Long-Term Hepatic Vascular Access in the Nonhuman Primate for Recurrent Portal Vein Infusion

Long-Term Management of Vascular Access Ports in Nonhuman Primates Used in Preclinical Efficacy and Tolerability Studies

Vascular access ports (VAPs) are an essential tool for long-term vascular access in preclinical studies and disease modeling in non-human primates (NHPs). We retrospectively reviewed central (inferior vena cava, IVC) and portal VAP implantation with the maintenance at our center from 15 January 2010 to 31 January 2018. In total, 209 VAPs were implanted for long-term drug administration and sampling. Patency was >95% at 6 months and >80% at 1 year for IVC VAPs and >90% at 6 months and >85% at 1 year for portal VAPs. The majority of animals had no complications and access was generally durable with device use ranging up to 7 years. In IVC, VAPs loss of patency occurred in 13% (0.035/100 d), surgical site infection in 2.9% (0.097/100 d), port pocket infection in 2.2% (0.004/100 d), erosion in 2.9%, 0.008/100 d), and mechanical failure in 4.3% (0.012/100 d). In portal, VAPs loss of patency occurred in 11.3% (0.028/100 d) and port pocket infection in 1.4% (0.003/100 d). About 12% of VAPs were removed as a result of complications.This study confirms VAP implant and maintenance is a beneficial and safe practice in NHPs resulting in favorable outcomes. High patency rates and low complication rates are comparable to the clinical setting. In addition to enabling comprehensive data collection, VAPs increase satisfaction and well-being by minimizing interference with daily routines and fostering cooperation. VAP implantation, together with an effective maintenance regimen and co-operative handling, is a reliable and convenient refined method for drug administration and blood sampling.Keywords: Vascular access port; nonhuman primates; refinement; central vascular access; portal vascular access; surgical technique; experimental surgery; animal model.

A technique for systemic mesenchymal stem cell transplantation in newborn rat pups

Mesenchymal stem cells (MSC) have the potential to aid tissue regeneration. Intravenous (IV) MSC administration is currently being assessed following tissue injury. However, few studies have been performed to establish a safe and effective method of IV MSC infusion for newborns. We have established a safe, nontraumatic and effective technique for systemic MSC transplantation in newborn rats. Yellow-fluorescent-protein (YFP)-labeled MSC were characterized using MSC markers and their differentiation potential was confirmed. Rat pups were delivered by C-section on gestational day 21. The umbilical vein (UV) was cannulated and used for IV injection of MSC or saline control, which was performed under ultrasonographic imaging. An additional control group consisted of UV MSC injection in adult mice. Mean operating time, success rate of cannulation and death rate were recorded. YFP-MSC quantification in multiple organs was performed. Mean operating time was 3.9 ± 1.1 min. The success of UV MSC injection was 92.8%. The immediate and 24 hr delayed death rate for rat pups was significantly lower than that of adult mice (p < .05). No pups receiving saline injection died. After locating the patent foramen ovale (PFO) of newborn pups by ultrasonographic imaging, extra pulse-waves and wave-shape changes were detected when MSC were injected. The number of YFP-MSC was 15.8 ± 4.1 cells per visual field (CPVF) in the lungs, 2.9 ± 1.2 CPVF in the heart, and 19.8 ± 5.0 CPVF in the intestines. We conclude that IV MSC infusion through the UV is a convenient, safe, and effective method for systemic MSC transplantation in prematurely delivered newborn rats.

The usefulness and limitations of the diabetic macaque model in evaluating long-term porcine islet xenograft survival

BACKGROUND

  Various groups have reported prolonged diabetes reversal and graft function after porcine islet transplantation into diabetic macaques using different experimental designs (macaque source, islet source, type of immunosuppression): subsequently, the International Xenotransplantation Association has published recommendations for entering a clinical trial. Our experiments showed limitations that affected consistent achievement of long-term survival. We aimed to identify these limitations and underlying causes to emphasize the translational value of this highly relevant type 1 diabetic macaque model.

METHODS

  We reviewed data from our institution and literature data on long-term porcine islet xenograft survival in the diabetic macaque model, especially focusing on aspects of incomplete diabetes reversal relative to macaque normal values. This phenomenon was compared with diabetes reversal in an allo-islet transplant model in macaques and with chronic insulin treatment of diabetic macaques, all with 180-day follow-up. This comparison enabled to identify potential model limitations and underlying causative factors.

RESULTS

  Especially in the xenograft model, the achievement of long-term graft survival revealed limitations including chronic, mild hyperglycemia and absence of body weight (BW) gain or even progressive BW loss. Metabolic incompatibilities in glycemic control (i.e., insulin kinetics) between the pig and macaque species underlie chronic, mild hyperglycemia. This phenomenon might not bear relevance for the pig-to-human species combination because the glycemic control in pigs and humans is similar and differs from that in nonhuman primates (NHP). Weight loss could be related to changes in the gastrointestinal tract related with local high exposure to orally administered immunosuppressants; these must be given at higher dose levels because of low bioavailability in macaques to achieve systemic exposure at therapeutic levels. This is aggravated by insufficient graft insulin production in proportion to the needs of macaques: this model limitation has no translational value to the pig-to-human setting. Nutritional deficits can result in incorrect interpretation of blood glucose levels and C-peptide levels regarding graft function. Likewise, nutritional status alters physiologic responses, influencing susceptibility to infectious and noninfectious complications.

CONCLUSION

  THE model-induced confounding described interferes with accurate interpretation of safety and efficacy studies, which affects the translational value of pig-to-NHP islet cell transplant studies to the pig-to-human transplant condition.

Prostaglandin E2 (PGE2) in portal blood in patients with pancreatic tumor--a single institution series

BACKGROUND

Cyclooxygenase-2 (COX-2) may play a significant role in the development of pancreatic cancer. One of COX-2 main metabolites is prostaglandin E2 (PGE2), which is involved both in inflammation and carcinogenesis. As PGE2 is inactivated in the lungs and the liver we assumed that the best medium to assess the level of PGE2 is not peripheral but portal blood.

PATIENTS AND METHODS

Fifty-seven patients with pathologically verified diagnosis of pancreatic ductal adenocarcinoma (PDAC group, n = 38) and chronic pancreatitis (CP group, n = 19) were enrolled in this study. Sample of blood from central line was collected before surgery. Intraoperatively portal vein was identified and sampled. PGE2 levels were determined using ELISA test. All the patients were followed-up for 1-35 months.

RESULTS

PGE2 portal blood levels in patients with PDAC were higher than in patients with CP (190.55 ± 149.86 versus 120.23 ± 132.60; p = .04). PGE2 concentration at a cut-off value of 94.46 pg/ml had a sensitivity of 91.67%, specificity of 50%, AUC = 0.631 (95% CI, 0.489-0.758).

CONCLUSION

The PGE2 portal blood levels in PDAC patients are higher than in those with CP. The PGE2 portal concentration cannot be a single marker in diagnosing PDAC due to low specificity.

Successful implementation of cooperative handling eliminates the need for restraint in a complex non-human primate disease model

BACKGROUND

Streptozotocin-induced diabetic non-human primates are used to study efficacy and safety of innovative immunosuppression after islet transplantation. We implemented a training program for medical management of a chronic disease state.

METHODS

Cooperation with hand feeding and drinking, shifting, and limb presentation were trained utilizing predominately positive but also negative reinforcement in 52 animals compared with 28 macaques subjected to conventional physical and/or chemical restraint. The success and timing of behavior acquisition was evaluated in a representative subset of 14 animals.

RESULTS

Over 90% of animals were successful in behavior acquisition. Programmatically this resulted in complete elimination of chair restraint and negligible requirement for sedation. About half of the trained animals had no-to-moderate thymic involution, indicative of a substantial reduction in stress.

CONCLUSION

Cooperative handling enhances animal well-being. This contributes to validity of scientific results and eliminates model-induced confounding that can obstruct interpretation of safety and efficacy data.