Acute Immune Response in Venoarterial and Venovenous Extracorporeal Membrane Oxygenation Models of Rats

Although experimental extracorporeal membrane oxygenation (ECMO) animal models have been reported, there are few studies on the immune response to ECMO. We developed the venoarterial (VA) and venovenous (VV) model in rats and serially investigated the changes in the distribution of immune cells. Forty rats underwent both VA and VV modes of ECMO, and blood samples were collected at 1 day before ECMO (D-1), at the end of ECMO run (D+0), and 3 days after the ECMO (D+3). Flow cytometry was used to characterize surface marker expression (CD3, CD4, CD8, CD43, CD45, CD45R, CD161, and His48) on immune cells. Granulocytes were initially activated in both ECMO types and were further reduced but not normalized until 3 days of decannulation. Monocyte and natural killer cells were decreased initially in VA mode. B lymphocytes, helper T lymphocytes, and cytotoxic T lymphocytes also significantly decreased in VA modes after ECMO, but this phenomenon was not prominent in the VV modes. Overall immune cells proportion changed after ECMO run in both modes, and the immunologic balance altered significantly in the VA than in VV mode. Our ECMO model is feasible for the hemodynamic and immunologic research, and further long-term evaluation is needed.

Extracorporeal circulation models in small animals: beyond the limits of preclinical research

Extracorporeal membrane oxygenation (ECMO) use has remarkably increased in recent years. Although ECMO has become essential for patients with refractory cardiac and respiratory failure, extracorporeal circulation (ECC) is associated with significant complications. Small-animal models of ECC have been developed and widely used to better understand ECC-induced pathophysiology. This review article summarizes the development of small-animal ECC models, including the animal species, circuit configuration, priming, perioperative procedures, cannulation, and future perspectives of small-animal ECMO models.

Rapid remodeling observed at mid-term in-vivo study of a smart reinforced acellular vascular graft implanted on a rat model

BACKGROUND

The poor performance of conventional techniques used in cardiovascular disease patients requiring hemodialysis or arterial bypass grafting has prompted tissue engineers to search for clinically appropriate off-the-shelf vascular grafts. Most patients with cardiovascular disease lack suitable autologous tissue because of age or previous surgery. Commercially available vascular grafts with diameters of < 5 mm often fail because of thrombosis and intimal hyperplasia.

RESULT

Here, we tested tubular biodegradable poly-e-caprolactone/polydioxanone (PCL/PDO) electrospun vascular grafts in a rat model of aortic interposition for up to 12 weeks. The grafts demonstrated excellent patency (100%) confirmed by Doppler Ultrasound, resisted aneurysmal dilation and intimal hyperplasia, and yielded neoarteries largely free of foreign materials. At 12 weeks, the grafts resembled native arteries with confluent endothelium, synchronous pulsation, a contractile smooth muscle layer, and co-expression of various extracellular matrix components (elastin, collagen, and glycosaminoglycan).

CONCLUSIONS

The structural and functional properties comparable to native vessels observed in the neoartery indicate their potential application as an alternative for the replacement of damaged small-diameter grafts. This synthetic off-the-shelf device may be suitable for patients without autologous vessels. However, for clinical application of these grafts, long-term studies (> 1.5 years) in large animals with a vasculature similar to humans are needed.

A Comparative Study Between Cold Static Storage and Normothermic Ex-Situ Donor Heart Preservation in a Rat Model of Heterotopic Heart Transplantation

INTRODUCTION

Cold static storage (CSS) and normothermic ex-situ preservation are the most widely used donor heart preservation techniques worldwide. The current study compares both CSS and normothermic ex-situ preservation methods in terms of graft performance, morphologic changes, and acute immune response in an experimental model.

METHOD AND MATERIALS

Twenty rats underwent heterotopic abdominal heart transplantation after 2 h of CSS (group 1; n = 10) or normothermic ex-situ perfusion (group 2; n = 10). Blood samples were obtained from recipients just before and after 4 h of transplantation to analyze surface markers of immune cells and cytokines. Electrocardiography and echocardiography were performed before donor heart harvesting and after heterotopic transplantation. After 4 h of transplantation, donor hearts were extracted for further histologic studies.

RESULTS

All recipient animals in both groups successfully survived after heterotopic transplantation. The mean ischemic time of the donor heart was 163 ± 8.34 mins in group 1 and 43.8 ± 6.97 mins in group 2 (P < 0.01). Ejection fraction significantly decreased after transplantation in both groups but were less significant in group 2 (the mean difference group 1: -34.3 ± 3.54, P < 0.01; group 2: -14.3 ± 15.47, P = 0.01). The percentage of granulocyte significantly increased in both group 1 and group 2, but the significance was more pronounced in group 1 (the mean difference group 1: 48.7 ± 5.36, P < 0.01; group 2: 39.7 ± 13.1, P < 0.01).

CONCLUSIONS

Normothermic ex-situ perfusion is associated with well-preserved donor hearts but a similar recipient acute immune response in comparison with CSS in the rat model.

Antibiofilm and antithrombotic hydrogel coating based on superhydrophilic zwitterionic carboxymethyl chitosan for blood-contacting devices

Blood-contacting devices must be designed to minimize the risk of bloodstream-associated infections, thrombosis, and intimal lesions caused by surface friction. However, achieving effective prevention of both bloodstream-associated infections and thrombosis poses a challenge due to the conflicting nature of antibacterial and antithrombotic activities, specifically regarding electrostatic interactions. This study introduced a novel biocompatible hydrogel of sodium alginate and zwitterionic carboxymethyl chitosan (ZW@CMC) with antibacterial and antithrombotic activities for use in catheters. The ZW@CMC hydrogel demonstrates a superhydrophilic surface and good hygroscopic properties, which facilitate the formation of a stable hydration layer with low friction. The zwitterionic-functionalized CMC incorporates an additional negative sulfone group and increased negative charge density in the carboxyl group. This augmentation enhances electrostatic repulsion and facilitates the formation of hydration layer. This leads to exceptional prevention of blood clotting factor adhesion and inhibition of biofilm formation. Subsequently, the ZW@CMC hydrogel exhibited biocompatibility with tests of in vitro cytotoxicity, hemolysis, and catheter friction. Furthermore, in vivo tests of antithrombotic and systemic inflammation models with catheterization indicated that ZW@CMC has significant advantages for practical applications in cardiovascular-related and sepsis treatment. This study opens a new avenue for the development of chitosan-based multifunctional hydrogel for applications in blood-contacting devices.

Rat Model of Normothermic Ex-Situ Perfused Heterotopic Heart Transplantation

Heart transplantation is the most effective therapy for end-stage heart failure. Despite the improvements in therapeutic approaches and interventions, the number of heart failure patients waiting for transplantation is still increasing. The normothermic ex situ preservation technique has been established as a comparable method to the conventional static cold storage technique. The main advantage of this technique is that donor hearts can be preserved for up to 12 h in a physiologic condition. Moreover, this technique allows resuscitation of the donor hearts after circulatory death and applies required pharmacologic interventions to improve donor function after implantation. Numerous animal models have been established to improve normothermic ex situ preservation techniques and eliminate preservation-related complications. Although large animal models are easy to handle compared to small animal models, it is costly and challenging. We present a rat model of normothermic ex situ donor heart preservation followed by heterotopic abdominal transplantation. This model is relatively cheap and can be accomplished by a single experimenter.

Immunological Analysis of Postoperative Delirium after Thoracic Aortic Surgery

Background

Delirium is a recognized neurological complication following cardiac surgery and is associated with adverse clinical outcomes, including elevated mortality and prolonged hospitalization. While several clinical risk factors for post-cardiac surgery delirium have been identified, the pathophysiology related to the immune response remains unexamined. This study was conducted to investigate the immunological factors contributing to delirium in patients after thoracic aortic surgery.

Methods

We retrospectively evaluated 43 consecutive patients who underwent thoracic aortic surgery between July 2017 and June 2018. These patients were categorized into 2 groups: those with delirium and those without it. All clinical characteristics were compared between groups. Blood samples were collected and tested on the day of admission, as well as on postoperative days 1, 3, 7, and 30. Levels of helper T cells (CD4), cytotoxic T cells (CD8), B cells (CD19), natural killer cells (CD56+CD16++), and monocytes (CD14+CD16-) were measured using flow cytometry.

Results

The median patient age was 71 years (interquartile range, 56.7 to 79.0 years), and 21 of the patients (48.8%) were male. Preoperatively, most immune cell counts did not differ significantly between groups. However, the patients with delirium exhibited significantly higher levels of interleukin-6 and lower levels of tumor necrosis factor-alpha (TNF-α) than those without delirium (p<0.05). Multivariate analysis revealed that lower TNF-α levels were associated with an increased risk of postoperative delirium (p<0.05).

Conclusion

Postoperative delirium may be linked to perioperative changes in immune cells and preoperative cytokine levels. Additional research is required to elucidate the pathophysiological mechanisms underlying delirium.

Combined effects of sepsis and extracorporeal membrane oxygenation on left ventricular performance in a murine model

Extracorporeal membrane oxygenation (ECMO) may be a viable salvage therapy in selected patients with septic shock. As ECMO use increases, we studied left ventricular (LV) performance during sepsis with and without ECMO using a pressure-volume (PV) loop in a murine model and aimed to understand LV hemodynamics in septic shock with ECMO. The rats were divided into Group 1 (ECMO applied to healthy rats), Group 2 (ECMO for septic rats), Group 3 (Controls, n = 20) and Group 4 (Sepsis induction only, n = 20). The cardiac parameters include end-diastolic volume (EDV), end-systolic volume (ESV), end-diastolic pressure (EDP), and end-systolic pressure (ESP), ejection fraction (EF), end-systolic elastance (Ees), diastolic time constant (Tau) index, arterial elastance (Ea), pressure-volume area (PVA), stroke work (SW), and potential energy (PE). We compared the changes of parameters in all groups. A total of 74 rats were included in the analyses. After 2 h on ECMO, Group 2 was associated with significant increases in ESP, EDV, ESV, PVA, PE, and SW. The difference ratio of PE and PVA was significantly higher in Group 2 compared to Group 1 (P < 0.01). In conclusion, myocardial oxygen consumption was higher in septic shock with ECMO than in controls.