Heterotopic Cervical Heart Transplantation in Mice

The Combination of Rhodosin and MMF Prolongs Cardiac Allograft Survival by Inhibiting DC Maturation by Promoting Mitochondrial Fusion

Despite being the gold-standard treatment for end-stage heart disease, heart transplantation is associated with acute cardiac rejection within 1 year of transplantation. The continuous application of immunosuppressants may cause side effects such as hepatic and renal toxicity, infection, and malignancy. Developing new pharmaceutical strategies to alleviate acute rejection after heart transplantation effectively and safely is of critical importance. In this study, we performed a murine model of MHC-full mismatch cardiac transplantation and showed that the combination of Rhodosin (Rho) and mycophenolate mofetil (MMF) could prevent acute rejection and oxidative stress injury and prolong the survival time of murine heart transplants. The use of Rho plus MMF in allografts improved the balance of Tregs/Teff cells, which had a protective effect on allotransplantation. We also isolated bone marrow-derived dendritic cells (BMDCs) and determined that Rho inhibited DC maturation by promoting mitochondrial fusion mainly through the mitochondrial fusion-related protein MFN1. Herein, we demonstrated that Rho, an active ingredient isolated from the plant Rhodiola rosea with antioxidant and anti-inflammatory activities, could efficiently alleviate acute rejection and significantly prolong murine heart allograft survival when used with a low dose of MMF. More importantly, we found that Rho restrained DC maturation by promoting mitochondrial fusion and decreasing reactive oxygen species (ROS) levels, which then alleviated acute rejection in murine cardiac transplantation. Interestingly, as a novel immunosuppressant, Rho has almost no side effects compared with other traditional immunosuppressants. Taken together, these results suggest that Rho has good clinical auxiliary applications as an effective immunosuppressant and antioxidant, and this study provides an efficient strategy to overcome the side effects of immunosuppressive agents that are currently used in organ transplantation.

Combination of matrine and tacrolimus alleviates acute rejection in murine heart transplantation by inhibiting DCs maturation through ROS/ERK/NF-κB pathway

Matrine, an alkaloid derived from traditional Chinese herbs, has been confirmed to regulate immunity and exert anti-inflammatory effects. Matrine injection has been widely used in clinic therapy for anti-tumor and anti-inflammatory diseases. Heart transplantation(HT) is the only solution for the end-stage heart failure, but it is restricted by the cardiac allograft rejection. One of the important pathophysiological processes of post-transplantation rejection is inflammatory cell infiltration. Matrine has been shown to exert a positive protective effect against oxidative stress injury and inflammation, which likely benefits allograft survival. However, it remains unclear whether matrine inhibits alloimmunity or allograft rejection. In this study, we established the heart transplantation model in mouse and extracted bone marrow-derived dendritic cells (BMDCs) to explore the function and mechanism of matrine in heart transplantation. Moreover, combination treatment with matrine and tacrolimus(FK506) had a synergistic effect in preventing acute rejection of heart transplants. Here we found that matrine can prolong the survival of post-transplant and inhibit inflammatory cell infiltration in transplanted hearts of mice. At the same time, matrine increased Treg ratio and decreased CD4+/CD8 + ratio in mice. More importantly, matrine inhibited DCs maturation in mice and reduced oxidative damage and apoptosis in allograft hearts. Furthermore, matrine also downregulated NF-κB pathway and upregulated ERK1/2 signaling pathway. Overall, our study reveals a novel immunosuppressive agent that has the potential to reduce the side effects of existing immunosuppressive agents when used in combination with them.

Artesunate Restrains Maturation of Dendritic Cells and Ameliorates Heart Transplantation-Induced Acute Rejection in Mice through the PERK/ATF4/CHOP Signaling Pathway

Background

Heart transplantation (HT) is the only effective treatment for end-stage heart failure because it can effectively improve the survival rate and quality of life of patients with heart failure. Artesunate (ART) is an artemisinin derivative, with good water solubility and higher oral bioavailability. The main aim of this study was to determine the role of ART in HT mice.

Methods

In animal experiments, mice were divided into the control group, HT group, low ART+HT group, and high ART+HT group. Next, inflammatory cell infiltration, oxidative stress injury, and myocardial cell apoptosis were determined in heart tissue. The proportion of multiple lymphocytes in spleen and lymph nodes was then determined using flow cytometry. In addition, cell experiments were conducted to determine the changes in expression of surface maturation markers of BMDC and changes in intracellular reactive oxygen species after LPS stimulation. Finally, western blot analysis was performed to determine the levels of endoplasmic reticulum stress-related proteins (CHOP/ATF4/PERK).

Results

The survival time of mice in the ART treatment group was significantly prolonged and was positively correlated with the dose. In animal experiments, ART significantly reduced inflammatory cell infiltration in heart tissue and the proportion of CD4+CD8+ T cells in spleens and lymph nodes. Moreover, ART treatment lowered the 8-OHdg in hearts and myocardial apoptosis. In cell experiments, ART treatment slowed down the development and maturation of BMDCs by inhibiting the expression of endoplasmic reticulum stress-related proteins. Furthermore, the treatment alleviated the oxidative stress damage of BMDCs.

Conclusion

ART can inhibit maturation of dendritic cells through the endoplasmic reticulum stress signaling pathway, thereby alleviating acute rejection in mice after heart transplantation.

Overexpression of miR-223 Promotes Tolerogenic Properties of Dendritic Cells Involved in Heart Transplantation Tolerance by Targeting Irak1

Dendritic cells (DCs) are key mediators of transplant rejection. Numerous factors have been identified that regulate transplant immunopathology by modulating the function of DCs. Among these, microRNAs (miRNAs), small non-coding RNA molecules, have received much attention. The miRNA miR-223 is very highly expressed and tightly regulated in hematopoietic cells. It plays an important role in modulating the immune response by regulating neutrophils and macrophages, and its dysregulation contributes to multiple types of immune diseases. However, the role of miR-223 in immune rejection is unclear. Here, we observed expression of miR-223 in patients and mice who had undergone heart transplantation and found that it increased in the serum of both, and also in DCs from the spleens of recipient mice, although it was unchanged in splenic T cells. We also found that miR-223 expression decreased in lipopolysaccharide-stimulated DCs. Increasing the level of miR-223 in DCs promoted polarization of DCs toward a tolerogenic phenotype, which indicates that miR-223 can attenuate activation and maturation of DCs. MiR-223 effectively induced regulatory T cells (Tregs) by inhibiting the function of antigen-presenting DCs. In addition, we identified Irak1 as a miR-223 target gene and an essential regulator of DC maturation. In mouse allogeneic heterotopic heart transplantation models, grafts survived longer and suffered less immune cell infiltration in mice with miR-223-overexpressing immature (im)DCs. In the miR-223-overexpressing imDC recipients, T cells from spleen differentiated into Tregs, and the level of IL-10 in heart grafts was markedly higher than that in the control group. In conclusion, miR-223 regulates the function of DCs via Irak1, differentiation of T cells into Tregs, and secretion of IL-10, thereby suppressing allogeneic heart graft rejection.

Skills to Perform Vessel Eversion in Mouse Cervical Cardiac Transplantation with Cuff Technique

INTRODUCTION

The mouse heterotopic cardiac transplant model has been extensively used to explore transplant immunity. Although the cuff technique facilitates the operation, the procedure remains difficult, and vessel eversion is the most difficult step. Cuff movement and everted vessel wall slippage are the main adverse factors in vessel eversion. Traditional strategies to prevent these factors focus on cuff fixation, while more steps or surgical instruments would be required.

METHODS

According to the reported protocols and our experience, the vessel eversion skills were modified and used for transplantation. Cardiac grafts from C57BL/6(H-2b) or BALB/c(H-2d) mice were transplanted into C57BL/6(H-2b) mice. The operating times of recent 90 operations, which were divided into 9 groups according to their sequence, were summarized and analyzed.

RESULTS

The mouse cervical cardiac transplantation was successfully performed by using the modified vessel eversion skills. The cuff movement, which is the most important adverse factor to prevent vessel eversion, was effectively prevented. In the recent 90 operations, the total operating time was 47.3±7.9 min and the success rate was 98%.

CONCLUSIONS

The modified surgical skills simplify the vessel eversion in mouse cervical cardiac transplantation with cuff technique, characterized by less cuff movement, fewer steps, and surgical instruments. Using these surgical skills, the transplant can be performed in a short time.

Reactivation of the Nkx2.5 cardiac enhancer after myocardial infarction does not presage myogenesis

Aims

The contribution of resident stem or progenitor cells to cardiomyocyte renewal after injury in adult mammalian hearts remains a matter of considerable debate. We evaluated a cell population in the adult mouse heart induced by myocardial infarction (MI) and characterized by an activated Nkx2.5 enhancer element that is specific for multipotent cardiac progenitor cells (CPCs) during embryonic development. We hypothesized that these MI-induced cells (MICs) harbour cardiomyogenic properties similar to their embryonic counterparts.

Methods and results

MICs reside in the heart and mainly localize to the infarction area and border zone. Interestingly, gene expression profiling of purified MICs 1 week after infarction revealed increased expression of stem cell markers and embryonic cardiac transcription factors (TFs) in these cells as compared to the non-mycoyte cell fraction of adult hearts. A subsequent global transcriptome comparison with embryonic CPCs and fibroblasts and in vitro culture of MICs unveiled that (myo-)fibroblastic features predominated and that cardiac TFs were only expressed at background levels.

Conclusions

Adult injury-induced reactivation of a cardiac-specific Nkx2.5 enhancer element known to specifically mark myocardial progenitor cells during embryonic development does not reflect hypothesized embryonic cardiomyogenic properties. Our data suggest a decreasing plasticity of cardiac progenitor (-like) cell populations with increasing age. A re-expression of embryonic, stem or progenitor cell features in the adult heart must be interpreted very carefully with respect to the definition of cardiac resident progenitor cells. Albeit, the abundance of scar formation after cardiac injury suggests a potential to target predestinated activated profibrotic cells to push them towards cardiomyogenic differentiation to improve regeneration.

The heterotopic heart transplantation in mice as a small animal model to study mechanical unloading - Establishment of the procedure, perioperative management and postoperative scoring

BACKGROUND

Unloading of failing hearts by left ventricular assist devices induces an extensive cardiac remodeling which may lead to a reversal of the initial phenotype-or to its deterioration. The mechanisms underlying these processes are unclear.

HYPOTHESIS

Heterotopic heart transplantion (hHTX) is an accepted model for the study of mechanical unloading in rodents. The wide variety of genetically modified strains in mice provides an unique opportunity to examine remodeling pathways. However, the procedure is technically demanding and has not been extensively used in this area. To support investigators adopting this method, we present our experience establishing the abdominal hHTX in mice and describe refinements to the technique.

METHODS

In this model, the transplanted heart is vascularised but implanted in series, and therefore does not contribute to systemic circulation and results in a complete mechanical unloading of the donor heart. Training followed a systematic program using a combination of literature, video tutorials, cadaveric training, direct observation and training in live animals.

RESULTS

Successful transplantation was defined as a recipient surviving > 24 hours with a palpable, beating apex in the transplanted heart and was achieved after 20 transplants in live animals. A success rate of 90% was reached after 60 transplants. Operative time was shown to decrease in correlation with increasing number of procedures from 200 minutes to 45 minutes after 60 operations. Cold/warm ischemia time improved from 45/100 to 10/20 minutes. Key factors for success and trouble shootings were identified.

CONCLUSION

Abdominal hHTX in the mouse may enable future examination of specific pathways in unloading induced myocardial remodeling. Establishment of the technique, however, is challenging. Structured training programs utilising a variety of training methods can help to expedite the process. Postoperative management, including daily scoring increases animal wellbeing and helps to predict survival.

A New Concept of the Old Inhibitor NSC 74859 in Alleviating Cardiac Allograft Rejection and Extending Allograft Survival in Mice

Background

STAT1/4 has been suggested to be involved in cardiac allograft rejection. However, no direct evidence regarding STAT3 has been established in cardiac allograft rejection. Here, we hypothesized that inhibition of STAT3 attenuates cardiac allograft rejection.

Material/Methods

To test our hypothesis, homotopic mouse heart transplantation was carried out in syngeneic C57BL/6 to C57BL/6 strain mice with or without oral gavage with NSC 74859, an inhibitor of STAT3. The immune response was investigated using real-time PCR for CD4 and CD8 surface makers of T cells and CD14 of monocytes and cytokines, including IL-2, IL-15, and IL-6 of allografts at 3, 6, and 9 days after transplantation. Prognosis was also evaluated.

Results

We found that allografts with oral gavage of NSC 74859 whose CD4, CD8 T, and CD14 monocytes were significantly lower than that of allograft without oral gavage of NSC 74859, and the same was true for the expression of IL-2, IL-15, and IL-6. Immunohistochemical analysis of grafts showed reduced infiltration of monocytes/macrophages into the graft myocardium. Survival was also markedly extended in the NSC 74859 group.

Conclusions

Inhibition of IL-6/STAT3 using NSC 74859 was shown to remarkably alleviate cardiac allograft rejection in mice, indicating that the target against IL-6/STAT3 pathway might be clinically used as an alternative therapy for cardiac allograft rejection.

Hemodynamic Assessment of a Murine Heterotopic Biventricularly Loaded Cardiac Transplant in vivo Model

BACKGROUND

Heterotopic heart transplantation (HHT) in rodent animal models represents an important technique enabling studies on organ transplantation immunology and pharmaceutical development. Recent investigations used nonworking HHT designs, with the left ventricle (LV) bypassed in the anastomosis system. In spite of their principal success, the lack of orthogonal ventricular filling leads to myocardial atrophy. However, when focusing on the cellular and molecular mechanisms involved in the in vivo remodeling of the myocardium or cell-based cardiovascular implants, a nonworking model is suboptimal as it lacks the native-analogous hemodynamic and metabolic situation. Here we present the hemodynamic and electrical assessment of a biventricularly loaded murine HHT method without the need for a combined heart-lung transplantation approach.

METHODS

Heterotopic transplantations (n = 13) were performed on C57BL/6J-(H-2b) inbred mice (n = 13 donors, n = 13 recipients) by creating end-to-side anastomoses between the donors' cranial vena cava (CrVC) and the recipients' abdominal caudal vena cava (CVC), between the donors' ascending aorta and the recipients' abdominal aorta (aAo), and between the grafts' pulmonary trunk and the left atrium. After transplantation, a hemodynamic assessment using echocardiography (including 2D speckle tracking analysis) and electrocardiography was performed.

RESULTS

The loaded HHT procedure in the mice was performed with an overall success rate of 61%. In 3 of the remaining 5 cases, only atrial function was restored. The median duration of the entire surgical procedure for the recipient animal was 190 (IQR 180-250) min. The mean heart rate in the loaded HHT group was 355 ± 6 bpm in comparison to the control group with an in situ heart rate of 418 ± 61 bpm. A native-like closing and opening pattern of the aortic and mitral valves (visible on both 2D and M-mode images) was observed, confirming a native-analogous loading of the LV. Pulsed-wave Doppler provided visualization of the flow across the region of anastomoses between the pulmonary trunk and the left atrium, reaching a mean maximum velocity of 382 ± 12 mm/s. Exemplary 2D speckle tracking analysis of the LV free wall and interventricular septum revealed some differences in vector directions in one animal when compared to the orthotopic native heart, indicating an asynchronous movement of the LV.

CONCLUSIONS

These results demonstrate the technical (micro)surgical feasibility of a fully loaded HHT procedure in the murine model without using a combined heart-lung transplantation approach. The acute hemodynamic performance of the HHT grafts approximated the native orthotopic situation. This model may open up new options for the investigation of cellular and molecular questions in the murine cardiovascular in vivo system in the near future.