Venous Allografts Research Articles

Cold stored femoral vessels as microvascular allografts: a preliminary study.

Cold stored femoral arteries or veins have been reinserted successfully as autografts into rabbits. The present study examines whether grafting with cold stored vascular allografts is equally successful. Rabbit femoral arteries and veins were stored at 4 degrees C for 4 weeks before insertion as allografts into unrelated animals. Three weeks after insertion into the femoral artery all venous allografts and 80% of arterial allografts were patent, but patency of both graft types declined over the next few weeks. A small number of cold stored venous allografts when inserted into the femoral vein occluded within 3 weeks. No histological evidence of rejection was apparent. The findings suggest that cold stored vascular allografts could be used successfully as an arterial "prosthesis" to support free flaps where relatively short term patency is required until the flap can establish sufficient peripheral inset to survive in its own right. This technique could be applied when autologous veins are not available or not justified.

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)

Cryopreserved venous allografts: Effects of immunosuppression and antiplatelet therapy on patency and function

Purpose: Experiments were designed to determine the function of the endothelium and smooth muscle in cryopreserved and fresh canine saphenous vein allografts.Methods: Reversed interposition saphenous vein grafts were implanted into the femoral arteries of two groups of dogs: group 1 received one freshly harvested saphenous vein allograft and group 2 received one cryopreserved saphenous vein allograft. The contralateral femoral artery in each group was replaced with a freshly harvested autogenous saphenous vein. Animals received oral cyclosporine alone (n = 3) or in combination with aspirin (325 mg/day; n = 20).Results: Four weeks after surgery, none of the cryopreserved grafts was patent in the group treated with cyclosporine alone. All grafts were patent in animals treated with cyclosporine and aspirin. At 4 weeks, blood flow through cryopreserved allografts was significantly greater than in freshly harvested allografts. Platelet deposition was comparable in cryopreserved and freshly harvested allografts immediately after implantation and at 4 weeks. Rings cut from the grafts were suspended for the measurement of isometric force in organ chambers. α-Adrenergic agonists and endothelin caused concentration-dependent contractions in fresh autografts and allografts. After submaximal contraction with prostaglandin F2α in these same grafts, calcium ionophore and thrombin caused relaxations in rings with endothelium, and nitric oxide caused relaxations in rings without endothelium. Cryopreserved allografts did not respond to any of the agonists tested. Histologic examination of the tissue indicated smooth muscle cells in cryopreserved grafts; evidence of rejection was observed in all allografts.Conclusion: These results indicate that cryopreserved allografts remain patent with antiplatelet and immunosuppressive therapy in spite of loss of functional smooth muscle.

Homologous Cryopreserved Saphenous Vein for Construction of a "Jump" Arterioarterial Access for Hemodialysis—A Case Report

An alternative technique enabling vascular access for hemodialysis is de scribed. A forty-year-old man suffering from end-stage renal failure underwent a radioradial arterioarterial jump bypass. This was done successfully by using a cryopreserved venous homograft, which remained patent and functional for twenty-two months.

Immunosuppressive treatment of venous allografts

In order to evaluate whether temporary immunosuppressive therapy is able to improve the results obtained with viable venous allografts and achieve better results than with synthetic grafts, 142 arterial reconstructions were performed in mongrel dogs bypassing their ligated femoral arteries. Histological as well as immunological studies were performed and patency determined by weekly palpation and regular angiography. The 6-month cumulative patency rates were: Group I: synthetic grafts (a) Dacron: 48%, (b) plasma-TFE: 53%. Group II: fresh grafts (a) autografts: 100%, (b) allografts: 37%, (c) allografts treated with cyclosporin 4 mg kg-1 daily for 1 month: 74% (100% after 1 month). Group III: grafts preserved in Hanks' solution with 15% DMSO at -160 degrees C for 1 month (a) autografts: 77%, (b) allografts: 35%, (c) allografts treated with methylprednisolone 1 mg kg-1 daily: 38%, (e) allografts treated with cyclosporin and methylprednisolone: 83%. Group IV: human saphenous veins implanted as xenografts and treated with cyclosporin and methylprednisolone: 18%. Immunosuppressive therapy with cyclosporin seems to be able to prevent early thromboses due to rejection seen after implantation of viable fresh or cryopreserved venous allografts, and the results are significantly better than those obtained with synthetic grafts. Tissue matching might further improve these results. This study suggests that cryopreserved venous allografts could be used for the creation of a vein-bank and their use, in combination with tissue typing and temporary immunosuppressive therapy may be warranted for arterial reconstructions when autologous saphenous vein is not available.

Venous allografts as arterial substitutes in dogs: Importance of donor-recipient histocompatibility

Venous allografts as arterial substitutes in dogs: Importance of donor-recipient histocompatibility

Long-term results with vein homograft in femoro-distal arterial reconstructions

There still is a need for an alternative to autologous vein especially for infra-inguinal vascular reconstructions. Since 1984 we have used a denatured venous homograft in patients in whom the saphenous vein was either absent or unsuitable. One hundred and five homografts were implanted in the femoro-popliteal and 51 in the femoro-infrapopliteal position. The results obtained were satisfactory, with a 5-year cumulative patency (life-table method) of 53% overall, 68.4% in patients with disabling claudication, and 42% in those with critical ischaemia. The cumulative aneurysm rate was rather high, at 18% after 3 years and 58% after 5 years. An excellent limb salvage rate of 85% was achieved in patients with critical ischaemia. The management of graft aneurysms and the indications for reconstructive surgery with a denatured venous homograft are discussed.

The use of venous allografts in vascular surgery

Biochemical, morphological and biomechanic study of various veins which were taken from 54 patients without trophic disorders during phlebectomy and kept for 7 days was made. 2% solution of neutral formalin and isotonic buffer solution (Henx solution) was used; results of the study show, that conserved veins can be used for grafting in arterial reconstructive surgery in cases of absence of autogenous vein material. Optimal period of conservation is 1 day.

Cryopreserved Venous Allografts Pretreated with Cyclosporine Revisited

In 1983 Bandlien et al reported that pretreatment of cryopreserved jugular allografts with cyclosporine (CsA) reduced immunogenicity and increased the patency of these grafts in the canine carotid artery. The purpose of this study was to determine whether CsA pretreatment of nonreversed cephalic venous allografts modifies the histologic events or increases patency in the canine femoral artery. The authors also wished to document the histologic events in the nonreversed cryopreserved cephalic autograft and allograft over a five-month period. Thirty-six nonreserved cephalic grafts were interposed in the canine femoral artery. Right venoarterial grafts were cryopreserved with CsA and the left grafts were cryopreserved without CsA. There were 28 allografts and 8 autografts so treated. Cryopreserved autograft endothelial cells (ECs) were quite well pre served on preoperative biopsies and rapidly repopulated the intima in one to three weeks like fresh autografts. All autografts remained patent. In contrast, allograft ECs disappeared early and were very slowly replaced with host ECs in the midgraft after five months. The allograft patency was more than 70 % in weighted analysis for the early periods studied without significant difference between CsA and control groups. Pretreatment with CsA did not appear to spare endothelium or influence the immune process significantly.

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 grafts 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.

The Use of Cryopreserved Venous Allografts in Free Tissue Transfers—Practical and Aesthetic Considerations

A case in which multiple cryopreserved allograft saphenous veins were used as vein grafts for a difficult mandible reconstruction with a free tissue transfer is reviewed. Use of allograft veins was recently reported for lower limb vascular reconstruction but not for free tissue transfers. Such grafts may represent a viable alternative to the use of autologous vein grafts and have the potential to decrease operating time and avoid necessary scars.

Vessel preservation with glycerol: An experimental study in rats

Arterial and venous allografts (aorta and femoral vein or artery) of Sprague-Dawley rats were preserved with glycerol (98%) or by lyophilization and subsequently implanted in Wistar rats. The grafts were removed for histologic examination of vessel patency on days 1, 30, 60, and 100 postoperatively. Whereas the glycerol-preserved vessels exhibited a high patency, the results obtained with the lyophilized vessels were less favorable. Lyophilized veins could not be successfully implanted.

Factors affecting patency of venous allografts in miniature swine

In immunologically defined National Institutes of Health miniswine, a segment of internal jugular vein was anastomosed to the carotid artery as an interposition graft. Patency of swine major histocompatibility complex matched, one haplotype mismatched, and complete mismatched veins was 9.8, 6.3, and 3.0 weeks respectively (p = 0.009). More than 90% of mismatched and 20% of matched allografts developed a positive crossmatch before occlusion (p = 0.006). The mixed lymphocyte response did not predict graft occlusion. Treatment of 10 swine with cyclosporine (10 mg/kg/day) did not significantly improve patency for one haplotype mismatched grafts. In haplotype mismatched veins, cryopreserved grafts occluded more rapidly than noncryopreserved grafts: mean 2.4 versus 6.3 weeks, respectively (p = 0.002). In all cryopreserved vein grafts, alloantibody appeared at or after graft occlusion rather than before occlusion as seen with fresh allografts (p = 0.046). The mean patency of cryopreserved versus fresh autografts was 3.3 and greater than 32 weeks, respectively (p = 0.004). In summary, these results indicate that (1) allograft patency is related to the degree of swine major histocompatibility complex match and development of cytotoxic alloantibodies; (2) moderate-dose cyclosporine does not prolong allograft patency nor suppress development of antibody; (3) cryopreservation may accelerate graft occlusion through nonimmunologic mechanisms.

Factors affecting patency of venous allografts in miniature swine

In immunologically defined National Institutes of Health miniswine, a segment of internal jugular vein was anastomosed to the carotid artery as an interposition graft. Patency of swine major histocompatibility complex matched, one haplotype mismatched, and complete mismatched veins was 9.8, 6.3, and 3.0 weeks respectively (p = 0.009). More than 90% of mismatched and 20% of matched allografts developed a positive crossmatch before occlusion (p = 0.006). The mixed lymphocyte response did not predict graft occlusion. Treatment of 10 swine with cyclosporine (10 mg/kg/day) did not significantly improve patency for one haplotype mismatched grafts. In haplotype mismatched veins, cryopreserved grafts occluded more rapidly than noncryopreserved grafts: mean 2.4 versus 6.3 weeks, respectively (p = 0.002). In all cryopreserved vein grafts, alloantibody appeared at or after graft occlusion rather than before occlusion as seen with fresh allografts (p = 0.046). The mean patency of cryopreserved versus fresh autografts was 3.3 and >32 weeks, respectively (p = 0.004). In summary, these results indicate that (1) allograft patency is related to the degree of swine major histocompatibility complex match and development of cytotoxic alloantibodies; (2) moderate-dose cyclosporine does not prolong allograft patency nor suppress development of antibody; (3) cryopreservation may accelerate graft occlusion through nonimmunologic mechanisms.

Absence of Rejection in Cryopreserved Saphenous Vein Allografts for Hemodialysis

Since November 1987, a total of 16 dialysis patients in the authors' Center, received a cryopreserved saphenous vein allograft (CSVA) as “third choice” vascular access. ABO and HLA-A-B compatibilities were determined but not considered. Saphenous veins were cryopreserved in liquid nitrogen for variable periods (1–6 mo), so that there was the opportunity to choose the most suitable in dimension. In February, 1989, a total of 13 patients retained a well-functioning access site, whereas three had died from causes unrelated to CSVA. Because rejection of venous allografts still is debated among angiologists, recipient T lymphocyte subsets (CD3-CD4-CD8 and CD4/8) were examined, as were lymphocytotoxic antibodies, before and on days 15 and 30 after implantation. No evidence of immunologic activation was found. Moreover, in 10 of 16 patients the surgeons subcutaneously implanted a fragment of CSVA, and an immunohistochemical study was carried out using an alkaline phosphatase-antialkaline phosphatase (APAAP) technique and a panel of monoclonal antibodies. Minimal infiltration of the outer layer of adventitia was found, mainly caused by monocyte macrophages (leu M3-t) with few T lymphocytes (CD3+). The authors conclude that rejection is not a major cause of failure in CSVA in dialysis patients.

Absence of rejection in cryopreserved saphenous vein allografts for hemodialysis.

Since November 1987, a total of 16 dialysis patients in the authors' Center, received a cryopreserved saphenous vein allograft (CSVA) as "third choice" vascular access. ABO and HLA-A-B compatibilities were determined but not considered. Saphenous veins were cryopreserved in liquid nitrogen for variable periods (1-6 mo), so that there was the opportunity to choose the most suitable in dimension. In February, 1989, a total of 13 patients retained a well-functioning access site, whereas three had died from causes unrelated to CSVA. Because rejection of venous allografts still is debated among angiologists, recipient T lymphocyte subsets (CD3-CD4-CD8 and CD4/8) were examined, as were lymphocytotoxic antibodies, before and on days 15 and 30 after implantation. No evidence of immunologic activation was found. Moreover, in 10 of 16 patients the surgeons subcutaneously implanted a fragment of CSVA, and an immunohistochemical study was carried out using an alkaline phosphatase-antialkaline phosphatase (APAAP) technique and a panel of monoclonal antibodies. Minimal infiltration of the outer layer of adventitia was found, mainly caused by monocyte macrophages (Leu M3+) with few T lymphocytes (CD3+). The authors conclude that rejection is not a major cause of failure in CSVA in dialysis patients.

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°C. CJV were deendothelialized with collagenase (165 μ/mg Worthington type II in phosphate-buffered saline) for 15 min at 37°C. Canine platelets were harvested, labeled with indium-III-oxine, and suspended in 1 liter of M 199. 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 < 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.

Three years experience with denaturated venous homografts as an arterial substitute: A clinical, pathological and immunological study

Over a three-year-period 105 peripheral arterial reconstructions were performed using a denaturated venous homograft in a group of patients with no suitable autologous vein. A retrospective analysis has been carried out to investigate the patency rate of this graft. After three years 64% of all grafts are functioning well (according to the Life Table Method, Kaplan & Meyer). No significant differences in patency rates were found between reversed autologous veins and the material tested in this study but analysis of grafts removed after failure showed obstruction due to thrombosis or aneurysmal dilatation. No evidence of an immune response to the grafts was seen.

Microsurgical application of freeze-dried venous allografts.

Freeze-dried venous interposition allografts with an internal diameter of 1.0 mm and a length of 1.0 cm were placed into the femoral arteries of 17 Sprague-Dawley albino male rats in order to investigate patency and host tissue response. The immediate patency rate was 88%. The epigastric island flap was monitored as a sign of patency in the early postoperative period (defined as 1 to 3 days). Twelve of the 17 subjects were observed for 2 months, at which point 66% (8/12) remained patent. There were two aneurysmal dilatations. Histopathological studies and transmission electron microscopy demonstrated that freeze-dried veins undergo complete remodeling in vivo by a normal reparative process and that they do not induce a cellular immune response in the host.

Immunosuppression with cyclosporine. A new approach to improve patency of venous allografts.

In cases in which an autogenous vein is not available, the venous allograft still represents an interesting alternative; however, early occlusion of the allograft is the rule. Forty-five mongrel dogs received jugular allografts transplanted into the carotid artery. Group 1 (n = 6) received no immunosuppression; group 2 (n = 5) received systemic azathioprine (2.5 mg/kg/day). In group 3 (n = 10) the grafts were pretreated with cyclosporine at 4 degrees C, and in group 4 (n = 9) the grafts were cryopreserved in a solution of 15% dimethyl sulfoxide and cyclosporine (50 mg/L) at -196 degrees C prior to implantation. Groups 3 and 4 received azathioprine as in group 2. Group 5 received cyclosporine systemically (15 to 20 mg/kg/day). Patency rates at one month (groups 1 and 2, 0%; group 3, 57.1%; groups 4 and 5, 100%) indicate that cyclosporine improves venous allograft survival both when used systemically and as a graft pretreatment modality.