Glutaraldehydetanned mandril-grown grafts as venous substitutes

Incomplete cellular depopulation may explain the high failure rate of bovine ureteric grafts

BACKGROUND

The aim was to assess the results of a decellularized bovine ureter graft (SynerGraft) for complex venous access.

METHODS

Bovine ureter conduits were implanted in patients with a failed fistula or access graft in whom native vessels were unsuitable as conduits. Graft histories were obtained from all patients who had undergone this procedure at one institution. Failed grafts were explanted and subjected to histological examination. A sample of fresh bovine ureter was immunostained for galactose (alpha1 --> 3) galactose (alpha-Gal).

RESULTS

Nine patients with a median age of 46 (range 25-70) years underwent complex venous access surgery between August 2004 and November 2006 using a SynerGraft. Graft types included loop superficial femoral artery to stump of long saphenous vein (four patients), loop brachial artery to vein (two), brachial artery to axillary vein (two) and left axillary artery to innominate vein (one). Three grafts developed aneurysmal dilatation and two thrombosed. Histological assessment of the explanted bovine ureters revealed acute and chronic transmural inflammation. Immunostaining of fresh bovine ureter suggested residual cells and the xenoantigen alpha-Gal.

CONCLUSION

Graft failure with aneurysmal dilatation and thrombosis in complex arteriovenous conduits using bovine ureter may be due to residual xenoantigens.

Depopulated bovine ureteric xenograft for complex haemodialysis vascular access

OBJECTIVES

To assess performance of a de-cellularised bovine ureter vascular graft for haemodialysis in patients for whom conventional access was not possible.

METHODS

The Syner Graft Vascular Graft Model 100 (SGVG 100) is a bovine ureter modified by a tissue-engineering depopulation technology and uniquely it is not chemically cross-linked. SGVG 100 was implanted in patients with a failed fistula or vascular access grafts. Graft patency was the primary outcome; secondary outcomes included adverse events and associated treatments.

RESULTS

25 SGVG 100 were implanted in 23 patients; mean age was 59+/-14 years. Mean follow-up was 370 days. The mean time to occlusion (19 events) was 215+/-141 days with patency re-established in 14 of 18 surgical interventions. Thirty angioplasties were performed on 14 SGVG 100 for luminal/anastomotic stenosis. Two grafts demonstrated areas of dilation; however, both grafts continue to be usable at last reported follow-up (930 and 602 days) with no further changes in graft size. Primary patency, assisted primary patency, secondary patency, and freedom from infection were 29, 45, 81, and 95% at 1 year, respectively.

CONCLUSIONS

This report demonstrates SGVG 100 is a stable vascular access conduit, providing a suitable graft alternative when autologous vein is not available.

Tissue Engineering für Herzklappen und Gefäße

Current prosthetic substitutes for heart valves and blood vessels have numerous limitations such as limited durability (biological valves), susceptibility to infection, the necessity of lifelong anticoagulation therapy (prosthetic valves), and reduced patency in small-caliber grafts, for example. Tissue engineering using either polymers or decellularized native allogeneic or xenogenic heart valve/vascular matrices may provide the techniques to develop the ideal heart valve or vascular graft. The matrix scaffold serves as a basis on which seeded cells can organise and develop into the valve or vascular tissue prior to or following implantation. The scaffold is either degraded or metabolised during the formation and organisation of the newly generated matrix, leading to vital living tissue. This paper summarises current research and first clinical developments in the tissue engineering of heart valves and vascular grafts.

Small intestine without mucosa as a growing vascular conduit: a porcine experimental study

OBJECTIVE

This study was conducted to check the feasibility of using small intestine without mucosa as a growing vascular conduit.

METHOD

Autologous proximal jejunum without mucosa after treatment with heparin bonding was used as a free inferior vena cava interpositional graft between the renal veins and bifurcation of inferior vena cava in 8 piglets. Intravenous ultrasonography was performed at 1 to 3 months after the operation and at autopsy.

RESULTS

One intraoperative death was related to anesthesia. At a mean follow-up of 80 days for the 7 surviving pigs, the weight had increased by 201%, from a mean of 32 kg to a mean of 94 kg. The grafts had increased in length by 128%, from a mean of 2.3 cm at implantation to a mean of 5.1 cm (P <.018) at explantation. In 6 animals the diameter of the graft was equal to that of the adjacent inferior vena cava. At postmortem examination, 6 grafts were patent. The single blocked graft had been patent 1 month after surgery. One graft had extensive septae inside, 2 had minor septae, 2 had microscopic septae, and 2 had no septae at all. Normal appearing adventitia, fibrous tissue, and endothelium (factor VIII-related antigen positive) lined all the grafts. In all 7 grafts, scattered proliferating fibroblasts (MIB1 positive) were observed.

CONCLUSIONS

Small intestine without mucosa remodels and acts like a live, growing, layered, endothelialized, nonthrombogenic (after re-endothelialization) vascular conduit in a growing pig. This graft material could have potential as a growing vascular conduit in children.

Percutaneous delivery of a heparin-impregnated collagen stent-graft in a porcine model of atherosclerotic disease

RATIONALE AND OBJECTIVES

To develop collagen stent-grafts impregnated with heparin to improve the biocompatibility of endovascular stents and to design a percutaneous delivery system for graft deployment in a swine model.

METHODS

Heparin-impregnated collagen stent-grafts were deployed, and follow-up angiograms were obtained every 15 minutes for 90 minutes to assess acute thromboses and again at 2 and 4 weeks afterward to assess patency. If stenosis or occlusion was detected at the 2-week evaluation, guidewire passage across the lesion was attempted and angioplasty was performed. If stenosis or occlusion was present at the 4-week evaluation, only guidewire passage was attempted; thereafter, the animals were killed and the stent-grafts were harvested and reviewed by a vascular pathologist.

RESULTS

Group A represents a feasibility study to optimize the deployment method applied in groups B and C. Fifteen of 17 stent-grafts were successfully deployed using this method. In group B, 89% of grafts were successfully deployed; 12% were patent at 2 weeks and none at 4 weeks. In group C, a 10-minute inflation time was added to the deployment procedure; 88% of grafts were successfully deployed and 28% were patent at 2 weeks and 14% at 4 weeks. Extensive luminal thrombosis and myointimal hyperplasia were present in every case.

CONCLUSIONS

A method was developed for percutaneous implantation of collagen stent-grafts into peripheral vessels. The heparin-impregnated grafts did not prevent vessel restenosis. Modification of the graft-processing technique may improve patency.