Fresh and Cryopreserved Arterial Homografts: Immunological and Clinical Results

[18F]-Fludeoxyglucose Positron Emission Tomography/Computed Tomography with Radiomics Analysis in Patients Undergoing Aortic In-Situ Reconstruction with Cryopreserved Allografts

BACKGROUND

The aim of this study was to evaluate the effectiveness of positron emission tomography/computed tomography with [¹⁸F]-fludeoxyglucose (FDG-PET/CT) and radiomics analysis in detecting differences between the native aorta and the abdominal aortic allograft after the total eradication of infection in patients undergoing infected graft removal and in situ reconstruction with cryopreserved allografts.

METHODS

Between January 2008 and December 2018, 56 vascular reconstructions with allografts have been performed at our department. The present series included 12 patients undergoing abdominal aortic in situ reconstruction with cryopreserved allografts. During the follow-up, all patients underwent a total-body [¹⁸F]FDG PET/CT with subsequent radiomics analysis. In all patients, a comparative analysis between the data extracted from native aorta and cryopreserved graft for each patient was performed.

RESULTS

All patients were male with a mean age of 72.8 years (range 63-84). Mean duration of follow-up was 51.3 months (range 3-120). During the follow-up, 2 patients (16.7%) needed a redo allograft-related surgical intervention. Overall, the rate of allograft dilatation was 33.3%. No patient had a redo infection during the follow-up. Radiomics analysis showed a different signature of implanted allograft and native aorta. Comparative analysis between the native aortas and cryopreserved allografts (dilated or not) showed several statistical differences for many texture features.

CONCLUSIONS

The higher metabolic activity of allografts could indicate a state of immune-mediated degeneration. This theory should be proven with prospective, multicentric studies with larger sample sizes.

Immunological Aspects Involved in the Degeneration of Cryopreserved Arterial Allografts

Introduction: Cryopreserved arterial allografts have remained an option in patients requiring distal revascularization or associated with vascular infection, in the absence of a valid autogenous saphenous vein. The objective of this study is to describe the different clinical, anatomopathological, and immunological findings related to vascular transplant rejection.

Methods: In a prospective trial, 35 patients who underwent cryopreserved allogeneic arterial bypass were studied, including demographics and conduit patency. Anti-HLA antibody production was stablished prior to the surgery, 7 days, 1, 3 months, and every 3 months since. Clinical and ultrasound evaluation was added after the first month. Donor HLA-typing was retrieved whenever available, allowing for the characterization and quantification of donor specific antibodies. Cytotoxic crossmatch test was also performed. A second group of patients with allograft degenerations registered during the follow up period was studied. In this group, exclusively for aneurysm description and histopathological analysis, they were included those degenerated vascular transplants from the original series, but also those implanted prior to the beginning of the study and degraded during follow up.

Results: All patients studied displayed an increase in anti-HLA antibodies one month after the intervention, regarding bypass patency. In total, 14 patients fulfilled requirements for the study of donor specific antibodies, equally showing IgG production detectable one month after surgery. The presence of complement-fixing antibodies was also confirmed. Antibody levels were not related to graft degeneration. No specific immune markers able to predict aneurysmal development and evolution were found. From the original group, 3 patients suffered aneurysmal degeneration during follow up, together with 9 bypasses previously implanted. Average time until the first degeneration was 33 ± 19.7 months, with 30.6 ± 17.7 and 54.5 ± 2.5 months for a second and third degeneration, when occurring. Therefore, subsequent vascular transplants frequently augmented the time for new degenerations, despite increasing sensibilization. Samples from eight degenerated allografts were available for analysis, unexpectedly showing inflammatory infiltrate in only four cases and immune complex deposition in 7.

Conclusions: Immune response against vascular transplants was confirmed in all cases, but chronic rejection did not necessarily provoke bypass degradation or reduced the time for new aneurysms to develop in subsequent allografts.

Editor's Choice - Cryopreserved Allografts for Arterial Reconstruction after Aorto-Iliac Infection: A Systematic Review and Meta-Analysis

OBJECTIVE

Native and aortic graft infections are rare, but they represent one of the most life threatening complications of vascular surgery. Several materials and surgical approaches have been developed so far. Among them, cryopreserved allografts have been proposed as a treatment option. A systematic review and meta-analysis was conducted to investigate the role of cryopreserved allografts for arterial reconstruction after aorto-iliac infection.

METHODS

The current meta-analysis was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Patient baseline characteristics were investigated, along with 30 outcomes after use of cryopreserved arterial allografts for reconstruction after aorto-iliac infection. Pooled proportions with 95% CIs of outcome rates were calculated.

RESULTS

A total of 31 studies, including 1,377 patients, finally participated in the meta-analysis. Among the early outcomes, 30 day mortality was 14.91% (95% CI 11.78-18.31). Peri-anastomotic rupture/allograft disruption rate was 5.90% (95% CI 2.77-9.88), while pooled aneurysmal degeneration/allograft dilatation was 4.99% (95% CI 1.60-9.68). A pooled rate of 3.11% (95% CI 1.60-4.98) was estimated for pseudoaneurysm formation after the use of cryopreserved arterial allografts, while the allograft thrombotic/stenotic complication rate and peri-anastomotic infection were 12.19% (95% CI 7.90-17.15) and 3.32% (95% CI 1.90-5.03), respectively. Mortality during follow up was 19.24% (95% CI 11.97-27.58), while allograft related mortality during follow up was 3.58% (95% CI 1.56-6.15). A pooled allograft related re-operation rate was estimated at 24.87% (95% CI 17.89-32.51).

CONCLUSIONS

The use of cryopreserved allograft seems to be a safe and durable option with acceptable outcomes for treatment of aorto-iliac infection.

Examples of dramatic failures and their effectiveness in modern surgical disciplines: can we learn from our mistakes?

Innovation can be variably defined, but when applied to healthcare is often considered to be the introduction of something new, whether an idea, method or device, into an unfilled void or needy environment. Despite the introduction of many positive surgical subspecialty altering concepts/devices however, epic failures are not uncommon. These failures can be dramatic in regards to both their human and economic costs. They can also be very public or more quiet in nature. As surgical leaders in our communities and advocates for patient safety and outcomes, it remains crucial that we meet new introductions in technology and patient care with a measured level of curiosity, skepticism and science-based conclusions. The aim of an expert committee was to identify the most dominant failures in technological innovation and/or dogmatic clinical beliefs within each major surgical subspecialty. In summary, this effort was pursued to highlight the past failures and remind surgeons to remain vigilant and appropriately skeptical with regard to the introduction of new innovations and clinical beliefs within our craft.

Calcification of Cryopreserved Arterial Graft Causing Delayed Obstruction of Portal Vein Flow After Liver Transplant

In patients with biliary atresia, portal vein problems may cause challenges for liver transplant. Interposition grafts have been used for vascular anastomoses in transplant recipients with varied success. A cryopreserved iliac artery graft was used for the reconstruction of the portal vein in a 29-month-old infant with biliary atresia. At 17 months after transplant, she developed upper gastrointestinal bleeding that was caused by portal vein occlusion because of vascular calcifications in the graft. Upper gastrointestinal endoscopy showed esophageal varices with fresh bleeding, and the varices were band ligated. At 3 months after the bleeding episode, the patient was asymptomatic and biochemical tests were normal. In summary, liver transplant with cryopreserved iliac artery graft may be complicated by calcifications and portal vein occlusion, and caution is advised in using this graft material for portal vein anastomoses.

Donor-specific anti-HLA antibodies after bone-graft transplantation. Impact on a subsequent renal transplantation: a case report

Immunological evaluation by panel-reactive antibody (PRA) and determination of anti-HLA specificity are important phases in the evaluation of patients awaiting kidney transplantation. The main causes of immunization are previous solid organ transplantation, hemotransfusion, and pregnancy. It is also possible that immunogenicity can be triggered by vascularized tissue grafts. Immune induction by cryopreserved bone prostheses is not yet understood. A 19-year-old patient with osteosarcoma had undergone resection of the left proximal tibia with reconstruction using human bone in 1997. The donor HLA typing was as follows: A3, A29 (19); B44 (12), Bw4; DR13 (6), DR7, DR52, DR53. The patient was subsequently enrolled onto the waiting list for cadaveric donor kidney transplantation due to chronic kidney failure caused by cisplatin toxicity. Pretransplantation immunological screening using the complement-dependent cytotoxicity (CDC) technique revealed a PRA of 63%. IgG antibody specificities were detected against class I and class II donor antigens, specifically anti-A3, B44, DR7 antibodies, using flow cytometry (Tepnel Luminex). Further immunological studies using single HLA specificity analysis (LSA Class I degrees -II degrees , Tepnel-Luminex) showed direct antibodies against all donor antigen specificities. This case showed immune induction after the implantation of bone prosthesis in a kidney transplant candidate, underlining the importance of the availability of HLA typing data of donors of a human prosthesis.

Fresh arterial homograft for bypass in critical limb ischaemia with infection

We present what we believe is Australia's first fresh peripheral arterial transplant for revascularisation of an ischaemic limb. Although cryopreserved homografts are accepted as a management option for revascularisation of critical limb ischaemia in infected fields, cryopreserved peripheral vascular tissue is not currently available in Australia. We describe a 72-year-old man without autologous conduit in whom infected prosthetic grafts were explanted, causing critical limb ischaemia of a below knee stump. Fresh peripheral arterial tissue was procured via the Australian organ donation authority, DonateLife, and was used to revascularise the stump with an axillofemoral bypass. This permitted successful healing of the stump within 6 weeks and mobilisation with a prosthesis. This case illustrates that fresh arterial homografts are a viable bridging solution for revascularisation of limb ischaemia with infection. However, it also highlights the need to establish a peripheral homograft bank so that cryopreserved conduits are readily available for similar scenarios.

Residual antibiotics in decontaminated human cardiovascular tissues intended for transplantation and risk of falsely negative microbiological analyses

We investigated the presence of antibiotics in cryopreserved cardiovascular tissues and cryopreservation media, after tissue decontamination with antibiotic cocktails, and the impact of antibiotic residues on standard tissue bank microbiological analyses. Sixteen cardiovascular tissues were decontaminated with bank-prepared cocktails and cryopreserved by two different tissue banks according to their standard operating procedures. Before and after decontamination, samples underwent microbiological analysis by standard tissue bank methods. Cryopreserved samples were tested again with and without the removal of antibiotic residues using a RESEP tube, after thawing. Presence of antibiotics in tissue homogenates and processing liquids was determined by a modified agar diffusion test. All cryopreserved tissue homogenates and cryopreservation media induced important inhibition zones on both Staphylococcus aureus- and Pseudomonas aeruginosa-seeded plates, immediately after thawing and at the end of the sterility test. The RESEP tube treatment markedly reduced or totally eliminated the antimicrobial activity of tested tissues and media. Based on standard tissue bank analysis, 50% of tissues were found positive for bacteria and/or fungi, before decontamination and 2 out of 16 tested samples (13%) still contained microorganisms after decontamination. After thawing, none of the 16 cryopreserved samples resulted positive with direct inoculum method. When the same samples were tested after removal of antibiotic residues, 8 out of 16 (50%) were contaminated. Antibiotic residues present in tissue allografts and processing liquids after decontamination may mask microbial contamination during microbiological analysis performed with standard tissue bank methods, thus resulting in false negatives.

Antibody-mediated rejection of arterialised venous allografts is inhibited by immunosuppression in rats

Objectives and Design

We determined in a rat model (1) the presence and dynamics of alloantibodies recognizing MHC complexes on quiescent Brown-Norway (BN) splenic cells in the sera of Lewis (LEW) recipients of Brown-Norway iliolumbar vein grafts under tacrolimus immunosuppression; and (2) the presence of immunoglobulins in the wall of acute rejected vein allografts.

Materials and Methods

Flow cytometry was used for the analysis of day 0, 14 and 30 sera obtained from Lewis recipients of isogeneic iliolumbar vein grafts (group A) or Brown-Norway grafts (group B, C) for the presence of donor specific anti-MHC class I and II antibodies. Tacrolimus 0.2 mg/kg daily was administered from day 1 to day 30 (group C). Histology was performed on day 30.

Results

Sera obtained preoperatively and on day 30 were compared in all groups. The statistically significant decrease of anti MHC class I and II antibody binding was observed only in allogenic non-immunosuppressed group B (splenocytes: MHC class I - day 0 (93%±7% ) vs day 30 (66%±7%), p = 0.02, MHC class II - day 0 (105%±3% ) vs day 30 (83%±5%), p = 0.003; B-cells: MHC class I - day 0 (83%±5%) vs day 30 (55%±6%), p = 0.003, MHC class II - day 0 (101%±1%) vs day 30 (79%±6%), p = 0.006; T-cells: MHC class I - day 0 (71%±7%) vs day 30 (49%±5%), p = 0.04). No free clusters of immunoglobulin G deposition were detected in any experimental group.

Conclusion

Arterialized venous allografts induce strong donor-specific anti-MHC class I and anti-MHC class II antibody production with subsequent immune-mediated destruction of these allografts with no evidence of immunoglobulin G deposition. Low-dose tacrolimus suppress the donor-specific antibody production.

Presensitization revisited: pitfalls of vascular allografts in transplant candidates

Vascular allografts in end-stage renal disease (ESRD) patients represent a particular immunological challenge. A broad HLA immunization led us to study in depth the history of two patients with vascular allografts. In Case 1 the allograft was added to a Gore-Tex graft used for haemodialysis access and no immunosuppression was administered. In Case 2 the allograft was used to prolong a renal artery from living donor and immunosuppression was suboptimal. In vascular surgery, immunosuppression is mainly used to improve graft patency. ESRD patients are potential organ recipients and immunosuppression should therefore be tailored to reduce HLA immunization.

The seven-year' secondary patency of a fresh arterial allograft in the femorocrural position in a heart transplant recipient

Critical limb ischemia in patients with diabetes at the organ complication stage represents a considerable challenge in vascular medicine. Because of the complexity of the disease and the often symmetric involvement of both lower limbs, a discrepancy between suitable vascular conduit availability and the actual requirement can occur: notably, the prevalence of multilevel and diffuse arterial disease often limits the possibilities of endovascular treatment, and, in surgical cases, frequently prohibits the effective use of prosthetic material. In our patient with bilateral critical limb ischemia and previous coronary artery bypass graft followed by cardiac transplantation, only one great saphenous vein remained available. That was used in its entirety to salvage one limb as a sequential femorocrural bypass. A similar surgical procedure with a fresh arterial allograft retrieved from a deceased donor was performed on the other extremity . ABO compatibility as well as the chronic immunosuppressive therapy in a heart transplant recipient may have contributed to the favorable long-term clinical outcome of the allogeneic arterial reconstruction.

Cryopreserved arterial allograft reconstruction after excision of thoracic malignancies

BACKGROUND

The purpose of this study was to evaluate the long-term clinical and immunologic outcome of cryopreserved arterial allograft (CAA) revascularization of intrathoracic vessels invaded by malignancies.

METHODS

Since January 2002, consecutive patients whose intrathoracic vessels were invaded by malignancies were operated on and revascularizion made using human lymphocyte antigen (HLA)- and ABO-mismatched CAAs. Immunologic studies were performed preoperatively, and 1, 3, 6, 12, and 24 months postoperatively. Postoperative oral anticoagulation therapy was not given.

RESULTS

Twenty-six patients aged 53.1 +/- 15 years with a nonsmall-cell lung cancer (n = 10), invasive mediastinal tumors (n = 7), pulmonary artery sarcoma (n = 3), laryngeal (n = 2), or other rare lung neoplasms (n = 4) underwent operation. Cardiopulmonary bypass was used in 10 cases (38%), and all resections were pathologically complete. Revascularization was either for venous (n = 12) or arterial (n = 14) vessels, and a total of 30 allografts revascularized the superior vena cava (n = 6), pulmonary artery (n = 7), innominate vein (n = 3) or artery (n = 2), ascendent (n = 4) or descending (n = 1) aorta, and subclavian vein (n = 3) or artery (n = 4). Hospital morbidity and mortality were 50% (n = 13) and 3.8% (n = 1), respectively, all CAA unrelated. With a median follow-up of 18 months (range, 3 to 60+), 5-year survival and allograft patency were 84% and 95%, respectively. Preoperative anti-HLA antibodies were detected in 2 patients (7.7%) and a postoperative anti-HLA antibody response, clinically irrelevant, in 1 of 24 patients (4%).

CONCLUSIONS

Revascularization of intrathoracic venous and arterial vessels in patients with malignancies using HLA- and ABO-mismatched CAA is technically feasible and clinically attractive because of no infection risk and postoperative anticoagulation, and excellent long-term survival, patency, and nonimmunogeneicity.

The “in situ” expression of Human Leukocyte Antigen Class I antigens is not altered by cryopreservation in human arterial allografts

This study was aimed to establish whether the cryopreservation procedure we currently use in clinics can modify arterial homograft antigenicity. To this purpose, we performed an immunohistochemical study on fresh and cryopreserved human arterial homografts to visualize the expression of HLA class I heavy and light chains "in situ" by using the HC-10 and Namb-1 monoclonal antibodies. Human femoral arteries and thoracic aortas were harvested from 18 heart-beating donors and sampled before and after cryopreservation. Arterial segments were frozen in liquid nitrogen vapors in a controlled rate freezing system. After thawing, samples were processed for routine immunohistochemistry. To standardize immunostaining, flow-cytometry indirect immunofluorescence analysis was performed on HUVEC; immunohistochemistry of human ovarian cortical vessels was performed as an additional positive control. Negative controls were performed by omitting tissue incubation with primary antibodies. HLA-class I antigens were markedly expressed by endothelial cells lining surface intima and adventitial vasa vasorum; a moderate expression was found in medial smooth muscle cells. Except for the surface unreactivity caused by loss of endothelium, results from cryopreserved arterial allografts were strictly comparable to those observed in fresh, unfrozen tissues. These results support the view that cryopreserved arterial allografts are immunogenic as their fresh counterparts; apart from smooth muscle cells which retained a moderate expression of HLA class I antigens following cryopreservation, our study suggests that the highly HC-10 positive endothelial cells we found to line the rich adventitial network of vasa vasorum are expected to be one of the major targets of the serological response in the recipient.

Smooth muscle cell injury after cryopreservation of human thoracic aortas

The cryopreservation protocol we use for arterial reconstructive surgery has been studied to evaluate smooth muscle cell (SMC) structural integrity and viability before implantation. Samples of human thoracic aortas (HTA) were harvested from five multi-organ donors. Sampling included unfrozen and cryopreserved specimens. Cryopreservation was performed using RPMI with human albumin and 10% Me(2)SO in a controlled-rate freezing apparatus. Thawing was accomplished by submerging bags in a water bath (39 degrees C) followed by washings in cooled saline. In situ cell preservation as investigated by light and transmission electron microscopy showed that SMCs from cryopreserved HTA had nuclear and cytoplasmic changes. A TUNEL assay, performed to detect DNA fragmentation in situ, showed increased SMC nuclear positivity in cryopreserved HTA when compared to unfrozen samples. 7-AAD flow cytometry assay of cells derived from cryopreserved HTA showed that an average of 49+/-16% cells were unlabeled after cryopreservation. Organ cultures aimed to study cell ability to recover cryopreservation damage showed a decreasing number of SMCs from day 4 to day 15 in cryopreserved HTA. In conclusion, the cryopreservation protocol applied in this study induces irreversible damage of a significant fraction of arterial SMCs.