Endothelial integrity after venous cryopreservation

Prospective Study of Recipient Human Leukocyte Antigen (HLA) Alloimmunization Following the Use of Cold-Stored Saphenous Vein Allografts in Vascular Surgery

Objectives: The aim of this study was to assess the HLA alloreactivity of cold-stored saphenous vein allografts (CSVAs) by identifying the production of HLA donor-specific antibodies (DSAs) in the recipient. The secondary objective was to evaluate CSVA rejection-related complications, such as CSVA thrombosis and/or aneurysmal degeneration in the recipient. Methods: This was a single-center, prospective, experimental before-and-after study which included participants undergoing CSVA placement, either to create a vascular access (VA) for hemodialysis or to create a lower limb arterial bypass. On Day 1, before CSVA placement, total blood samples were taken for HLA typing by sequence-specific primers (SSPs) and anti-HLA antibody detection using a Luminex assay. One month after CSVA placement, a second blood sample was taken to assess the appearance of donor-specific antibodies or an increase in the level of anti-HLA antibodies. Patency of the CSVA and potential aneurysmal degeneration were evaluated at 3 and 6 months with a Doppler ultrasound checkup. Results: From September 2022 to November 2023, 45 patients were included (30 men, 67%; mean age: 71 ± 12 years). One month after CSVA placement, no appearance of de novo anti-HLA antibody was detected in anti-HLA antibody-negative patients at inclusion (n = 28). Among the patients who already had anti-HLA antibodies at inclusion (n = 17), no increase in anti-HLA antibody levels or appearance of de novo anti-HLA antibodies was detected. Conclusions: This prospective study evaluating the immunogenicity of CSVAs through the appearance of anti-HLA antibodies one month after placement demonstrates that they do not seem to induce any HLA alloreactivity. Therefore, they may be used without the risk of HLA immunization in patients awaiting organ transplantation.

Limb salvage after aneurysmal degeneration of a cryopreserved vein allograft: Searching the autologous veins of the arm is worth the effort

CLINICAL DATA

We hereby report a case of limb salvage involving a 64-year-old man who was hospitalized with ischemic foot ulcers for two months. Endarterectomy with patching and stenting of the left iliofemoral artery failed. A composite bypass of two segments of the endarterectomized superficial femoral artery and a cryopreserved saphenous vein graft was implanted one week later. On day 4 postoperatively, an infection (Staphylococcus epidermidis and Pseudomonas aeruginosa) was treated empirically with antibiotics. Four months later, the femoro-tibial bypass thrombosed and the patency was restored by thrombolysis. The aneurysmal cryopreserved vein was excised. Iterative complications followed and final success was attained after implantation of autologous cephalic and basilic veins. Four years later, this femoro-tibial is still patent.

PATHOLOGICAL ANALYSES

After a gross observation, the explant was dissected and the most significant sections were processed for histology, followed by analyses in scanning electron microscopy, light microscopy and transmission electron microscopy.

RESULTS

The explanted specimen showed a smooth flow surface proximally but a severe distortion distally, with an accumulation of poorly organized mural thrombi. The wall of the arterialized vein was accompanied with an important inflammatory reaction. The degradation of the collagen structure was evidenced in TEM. The fibrils of collagen were still individualized but were fragmented and did not display parallelly. The regular banding was preserved. The presence of Pseudomonas aeruginosa was shown inside the wall of the homologous vein.

COMMENTS

In case of sepsis, the most aggressive antibiotic treatments cannot fully eliminate the bacteremic colonizations within the wall of an alternative conduit. The cephalic and basilic autologous veins are proved to be preferable in absence of the autologous saphenous vein. The amputation was prevented and four years later the bypass is still patent. This is an outstanding result based upon the comorbidities of the patient. The most aggressive harvesting shall be recommended. This patient represented a considerable challenge and the clinical result is highly gratifying: the search for the autologous cephalic and basilic veins proved to be worth the effort.

Cryopreservation of the common carotid artery of the rabbit: Optimization of dimethyl sulfoxide concentration and cooling rate

This paper describes the continuation of studies that demonstrated the suitability of CP-Tes solution as a medium for the introduction and removal of dimethyl sulfoxide in rabbit common carotid arteries and established the kinetics of cryoprotectant permeation in that tissue. In this paper we report the tolerance of rabbit common carotid artery to dimethyl sulfoxide, in concentrations up to 30% (w/w), using a technique of exposure that was designed to control osmotic stress. The maximum concentration achieved without damage was 15% (w/w). Vessels were then equilibrated with 15% dimethyl sulfoxide and cooled to -80 °C at 0.22, 0.69, 2.15, or 9.63 °C/min: they were then transferred to the gas phase of a liquid nitrogen refrigerator {temperature below -160 °C) for storage. Thawing was carried out in a 37 °C water bath. The optimum rate of cooling for these conditions was found to be 0.69 °C/min. The maximal recovery of contractile force in response to 10^-6 M norepinephrine was 30-40%; relaxation to acetylcholine (an endothelium-mediated function) was 80% of control, and an estimated 71% of endothelial cells survived with minimal ultrastructural change.

Cryopreservation of vascular tissues

Cryopreservation of human blood vessels may become an important tool in bypass surgery and peripheral vascular reconstruction. Ideally cryopreservation of a blood vessel should preserve functional characteristics comparable to those of fresh controls. The key advantage of cryopreservation is the fact that storage at deep subzero temperatures allows storage of structurally intact living vascular tissues for virtually infinite time. Originally developed for long-time storage of isolated cells, the techniques of cryopreservation of tissues are challenged by the fact that these are complex multicellular systems containing diverse types of cells with differing requirements for optimal preservation. Therefore, the post-thaw functional activity of vascular tissues is determined by the type of blood vessel and, in addition, by the cell packing effect. Moreover, evidence from pharmacological studies suggests that cryopreservation induces tissue specific changes in transmembrane signaling and the mechanisms coupling intracellular calcium release, sensitivity and calcium entry into the smooth muscle cells.

Decellularized cadaver vein allografts used for hemodialysis access do not cause allosensitization or preclude kidney transplantation

BACKGROUND

Dimethyl sulfoxide-cryopreserved (CRY) cadaver vein allografts used for hemodialysis access in patients with renal failure recently have been shown to cause broad recipient allosensitization, measured by panel reactive antibody (PRA) assay. Synergraft (SYN) processing is a novel method of treating tissue that decellularizes the graft (including mismatched major histocompatibility antigens) and potentially should prevent allosensitization.

METHODS

Twenty hemodialysis patients underwent placement of an SYN-processed cadaver vein allograft. PRA assay was used prospectively to assess allosensitization in these patients at baseline and 1-month intervals after engraftment. These results were compared with our historic series of CRY allograft recipients.

RESULTS

There was no significant difference in baseline PRA values for SYN and CRY patients (2.8% versus 2.6%, respectively). None of the SYN patients became allosensitized at 3 months postengraftment (mean PRA, 3.2%), whereas all CRY recipients became highly sensitized at a mean of 3.1 months (mean PRA, 84.1%). This result was highly significant (P < 0.0001).

CONCLUSION

SYN processing of cadaver vein allografts successfully removes antigenic material. The use of SYN allografts in patients with renal failure for hemodialysis access does not cause allosensitization and therefore should not preclude kidney transplantation.

Use of cryopreserved cadaveric vein allograft for hemodialysis access precludes kidney transplantation because of allosensitization

BACKGROUND

Dimethyl sulfoxide-cryopreserved cadaveric vein allografts have recently been proposed as an alternative to prosthetic grafts in the problem hemodialysis population. The transfer of mismatched major histocompatibility complex I and II molecules in association with these allografts can potentially lead to allosensitization in nonimmunosuppressed individuals.

METHODS

In a university-affiliated medical center, 20 consecutive patients receiving technically successful upper arm cadaveric vein allograft fistulas (CAVFs) for hemodialysis between April 1999 and April 2000 were studied. A control cohort of 20 patients on a kidney transplantation waiting list was selected by nurses blinded to the study. These patients were matched for age, sex, history of transfusion, pregnancy, cause of kidney failure, and prior transplantation. The panel reactive antibody (PRA) values were recorded in this group over the same time period as the CAVF group.

RESULTS

Patients receiving CAVFs had a mean PRA assay value of 84.1% (median, 96.5%) at an average of 3.1 months after engraftment (median, 1.5 months). The preengraftment PRA values were available for seven patients who were on the transplant waiting list. Six of these patients had nonreactive PRA assays before CAVF creation. All of these patients converted to positive PRA assays after CAVF creation with a mean value of 92.3% (median, 98%) at 2.85 months follow-up (median, 1.3 months). The mean PRA value for the control cohort was 5.5% (median, 2.5%), with no patients converting from a nonreactive to a reactive PRA assay during this same time interval.

CONCLUSION

The use of dimethyl sulfoxide-cryopreserved cadaveric vein allografts for hemodialysis access leads to broad allosensitization as measured by PRA assay. Cryopreserved cadaveric vein allografts should not be used for hemodialysis access in potential kidney transplant recipients.

Immunosuppression for human saphenous vein allograft bypass surgery: a prospective randomized trial

PURPOSE

Vein allografts are an alternative bypass conduit for patients who lack adequate autogenous vein. Animal studies have demonstrated that patency can be augmented by low-dose immunosuppression with azathioprine.

METHODS

In a prospective trial, 40 patients (20 men, 20 women) were randomly assigned to receive (17) or to not receive (23) azathioprine (1 mg/kg/day) after cryopreserved vein allograft bypass grafting. Patients had pain or tissue loss that required bypass grafting to pedal or crural outflow and lacked adequate autogenous saphenous vein. Anti-HLA antibody screens were obtained before and after surgery. Biopsies of allografts were performed at implantation and at all subsequent opportunities. Postoperative physical and vascular laboratory examinations occurred every 3 months.

RESULTS

During the 31-months follow-up interval (mean, 15.7 months) there were 10 deaths (none immunosuppression-related). The primary graft patency rate at 12 months was 13%, and the limb salvage rate was 42%. No significant difference (p > 0.05) was noted between immunosuppressed and control groups for mortality rate, primary graft patency rate, or limb salvage rate. As a predictor of graft failure, positive preoperative anti-HLA antibody screen (8 patients) approached significance (p = 0.09). Of 22 explanted grafts, 13 (59%) had histologic evidence of rejection (six immunosuppressed, seven control). Seven patients who had negative results of preoperative anti-HLA antibody screens converted after surgery, and six patients had positive results of preoperative screens that became more strongly positive.

CONCLUSION

Vein allograft failure is in part mediated by rejection, which is not eliminated by low-dose azathioprine. Both humoral (antibody) and cellular responses to vein allografts develop. The poor patency rates of vein allograft bypass grafts may be improved by more potent immunosuppression as well as improvement in allograft procurement, preservation, and matching.

Carotid endarterectomy with homologous vein patch angioplasty: a review of 1006 cases

PURPOSE

Because homologous vein is rarely used in vascular reconstructions, we evaluated the homologous vein as a patch for the reconstruction of the carotid bifurcation after endarterectomy.

METHODS

Excess vein harvested during open heart operations was either refrigerated in saline solution or cryopreserved in a solution of 10% dimethyl sulfoxide. Donors were tested for transmissible infections, and the veins were cultured for common pathogens. Data were analyzed from 837 consecutive patients (1006 cases) who underwent carotid endarterectomy with homologous vein patch angioplasty between 1981 and 1993.

RESULTS

The perioperative mortality rate was 0.8% (eight patients). Two deaths (0.2%) were attributed to ipsilateral strokes. Ischemic strokes occurred in 12 patients (1.2%; 10 ipsilateral), and ipsilateral transient ischemic attacks occurred in three patients (0.3%). Follow-up data were obtained for 482 patients (56%; mean follow-up time, 61 months; range, 1 to 132 months). Ipsilateral recurrent symptoms occurred in eight patients (1.7%; seven strokes, one transient ischemic attack). Of the 63 late deaths (13%), the majority (25 patients; 40%) were caused by complications of coronary artery disease. The 10-year overall survival rate was 76% +/- 3.2%, and the 10-year rate of freedom from late ipsilateral morbidity was 96% +/- 1.4%. The 10-year rate of freedom from late stenosis (a reduction in diameter of > or = 20%) in the 220 arteries (22%) that were studied by duplex scan was 84% +/- 2.3%.

CONCLUSIONS

The postoperative mortality and neurologic morbidity rates of carotid endarterectomy with homologous vein patch angioplasty are similar to those in the best series with all types of closure. The existing long-term follow-up data indicate that the homologous vein is a durable patch that behaves like other patches used in the same location.

Cryopreserved saphenous vein allografts for below-knee lower extremity revascularization

OBJECTIVE

Cryopreserved saphenous vein allografts have been offered as an alternative conduit for bypass in ischemic limbs. The authors examined the efficacy of this conduit for arterial bypass to the distal popliteal and tibial arteries in patients in whom autogenous vein was not available.

SUMMARY BACKGROUND DATA

Previous experience with arterial and venous allografts has been unsatisfactory because of aneurysmal degeneration and poor patency. Endothelial loss and host rejection have been suggested as mechanisms of graft failure. Cryopreservation by modern techniques with rate controlled freezing, dimethyl sulfoxide (DMSO), and other cryopreservants, has addressed these issues and rekindled interest in vein allografts.

METHODS

Over a period of more than 5 years, 115 cryopreserved vein allografts were implanted in 87 limbs to the distal popliteal (14) or tibial (101) arteries. The indication for surgery was rest pain in 56 procedures (49%), gangrene in 36 (31%), claudication in 21 (18%), and replacement of aneurysmal allografts in 2. Follow-up was 1 to 61 months (mean 25 months).

RESULTS

There was no significant difference in patency related to site of proximal or distal anastomosis, patency of runoff vessels, use of anticoagulation, age, sex, diabetes, hypertension, smoking, indication, source of graft, or use of multiple segments. Revision was required in six grafts for aneurysmal dilatation. Histologic examination of explanted sections of allografts showed no immune response, and immunosuppressive drugs were not used.

CONCLUSIONS

Although limb salvage has been satisfactory, long-term patency rates for cryopreserved vein allografts are poor when compared with autogenous vein. The cost of cryopreserved allografts far exceeds that of prosthetic grafts, for which comparable and superior results have been reported. Use of cryopreserved vein allografts should be reserved for situations in which adequate lengths of autogenous vein do not exist and the risk of infection of prosthetic grafts is high.

Cryopreserved arterial homografts: preliminary study

The use of arterial or venous allografts for vascular reconstruction was first reported in 1951, but long-term results have been disappointing. Rejection and inappropriate methods of preservation are the main reasons for failure. A successful solution to this problem could be achieved by programmed cryopreservation with cryoprotectant. Our study had two aims: to define the biomechanical properties of cryopreserved arterial allografts and to study their histologic appearance. Arteries were removed as part of a protocol for multiorgan harvesting for transplantation. Cryopreservation was performed within the first 24 hours after harvesting. Programmed cryopreservation with 15% dimethyl sulfoxide (cryoprotectant) was used. Mechanical testing was done immediately after thawing. Two groups were tested: a control group of fresh aortas and a group of cryopreserved aortas. Axial and circumferential strips were tested. High strain modulus and stress and strain characteristics were calculated for each strip. There was no statistically significant difference between the mechanical properties of fresh and cryopreserved human descending thoracic aortas. Biochemical tests were performed in the preservative solution at 1 and 7 days in both groups. There was no statistically significant difference between the two groups at day 1 or day 7 (p > 0.05). Histologic studies before and after arterial cryopreservation included standard and electron microscopy and showed that arteries had normal structure after cryopreservation. These results confirm that programmed cryopreservation with cryoprotectant does not alter the molecular or geometric configuration of collagen or elastic fibers. Endothelial cells were still present, however, their viability and function were not assessed.(ABSTRACT TRUNCATED AT 250 WORDS)

Transplantation of cryopreserved canine venous allografts

Local vascular reconstructions frequently require the use of vein grafts to bridge arterial or venous defects. Most previous studies on the use of cryopreserved veins have used relatively large caliber vessels. There have been few studies on the effectiveness of cryopreserved micro- or small-venous allografts. Here, we tested two types of cryopreserved venous allografts: (1) 1.5- to 1.9-mm diameter microvenous grafts (MVG); and (2) 4- to 5-mm diameter small venous grafts (SVG). Cryopreserved MVG allografts were placed into saphenous arteries of six experimental dogs and SVG cryopreserved allografts were placed into femoral arteries of six experimental dogs for 3 to 6 weeks. Two fresh MVG autografts were also transplanted into experimental dogs as controls and autografts were transferred to the contralateral side in SVG dogs as controls. None of the six cryopreserved MVG grafts retained patency but three/six cryopreserved SVG allografts were patent at harvest. Histological examination of grfts revealed control autografts were undergoing arterialization with an intact intima. Experimental cryopreserved allografts showed extensive medial fibrosis, significant lymphocytic infiltrates, and sporadic areas of intact intima for both patent and nonpatent grafts.

Retention of endothelium-dependent vasodilatory responses in canine coronary arteries following cryopreservation

In the present study, the cryoprotective effect of dimethyl sulfoxide (Me2SO) and fetal calf serum (FCS) on coronary endothelium and endothelium-dependent relaxation (EDR) responses was studied in isolated canine coronary arteries following cryostorage at -75 degrees C. Compared to the freshly isolated coronary arteries, the EDR responses to acetylcholine, thrombin, and calcium ionophore were not significantly altered following 1 day storage at -75 degrees C in the presence of 1.8 M Me2SO and 20% FCS. Prolonged cold storage to 7 days, however, resulted in a slight, but significant, rightward shift of the concentration-response curves of acetylcholine and thrombin, but not calcium ionophore. The maximum relaxant response after 7-day cryostorage was 80 to 85% of fresh controls. Omission of FCS from the cryostorage incubation medium further accentuated the loss of EDR responses to all three endothelium-dependent vasodilators tested. Scanning electron microscopic examinations of the intimal surface of the Me2SO and FCS cryostored canine coronary arteries confirmed the preservation of intimal endothelial cells following 1 or 7 days of storage at -75 degrees C, while significant patches of loss of endothelial cells were observed in the arteries cryostored only in the presence of Me2SO. No significant inhibitory effect of cryostorage was observed for the direct, endothelium-independent relaxation induced by isoproterenol, regardless of the presence or absence of FCS. These results demonstrate that slow freezing of canine coronary arteries to -75 degrees C in Krebs-Henseleit solution containing Me2SO and FCS provides good preservation of the vascular smooth muscle function and endothelium-dependent vasodilatory responses.

The preservation of functional activity of smooth muscle and endothelium in pig coronary arteries after storage at -190 degrees C

Pig coronary arteries have been investigated in-vitro using fresh tissue or after storage at -190 C in foetal calf serum containing 1.8 M dimethyl sulphoxide. Attention was paid to modulation of contractile activity and endothelium-dependent relaxation. After cryopreservation of the arteries maximal contractile responses to both 5-hydroxytryptamine (5-HT) and prostaglandin F2 alpha (PGF2 alpha) were markedly reduced and the pD2 values for both agonists were slightly, but significantly, diminished. Nevertheless, 5-HT antagonism by ketanserin and pizotifen was unchanged. Endothelium-independent relaxant responses of precontracted arteries to isoprenaline, forskolin, 3-isobutyl-1-methylxanthine, nitroprusside, atriopeptin III and cromakalim were generally unchanged after storage. Mechanical removal of the endothelium by rubbing enhanced the contractile response to PGF2 alpha in both fresh and stored arteries to a similar extent. In addition, endothelium-dependent relaxant responses to both 5-HT and substance P were well maintained, suggesting release of endothelium-derived relaxing factor by the stored arteries. The evidence suggests that after cryopreservation of pig coronary arteries at -190 degrees C mechanisms of relaxation, in particular those which are endothelium-dependent, are well maintained.

Platelet avidity of cryopreserved veins: thrombogenicity of cryopreserved veins

Prior work has suggested that cryopreserved venous allografts may serve as an effective arterial substitute. To determine the relative thrombogenicity of this material, platelet uptake of cryopreserved canine jugular veins (CJV) before and after deendothelialization was compared to fresh CJV before and after deendothelialization, and to PTFE. CJV were frozen in Medium 199 (M199) with 10% dimethylsulfoxide to -70 degrees C. CJV were deendothelialized with collagenase (165 u/mg Worthington type II in phosphate-buffered saline) for 15 min at 37 degrees C. Canine platelets were harvested, labeled with indium-III-oxine, and suspended in 1 liter of M199. Labeled platelets were used to perfuse each graft in a nonpulsatile flow loop for 120 min. Deendothelialization led to a significant increase in platelet uptake (P less than 0.05). Frozen deendothelialized CJV showed the highest affinity for platelets. PTFE, cryopreserved, and fresh CJV showed similar affinity for platelets. Cryopreservation alone did not seem to inhibit the ability of endothelial cells to act as a nonthrombogenic surface and did not alter the histologic structure of the veins.