Modes of action and diagnostic value of miRNAs in sepsis

Significances of miRNAs for predicting sepsis mortality: a meta-analysis

Background

Sepsis is a life-threatening condition caused by a dysregulated immune response to infection and remains a major cause of mortality in intensive care units (ICUs). Recent studies have identified microRNAs (miRNAs), a class of small RNA molecules, as potential biomarkers for diagnosing and predicting outcomes in sepsis patients. However, the results of these studies have been inconsistent. This meta-analysis aims to comprehensively evaluate the diagnostic and prognostic value of miRNAs in predicting sepsis-related mortality.

Methods

A comprehensive literature search was performed across major databases, including PubMed, Cochrane Library, EMBASE, and CNKI, up to April 7, 2024. Data extraction and meta-analysis were conducted using Meta-disk 1.4 and STATA 15.1, employing both fixed- and random-effects models to ensure robust statistical analysis.

Results

A total of 55 studies met the inclusion criteria and were analyzed. The pooled sensitivity, specificity, and area under the summary receiver operating characteristic (SROC) curve for miRNA detection were calculated. The overall performance of total miRNA detection demonstrated a sensitivity of 0.76 (95% confidence interval [CI]: 0.74-0.77), a specificity of 0.72 (95% CI: 0.71-0.73), and an SROC value of 0.83. Subgroup analyses revealed that miR-133a-3p exhibited the highest diagnostic accuracy, with a pooled sensitivity of 0.83 (95% CI: 0.70-0.92), specificity of 0.79 (95% CI: 0.71-0.86), and an SROC value of 0.90. Additionally, other miRNAs, including miR-146a, miR-21, miR-210, miR-223-3p, miR-155, miR-25, miR-122, miR-125a, miR-125b, and miR-150, also demonstrated high SROC values (0.84 to 0.76).

Conclusion

This meta-analysis underscores the potential of several microRNAs (miRNAs) as reliable biomarkers for predicting sepsis mortality. Specifically, miR-133a-3p, miR-146a, miR-21, miR-210, miR-223-3p, miR-155, miR-25, miR-122, miR-125b, and miR-150 emerge as promising candidates for clinical applications in sepsis prognosis.

LncRNA FENDRR/ miR-424-5p serves as a diagnostic biomarker for sepsis and its predictive value for clinical outcomes

PURPOSE

This study intends to investigate the relationship between FENDRR and miR-424-5p and their clinical significance in sepsis, aiming to provide new diagnostic markers and prognostic markers for sepsis.

METHODS

136 patients with sepsis and 132 healthy volunteers were included as study subjects. The expression levels of FENDRR and miR-424-5p were detected by qPCR. ROC was applied to evaluate the diagnostic value of FENDRR and miR-424-5p. COX analyzed the independent risk factors for the occurrence of death in sepsis patients. Dual luciferase reporter assay detected the binding of FENDRR and miR-424-5p. The miR-424-5p target genes were predicted and enriched for GO function and KEGG pathway.

RESULTS

FENDRR was up-regulated and miR-424-5p was down-regulated in patients with sepsis. FENDRR can target and bind to miR-424-5p. Both FENDRR and miR-424-5p showed significant diagnostic potential in sepsis and their combination significantly improved the diagnostic efficiency. FENDRR/miR-424-5p were significantly correlated with WBC, CRP, APACH II, and SOFA of sepsis patients. FENDRR and miR-424-5p were independent risk factors for mortality in sepsis patients. Sepsis patients with high FENDRR levels or low miR-424-5p levels had higher mortality. GO and KEGG enrichment analyses revealed that the targets of miR-424-5p were predominantly associated with cell functions and inflammatory signaling pathways.

CONCLUSION

Upregulated FENDRR and downregulated miR-424-5p expression can serve as biomarkers of sepsis with predictive value on the onset and prognostic outcome. FENDRR and miR-424-5p were correlated with the severity of sepsis and FENDRR can play a function in the sepsis progression via targeting miR-424-5p.

Profiling of miRNAs Contained in Circulating Extracellular Vesicles and Associated with Sepsis Development in Burn Patients: A Proof-of-Concept Study

Sepsis is the leading cause of mortality in patients with burn injuries and it may represent, in these patients, a real diagnostic challenge. Here we studied the profile of miRNAs contained in extracellular vesicles (EVs) (EV-miRNAs) isolated from plasma from burn patients complicated by sepsis at admission and 7 days later. We enrolled 28 burn patients, 18 with (Burn Septic Patients-BSPs) and 10 without (Burn non-Septic Patients-BnSPs) sepsis. Ten healthy subjects (HSs) were used as additional controls. After EV isolation by charge precipitation and miRNA extraction, we proceeded with a two-phase approach. Through a first screening phase, we identified 178 miRNAs differentially expressed in BSPs compared to HSs. Among these, by a validation phase based on qRT-PCR, we found that miR-483-5p, miR-193a-5p, and miR-188-3p were increased in the BSPs compared to the BnSPs and HSs. Upon ROC analysis, all three miRNAs showed a good accuracy in differentiating BSPs from BnSPs, especially miR-483-5p (AUC = 0.955, p-value = 0.001). Moreover, we found 173 miRNAs differentially expressed in BSPs after 7 days from enrollment compared to T0, among whose miR-1-3p, miR-34a-3p, and miR-193a-5p decreased in BSPs after 7 days, in parallel with a decrease in SOFA scores. Finally, the other two miRNAs, miR-34a-3p and miR-193a-5p, positively correlated with the SOFA score. In conclusion, we identified several miRNAs-namely miR-483-5p, miR-193a-5p, and miR-188-3p-with potential clinical utility as diagnostic biomarkers in a heterogeneous population of burn patients at high risk of developing sepsis. Moreover, we found some miRNAs (miR-1-3p, miR-34a-3p, and miR-193a-5p) that vary according to the course of sepsis and others (miR-34a-3p and miR-193a-5p) that are associated with its clinical severity.

Circulating extracellular vesicles as potential biomarkers and mediators of acute respiratory distress syndrome in sepsis

The early sequence of respiratory failure events after the onset of sepsis is still unknown. We hypothesize that the lung should signal through circulating extracellular vesicles (EVs) when it is affected by a systemic inflammatory response. Blood samples were obtained from septic patients with (n = 5) and without acute respiratory distress syndrome (ARDS) (n = 13) at 24 h of intensive care unit admission and 3 days later at Sírio-Libanês Hospital. Pulmonary-originated sepsis was not considered. The characteristics of the plasma-isolated EVs were compatible with exosomes. 48 miRNAs were evaluated by real-time PCR. Comparing all samples from patients with sepsis + ARDS to sepsis only, 9 miRNAs are transported in smaller amounts: miR-766 (-35.7, p = 0.002), miR-127 (-23.8, p = 0.001), miR-340 (-13.5, p = 0.006), miR-29b (-12.8, p = 0.001), miR-744 (-7.1, p = 0.05), miR-618 (-4.0, p = 0.02), miR-598 (-3.8, p = 0.035), miR-1260 (-2.5, p = 0.035); and miR-885-5p is expressed at higher levels (9.5; p = 0.028). In paired samples, the set of altered miRNAs is generally different (p < 0.05) between sepsis + ARDS (miR-1183,-1267,-1290,-17,-192,-199a-3p,-25,-485-3p,-518d,-720) or sepsis only (miR-148a,-193a-5p,-199a-3p,-222,-25,-340,744). Bioinformatic analysis showed that when sepsis is associated with ARDS, those differentially expressed miRNAs potentially target messenger RNAs from the Glycoprotein VI/GP6 signaling pathway. Circulating EV-miRNA cargo could be potential biomarkers of lung inflammation during sepsis in patients requiring mechanical ventilation.

miRNA sequencing identifies immune-associated miRNAs and highlights the role of miR-193b-5p in sepsis and septic shock progression

This study aimed to evaluate the diagnostic value of miR-193b-5p and miR-511-5p in sepsis and septic shock from the perspective of immune regulation. Initially, serum exosomal miRNA sequencing was conducted on patients with sepsis (n = 6), septic shock (n = 6), and healthy controls (n = 3). Using bioinformatics analysis, miR-193b-5p and miR-511-5p were identified as immune-related miRNAs differentiating sepsis from septic shock. Subsequently, quantitative real-time polymerase chain reaction (qRT-PCR) was performed to validate the identified miRNAs in a cohort of 90 participants, including 30 patients with sepsis, 30 with septic shock, and 30 general surgery patients serving as controls. The results indicated that miR-193b-5p expression level was significantly reduced in septic patients and septic shock patients compared with healthy controls. Both miR-193b-5p and miR-511-5p exhibited diagnostic potential, distinguishing sepsis from the control group, with area under the curve values of 0.797 and 0.795, respectively (P < 0.05). Furthermore, miR-193b-5p expression level was inversely correlated with C-reactive protein level (r = -0.40, P < 0.001), procalcitonin level (r = -0.31, P = 0.003), and interleukin-6 level (r = -0.39, P < 0.001). A positive correlation was identified between miR-193b-5p and lymphocyte count (r = 0.26, P = 0.014). In conclusion, serum miR-193b-5p demonstrated potential as a diagnostic biomarker for sepsis and was associated with inflammation and immune regulation in sepsis.

Unlocking the Potential of miRNAs in Sepsis Diagnosis and Prognosis: From Pathophysiology to Precision Medicine

The clinical syndrome appears as a dysregulated host response to infection that results in life-threatening organ dysfunction known as Sepsis. Sepsis is a serious public health concern where for every five deaths in ICU there is one patient who dies with sepsis worldwide. Sepsis is featured as unbalanced inflammation and immunosuppression which is sustained and profound, increasing patient susceptibility to secondary infections and mortality. microRNAs (miRNAs) play a central role in the control of many biological processes, and the deregulation of their expression has been linked to the development of oncological, cardiovascular, neurodegenerative, and metabolic diseases. In this review, we discuss the role of miRNAs in sepsis pathophysiology. Overall, miRNAs are seen as promising biomarkers, and it has been proposed to develop miRNA-based diagnosis and therapies for sepsis. Yet, the picture is not so straightforward because of miRNAs' versatile and dynamic features. More research is needed to clarify the expression and role of miRNAs in sepsis and promote the use of miRNAs for sepsis management. This study provides an extensive, current, and thorough analysis of the involvement of miRNAs in sepsis. Its purpose is to encourage future research in this area, as tiny miRNAs have the potential to be used for rapid diagnosis, prognosis, and treatment of sepsis.

The Diagnostic Utility of Host RNA Biosignatures in Adult Patients With Sepsis: A Systematic Review and Meta-Analysis

OBJECTIVES

Sepsis is a life-threatening medical emergency, with a profound healthcare burden globally. Its pathophysiology is complex, heterogeneous and temporally dynamic, making diagnosis challenging. Medical management is predicated on early diagnosis and timely intervention. Transcriptomics is one of the novel "-omics" technologies being evaluated for recognition of sepsis. Our objective was to evaluate the performance of host gene expression biosignatures for the diagnosis of all-cause sepsis in adults.

DATA SOURCES

PubMed/Ovid Medline, Ovid Embase, and Cochrane databases from inception to June 2023.

STUDY SELECTION

We included studies evaluating the performance of host gene expression biosignatures in adults who were diagnosed with sepsis using existing clinical definitions. Controls where applicable were patients without clinical sepsis.

DATA EXTRACTION

Data including population demographics, sample size, study design, tissue specimen, type of transcriptome, health status of comparator group, and performance of transcriptomic biomarkers were independently extracted by at least two reviewers.

DATA SYNTHESIS

Meta-analysis to describe the performance of host gene expression biosignatures for the diagnosis of sepsis in adult patients was performed using the random-effects model. Risk of bias was assessed according to the Quality Assessment of Diagnostic Accuracy Studies-2 tool. A total of 117 studies (n = 17,469), comprising 132 separate patient datasets, were included in our final analysis. Performance of transcriptomics for the diagnosis of sepsis against pooled controls showed area under the receiver operating characteristic curve (AUC, 0.86; 95% CI, 0.84-0.88). Studies using healthy controls showed AUC 0.87 (95% CI, 0.84-0.89), while studies using controls with systemic inflammatory response syndrome (SIRS) had AUC 0.84 (95% CI, 0.78-0.90). Transcripts with excellent discrimination against SIRS controls include UrSepsisModel, a 210 differentially expressed genes biosignature, microRNA-143, and Septicyte laboratory.

CONCLUSIONS

Transcriptomics is a promising approach for the accurate diagnosis of sepsis in adults and demonstrates good discriminatory ability against both healthy and SIRS control subjects.

BMSCs Downregulate CXCL12 by Secreting Exosomal miR-20a-5p to Promote Macrophage M2 Polarization and Alleviate the Development of Sepsis

OBJECTIVE

Sepsis is a syndrome of the systemic inflammatory response caused by infection that can endanger a patient's life. The aim of this study was to explore the molecular mechanism by which bone marrow mesenchymal stem cells-derived exosomes (BMSCs-exo) carrying miR-20a-5p regulate the progression of sepsis.

METHODS

Clinical samples from sepsis patients were collected. Mouse and cell models of sepsis were induced by lipopolysaccharide (LPS). The levels of related genes and proteins were determined by RT‒qPCR, Western blotting and ELISA. CCK-8 and flow cytometry assays were used to assess cell viability, apoptosis, and markers of macrophage polarization.

RESULTS

In septic patients, miR-20a-5p levels were significantly lower and CXCL12 expression was significantly increased. After LPS induction, M2 polarization of macrophages was significantly reduced, the level of inflammatory factors was increased, and apoptosis was increased. The addition of BMSCs-exo increased the miR-20a-5p level and decreased the expression of CXCL12 in macrophages, thereby promoting macrophage M2 polarization and reducing the levels of inflammatory factors.

CONCLUSION

This study demonstrated for the first time that BMSCs-exo promoted the polarization of M2 macrophages through the miR-20a-5p/CXCL12 axis, thus alleviating the development of sepsis. These findings provide a new theoretical basis for the targeted treatment of sepsis with exosomes or miR-20a-5p.

Postmortem analyses of myocardial microRNA expression in sepsis

BACKGROUND

Sepsis can lead to myocardial depression, playing a significant role in sepsis pathophysiology, clinical care, and outcome. To gain more insight into the pathophysiology of the myocardial response in sepsis, we investigated the expression of microRNA in myocardial autopsy specimens in critically ill deceased with sepsis and non-septic controls.

MATERIALS AND METHODS

In this retrospective observational study, we obtained myocardial tissue samples collected during autopsy from adult patients deceased with sepsis (n = 15) for routine histological examination. We obtained control myocardial tissue specimens (n = 15) from medicolegal autopsies of cadavers whose cause of death was injury or who were found dead at home and the cause of death was coronary artery disease with sudden cardiac arrest. RNA was isolated from formalin-fixed paraffin- embedded (FFPE) cardiac samples using the RecoverAll Total Nucleic Acid Isolation Kit for FFPE (Invitrogen). Differentially expressed miRNAs were identified using edgeR v3.32. MicroRNA was considered up- or down-regulated if the false discovery rate was < 0.05 and logarithmic fold change (log2FC) ≥ 1 for up-regulated or log2FC ≤ -1 for down-regulated miRNAs. The mean difference and 95% confidence interval (CI) were calculated for normalized read counts. Predicted miRNA targets were retrieved using Ingenuity Pathway Analysis (IPA) software, and pathway enrichment and classification were performed using PantherDB. For miRNA - mRNA interaction analysis, differentially expressed genes were analyzed by 3`mRNA sequencing.

RESULTS

Differential expression analysis identified a total of 32 miRNAs in the myocardial specimens. Eight miRNAs had a significant change in the mean difference based on the 95% CI, with the largest increase in mean counts in septic samples with hsa-miR-12136 and the highest fold change with hsa-miR-146b-5p. The threshold for down-regulated miRNAs in sepsis compared to controls was obtained with hsa-miR-144-5p and hsa-miR-451a, with the latter having the largest decrease in mean counts and fold decrease. The miRNA - mRNA interaction analysis identified eight miRNAs with target genes also differentially expressed in septic hearts. The highest number of potential targets were identified for hsa-miR-363-3p.

CONCLUSIONS

Several regulatory miRNAs were up-or down-regulated in the myocardial tissue of patients deceased with sepsis compared to non-septic subjects. The predicted target genes of miRNAs and miRNA-mRNA interaction analysis are associated with biological functions related to cardiovascular functions, cell viability, cell adhesion, and regulation of inflammatory and immune response.

Long-Term and Continuous Plasmonic Oligonucleotide Monitoring Enabled by Regeneration Approach

The demand for continuous monitoring of biochemical markers for diagnostic purposes is increasing as it overcomes the limitations of traditional intermittent measurements. This study introduces a method for long-term, continuous plasmonic biosensing of oligonucleotides with high temporal resolution. Our method is based on a regeneration-based reversibility approach that ensures rapid reversibility in less than 1 minute, allowing the sensor to fully reset after each measurement. We investigated label-free and AuNP enhancements for different dynamic ranges and sensitivities, achieving a limit of detection down to pM levels. We developed a regeneration-based reversibility approach for continuous biosensing, optimizing buffer conditions using the Taguchi method to achieve rapid, consistent reversibility, ensuring reliable performance for long-term monitoring. We detected oligonucleotides in buffered and complex solutions, including undiluted and unfiltered human serum, for up to 100 sampling cycles in a day. Moreover, we showed the long-term stability of the sensor for monitoring capabilities in buffered solutions and human serum, with minimal signal value drift and excellent sensor reversibility for up to 9 days. Our method opens the door to new prospects in continuous biosensing by providing insights beyond intermittent measurements for numerous analytical and diagnostic applications.

A Tetrahedral Framework DNA-Based Bioswitchable miR-150 Delivery System for Sepsis

Sepsis is a disease with high morbidity and mortality, for which effective treatments are lacking. In recent years, microRNAs (miRs) have been shown to regulate numerous biological processes and can function as therapeutic options for various diseases. However, the poor stability and cell entry properties of miRs have greatly limited their clinical application. In this study, we developed a tetrahedral framework nucleic acid (tFNA)-based bioswitchable miR delivery system (BiRDS) to deliver miR-150 for the treatment of sepsis. BiRDS showed anti-inflammatory effects both in vitro and in vivo by regulating the NF-κB and Notch1 pathways. Therefore, this system holds promise as an ideal candidate for tackling systemic inflammation and multiorgan dysfunction in septic patients in the future.

MicroRNAs in Sepsis

Sepsis is an insidious and frequent condition of severe inflammation due to infections. Several biomarkers have been established for initial screening, but the non-specific nature of the existing biomarkers has led to the investigation of more sensitive and specific tools, such as microRNAs (miRs). These non-coding RNAs are involved in several diseases, including sepsis, due to their roles in cellular homeostasis. Herein, a literature overview was attempted to distinguish the most prominent miRs identified in septic conditions and their usefulness in diagnosis, prognosis and even classification of sepsis. miRs implicated in the regulation of pro and anti-inflammatory mechanisms, such as MIR-146a, MIR-155, MIR-181b, MIR-223-5p, MIR-494-3p, MIR-2055b, MIR-150 and MIR-143 have been pinpointed as acceptable testing tools. Furthermore, the use of miRs as screening panels, specific for septic parameters, such as type of causal infection, inflammation immune pathways affected (NF-kB, STAT/JACK), organs inflicted, as well as parallel screening of certain miRs alongside other long non-coding RNAs (LNCs), as co-regulators of sepsis progression. Overall, miRs exhibit benefits in terms of specificity and sensitivity, as well as practical ease of use and test stability. Furthermore, miRs could offer valuable insights into the molecular basis of disease causality and provide valuable therapeutic information.

Pediatric Sepsis - Sailing the Unchartered Waters with Omics

How to cite this article: Baalaaji M. Pediatric Sepsis - Sailing the Unchartered Waters with Omics. Indian J Crit Care Med 2024;28(9):818-819.

A point-of-care electrochemical biosensor for the rapid and sensitive detection of biomarkers in murine models with LPS-induced sepsis

Sepsis is a life-threatening condition, which is irreversible if diagnosis and intervention are delayed. The response of the immune cells towards an infection triggers widespread inflammation through the production of cytokines, which may result in multiple organ dysfunction and eventual death. Conventional detection techniques fail to provide a rapid diagnosis because of their limited sensitivity and tedious protocol. This study proposes a point-of-care (POC) electrochemical biosensor that overcomes the limitations of current biosensing technologies in the clinical setting by its integration with electrokinetics, enhancing the sensitivity to picogram level compared with the nanogram limit of current diagnostic technologies. This biosensor promotes the use of a microelectrode strip to address the limitations of conventional photolithographic fabrication methods. Tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and microRNA-155 (miR-155) were monitored in a lipopolysaccharide (LPS)-induced septic mouse model. The optimum target hybridization time in a high conductivity medium was observed to be 60 s leading to the completion of the whole operation within 5 min compared with the 4-h detection time of the traditional enzyme-linked immunosorbent assay (ELISA). The limit of detection (LOD) was calculated to be 0.84, 0.18, and 0.0014 pg mL-1, respectively. This novel sensor may have potential for the early diagnosis of sepsis in the clinical setting.

MicroRNA as Sepsis Biomarkers: A Comprehensive Review

Sepsis, a life-threatening condition caused by the body's dysregulated response to infection, presents a significant challenge in clinical management. Timely and accurate diagnosis is paramount for initiating appropriate interventions and improving patient outcomes. In recent years, there has been growing interest in identifying biomarkers that can aid in the early detection and prognostication of sepsis. MicroRNAs (miRNAs) have emerged as potential biomarkers for sepsis due to their involvement in the regulation of gene expression and their stability in various biological fluids, including blood. MiRNAs are small non-coding RNA molecules that play crucial roles in post-transcriptional gene regulation by binding to target messenger RNAs (mRNAs), leading to mRNA degradation or translational repression. The diagnostic and prognostic potential of miRNAs in sepsis stems from their ability to serve as sensitive and specific biomarkers reflective of the underlying pathophysiological processes. Compared to traditional biomarkers such as C-reactive protein (CRP) and procalcitonin (PCT), miRNAs offer several advantages, including their early and sustained elevation during sepsis, as well as their stability in stored samples, making them attractive candidates for clinical use. However, despite their promise, the clinical translation of miRNAs as sepsis biomarkers faces several challenges. These include the need for standardized sample collection and processing methods, the identification of optimal miRNA panels or signatures for differentiating sepsis from other inflammatory conditions, and the validation of findings across diverse patient populations and clinical settings. In conclusion, miRNAs hold great promise as diagnostic and prognostic biomarkers for sepsis, offering insights into the underlying molecular mechanisms and potential therapeutic targets. However, further research is needed to overcome existing challenges and realize the full clinical utility of miRNAs in improving sepsis outcomes.

Exploring ncRNA-mediated pathways in sepsis-induced pyroptosis

Sepsis, a potentially fatal illness caused by an improper host response to infection, remains a serious problem in the world of healthcare. In recent years, the role of ncRNA has emerged as a pivotal aspect in the intricate landscape of cellular regulation. The exploration of ncRNA-mediated regulatory networks reveals their profound influence on key molecular pathways orchestrating pyroptotic responses during septic conditions. Through a comprehensive analysis of current literature, we navigate the diverse classes of ncRNAs, including miRNAs, lncRNAs, and circRNAs, elucidating their roles as both facilitators and inhibitors in the modulation of pyroptotic processes. Furthermore, we highlight the potential diagnostic and therapeutic implications of targeting these ncRNAs in the context of sepsis, aiming to cover the method for novel and effective strategies to mitigate the devastating consequences of septic pathogenesis. As we unravel the complexities of this regulatory axis, a deeper understanding of the intricate crosstalk between ncRNAs and pyroptosis emerges, offering promising avenues for advancing our approach to sepsis intervention. The intricate pathophysiology of sepsis is examined in this review, which explores the dynamic interaction between ncRNAs and pyroptosis, a highly regulated kind of programmed cell death.

Sepsis-associated encephalopathy: Autophagy and miRNAs regulate microglial activation

Sepsis-associated encephalopathy (SAE) describes diffuse or multifocal cerebral dysfunction caused by the systemic inflammatory response to sepsis. SAE is a common neurological complication in patients in the middle and late stages of sepsis in the intensive care unit. Microglia, resident macrophages of the central nervous system, phagocytose small numbers of neuronal cells and apoptotic cells, among other cells, to maintain the dynamic balance of the brain's internal environment. The neuroinflammatory response induced by activated microglia plays a central role in the pathogenesis of various central nervous system diseases. In this paper, we systematically describe the functions and phenotypes of microglia, summarize how microglia mediate neuroinflammation and contribute to the occurrence and development of SAE, and discuss recent progress in autophagy- and microRNA-mediated regulation of microglial activation to provide a theoretical basis for the prevention and treatment of SAE and identify related therapeutic targets.

Myeloid-Derived Suppressor-like Cells as a Prognostic Marker in Critically Ill Patients: Insights from Experimental Endotoxemia and Intensive Care Patients

Patients admitted to the intensive care unit (ICU) often experience endotoxemia, nosocomial infections and sepsis. Polymorphonuclear and monocytic myeloid-derived suppressor cells (PMN-MDSCs and M-MDSCs) can have an important impact on the development of infectious diseases, but little is known about their potential predictive value in critically ill patients. Here, we used unsupervised flow cytometry analyses to quantify MDSC-like cells in healthy subjects challenged with endotoxin and in critically ill patients admitted to intensive care units and at risk of developing infections. Cells phenotypically similar to PMN-MDSCs and M-MDSCs increased after endotoxin challenge. Similar cells were elevated in patients at ICU admission and normalized at ICU discharge. A subpopulation of M-MDSC-like cells expressing intermediate levels of CD15 (CD15int M-MDSCs) was associated with overall mortality (p = 0.02). Interestingly, the high abundance of PMN-MDSCs and CD15int M-MDSCs was a good predictor of mortality (p = 0.0046 and 0.014), with area under the ROC curve for mortality of 0.70 (95% CI = 0.4-1.0) and 0.86 (0.62-1.0), respectively. Overall, our observations support the idea that MDSCs represent biomarkers for sepsis and that flow cytometry monitoring of MDSCs may be used to risk-stratify ICU patients for targeted therapy.

Organotypic heterogeneity in microvascular endothelial cell responses in sepsis-a molecular treasure trove and pharmacological Gordian knot

In the last decades, it has become evident that endothelial cells (ECs) in the microvasculature play an important role in the pathophysiology of sepsis-associated multiple organ dysfunction syndrome (MODS). Studies on how ECs orchestrate leukocyte recruitment, control microvascular integrity and permeability, and regulate the haemostatic balance have provided a wealth of knowledge and potential molecular targets that could be considered for pharmacological intervention in sepsis. Yet, this information has not been translated into effective treatments. As MODS affects specific vascular beds, (organotypic) endothelial heterogeneity may be an important contributing factor to this lack of success. On the other hand, given the involvement of ECs in sepsis, this heterogeneity could also be leveraged for therapeutic gain to target specific sites of the vasculature given its full accessibility to drugs. In this review, we describe current knowledge that defines heterogeneity of organ-specific microvascular ECs at the molecular level and elaborate on studies that have reported EC responses across organ systems in sepsis patients and animal models of sepsis. We discuss hypothesis-driven, single-molecule studies that have formed the basis of our understanding of endothelial cell engagement in sepsis pathophysiology, and include recent studies employing high-throughput technologies. The latter deliver comprehensive data sets to describe molecular signatures for organotypic ECs that could lead to new hypotheses and form the foundation for rational pharmacological intervention and biomarker panel development. Particularly results from single cell RNA sequencing and spatial transcriptomics studies are eagerly awaited as they are expected to unveil the full spatiotemporal signature of EC responses to sepsis. With increasing awareness of the existence of distinct sepsis subphenotypes, and the need to develop new drug regimen and companion diagnostics, a better understanding of the molecular pathways exploited by ECs in sepsis pathophysiology will be a cornerstone to halt the detrimental processes that lead to MODS.

Septic encephalopathy in the elderly - biomarkers of potential clinical utility

Next to acute sickness behavior, septic encephalopathy is the most frequent involvement of the brain during infection. It is characterized by a cross-talk of pro-inflammatory cells across the blood-brain barrier, by microglial activation and leukocyte migration, but not by the entry of infecting organisms into the brain tissue. Septic encephalopathy is very frequent in older persons because of their limited cognitive reserve. The predominant clinical manifestation is delirium, whereas focal neurological signs and symptoms are absent. Electroencephalography is a very sensitive method to detect functional abnormalities, but these abnormalities are not specific for septic encephalopathy and of limited prognostic value. Routine cerebral imaging by computer tomography usually fails to visualize the subtle abnormalities produced by septic involvement of the brain. Magnetic resonance imaging is by far more sensitive to detect vasogenic edema, diffuse axonal injury or small ischemic lesions. Routine laboratory parameters most suitable to monitor sepsis, but not specific for septic encephalopathy, are C-reactive protein and procalcitonin. The additional measurement of interleukin (IL)-6, IL-8, IL-10 and tumor necrosis factor-α increases the accuracy to predict delirium and an unfavorable outcome. The most promising laboratory parameters to quantify neuronal and axonal injury caused by septic encephalopathy are neurofilament light chains (NfL) and S100B protein. Neuron-specific enolase (NSE) plasma concentrations are strongly influenced by hemolysis. We propose to determine NSE only in non-hemolytic plasma or serum samples for the estimation of outcome in septic encephalopathy.

Biomarkers of Neonatal Sepsis: Where We Are and Where We Are Going

Neonatal sepsis is a bacterial bloodstream infection leading to severe clinical manifestations frequently associated with death or irreversible long-term deficits. Antibiotics are the drug of choice to treat sepsis, regardless of age. In neonates, the lack of reliable criteria for a definite diagnosis and the supposition that an early antibiotic administration could reduce sepsis development in children at risk have led to a relevant antibiotic overuse for both prevention and therapy. The availability of biomarkers of neonatal sepsis that could alert the physician to an early diagnosis of neonatal sepsis could improve the short and long-term outcomes of true sepsis cases and reduce the indiscriminate and deleterious use of preventive antibiotics. The main aim of this narrative review is to summarize the main results in this regard and to detail the accuracy of currently used biomarkers for the early diagnosis of neonatal sepsis. Literature analysis showed that, despite intense research, the diagnosis of neonatal sepsis and the conduct of antibiotic therapy cannot be at present decided on the basis of a single biomarker. Given the importance of the problem and the need to reduce the abuse of antibiotics, further studies are urgently required. However, instead of looking for new biomarkers, it seems easier and more productive to test combinations of two or more of the presently available biomarkers. Moreover, studies based on omics technologies should be strongly boosted. However, while waiting for new information, the use of the clinical scores prepared by some scientific institutions could be suggested. Based on maternal risk factors and infant clinical indicators, sepsis risk can be calculated, and a significant reduction in antibiotic consumption can be obtained.

The Role of Transcriptomics in Redefining Critical Illness

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2023. Other selected articles can be found online at  https://www.biomedcentral.com/collections/annualupdate2023 . Further information about the Annual Update in Intensive Care and Emergency Medicine is available from  https://link.springer.com/bookseries/8901 .

A summary of the current diagnostic methods for, and exploration of the value of microRNAs as biomarkers in, sepsis-associated encephalopathy

Sepsis-associated encephalopathy (SAE) is an acute neurological deficit caused by severe sepsis without signs of direct brain infection, characterized by the systemic inflammation and disturbance of the blood-brain barrier. SAE is associated with a poor prognosis and high mortality in patients with sepsis. Survivors may exhibit long-term or permanent sequelae, including behavioral changes, cognitive impairment, and decreased quality of life. Early detection of SAE can help ameliorate long-term sequelae and reduce mortality. Half of the patients with sepsis suffer from SAE in the intensive care unit, but its physiopathological mechanism remains unknown. Therefore, the diagnosis of SAE remains a challenge. The current clinical diagnosis of SAE is a diagnosis of exclusion; this makes the process complex and time-consuming and delays early intervention by clinicians. Furthermore, the scoring scales and laboratory indicators involved have many problems, including insufficient specificity or sensitivity. Thus, a new biomarker with excellent sensitivity and specificity is urgently needed to guide the diagnosis of SAE. MicroRNAs have attracted attention as putative diagnostic and therapeutic targets for neurodegenerative diseases. They exist in various body fluids and are highly stable. Based on the outstanding performance of microRNAs as biomarkers for other neurodegenerative diseases, it is reasonable to infer that microRNAs will be excellent biomarkers for SAE. This review explores the current diagnostic methods for sepsis-associated encephalopathy (SAE). We also explore the role that microRNAs could play in SAE diagnosis and if they can be used to make the SAE diagnosis faster and more specific. We believe that our review makes a significant contribution to the literature because it summarizes some of the important diagnostic methods for SAE, highlighting their advantages and disadvantages in clinical use, and could benefit the field as it highlights the potential of miRNAs as SAE diagnostic markers.