First-in-human feasibility study of the aXess graft (aXess-FIH): 6-Month results

OBJECTIVE

The creation of an arteriovenous fistula (AVF) is considered the most effective hemodialysis (HD) vascular access. For patients who are not suitable for AVF, arteriovenous grafts (AVGs) are the best access option for chronic HD. However, conventional AVGs are prone to intimal hyperplasia, stenosis, thrombosis, and infection. Xeltis has developed an AVG as a potential alternative to currently available AVGs based on the concept of endogenous tissue restoration. The results of the first 6-month follow-up are presented here.

METHODS

The aXess first-in-human (FIH) study [NCT04898153] is a prospective, single-arm, multicenter feasibility study that evaluates the early safety and performance of the aXess Hemodialysis Graft. A total of 20 patients with end-stage renal disease were enrolled across six European investigational sites.

RESULTS

At 6-months follow-up, all grafts were patent with primary and secondary patency rates were 80% and 100%, respectively. Three patients required a re-intervention to maintain graft patency, while one re-intervention was required to restore patency. One graft thrombosis and zero infections were reported.

CONCLUSION

The expected advantages of the novel aXess Hemodialysis Graft over conventional AVGs would be evaluated by the analysis on long-term safety and effectiveness during the 5-year follow-up of the currently ongoing trial.

Susceptibility of ePTFE vascular grafts and bioengineered human acellular vessels to infection

BACKGROUND

Synthetic expanded polytetrafluorethylene (ePTFE) grafts are routinely used for vascular repair and reconstruction but prone to sustained bacterial infections. Investigational bioengineered human acellular vessels (HAVs) have shown clinical success and may confer lower susceptibility to infection. Here we directly compared the susceptibility of ePTFE grafts and HAV to bacterial contamination in a preclinical model of infection.

MATERIALS AND METHODS

Sections (1 cm²) of ePTFE (n = 42) or HAV (n = 42) were inserted within bilateral subcutaneous pockets on the dorsum of rats and inoculated with Staphylococcus aureus (10⁷ CFU/0.25 mL) or Escherichia coli (10⁸ CFU/0.25 mL) before wound closure. Two weeks later, the implant sites were scored for abscess formation and explanted materials were halved for quantification of microbial recovery and histological analyses.

RESULTS

The ePTFE implants had significantly higher abscess formation scores for both S. aureus and E. coli inoculations compared to that of HAV. In addition, significantly more bacteria were recovered from explanted ePTFE compared to HAV. Gram staining of explanted tissue sections revealed interstitial bacterial contamination within ePTFE, whereas no bacteria were identified in HAV tissue sections. Numerous CD45⁺ leukocytes, predominantly neutrophils, were found surrounding the ePTFE implants but minimal intact neutrophils were observed within the ePTFE matrix. The host cells surrounding and infiltrating the HAV explants were primarily nonleukocytes (CD45^-).

CONCLUSIONS

In an established animal model of infection, HAV was significantly less susceptible to bacterial colonization and abscess formation than ePTFE. The preclinical findings presented in this manuscript, combined with previously published clinical observations, suggest that bioengineered HAV may exhibit low rates of infection.

Favorable outcome in a renal transplant recipient with donor-derived infection due to multidrug-resistant Pseudomonas aeruginosa

Most cases of donor-derived infection due to Pseudomonas aeruginosa reported in the literature are associated with vascular dehiscence, all of which resulted either in death or graft failure requiring graft removal. We report the successful treatment of donor-derived infection due to multidrug-resistant P. aeruginosa in a 64-year-old male who presented with bacteremia and peritransplant renal fluid collection after undergoing deceased-donor renal transplantation. As a result of the report of positive donor cultures by the host Organ Procurement Organization, the infection was promptly identified by blood cultures drawn before appearance of symptoms. Surveillance blood cultures in recipients are not usually recommended. However, they should be done if donor cultures turn positive. Therefore, it is crucial to perform cultures in donors and to closely follow them up for early identification and prompt treatment of donor-transmitted infections due to organisms like P. aeruginosa that can be graft and/or life threatening.

Porphyromonas gingivalis infection accelerates intimal thickening in iliac arteries in a balloon-injured rabbit model

BACKGROUND

Current epidemiologic data suggest that a localized infection (periodontitis) can disseminate into the distant tissues, and subgingival bacteria can migrate in the bloodstream, thereby contributing to independent systemic disease processes. To test this hypothesis, we investigated the effect of repeated systemic inoculations with Porphyromonas gingivalis (Pg) on intimal hyperplasia in iliac arteries in a rabbit model of balloon injury.

METHODS

One week after single balloon injury to the iliac artery, 30 male New Zealand rabbits were randomly assigned to intravenous inoculation with 100 microl live Pg (10(7) colony-forming units; n = 15) or vehicle (n = 15) once weekly for 4, 8, or 12 consecutive weeks. Arteries were fixed by perfusion and removed for analysis of neointimal lesion formation. We measured intimal and medial lesion areas in iliac artery cross-sections as well as the intimal/medial ratio (I/M). We also analyzed Pg 16S ribosomal DNA amplification with polymerase chain reaction, systemic proinflammatory mediators with enzyme-linked immunosorbent assay, and immunolocalization of macrophages in the balloon-injured arteries.

RESULTS

At 12 weeks, iliac intimal hyperplasia was accelerated, and I/M was significantly increased in Pg-inoculated animals (I/M 3.961 +/- 0.536 in the Pg group versus 3.585 +/- 0.353 in the control animals; P <0.01). Pg-inoculated animals also had significant increases in macrophage infiltration at 12 weeks, C-reactive protein levels at all time points, and interleukin-6 levels at 12 weeks. Moreover, Pg ribosomal DNA was found in the injured arteries of Pg-inoculated animals, but only after 12 weeks.

CONCLUSION

Long-term systemic challenge with Pg, an oral pathogen, may accelerate intimal hyperplasia in balloon-injured iliac arteries.

A reproducible porcine ePTFE arterial bypass model for neointimal hyperplasia

BACKGROUND

Late failure of prosthetic vascular bypass grafting using expanded polytetrafluoroethylene (ePTFE) is secondary to the development of neointimal hyperplasia, most commonly at the distal anastomosis. To develop therapies that can improve upon current prosthetic vascular bypass grafting, a large animal model of prosthetic bypass grafting that results in reproducible neointimal hyperplasia is necessary.

METHODS

We performed bilateral end-to-side carotid artery bypasses with 6 mm ePTFE in a porcine model (n = 11). We studied graft patency using magnetic resonance angiography (MRA, 3 wk), duplex ultrasonography (4 wk), and digital-subtraction contrast angiography (4 wk). Animals were sacrificed at 4 wk and morphometric analysis was performed.

RESULTS

Of the 11 animals that underwent surgery, one pig died from respiratory compromise; of the remaining 10, graft patency was 90% at 4 wk. Peak systolic and end diastolic velocities were established for this model using ultrasonography. MRA, ultrasonography, and angiography confirmed graft patency and were complimentary tools to evaluate the grafts. Development of neointimal hyperplasia was reproducible at 4 wk in both the proximal and distal anastomoses (2.5 to 3 mm(2)) of the ePTFE bypass grafts.

CONCLUSION

We developed a reproducible porcine ePTFE carotid artery bypass model for studying neointimal hyperplasia. Not only does this model allow for the manipulation and evaluation of potential therapies, but patency and neointimal hyperplasia can be easily evaluated by traditional means, such as MRA, ultrasonography, and angiography. This preclinical model is ideal for evaluation of novel therapies in vivo designed to inhibit neointimal hyperplasia following arterial reconstruction with prosthetic bypass grafting.