Exosome-derived galectin-9 may be a novel predictor of rejection and prognosis after liver transplantation

Role of Donor-derived Cell-free DNA In Predicting Short-term Allograft Health In Liver Transplant Recipients

BACKGROUND/AIMS

Predicting allograft dysfunction prior to clinical or biochemical evidence remains one of the challenges in transplantation, and a preclinical detection and early management of its cause allows for improved post-transplant outcomes. Donor-derived cell-free DNA (ddcfDNA) has been proposed as an important biomarker of allograft injury and has shown to predict dysfunction prior to any biochemical derangements. We aimed to investigate the diagnostic performance of ddcfDNA in detecting and differentiating the causes of early pre-biochemical detection of graft injury and in predicting the short-term outcomes of graft health using a patented protocol and proprietary set of single-nucleotide polymorphisms.

METHODS

Blood samples were collected on defined postoperative days (1, 3, 7, and at 3 months) and were analysed through relatively economical patented protocol (Trunome™). Biopsy, biochemical tests, and clinical criteria were analysed between various subgroups.

RESULTS

Of a total 50 patients, percentage ddcfDNA (%ddcfDNA) levels were significantly elevated in the rejection group (n = 8) as compared to that in the non-rejection group (n = 42; median elevation: 12.8% vs 4.3%, respectively), with a significant correlation (r = 0.92, P < 0.0001). Area under the receiver operating characteristic curve (AUC-ROC) analysis revealed that the %ddcfDNA levels can predict graft health more precisely than the conventional liver function tests (AUC for %ddcfDNA: 0.86; P < 0.001; AUC for aspartate transaminase 0.65, P = 0.08; AUC for alanine transaminase: 0.75, P < 0.01). Moreover, %ddcfDNA levels (with a threshold of >10.2%) on post-operative day 7 accurately predicted short-term (3 months) health status of the graft with 93.33% sensitivity, 94.44% specificity, 87.50% positive predictive value, 97.14% negative predictive value, and 94.12% accuracy.

CONCLUSION

A single-timepoint ddcfDNA on postoperative day 7 accurately predicts graft health and improves risk stratification in the short-term.

Clinical Application of Different Liquid Biopsy Components in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the most common form of primary liver cancer, usually occurring in the background of chronic liver disease. HCC lethality rate is in the third highest place in the world. Patients with HCC have concealed early symptoms and possess a high-level of heterogeneity. Once diagnosed, most of the tumors are in advanced stages and have a poor prognosis. The sensitivity and specificity of existing detection modalities and protocols are suboptimal. HCC calls for more sophisticated and individualized therapeutic regimens. Liquid biopsy is non-invasive, repeatable, unaffected by location, and can be monitored dynamically. It has emerged as a useable aid in achieving precision malignant tumor treatment. Circulating tumor cells (CTCs), circulating nucleic acids, exosomes and tumor-educated platelets are the commonest components of a liquid biopsy. It possesses the theoretical ability to conquer the high heterogeneity and the difficulty of early detection for HCC patients. In this review, we summarize the common enrichment techniques and the clinical applications in HCC for different liquid biopsy components. Tumor recurrence after HCC-related liver transplantation is more insidious and difficult to treat. The clinical use of liquid biopsy in HCC-related liver transplantation is also summarized in this review.

Extracellular Vesicles in Liver Transplantation: Current Evidence and Future Challenges

Extracellular vesicles (EVs) are emerging as a promising field of research in liver disease. EVs are small, membrane-bound vesicles that contain various bioactive molecules, such as proteins, lipids, and nucleic acids and are involved in intercellular communication. They have been implicated in numerous physiological and pathological processes, including immune modulation and tissue repair, which make their use appealing in liver transplantation (LT). This review summarizes the current state of knowledge regarding the role of EVs in LT, including their potential use as biomarkers and therapeutic agents and their role in graft rejection. By providing a comprehensive insight into this emerging topic, this research lays the groundwork for the potential application of EVs in LT.

Extracellular Vesicles: The Future of Diagnosis in Solid Organ Transplantation?

Solid organ transplantation (SOT) is a life-saving treatment for end-stage organ failure, but it comes with several challenges, the most important of which is the existing gap between the need for transplants and organ availability. One of the main concerns in this regard is the lack of accurate non-invasive biomarkers to monitor the status of a transplanted organ. Extracellular vesicles (EVs) have recently emerged as a promising source of biomarkers for various diseases. In the context of SOT, EVs have been shown to be involved in the communication between donor and recipient cells and may carry valuable information about the function of an allograft. This has led to an increasing interest in exploring the use of EVs for the preoperative assessment of organs, early postoperative monitoring of graft function, or the diagnosis of rejection, infection, ischemia-reperfusion injury, or drug toxicity. In this review, we summarize recent evidence on the use of EVs as biomarkers for these conditions and discuss their applicability in the clinical setting.

Exosomes in chronic liver disease

Chronic liver disease (CLD) is the major cause of mortality and morbidity, particularly in developing countries. Although there has been a significant advancement in the identification and treatment of liver diseases over time, clinical results are not satisfactory in advanced liver disease. Thus, it is crucial to develop certain technology for early detection, and curative therapies and to investigate the molecular mechanisms behind CLD's pathogenesis. The study of exosomes in CLD is a rapidly developing field. They are structurally membrane-derived nano vesicles released by various cells. In CLD, exosomes released from injured hepatic cells affect intercellular communication, creating a microenvironment conducive to the illness's development. They also carry liver cell-specific proteins and miRNAs, which can be used as diagnostic biomarkers and treatment targets for various liver diseases. End-stage liver disease can only be treated by a liver transplant, however, the low availability of compatible organs, high expenses of treatment, and surgical complications significantly lower patient survival rates. Early diagnosis and therapeutic intervention of CLD positively affect the likelihood of curative treatment and high patient survival rates. Considering the possibility that exosomes could be employed as tools for disease diagnostics and clinical intervention, The current study briefly summarizes the roles of exosomes and their cargo in diagnosing and treating liver diseases.

New Approaches to the Diagnosis of Rejection and Prediction of Tolerance in Liver Transplantation

Immunosuppression after liver transplantation is essential for preventing allograft rejection. However, long-term drug toxicity and associated complications necessitate investigation of immunosuppression minimization and withdrawal protocols. Development of such protocols is hindered by reliance on current paradigms for monitoring allograft function and rejection status. The current standard of care for diagnosis of rejection is histopathologic assessment and grading of liver biopsies in accordance with the Banff Rejection Activity Index. However, this method is limited by cost, sampling variability, and interobserver variation. Moreover, the invasive nature of biopsy increases the risk of patient complications. Incorporating noninvasive techniques may supplement existing methods through improved understanding of rejection causes, hepatic spatial architecture, and the role of idiopathic fibroinflammatory regions. These techniques may also aid in quantification and help integrate emerging -omics analyses with current assessments. Alternatively, emerging noninvasive methods show potential to detect and distinguish between different types of rejection while minimizing risk of adverse advents. Although biomarkers have yet to replace biopsy, preliminary studies suggest that several classes of analytes may be used to detect rejection with greater sensitivity and in earlier stages than traditional methods, possibly when coupled with artificial intelligence. Here, we provide an overview of the latest efforts in optimizing the diagnosis of rejection in liver transplantation.

Nucleic acids and proteins carried by exosomes from various sources: Potential role in liver diseases

Exosomes are extracellular membrane-encapsulated vesicles that are released into the extracellular space or biological fluids by many cell types through exocytosis. As a newly identified form of intercellular signal communication, exosomes mediate various pathological and physiological processes by exchanging various active substances between cells. The incidence and mortality of liver diseases is increasing worldwide. Therefore, we reviewed recent studies evaluating the role of exosomes from various sources in the diagnosis and treatment of liver diseases.

Increased Expressions of Programmed Death Ligand 1 and Galectin 9 in Transplant Recipients Who Achieved Tolerance After Immunosuppression Withdrawal

Programmed death 1 (PD1)/its ligand PD-L1 concomitant with T cell immunoglobulin and mucin domain-containing protein 3 (TIM-3)/its ligand galectin 9 (Gal-9) and the forkhead box P3 (FOXP3) might be involved in tolerance after liver transplantation (LT). Liver biopsies from 38 tolerant, 19 nontolerant (including 16 samples that triggered reintroduction of immunosuppression [IS] and 19 samples after IS reintroduction), and 38 control LT patients were studied. The expressions of PD1, PD-L1, Gal-9, and FOXP3 were determined by immunohistochemical and immunofluorescence (IF) staining. The success period of IS withdrawal was calculated using Kaplan-Meier curve analysis. Tolerant and control patients exhibited higher PD-L1, Gal-9, and FOXP3 levels than nontolerant patients at the moment of triggering IS reintroduction. High expressions of PD-L1 and Gal-9 were associated with prolonged success of tolerance (83.3% versus 36.7% [P < 0.01] and 73.1% versus 42.9% [P = 0.03]). A strong correlation between PD-L1 and Gal-9 expression levels was detected (Spearman r = 0.73; P ≤ 0.001), and IF demonstrated colocalization of PD-L1 and Gal-9 in the cytoplasm of hepatocytes. In conclusion, the present study demonstrated that increased expressions of PD-L1 and Gal-9 were associated with sustained tolerance after IS withdrawal in pediatric liver transplantation.

Small Extracellular Vesicles in Transplant Rejection

Small extracellular vesicles (sEV), which are released to body fluids (e.g., serum, urine) by all types of human cells, may stimulate or inhibit the innate and adaptive immune response through multiple mechanisms. Exosomes or sEV have on their surface many key receptors of immune response, including major histocompatibility complex (MHC) components, identical to their cellular origin. They also exhibit an ability to carry antigen and target leukocytes either via interaction with cell surface receptors or intracellular delivery of inflammatory mediators, receptors, enzymes, mRNAs, and noncoding RNAs. By the transfer of donor MHC antigens to recipient antigen presenting cells sEV may also contribute to T cell allorecognition and alloresponse. Here, we review the influence of sEV on the development of rejection or tolerance in the setting of solid organ and tissue allotransplantation. We also summarize and discuss potential applications of plasma and urinary sEV as biomarkers in the context of transplantation. We focus on the attempts to use sEV as a noninvasive approach to detecting allograft rejection. Preliminary studies show that both sEV total levels and a set of specific molecules included in their cargo may be an evidence of ongoing allograft rejection.

The Role of Galectins in Chronic Lung Allograft Dysfunction

Background

Galectins are proteins that bind β-galactosides such as N-acetyllactosamine present in N-linked and O-linked glycoproteins and that seem to be implicated in inflammatory and immune responses as well as fibrotic mechanisms. This preliminary study investigated serum galectins as clinical biomarkers in lung transplant patients with chronic lung allograft dysfunction (CLAD), phenotype bronchiolitis obliterans syndrome (BOS).

Materials and Methods

Nineteen lung transplant patients [median age (IQR), 55 (45–62) years; 53% males] were enrolled in the study. Peripheral blood concentrations of galectins-1, 3 and 9 were determined with commercial ELISA kits.

Results

Galectin-1 concentrations were higher in BOS than in stable LTX patients (p = 0.0394). In logistic regression analysis, testing BOS group as dependent variable with Gal-1 and 3 as independent variables, area under the receiver operating characteristics (AUROC) curve was 98.9% (NPV 90% and PPV 88.9%, p = 0.0003). With the stable LTX group as dependent variable and Gal-1, 3 and 9 as independent variables, AUROC was 92.6% (NPV 100% and PPV 90%, p = 0.0023). In stable patients were observed an inverse correlation of Gal-3 with DLCO% and KCO%, and between Gal-9 and KCO%.

Conclusion

Galectins-1, 3 and 9 are possible clinical biomarkers in lung transplant patients with diagnostic and prognostic meaning. These molecules may be directly implicated in the pathological mechanisms of BOS. The hypothesis that they could be new therapeutic targets in BOS patients is intriguing and also worth exploring.

Extracellular vesicles in hepatology: Physiological role, involvement in pathogenesis, and therapeutic opportunities

Since the first descriptions of hepatocyte-released exosome-like vesicles in 2008, the number of publications describing Extracellular Vesicles (EVs) released by liver cells in the context of hepatic physiology and pathology has grown exponentially. This growing interest highlights both the importance that cell-to-cell communication has in the organization of multicellular organisms from a physiological point of view, as well as the opportunity that these circulating organelles offer in diagnostics and therapeutics. In the present review, we summarize systematically and comprehensively the myriad of works that appeared in the last decade and lighted the discussion about the best opportunities for using EVs in liver disease therapeutics.

The roles of galectins in hepatic diseases

Hepatic diseases include all diseases that occur in the liver, including hepatitis, cirrhosis, hepatocellular carcinoma, etc. Hepatic diseases worldwide are characterized by high incidences of digestive system diseases, which present with subtle symptoms, are difficult to treat and have high mortality. Galectins are β-galactoside-binding proteins that have been found to be aberrantly expressed during hepatic disease progression. An increasing number of studies have shown that abnormal expression of galectins is extensively involved in hepatic diseases, such as hepatocellular carcinoma (HCC), liver cirrhosis, hepatitis and liver fibrosis. Galectins function as intracellular and extracellular hepatic disease regulators mainly through the binding of their carbohydrate recognition domain to glycoconjugates expressed in hepatocytes. In this review, we summarize current research on the various roles of galectins in cirrhosis, hepatitis, liver fibrosis and HCC, which may provide a preliminary theoretical basis for the exploration of new targets for the treatment of hepatic diseases.

Top 100 most-cited articles on exosomes in the field of cancer: a bibliometric analysis and evidence mapping

Several studies have demonstrated that exosomes have a very broad prospect in the field of cancer therapy. This study aims to identify the general characteristics, cooperation of authors, countries and explore the hot topics of the top 100 cited articles on tumor-related exosomes. We searched the Web of Science Core Collection on June 28, 2019, to collect related publications. Microsoft Excel 2016 and VOSviewer 1.6.9 were applied to analyze the publication year, citations, authors, countries, institutions, journals, and keywords. The top 100 articles were published between 1998 and 2017 with citations ranging from 181 to 2275. Cancer Research (n = 9) had the highest number of publications. Nature Cell Biology, Nature, and Nature Medicine are considered to be the core journals of tumor-related exosomes because they are among top 10 from different analytical perspectives. The USA (n = 49) and Harvard University (n = 9) were the most productive country and institution, respectively. There were active collaborations between countries. Kalluri R (n = 6) contributed the largest number of articles, and Taylor DD was the most co-cited author. Théry C and Al-Nedawi K are probably the two important experts as they are both the top 10 authors and top 10 co-cited authors. Three clusters were obtained after clustering analysis of the keywords. The main hot topics were the proteomic analysis and mechanism of vesicle activation and the role of exosomes in the diagnosis and progression of tumors. Further research should expand and develop new topics such as the role of exosomes in the treatment of cancers.