The Structural and Cellular Viability in Cryopreserved Rabbit Carotid Arteries

OBJECTIVE

We investigated the histological and mechanical changes in addition to viable cellular recovery in cryopreserved blood vessels.

MATERIALS AND METHODS

Rabbit carotids were cryopreserved in a cryoprotective medium containing 1.5 M of 1,2-propanediol (PD) and then were thawed slowly in an ice bag that had been precooled in liquid nitrogen. Fresh carotids were used as the control. The fresh and freeze-thawed arteries were cultured for the growth of vascular smooth muscle cells (VSMCs). The freeze-thawed arterial tissues were perfused in vitro for 6, 12, or 24 h, respectively, to assess the integrity of carotid walls and the mechanical properties.

RESULTS

The results showed that it took almost the same time (24 approximately 36 h) for the VSMCs of the PD-cryopreserved arteries to regenerate as those from the fresh arteries. Their growing speeds also were similar. On the contrary, Me2SO-cryopreserved (1.5 M) arteries were unable to regenerate VSMCs in culture. After freeze-thawing, the mechanical properties decreased significantly (P < 0.003 for elastic modulus and P < 0.001 for fracture strength). After in vitro perfusion of the freeze-thawed carotid arteries, all of the survived endothelial cells fell off, and some of the VSMCs denaturalized or necrosed. The internal elastic fibers and collagen showed various degrees of cracking. The mechanical properties were decreased (P < 0.05).

CONCLUSION

Our findings demonstrate that the PD-containing cryoprotective medium can preserve regenerative capacity of VSMCs, which makes it a useful technique for viable VSMC recovery. However, the freeze-thawing process and the in vitro perfusion caused serious disruption in the arterial mechanical properties, rendering the cryopreserved blood vessels less useful for vessel reconstruction.

Cryopreservation prevents arterial allograft dilation

Historically, immune-mediated degradation and subsequent aneurysm formation have limited the usefulness of cryopreserved arterial allografts. This study tested the hypothesis that modern cryopreserved arterial allografts are protected from immune-mediated dilation. Abdominal aortas were harvested from anesthetized rats (Lewis and Brown-Norway) for immediate implantation or cryopreservation. Subsequently, Lewis rats underwent infrarenal aortic replacement with either an acutely harvested or a cryopreserved graft. There were four experimental groups: (1) acutely harvested isografts (Iso; n = 6), (2) cryopreserved isografts (C-Iso; n = 6), (3) cryopreserved allografts (C-Allo; n = 6), and (4) acutely harvested allografts (Allo; n = 6). All grafts were explanted at 8 weeks. A video camera and edge detection software were used to measure systolic and diastolic in vivo graft diameter (d). Measurement of arterial blood pressure (p) allowed calculation of compliance (Dd/Dp). Tail-cuff plethysmography was used to assess graft patency at 1 week. Graft diameter and blood pressure measurements were repeated at harvest. All harvested grafts were examined histologically. Our results showed that cryopreservation prevented immune-mediated dilation in arterial allografts in our 8-week rat implant model. Furthermore, the compliance of the cryopreserved grafts and was similar to that of controls. Further investigation is needed to delineate the exact mechanism of these potential clinically significant findings.

Management of infected hemodialysis access grafts using cryopreserved human vein allografts

BACKGROUND

One of the most feared complications of dialysis access is prosthetic arteriovenous (AV) graft infection, which is typically treated with AV graft removal followed by a staged dialysis graft placement elsewhere. Such a treatment approach often presents a challenge since many hemodialysis-dependent patients have limited venous access that may preclude a new AV graft or dialysis catheter placement. In this article, we review the management of AV graft infection using in situ cryopreserved human vein allografts.

DATA SOURCES

Functional and antigenic characteristics as well as the clinical experience of cryopreserved human vein allograft in dialysis access are reviewed. Surgical technique of in situ cryopreserved human allograft placement for infected prosthetic AV graft is also described.

CONCLUSIONS

Cryopreserved vein allograft is an acceptable graft conduit in difficult hemodialysis access situations. It offers surgeons the ability to deal with the infected graft in one operative procedure with low incidence reinfection and graft patency similar to conventional prosthetic graft replacement.

Comparison of healing in fresh and preserved arterial allografts in the dog

The use of aortic allografts for the management of vascular prosthetic infections has recently been reintroduced. Impressive results have been obtained; however, the possibility of late degeneration remains a major concern. The healing behavior of aortic allografts, either fresh or preserved, in antibiotic-supplemented nutrient medium at 4 degrees C for 1 week and used as thoracic aorta substitutes in dogs was investigated after 6 months of implantation. Four dogs received a fresh aortic allograft from four different donors, and four dogs received a preserved allograft from two different donors. Autografts in two dogs were performed as controls. The in vivo investigation was conducted to describe (1) the histological characteristics of the arterial wall, (2) the macroscopic and thrombogenic aspect of the luminal surface, (3) the integrity of the endothelial lining by scanning electron microscopy, and (4) its biochemical function by prostacyclin (PGI2) and thromboxane A2 (TXA2) secretion. Immune-mediated reactions directed toward the grafts were measured by sequential screening of donor-specific serum antibody development. All donor-recipient pairs of dogs were major histocompatibility complex (MHC)-incompatible according to a mixed lymphocyte reaction (MLR) assay. From the results of this study we concluded that although preserved arterial allografts exhibited similar surface characteristics as those of fresh allografts in terms of re-endothelialization and long-term graft function, an elicited immune response, a degenerative process in the media, and a hyperplasic reaction in the intima could not be prevented using this method of preservation.