Long-term results of autologous scaffold-free tissue-engineered vascular graft for hemodialysis access

BACKGROUND

The growing size of the end stage renal disease (ESRD) population highlights the need for effective dialysis access. Exhausted native vascular access options have led to increased use of catheters and prosthetic shunts, which are both associated with high risks of access failure and infection. Emerging alternatives include tissue-engineered vascular grafts (TEVG). Here we present the endpoint results for 10 ESRD patients with the scaffold-free tissue-engineered vascular access produced from sheets of extracellular matrix produced in vitro by human cells in culture.

METHODS

Grafts were implanted as arteriovenous shunts in 10 ESRD patients with a complex history of access failure. Follow-up included ultrasound control of graft morphology and function, dialysis efficiency, access failure, intervention rate, as well as immunohistochemical analysis of graft structure.

RESULTS

One patient died of unrelated causes and three shunts failed to become useable access grafts during the 3-month maturation phase. The 12-month primary and secondary patency for the other six shunts was 86%. Survival of six shunts functioning as the vascular access was 22 ± 12 months with longest primary patency of 38.6 months. The dialysis event rate of 3.34 per patient-year decreased significantly with the use of this TEVG to 0.67.

CONCLUSIONS

This living autologous tissue-engineered vascular graft seems to be an alternative to synthetic vascular access options, exhibiting advantages of native arteriovenous fistula.

Hypogastric artery stenosis in a patient with severe chronic ischemia

Atherosclerotic lesions of the hypogastric artery have been recognized as a cause of buttock claudication, thigh claudication, and impotence, and usually treated by endovascular procedures and in some instances with open surgery. We report an unusual case of a total occlusion of the left external iliac artery, severe stenosis of the left hypogastric artery with rest pain, and ischemic lesion in the left foot that was successfully treated with hypogastric angioplasty and covered self-expanding stent implant. The patient recovered distal pulses, rest pain disappeared, and the ischemic lesion healed; currently the patient walks without intermittent claudication, and the lesion of the toe has healed.

Effectiveness of haemodialysis access with an autologous tissue-engineered vascular graft: a multicentre cohort study

BACKGROUND

Application of a tissue-engineered vascular graft for small-diameter vascular reconstruction has been a long awaited and much anticipated advance for vascular surgery. We report results after a minimum of 6 months of follow-up for the first ten patients implanted with a completely biological and autologous tissue-engineered vascular graft.

METHODS

Ten patients with end-stage renal disease who had been receiving haemodialysis through an access graft that had a high probability of failure, and had had at least one previous access failure, were enrolled from centres in Argentina and Poland between September, 2004, and April, 2007. Completely autologous tissue-engineered vascular grafts were grown in culture supplemented with bovine serum, implanted as arteriovenous shunts, and assessed for both mechanical stability during the safety phase (0-3 months) and effectiveness after haemodialysis was started.

FINDINGS

Three grafts failed within the safety phase, which is consistent with failure rates expected for this high-risk patient population. One patient was withdrawn from the study because of severe gastrointestinal bleeding shortly before implantation, and another died of unrelated causes during the safety period with a patent graft. The remaining five patients had grafts functioning for haemodialysis 6-20 months after implantation, and a total of 68 patient-months of patency. In these five patients, only one intervention (surgical correction) was needed to maintain secondary patency. Overall, primary patency was maintained in seven (78%) of the remaining nine patients 1 month after implantation and five (60%) of the remaining eight patients 6 months after implantation.

INTERPRETATION

Our proportion of primary patency in this high-risk cohort approaches Dialysis Outcomes Quality Initiative objectives (76% of patients 3 months after implantation) for arteriovenous fistulas, averaged across all patient populations.

Mechanical properties of completely autologous human tissue engineered blood vessels compared to human saphenous vein and mammary artery

We have previously reported the initial clinical feasibility with our small diameter tissue engineered blood vessel (TEBV). Here we present in vitro results of the mechanical properties of the TEBVs of the first 25 patients enrolled in an arterio-venous (A-V) shunt safety trial, and compare these properties with those of risk-matched human vein and artery. TEBV average burst pressures (3490+/-892 mmHg, n=230) were higher than native saphenous vein (SV) (1599+/-877 mmHg, n=7), and not significantly different from native internal mammary artery (IMA) (3196+/-1264 mmHg, n=16). Suture retention strength for the TEBVs (152+/-50 gmf) was also not significantly different than IMA (138+/-50 gmf). Compliance for the TEBVs prior to implantation (3.4+/-1.6%/100 mmHg) was lower than IMA (11.5+/-3.9%/100 mmHg). By 6 months post-implant, the TEBV compliance (8.8+/-4.2%/100 mmHg, n=5) had increased to values comparable to IMA, and showed no evidence of dilation or aneurysm formation. With clinical time points beyond 21 months as an A-V shunt without intervention, the mechanical tests and subsequent lot release criteria reported here would seem appropriate minimum standards for clinical use of tissue engineered vessels.

[Kidney revascularization and function recovery in patients in dialysis]

The available literature was reviewed to analyze the indications and results of the surgical restoration of flow to ischemic kidneys in dialyzed patients with ischemic nephropathy. Only 57 were found, a small number compared with the estimated percentage (5 to 15%) of ischemic insufficiency in dialyzed patients. Atherosclerosis was the main cause of ischemia and most patients were over the seventh decade of life. Common clinical findings were uncontrolled hypertension and/or acute cardiac failure, symptomatic atherosclerotic disease in other areas and rapid deterioration of renal function. Kidneys recovered after variable periods of ischemia (days to 13 months of dialysis, mean 30.5 days), with small size, 9, 8 or even 7 cm, absent nephrograms of flat flow curves in isotopic studies or without distal arteries and/or collaterals in the angiogram. Total arterial occlusion was more frequent than stenosis. After surgery the patients recovered immediately (35%) or required transitory dialysis (52%); in a few (12.2%) function was not restored. Hypertension improved or was cured in almost all patients. The good results persisted during long periods. A better knowledge of the disease, early detection and treatment, will improve the quality of life and survival of patients with ischemic nephropathy.

Relationship between the development of diaphragma sellae and the morphology of the sella turcica and its content

The impaired formation of the diaphragma sellae may lead to the development of the empty-sella syndrome. This structure, when fully formed, is a protective barrier against the pulsating action that the cerebrospinal fluid exerts on the sellar content. There are anatomical features which support this belief, but they also suggest that the development of the diaphragma sellae is a factor which determines the morphology of the sella turcica and its contents. Those human specimens which do not have diaphragma sellae or in which it is only partially developed, are characterized by a smaller hypophysis, always located at the inferior and/or posterior half of the sella, with a larger sellar volume and frequently greater fragility of its bony walls. These findings, although rare (5% of the cases), are indirect signs of the important role which the diaphragma sellae plays in the sellar region.