrastructural studies. PGI2 therapy resulted in significant amelioration of reperfusion injury, with superior oxygenation at both 1 and 4 hr (PaO2 at 1 and 4 hr, respectively; PGI2: 145 mmHg +/- 17.0 and 114 +/- 11.2; no PGI2: 59 mmHg +/- 5.8 and 51 +/- 4.5; P less than 0.01 at both times), lower pulmonary vascular resistance index at 4 hr (PVRI; PGI2: 913 dynes sec cm-5m-2 +/- 91; no PGI2: 1239 +/- 68; P less than 0.05) and lower lung weight (PGI2: 76 g +/- 4; no PGI2: 146 +/- 10; P less than 0.001). Bronchoalveolar lavage studies revealed an influx of neutrophils following reperfusion that was less marked in the PGI2 group (increase in % neutrophils; PGI2: 50.4 +/- 6.7; no PGI2: 76.9 +/- 6.0; P less than 0.05). Lung injury score assessed by electron microscopy was lower in the PGI2 group (PGI2: 5.2 +/- 1.1; no PGI2; 8.1 +/- 0.5; P less than 0.05). It is concluded that PGI2 treatment is protective against ischemic lung injury in this model.