Transplant allograft vasculopathy: Role of multimodality imaging in surveillance and diagnosis

Optical Coherence Tomography in Cardiac Allograft Vasculopathy: State-of-the-Art Review

Cardiac allograft vasculopathy (CAV) is a challenging complication of heart transplantation. CAV pathophysiology is incompletely understood, standard screening modalities such as angiography have significant limitations, and currently available therapies have only modest efficacy in preventing progression. Optical coherence tomography is a light-based technique that provides microscopic level catheter-based intravascular imaging and has dramatically expanded our understanding of CAV, demonstrating it to be a complex, heterogeneous, and dynamic process. This review covers characteristics and uses of optical coherence tomography, including vessel characterization, serial use to assess progression of disease, guiding percutaneous intervention, and monitoring response to CAV therapies. We also discuss the potential of optical coherence tomography in providing individualized assessment and enable customized CAV therapies, which may lead to improvements in long-term transplant outcomes.

Sterile inflammation in thoracic transplantation

The life-saving benefits of organ transplantation can be thwarted by allograft dysfunction due to both infectious and sterile inflammation post-surgery. Sterile inflammation can occur after necrotic cell death due to the release of endogenous ligands [such as damage-associated molecular patterns (DAMPs) and alarmins], which perpetuate inflammation and ongoing cellular injury via various signaling cascades. Ischemia-reperfusion injury (IRI) is a significant contributor to sterile inflammation after organ transplantation and is associated with detrimental short- and long-term outcomes. While the vicious cycle of sterile inflammation and cellular injury is remarkably consistent amongst different organs and even species, we have begun understanding its mechanistic basis only over the last few decades. This understanding has resulted in the developments of novel, yet non-specific therapies for mitigating IRI-induced graft damage, albeit with moderate results. Thus, further understanding of the mechanisms underlying sterile inflammation after transplantation is critical for identifying personalized therapies to prevent or interrupt this vicious cycle and mitigating allograft dysfunction. In this review, we identify common and distinct pathways of post-transplant sterile inflammation across both heart and lung transplantation that can potentially be targeted.

Review of cardiovascular imaging in the Journal of Nuclear Cardiology 2019: Single-photon emission computed tomography

In 2019, the Journal of Nuclear Cardiology published excellent articles pertaining to imaging in patients with cardiovascular disease. In this review, we will summarize a selection of these articles to provide a concise review of the main advancements that have recently occurred in the field and provide the reader with an opportunity to review a wide selection of articles. In the first article of this 2-part series, we focused on publications dealing with positron emission tomography, computed tomography, and magnetic resonance. This review will place emphasis on myocardial perfusion imaging using single-photon emission computed tomography summarizing advances in the field including in diagnosis and prognosis, non-perfusion variables, safety of testing, imaging in patients with heart failure and renal disease.

Multi-modality imaging: Bird's eye view from the 2017 American Heart Association Scientific Sessions

This review summarizes key imaging studies that were presented in the American Heart Association Scientific Sessions 2017 related to the fields of nuclear cardiology, cardiac computed tomography, cardiac magnetic resonance, and echocardiography. The aim of this bird's eye view is to inform readers about multiple studies reported at the meeting from these different imaging modalities. While such a review is most useful for those that did not attend the conference, we find that a general overview may also be useful to those that did since it is often difficult to get exposure to many abstracts at large meetings. The review, therefore, aims to help readers stay updated on the newest imaging studies presented at the meeting and will hopefully stimulate new ideas for future research in imaging.

The Matrikine Acetylated Proline-Glycine-Proline Couples Vascular Inflammation and Acute Cardiac Rejection

The extracellular matrix (ECM) is a dynamic, bioactive structure critical to organ development, structure and function. Excessive remodeling of the ECM is a hallmark of a variety of inflammatory conditions including vascular disease. Endothelin-1 (ET1) synthesis is understood to promote cardiovascular diseases including acute cardiac transplant rejection; however, the contribution of ECM-derived chemokines (matrikines) to vascular inflammation remains poorly understood. Herein we report that the matrikine acetylated Pro-Gly-Pro (PGP) stimulates vascular inflammation through activation of endothelial CXC Chemokine Receptor 2 (CXCR2) and production of endothelin-1 both in vitro and in vivo. As a proof of hypothesis, we demonstrate that coronary PGP levels associate with both circulating endothelin-1 and acute rejection in cardiac transplant patients (sensitivity of 100% and specificity of 86%). These findings establish PGP as a novel mediator in cardiovascular disease, and implicate bioactive matrix fragments as underappreciated agents potentially active in numerous conditions propagated by progressive vascular inflammation.

Erythroblast transformation-specific 2 correlates with vascular smooth muscle cell apoptosis in rat heterotopic heart transplantation model

BACKGROUND

Cardiac allograft vasculopathy (CAV) decreases the long-term survival of heart transplantation recipients. Vascular smooth muscle cell (VSMC) apoptosis is an important pathological feature of CAV. Erythroblast transformation-specific 2 (Ets-2), as a transcription factor, participates in cell apoptosis and plays an important role in organ transplantation.

METHODS

Hearts from Wistar-Furth (WF:RT1u) rats were heterotopically transplanted into Lewis (Lew:RT1(l)) rats without immunosuppression. Additional syngeneic heterotopic cardiac transplantations were performed in Lewis rats. HE staining was used to identify CAV. Ets-2 expression was examined by western blot. Ets-2 tissue location was examined by immunohistochemical assay and double immunostaining. Cleaved caspase 3 expression was detected by western blot. Co-localization of Ets-2 and cleaved caspase 3 was detected by double immunostaining. Ets-2, p53, cleaved caspase 3 and Bcl-xl expression in rat VSMC line A7R5 was examined after Ets-2 siRNA transfection. TUNEL assay was applied to detect A7R5 apoptosis with or without ETS-2 siRNA transfection. Immunoprecipitation was performed to explore the interaction between Ets-2 and p53.

RESULTS

Ets-2 expression decreased in the allograft group but had no obvious change in the isograft group. Meanwhile, the phenomenon of CAV was observed in the allograft group and there is neointima formation in the isograft group which is not obvious compared with allograft group. Additionally, Ets-2 expression was opposite to VSMC apoptosis in the allograft group. In vitro, Ets-2 siRNA transfection in A7R5cells resulted in enhanced cell apoptosis. Finally, Ets-2 interacted with p53.

CONCLUSIONS

Ets-2 might inhibit VSMC apoptosis via p53 pathway. The results further elucidate the molecular mechanism of VSMC apoptosis after heart transplantation during CAV and provide theoretical basis for seeking new specific drug targets for CAV prevention and treatment.