Exosomes in transplantation: Role in allograft rejection, diagnostic biomarker, and therapeutic potential

miRNAs, dd-cf-DNA, and Chemokines as Potential Noninvasive Biomarkers for the Assessment of Clinical Graft Evolution and Personalized Immunosuppression Requirement in Solid Organ Transplantation

ABSTRACT

The use of noninvasive biomarkers may reduce the need for biopsy and guide immunosuppression adjustments during transplantation. The scientific community in solid organ transplantation currently considers that chemokines, T- and B-cell immunophenotypes, and gene expression, among other molecular biomarkers, have great potential as diagnostic and predictive biomarkers for graft evolution; however, in clinical practice, few valid early biomarkers have emerged. This review focuses on the most relevant scientific advances in this field in the last 5 years regarding the role of 3 biomarkers: miRNAs, chemokines, and ddcf-DNA, in both adult and pediatric populations. An update was provided on the scores based on the combination of these biomarkers. The most-featured articles were identified through a literature search of the PubMed database. This review provides a comprehensive analysis of the potential clinical applications of these biomarkers in the diagnosis and prediction of graft outcomes and discusses the reasons why none have been implemented in clinical practice to date. Translating these biomarkers into routine clinical practice and combining them with pharmacogenetics and pharmacokinetic monitoring is challenging; however, it is the key to present/future individualized immunosuppressive therapies. It is essential that they be shown to be applicable and robust in real-life patient conditions and properly evaluate their added value when combined with the standard-of-care factor monitoring for graft clinical assessment. Partnership strategies among scientists, academic institutions, consortia, including expert working groups and scientific societies, and pharmaceutical and/or biotechnology companies should promote the development of prospective, randomized, multicenter intervention studies for adequate clinical validation of these biomarkers and their monitoring frequency, and their commercialization to make them available to transplant physicians.

Circulating Vesicular-bound HLA-G as Noninvasive Predictive Biomarker of CLAD After Lung Transplantation

BACKGROUND

Circulating extracellular vesicles (EVs) have shown promising results as noninvasive biomarkers for predicting disease outcomes in solid organ transplantation. Because in situ graft cell expression of the tolerogenic molecule HLA-G is associated with acceptance after lung transplantation (LTx), we hypothesized that plasma EV-bound HLA-G (HLA-GEV) levels could predict chronic lung allograft dysfunction (CLAD) development.

METHODS

We analyzed 78 LTx recipients from the Cohort-for-Lung-Transplantation cohort, all in a stable (STA) state within the first year post-LTx. At 3 y, 41 patients remained STA, and 37 had CLAD (bronchiolitis obliterans syndrome, BOS, [n = 32] or restrictive allograft syndrome [n = 5]). HLA-GEV plasma levels were measured at month 6 (M6) and M12 in 78 patients. CLAD occurrence and graft failure at 3 y post-LTx were assessed according to early HLA-GEV plasma levels.

RESULTS

In patients with subsequent BOS, (1) HLA-GEV levels at M12 were significantly lower than those in STA patients (P = 0.013) and (2) also significantly lower than their previous levels at M6 (P = 0.04).A lower incidence of CLAD and BOS and higher graft survival at 3 y were observed in patients with high HLA-GEV plasma levels at M12 (high versus low HLA-GEVs patients [cutoff 21.3 ng/mL]: freedom from CLAD, P = 0.002; freedom from BOS, P < 0.001; and graft survival, P = 0.04, [log-rank]). Furthermore, in multivariate analyses, low HLA-GEV levels at M12 were independently associated with a subsequent risk of CLAD, BOS, and graft failure at 3 y (P = 0.015, P = 0.036, and P = 0.026, respectively [Cox models]).

CONCLUSIONS

This exploratory study suggests the potential of EV-bound HLA-G plasma levels as a liquid biopsy in predicting CLAD/BOS onset and subsequent graft failure.

Diabetic Cardiomyopathy: Role of Cell Death, Exosomes, Fibrosis and Epicardial Adipose Tissue

Diabetic cardiomyopathy (DCM) represents one of the typical complications associated with diabetes. It has been described as anomalies in heart function and structure, with consequent high morbidity and mortality. DCM development can be described by two stages; the first is characterized by left ventricular hypertrophy and diastolic dysfunction, and the second by heart failure (HF) with systolic dysfunction. The proposed mechanisms involve cardiac inflammation, advanced glycation end products (AGEs) and angiotensin II. Furthermore, different studies have focused their attention on cardiomyocyte death through the different mechanisms of programmed cell death, such as apoptosis, autophagy, necrosis, pyroptosis and ferroptosis. Exosome release, adipose epicardial tissue and aquaporins affect DCM development. This review will focus on the description of the mechanisms involved in DCM progression and development.

The role of cancer-associated fibroblasts and exosomal miRNAs-mediated intercellular communication in the tumor microenvironment and the biology of carcinogenesis: a systematic review

CAFs (cancer-associated fibroblasts) are highly flexible cells of the cancer microenvironment. They produce the extracellular matrix (ECM) constituents that form the structure of the tumor stroma but are also a source of metabolites, growth factors, chemokines, and exosomes that impact every aspect of the tumor, including its response to treatment. It is believed that exosomal miRNAs facilitate intercellular signaling, which is essential for the development of cancer. The role of miRNAs and CAFs in the tumor microenvironment (TME) and carcinogenesis is reviewed in this paper. The preferred reporting items for systematic reviews and meta-analyses (PRISMA) 2020 guidelines were used to perform a systematic review. Several databases, including Web of Science, Medline, Embase, Cochrane Library, and Scopus, were searched using the following keywords: CAFs, CAF, cancer-associated fibroblasts, stromal fibroblasts, miRNA, exosomal miRNAs, exosome and similar terms. We identified studies investigating exosomal miRNAs and CAFs in the TME and their role in carcinogenesis. A total of 12,572 papers were identified. After removing duplicates (n = 3803), 8774 articles were screened by title and abstract. Of these, 421 were excluded from further analysis. It has been reported that if exosomal miRNAs in CAFs are not functioning correctly, this may influence the secretory phenotype of tip cells and contribute to increased tumor invasiveness, tumor spread, decreased treatment efficacy, and a poorer prognosis. Under their influence, normal fibroblasts (NFs) are transformed into CAFs. Furthermore, they participate in metabolic reprogramming, which allows for fast proliferation of the cancer cell population, adaptation to growing energy demands, and the capacity to avoid immune system identification.

Alternative therapeutic strategies in diabetes management

Diabetes is a heterogeneous metabolic disease characterized by elevated blood glucose levels resulting from the destruction or malfunction of pancreatic β cells, insulin resistance in peripheral tissues, or both, and results in a non-sufficient production of insulin. To adjust blood glucose levels, diabetic patients need exogenous insulin administration together with medical nutrition therapy and physical activity. With the aim of improving insulin availability in diabetic patients as well as ameliorating diabetes comorbidities, different strategies have been investigated. The first approaches included enhancing endogenous β cell activity or transplanting new islets. The protocol for this kind of intervention has recently been optimized, leading to standardized procedures. It is indicated for diabetic patients with severe hypoglycemia, complicated by impaired hypoglycemia awareness or exacerbated glycemic lability. Transplantation has been associated with improvement in all comorbidities associated with diabetes, quality of life, and survival. However, different trials are ongoing to further improve the beneficial effects of transplantation. Furthermore, to overcome some limitations associated with the availability of islets/pancreas, alternative therapeutic strategies are under evaluation, such as the use of mesenchymal stem cells (MSCs) or induced pluripotent stem cells for transplantation. The cotransplantation of MSCs with islets has been successful, thus providing protection against proinflammatory cytokines and hypoxia through different mechanisms, including exosome release. The use of induced pluripotent stem cells is recent and requires further investigation. The advantages of MSC implantation have also included the improvement of diabetes-related comorbidities, such as wound healing. Despite the number of advantages of the direct injection of MSCs, new strategies involving biomaterials and scaffolds have been developed to improve the efficacy of mesenchymal cell delivery with promising results. In conclusion, this paper offered an overview of new alternative strategies for diabetes management while highlighting some limitations that will need to be overcome by future approaches.

Inflammatory and hypoxic stress-induced islet exosomes released during isolation are associated with poor transplant outcomes in islet autotransplantation

Islets experience enormous stress during the isolation process, leading to suboptimal endocrine function after total pancreatectomy with islet autotransplantation (TPIAT). Our investigation focused on inducing isolation stress in islets ex vivo, where proinflammatory cytokines and hypoxia prompted the release of stress exosomes (exoS) sized between 50 and 200 nm. Mass spectrometry analysis revealed 3 distinct subgroups of immunogenic proteins within these exoS: damage-associated molecular patterns (DAMPs), chaperones, and autoantigens. The involvement of endosomal-sorting complex required for transport proteins including ras-associated binding proteins7A, ras-associated binding protein GGTA, vacuolar protein sorting associated protein 45, vacuolar protein sorting associated protein 26B, and the tetraspanins CD9 and CD63, in exoS biogenesis was confirmed through immunoblotting. Next, we isolated similar exoS from the islet infusion bags of TPIAT recipients (N = 20). The exosomes from infusion bags exhibited higher DAMP (heat shock protein family A [Hsp70] member 1B and histone H2B) levels, particularly in the insulin-dependent TPIAT group. Additionally, elevated DAMP protein levels in islet infusion bag exosomes correlated with increased insulin requirements (P = .010) and higher hemoglobin A1c levels 1-year posttransplant. A deeper exploration into exoS functionality revealed their potential to activate monocytes via the toll-like receptor 3/7: DAMP axis. This stimulation resulted in the induction of inflammatory phenotypes marked by increased levels of CD68, CD80, inducible nitric oxide synthase, and cyclooxygenase-2. This activation mechanism may impact the successful engraftment of transplanted islets.

Immunogenicity and tolerance induction in vascularized composite allotransplantation

Vascularized composite allotransplantation (VCA) is the transplantation of multiple tissues such as skin, muscle, bone, nerve, and vessels, as a functional unit (i.e., hand or face) to patients suffering from major tissue trauma and functional deficits. Though the surgical feasibility has been optimized, issues regarding graft rejection remains. VCA rejection involves a diverse population of cells but is primarily driven by both donor and recipient lymphocytes, antigen-presenting cells, macrophages, and other immune as well as donor-derived cells. In addition, it is commonly understood that different tissues within VCA, such as the skin, elicits a stronger rejection response. Currently, VCA recipients are required to follow potent and lifelong immunosuppressing regimens to maximize graft survival. This puts patients at risk for malignancies, opportunistic infections, and cancers, thereby posing a need for less perilous methods of inducing graft tolerance. This review will provide an overview of cell populations and mechanisms, specific tissue involved in VCA rejection, as well as an updated scope of current methods of tolerance induction.

Immunological Regulation of Gut-Tropic Immune Cells by Extracellular Vesicles

The remarkable diversity of lymphocytes, essential components of the immune system, serves as an ingenious mechanism for maximizing the efficient utilization of limited host defense resources. While cell adhesion molecules, notably in gut-tropic T cells, play a central role in this mechanism, the counterbalancing molecular details have remained elusive. Conversely, we've uncovered the molecular pathways enabling extracellular vesicles secreted by lymphocytes to reach the gut's mucosal tissues, facilitating immunological regulation. This discovery sheds light on immune fine-tuning, offering insights into immune regulation mechanisms.