Chronic cannulation and fistulization procedures in swine: a review and recommendations

Development of a Special Catheterbag to Enable Artificial Organ Evaluation in Conscious, Unrestrained Pigs: Technical Note

Pigs are widely used as models for a variety of human diseases, because many of their physiological functions closely resemble those of humans. However, information on instrumentation techniques is still scarce. In particular, experiments in conscious pigs focused on extracorporeal circuits are connected to a variety of methodical problems with respect to the handling of the animals. Usually, pigs are placed in restraint-slings during the application of an extracorporeal system. However, this method of restraint may lead to excessive mental distress even in trained animals. The latter might influence the results and certainly affects principles of animal welfare. Our own experiences with instrumented, conscious, but unrestrained dogs encouraged us to modify methods used for the fixation of in-dwelling central venous catheters in dogs with special regard to the species specific behaviour and phenotype of pigs. A cord retractable leash (CRL) was used for maintaining a safe distance between the animal and the outer ends of the catheters. To prevent dehiscences of the required fixation sutures a new catheter bag (CB) was designed to counteract tension forces caused by the CRL's spring-mechanism. The combination of both the CRL and CB enabled us to conduct safe experiments with conscious, unrestrained pigs. We alleviated the mental distress these animals were exposed to in comparison to former methods based on restraint of the animals.

Recent advances in ureteral tissue engineering

Reconstruction of long ureteral defects often warrants the use of graft tissue and extensive surgical procedures to maintain the safe transport of urine from the kidneys to the urinary bladder. Complication risks, graft failure-related morbidity, and the lack of suitable tissue are major concerns. Tissue engineering might offer an alternative treatment approach in these cases, but ureteral tissue engineering is still an underreported topic in current literature. In this review, the most recent published data regarding ureteral tissue engineering are presented and evaluated, with a focus on cell sources, implantation strategies, and (bio)materials.

Pilot laparoscopic ileal cannulation in pigs

Zhang, S. X., Wang, H. B., Zhang, H., Liu, H. F., Zhou, Z. F., Zhang, J. T. and Gao, L. 2014. Pilot laparoscopic ileal cannulation in pigs. Can. J. Anim. Sci. 94: 371–377. Pilot laparoscopic ileal cannulation was performed in eight anesthetized pigs (40.5±1.9 kg) positioned in dorsal recumbency using three portals in the abdomen. The T-shaped ileal cannulation site was located 15 cm anterior to the ileocecal valve on the antimesenteric section of the ileum. A transabdominal suspension suture was placed approximately 3 cm caudal to the ileal cannulation site. A purse-string suture was placed first around the insertion site, and a stab incision was made in the middle of the purse-string suture. The T-shaped cannula was inserted into the ileal lumen through the stab incision, and the purse-string suture was tightened. The T-shaped ileal cannula was pulled out of the abdominal cavity through the exit wound located 3–5 cm lateral and 10–12 cm caudal to the right or left side of the umbilicus. The transabdominal suspension suture was then removed. The T-shaped cannula was secured to the skin with a finger-trap suture. Surgical time and complications were recorded. Repeat laparoscopy was performed 35 d later. No major intraoperative or postoperative complications were encountered. The ileal contents were collected easily. On repeat laparoscopy, firm adhesion between the ileum and the abdominal wall was observed in all pigs, and there was no evidence of digesta leakage or consequential peritonitis.

Hybrid pig versus Göttingen minipig-derived cartilage and chondrocytes show pig line-dependent differences

Minipigs are widely used as a large animal model for cartilage repair. However, many in vitro studies are based on porcine chondrocytes derived from abundantly available premature hybrid pigs. It remains unclear whether pig line-dependent differences exist which could limit the comparability between in vitro and in vivo results using either hybrid or miniature pig articular chondrocytes. Porcine knee joint femoral cartilage was isolated from 3- to 5-month-old hybrid pigs and Göttingen minipigs. Cartilage from both pig lines was analysed for thickness, zonality, cell content, size and proteoglycan deposition. Cultured articular chondrocytes from both pig lines were investigated for gene and/or protein expression of cartilage-specific proteins such as type II collagen, aggrecan, the chondrogenic transcription factor Sox9, non-specific type I collagen and the cell-matrix receptor β1-integrin. Cartilage was significantly thinner in the miniature pig compared to the hybrid pig, but the differences between the medial and lateral femur condyles did not reach a significant level. Knee joint cartilage zone formation started only in the minipig, whereas cellularity and cell diameters were comparable in both pig lines. Blood vessels could be detected in the hybrid pig but not the minipig cartilage. Sulphated proteoglycan deposition was more pronounced in cartilage zones II–IV of both pig lines. Minipig chondrocytes expressed type II and I collagen, Sox9 and β1-integrin at a higher level than hybrid pig chondrocytes. These distinct line-dependent differences should be considered when using hybrid pig-derived chondrocytes for tissue engineering and Göttingen minipigs as a large animal model.

Best practices for performing experimental surgery in swine

The authors have extensive experience in surgery, anesthesia, and perioperative care in both miniature and domestic swine in the research setting. This manuscript describes the techniques that have been developed over the last four decades while developing porcine surgical models and their use in translational research. Swine are conditioned and socialized during a seven-day period prior to entering into a survival surgical protocol. Housing is designed to be nonstressful and accommodate the needs of the species. Induction of anesthesia is generally performed in the animal's pen. Injectable agents are administered sc in the neck using a butterfly catheter technique. The anesthetic protocol is designed to consider the physiologic effects of the agents and their potential effects on the research being performed. Complete aseptic technique is performed and includes final application of adhesive iodine impregnated drapes over the surgical site. Preemptive analgesia is performed using parenteral analgesics, local anesthetics, and/or epidural analgesics. Animals are monitored intensively intraoperatively and during the postoperative period with frequent recordings of physiologic parameters. Observation during the postoperative period is continuous until the animal fully recovers the righting reflex. Observations of the animals in the postoperative period are performed at least daily until surgical incisions are healed. In protocols which create defects or impede physiologic function daily monitoring may have to be performed in conjunction with specific therapies or tests throughout the duration of the protocol.

Tissue engineered tubular construct for urinary diversion in a preclinical porcine model

PURPOSE

The ileal conduit has been considered the gold standard urinary diversion for patients with bladder cancer and pediatric patients. Complications are mainly related to the use of gastrointestinal tissue. Tissue engineering may be the technical platform on which to develop alternatives to gastrointestinal tissue. We developed a collagen-polymer conduit and evaluated its applicability for urinary diversion in pigs.

MATERIALS AND METHODS

Tubular constructs 12 cm long and 15 mm in diameter were prepared from bovine type I collagen and Vypro® II synthetic polymer mesh. Characterized tubes were sterilized, seeded with and without primary porcine bladder urothelial cells, and implanted as an incontinent urostomy using the right ureter in 10 female Landrace pigs. At 1 month the newly formed tissue structure was functionally and microscopically evaluated by loopogram and immunohistochemistry, respectively.

RESULTS

The survival rate was 80% with 1 related and 1 unrelated death. By 1 month the collagen was resorbed and a retroperitoneal tunnel had formed that withstood 40 cm H(2)O water pressure. In 5 cases the tunnel functioned as a urostomy. Histological analysis revealed a moderate immune response, neovascularization and urothelial cells in the construct lumen. The polymer mesh provoked fibroblast deposition and tissue contraction. No major differences were observed between cellular and acellular constructs.

CONCLUSIONS

After implanting the tubular constructs a retroperitoneal tunnel was formed that functioned as a urinary conduit in most cases. Improved large tubular scaffolds may generate alternatives to gastrointestinal tissue for urinary diversion.

Transsplenic portal catheterization combined with a jugular double-lumen catheter for pharmacokinetic and presystemic metabolization studies in pigs

The reliability of a silicone double-lumen catheter implanted into the external jugular vein and tunnelled towards the neck region was investigated in eight pigs. Surgery was uneventful without interference with the normal homoeostasis during 8 days. After injection of amoxicillin/clavulanic acid through the distal port of the catheter, analysis of drug components in the simultaneous blood samples obtained by the proximal port and a Venoject system were comparable in one pig. Histological control of the catheterized jugular veins pointed to an acceptable tissue reaction while bacteriological examination of the tip of the catheters was negative in only three animals. A moulding of the intestinal veins was made in a pig cadaver to determine the optimal length of insertion of a silicone portal catheter from the splenic vein towards the portal vein. Surgery was straightforward in four pigs whereby the catheter was exteriorized towards the back region. No complications were encountered during and after surgery for 9 days. The technique of a double-lumen catheter placed into the jugular vein and a transsplenic portal catheter is a useful tool for the study of the pharmacokinetics and also the first-pass effect of drugs in experimental pigs.

Risk factors associated with surgical site infection and the development of short-term complications in macaques undergoing indwelling vascular access port placement

BACKGROUND

Risk factors associated with surgical site infection (SSI) and the development of short-term complications in macaques undergoing vascular access port (VAP) placement are evaluated in this study.

METHODS

Records from 80 macaques with VAPs were retrospectively reviewed. Logistic regression was used to identify factors associated with short-term post-operative complications.

RESULTS

The primary outcome was SSI, which occurred in 21.6% (52.6% in the first 12 months vs. 13% thereafter) of procedures. SSI was associated with major secondary complications including VAP removal (11.4%), wound dehiscence (5.7%), and mechanical catheter occlusion (5.7%). In multivariate modeling, only surgical program progress was a statistically significant predictor of SSI, while animal compliance had a slightly protective effect.

CONCLUSIONS

Vascular access ports have a moderate risk of complications, provided the surgical program optimizes best practices. Under complex experimental conditions, VAPs represent an important refinement, both improving animals' overall well-being and environment and reducing stress.

Preparation of swine for the laboratory

Swine are an important model in many areas of biomedical research. These animals have been used predominantly as preclinical models involving surgical and interventional protocols. The systems most commonly studied include cardiovascular, integumentary, digestive, and urological. Swine are intelligent social animals and require species-specific socialization and handling techniques. It is important to acclimate the animals to the facility and to personnel before they are placed on chronic protocols. Gentle handling techniques instead of forceful procedures are essential to their socialization. They require sturdy caging with specific construction standards, and toys for environmental enrichment. Because the species is covered by both the Animal Welfare Act and the US Department of Agriculture, interstate transport requires a health certificate with destination state-specific disease screening standards. This manuscript provides an overview of best practices that have been utilized in the authors' facility.

New surgical technique for portal venous port system in Swine

The need for serial blood sampling and continuous infusion using the portal vein for experimental surgery and pharmacological studies is evident. As suitable animal models are rare, we established a new technique to implant a permanent vascular access device to the portal vein in swine. All operations in study animals (n=8) were technically feasible due to a regularly detected side branch of the portal vein within the inferior pancreatic region; complications did not occur. Mean operation time was 48+/-17 min. This study clearly shows that the portal venous access is feasible and can be achieved safely using the inferior pancreatic vein for a permanent vascular access port system.

Myelination of the Pig’s Brain: A Correlated MRI and Histological Study

Minipigs, 2, 4, 6 months old, were used to evaluate the relationship between myelination in the fiber tracts of the central nervous system (CNS) of this animal during development. Histological results showed an increased density of the myelinated fibers as well as branching of these fibers in the areas studied, including the cortical white matter, olfactory tract, the corticospinal tract, the fasciculus cuneatus and the spinal V nucleus from 2 to 6 months old. By 6 months, the pig was sexually matured. Concomitantly, there was an increase in high signal-intensity regions (sites) in the magnetic resonance T(1)-weighted images as myelination progressed. There is a good correlation between the histologically observed progress of myelination and the T(1)-weighted images in the development of the CNS of the pig.