EP4430210A1

EP4430210A1 - Depression biomarkers, uses and method thereof

Info

Publication number: EP4430210A1
Application number: EP22826405.7A
Authority: EP
Inventors: João BRÁS; Maria Inês ALMEIDA; Susana SANTOS; Mário BARBOSA
Original assignee: Ineb-Instituto Nacional De Engenharia Biomedica; Universidade do Porto
Current assignee: Ineb-Instituto Nacional De Engenharia Biomedica; Universidade do Porto
Priority date: 2021-11-12
Filing date: 2022-11-14
Publication date: 2024-09-18
Also published as: WO2023084478A1

Abstract

The present disclosure relates to an in vitro or ex vivo use of miR-342-3p as a biomarker of depression in an isolated biological sample, preferably blood or peripheral blood mononuclear cells. Furthermore, the present disclosure relates to an in vitro or ex vivo method diagnosis or prognosis of depression in a subject.

Description

DEPRESSION BIOMARKERS, USES AN D METHOD TH EREOF

TECH NICAL FIELD

[0001] The present disclosure relates to an in vitro or ex vivo use of biomarkers to detect depression, in particular microRNAs (miRNAs).

BACKGROUND

[0002] Depression ranks as the most prevalent psychiatric disorder, with estimated over 260 million sufferers worldwide (WH02020), and a lifetime prevalence of 10-20% (1). It also figures among the top three causes of disability worldwide and can affect individuals of all ages throughout their entire lifespan, with a higher prevalence in women (1). Conventional pharmacological treatments for depression are mainly based on the monoamines theory of depression, targeting neurotransmission regulation (2). However, it is estimated that between 30 to 50% of patients with major depression do not respond to the prescribed schemes of antidepressant medication (3, 4), reinforcing the need to stratify patients, and understand the multifactorial aetiology of this disorder. It is now clear that the major reason, still preventing a most accurate diagnosis as well as the development of better pharmacotherapies, is the poor understanding of the molecular pathology underlying depression. This leads to narrative and observationbased diagnosis, disregarding the biological particularities of each patient (5). Thus, there is an urgent need to establish complementary diagnostics tests, by defining diagnosis follow-up and prognosis biomarkers based on the underlying disease mechanisms. In this sense, microRNAs (miRNAs) have recently emerged as important mediators in the pathophysiology of depression, with potential to be used as therapeutical targets and/or biomarkers (6, 7). miRNAs are small non-coding RNAs that regulate multiple target transcripts, influencing entire gene networks in processes such as neurogenesis and neuronal plasticity (8, 9). Since brain tissue is rarely available for study, the analysis of other peripheral information sources, such as saliva, plasma, serum and particularly Peripheral Blood Mononuclear Cells (PBMCs), has received increasing attention. In fact, previous studies have shown that peripheral blood cells share more than 80% of the transcriptome with brain tissue, therefore offering a potential diagnostic tool that can dynamically reflect changes in brain macro- and microenvironments (10).

[0003] These facts are disclosed in order to illustrate the technical problem addressed by the present disclosure, which relates to a blood-based biomarker panel associated to the pathogenesis of depression.

GENERAL DESCRIPTION

[0004] The present disclosure relates to an in vitro or ex vivo use of miR-342-3p miRNA as a biomarker of depression, alone or in combination with other miRNA's (miR-146a- 5p and/or miR-155-5p) in an isolated biological sample, preferably blood or peripheral blood mononuclear cells. Furthermore, the present disclosure relates to an in vitro or ex vivo method diagnosis or prognosis of depression in a subject.

[0005] Unexpectedly, the inventors have observed that miR-342-3p is upregulated in the PBMCs of depression patients and is positively correlated with depressive-like behaviours. Additionally, considering the expression of additional miRNA's ( miR-146a- 5p and miR-155-5p) and tested as a miRNA panel, sensitivity increased significantly and the use of the three miRNAs in combination was the best classifier (AUC=0.842, sensitivity of 80.6% and specificity of 72.5%).

[0006] The present invention stems from the study of how peripubertal stress (PPS) combined with differential corticosterone (CORT)-stress responsiveness (CSR) influences depressive-like behaviours in male rats in adulthood, and how these alterations relate to expression of miRNAs. Surprisingly, High-CORT stress-responsive (H- CSR) male rats that underwent PPS, which exhibit depressive-like behaviour, show hippocampal upregulation of specific miRNAs, in particular of miR-342-3p. These findings in a rat model allow to assess that miR-342-3p expression is positively correlated with passive coping responses, which are characteristic of depression, and highlight miR-342-3p as a potential biomarker for the diagnosis of depression in humans. Analysis of the expression of the homologous human miR-342-3p, along with other miRNAs, in the PBMCs originally reveals diagnostic potential for depression, as assessed in a case-control study. The present invention thus refers to the use of primer and probe sequence compositions and to a method developed in vitro for diagnosis and monitoring of depression, the said method comprising the steps of extracting RNA from PBMCs and quantifying levels of miR-342-3p, alone or in combination with other miRNAs.

[0007] Depression or major depressive disorder is a common and serious medical illness that negatively affects how you feel, the way you think and how you act. Fortunately, it is also treatable. Depression causes feelings of sadness and/or a loss of interest in activities you once enjoyed. It can lead to a variety of emotional and physical problems and can decrease your ability to function at work and at home.

[0008] Within the present disclosure, when miR-342 is mentioned, it refers to miR-342- 3p; when miR-155 is mentioned, it refers to miR-155-5p; when miR-146a is mentioned, it refers to miR-146a-5p; when miR-145 is mentioned, it refers to miR-145-5p.

[0009] In the present disclosure, PBMC refers to peripheral blood mononuclear cells.

[0010] In the present disclosure, CSR refers to corticosterone (CORT)-stress responsiveness.

[0011] In the present disclosure, N-CSR refers to Normative- CORT stress-responsive.

[0012] In the present disclosure, H-CSR refers to High-CORT stress-responsive.

[0013] In the present disclosure, CTR refers to control

[0014] In the present disclosure, PPS refers to peripubertal stress.

[0015] The accession number of each miRNA herein disclosed can be accessed in the 3iRbase database, available in the following link:

[0016] The microRNA miR-145-5p is also referred as hsa-miR-145-5p (Homo Sapiens (Hsa) miR-145-5p) and is identified by the miRbase accession number MIMAT0000437.

[0017] The microRNA miR-146a-5p is also referred as hsa-miR-146a-5p and is identified by the miRbase accession number MIMAT0000449.

[0018] The microRNA miR-155-5p 5p is also referred as hsa-miR-155-5p and is identified by the miRbase accession number MIMAT0000646 [0019] The microRNA miR-342-3p is also referred as hsa-miR-342-3p and is identified by the miRbase accession number MIMAT0000753.

[0020] "Biological sample," as used herein, generally refers to a sample obtained from a biological subject/patient, including sample of biological tissue or fluid origin, obtained, reached, or collected in situ or in vivo. Such samples can be, but are not limited to, organs, tissues, fractions and cells isolated from a mammal. Exemplary biological samples include but are not limited to cell lysate, a cell culture, a cell line, a tissue, oral tissue, gastrointestinal tissue, an organ, an organelle, a biological fluid, a blood sample, a serum sample, a urine sample, a skin sample, and the like. Preferred biological samples include but are not limited to a blood, a plasma, a serum, a PBMC, a tissue biopsy, an oral mucosa, a saliva, an interstitial fluid, or a urine sample, and the like. More preferably, the biological sample blood. Even more preferably, the biological sample is PBMC.

[0021] An aspect of the present disclosure relates to an in vitro or ex vivo use of miR- 342-3p miRNA as a biomarker of depression or major depressive disorder.

[0022] In an embodiment, the use further comprises the use of miR-155-5p and miR- 146a-5p as biomarkers of depression or major depressive disorder.

[0023] In an embodiment, a measured level of expression of miR-342-3p into an isolated biological sample is compared to a control reference value, and wherein an increase of said measured level relative to said control reference value is indicative of depression.

[0024] In an embodiment, the use comprises the measured levels of expression of a biomarker combination, wherein said biomarker combination miR-342-3p and miR- 146a-5p into the isolated biological sample are compared to a control reference value, and wherein an increase of miR-342-3p measured level and decrease of miR-146a-5p measured level relative to said control reference value is indicative of depression.

[0025] In an embodiment, the use comprises the measured levels of expression of a biomarker combination, wherein said biomarker combination miR-342-3p and miR-155- 5p into the isolated biological sample are compared to a control reference value, and wherein an increase of miR-342-3p measured level and decrease of miR-155-5p measured level relative to said control reference value is indicative of depression. [0026] In an embodiment, the use comprises the measured levels of expression of a biomarker combination, wherein said biomarker combination miR-342-3p, miR-146a-5p and miR-155-5p into the isolated biological sample are compared to a control reference value, and wherein an increase of miR-342-3p measured level and decrease of miR- 146a-5p and miR-155-5p measured levels relative to said control reference value is indicative of depression.

[0027] In an embodiment, the biological sample is blood.

[0028] In an embodiment, the biological sample is peripheral blood mononuclear cells.

[0029] Another aspect of the present disclosure relates to an in vitro or ex vivo method for diagnosis or prognosis of depression or major depressive disorder in a subject, comprising the following the steps: measuring a presence or an expression level of miR-342-3p miRNA, in a biological sample previously obtained from said subject; and comparing said presence or expression level to a control reference value, wherein an increased presence or level of expression of said miRNA relative to said control reference value is indicative of depression.

[0030] In an embodiment, the biological sample is blood.

[0031] In an embodiment, the biological sample is peripheral blood mononuclear cells.

[0032] Another aspect of the present disclosure relates to a biomarker for use in vitro or ex vivo diagnostic of depression or major depressive disorder, wherein said biomarker is miR-342-3p, preferably combined with miR-146a-5p and/or miR-155-5p.

[0033] In an embodiment, the biomarker is the combination of miR-342-3p and miR- 155-5p; or miR-342-3p and miR-146a-5p.

[0034] In an embodiment, the biomarker further comprises miR-342-3p, miR-155-5p and miR-146a-5p.

[0035] Another aspect of the present disclosure relates to a kit for use in vitro or ex vivo diagnostic of depression comprising the biomarker herein described. BRI EF DESCRI PTION OF THE DRAWI NGS

[0036] The following figures provide preferred embodiments for illustrating the disclosure and should not be seen as limiting the scope of invention.

[0037] Figure 1. miR-342-3p is overexpressed in the hippocampus of rats exhibiting depressive-like behaviors (H-CSR PPS rats). miR-342-3p expression levels were significantly impacted by stress exposure. Post hoc analysis revealed that miR-342-3p expression levels were significantly increased in high-CORT responsiveness (H-CSR) rats undergoing peripubertal stress (PPS) compared with the respective non-PPS control rats. miR-342-3p expression levels in the hippocampus were evaluated by RT-qPCR using U6 snRNA as an internal control. Relative expression levels were calculated using the quantification cycle (Cq) method, according to the MIQE guidelines, and results are presented as the mean ± SEM. N: N-CSR = 18 (9 CTR and 9 PPS); H-CSR = 24 (12 CTR and 12 PPS). Two-way ANOVA followed by Sidak's multiple comparisons test, *p < 0.05.

[0038] Figure 2A-2B. miR-342-3p hippocampal expression positively correlates with depressive-like behaviors. Correlations between hippocampal miR-342-3p expression and depressive-like behaviors revealed a significant positive correlation between miR- 342-3p levels and the percentage of time spent floating on the second day of the forced- swim test (FST) (Fig. 2B) and a tendency towards a negative correlation with saccharin preference (Fig. 2A). These results suggest that hippocampal miR-342-3p expression may be a factor in depression susceptibility. Pearson correlations were performed considering all animals (N=42). The coefficient r and p-value for each correlation are presented in a box. Statistically significant correlations are highlighted in green (p<0.05).

[0039] Figure 3. miR-342-3p tends to be upregulated in the PBMCs of rats exhibiting depressive-like behaviors. miR-342-3p expression levels in the PBMCs of rats undergoing PPS, particularly those exhibiting increased depressive-like behaviors (H-CSR PPS), suggesting that dysregulated levels may be also detected systemically. miR-342-3p expression levels were evaluated by RT-qPCR using U6 snRNA as an internal control. Relative expression levels were calculated using the quantification cycle (Cq) method, according to the MIQE guidelines, and results are presented as the mean ± SEM. N: N- CSR = 18 (9 CTR and 9 PPS); H-CSR = 24 (12 CTR and 12 PPS). [0040] Figure 4A-4D. Levels of miR-342-3p are upregulated, while miR-146a-5p and miR-155-5p are downregulated in the PBMCs of depression patients. The expression levels of the newly identified miRNA in the context of depression (miR-342-3p) and other additional miRNAs previously reported to be dysregulated in depression (miR-145-5p, miR-146a-5p and miR-155-5p) were evaluated in the PBMCs by RT-qPCR using U6 snRNA as internal control. Results revealed that miR-342-3p is significantly upregulated, while miR-146a-5p and miR-155-5p levels are significantly downregulated in the PBMCs of depression patients compared with healthy controls. Relative expression levels were calculated using the quantification cycle (Cq) method, according to MIQE guidelines, and results are presented as mean ± SEM. Each dot represents an individual (Control or Depression patient). Statistical differences between groups were evaluated using Mann- Whitney non-parametric unpaired test or unpaired T-test (** p<0.01, * p<0.05 and + p<0.1). N: Healthy controls = 40; Depression patients = 32.

[0041] Figure 5A-5D. ROC analysis of the differently expressed miRNAs. ROC analysis was performed to evaluate the sensitivity of miR-342-3p, miR-146a-5p and miR-155-5p to distinguish between depression patients and controls when used individually or in combination as a miRNA panel. When tested as a miRNA panel, sensitivity increased significantly and the use of the three miRNAs in combination was the best classifier (AUC=0.842, sensitivity of 80.6% and specificity of 72.5%). The area under the curve (AUC) represents the measure of the ability of each miRNA or the miRNA panel to distinguish between both groups, and the p-value tests the null hypothesis AUC equals 0.5. N: Healthy controls = 40; Depression patients = 32.

DETAILED DESCRI PTION

[0042] The present disclosure relates to an in vitro or ex vivo use of miR-342-3p miRNA as a biomarker of depression, alone or in combination with other miRNA's (miR-146a- 5p and/or miR-155-5p) in an isolated biological sample, preferably blood or peripheral blood mononuclear cells. Furthermore, the present disclosure relates to an in vitro or ex vivo method diagnosis or prognosis of depression in a subject.

[0043] The present invention comprises the study of how peripubertal stress (PPS) combined with differential corticosterone (CORT)-stress responsiveness (CSR) influences depressive-like behaviours in rats in adulthood, and how these alterations relate to the brain expression of microRNAs (miRNAs). These findings in an animal model, highlight miR-342-3p as a potential biomarker for diagnostics of depression in humans. The present invention further refers to a method developed in vitro, employing specific primer and probe compositions for diagnostic and monitoring of depression, the said method comprising the steps of extracting RNA from PBMCs and quantifying levels of miR-342-3p, alone or in combination with other miRNAs. The said compositions and methods of the present invention may be advantageously used to improve accuracy in diagnosis and monitoring of depression, which remains inaccurate as it is mostly narrative and observation based. The present disclosure relates to the use of biomarkers to detect depression, in particular miRNAs.

[0044] An aspect of the present disclosure refers to the use of miR-342-3p specific primer and probe RT-PCR compositions for diagnostic and monitoring of depression. The present invention further refers to a method developed in vitro, employing the said compositions, for diagnostic and monitoring of depression, the said method comprising the steps of extracting RNA from PBMCs and quantifying levels of miR-342-3p, alone or in combination with other miRNAs.

[0045] In an embodiment, an in vivo study is performed to explore how, two key risk factors for depression, i.e. peripubertal stress (PPS) combined with differential corticosterone (CORT)-stress responsiveness (CSR), influence protracted depressive-like behaviors and the expression of brain molecular markers in male rats. Briefly, selective breeding of rats according to their individual differences in CSR is performed as previously described by Walker et al. (11). This results in litters of Normative (N)-CSR and High (H)-CSR. At postnatal day 21 (P 21) rats from both groups are randomly assigned to control (CTR) and PPS conditions. Between P 28 and P 42, rats are maintained in control conditions (CTR group) or subjected to the PPS protocol (PPS group). PPS protocol is based on exposure to fear-induction procedures, according to Marquez et al. (12), and include the exposure to an open-field, a synthetic fox odor and an elevated platform. In adulthood (P 90), CTR and PPS rats undergo sequential behavioral tests to evaluate depressive-like behaviors (saccharin preference and forced- swim test). In total, 42 animals are used, namely 18 N-CSR (9 CTR and 9 PPS) and 24 H- CSR (12 CTR and 12 PPS). Rats are sacrificed by decapitation and brains freshly dissected for isolation of the medial prefrontal cortex (mPFC), nucleus accumbens (NAc), amygdala (Amg) and hippocampus (HPC). Each brain region is placed in an RNAse-free cryotube, fresh frozen in liquid nitrogen, and stored at -80°C prior to RNA extraction. Trunk blood is also collected and immediately processed for PBMCs isolation. Total RNA from brain regions and PBMCs is extracted using TRIzol reagent (Invitrogen). miR-342- 3p expression is evaluated using a TaqMan microRNA assay (Applied Biosystems). Briefly, cDNA is synthesized using 30 ng of RNA as a template, gene-specific stem-loop Reverse Transcription primer, and the TaqMan microRNA reverse transcription kit (Applied Biosystems). Oligonucleotide primers and Taqman probes are used to amplify and detect the synthetic DNA fragment obtained from cDNA synthesis. Compositions comprising the above-mentioned assay are prepared by adding reactant solutions to the RT-PCR, available from the market, in specific concentrations and qPCR is carried out in Real-Time PCR Detection System (Bio-Rad) using cDNA and SsoAdvancedTM Universal Probes Supermix (Bio-Rad). Small nuclear RNA U6 is used as reference gene. Relative expression levels is calculated using the quantification cycle (Cq) method. Statistical analysis is performed using GraphPad Prism version 7. When analyzing the difference between the means of more than two groups, 2-way ANOVA is performed to estimate how the mean of the quantitative variables changed according to the levels of the independent variables (CSR and stress exposure). To test which levels were actually different between the CTR and PPS groups, Sidak's post hoc multiple comparisons test is performed. Pearson correlation analysis is performed to compare behavioural performance with brain miR-342-3p expression levels, and accounts all animals (N=42). p<0.05 is considered statistically significant.

[0046] In an embodiment, patients ranging in age from 18-65 years are studied after screening and diagnosis of major depressive disorder by psychiatrists. Briefly, clinical depression diagnostics may further include a structured clinical interview to assess the presence of major psychiatric syndromes according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), an assessment of current psychiatric symptoms, and a determination of previous antidepressant treatment. [0047] In an embodiment, blood samples are obtained from depression patients at baseline, as well as before undergoing treatment. Patients may be excluded from the analysis if presenting any of the following: i) psychotic symptoms; ii) presence of an infectious or inflammatory illness or the regular use of anti-inflammatory medication; iii) Inability to completely understand and fill in the self-assessment instruments; iv) Being part of a trial or with other psychological/psychopharmacological treatment.

[0048] In an embodiment, peripheral blood is collected using VACUETTE® Tubes EDTA K3 (Greiner Bio-One, France). Blood components are separated by centrifuging at 1200g, for 20 min, at room temperature (RT), without break. Plasma is collected and centrifuged twice at 2500g, for 10 min at 4 °C before being aliquoted and stored at -80 °C. Medial layer containing PBMCs are slowly collected and transferred into a new 15mL centrifuge tube. PBMCs are diluted in an equal volume of PBS lx, slowly layered over Lymphoprep (Ratio 1:1) and centrifuged at 800g, for 20min, at RT, without break. Medial layer containing enriched PBMCs is collected, and cells washed twice with PBS lx (300g, lOmin, at 4°C) before being lysed with TRIzol®.

[0049] For the scope and interpretation of the present disclosure it is defined that "room temperature" should be regarded as a temperature between 15-30 °C, preferably between 18-25 °C, more preferably between 20-22 °C.

[0050] In an embodiment, total RNA is extracted using TRIzol® reagent (Invitrogen) according to the manufacturer's instructions. RNA concentration and purity is evaluated in a NanoDrop 1000 (Thermo Scientific). RNA integrity is evaluated by agarose gel electrophoresis or by Experion™ automated electrophoresis system (Bio-Rad, USA).

[0051] In an embodiment, miR-342-3p and miR-145-5p, miR-146a-5p, miR-155-5p expression was evaluated using TaqMan miRNA assays (Applied Biosystems). Briefly, cDNA is synthesized using 30 ng of RNA as a template, gene-specific stem-loop Reverse Transcription primer, and the TaqMan microRNA reverse transcription kit (Applied Biosystems). Oligonucleotide primers and Taqman probes are used to amplify and detect the synthetic DNA fragment obtained from cDNA synthesis. Table 1: Oligonucleotides sequences and ID's of the Taqman® assays used for RT-qPCR for miR-145-5p, miR-146a-5p, miR-155-5p, miR-342-3p and U6 SnRNA. miRBase Taqman® miRNA name Accession Mature sequence miRNA assay ID

Number hsa-miR-145-5p MIMAT0000437 GUCCAGUUUUCCCAGGAAUCCCU 002278 hsa-miR-146a-5p MIMAT0000449 UGAGAACUGAAUUCCAUGGGUU 000468 hsa-miR-155-5p MIMAT0000646 UUAAUGCUAAUCGUGAUAGGGGUU 002623 hsa-miR-342-3p MIMAT0000753 UCUCACACAGAAAUCGCACCCGU 002260

Taqman® Negative control NCBI Accession Control sequence miRNA control name Number assay ID

GTG CTCG CTTCG G CAG CACATATACTAAAAT

TGGAACGATACAGAGAAGATTAGCATGGCC U6 SnRNA NR 004394 001973

CCTGCGCAAGGATGACACGCAAATTCGTGA

AGCGTTCCATATTTT

[0052] The above-mentioned assays can be obtained in the market, for example from ThermoFisher.

[0053] Compositions comprising the above-mentioned assays are prepared by adding reactant solutions to the RT-PCR, available from the market, in specific concentrations and qPCR is carried out in Real-Time PCR Detection System (Bio-Rad) using cDNA and SsoAdvancedTM Universal Probes Supermix (Bio-Rad). Small nuclear RNA U6 is used as reference gene. Relative expression levels were calculated using the quantification cycle (Cq) method.

[0054] The diagnostic value of the tested miRNAs (individually or combined) was calculated using Receiver Operating Characteristics (ROC) curve in GraphPad.

[0055] For that, miRNAs relative expression values were previously combined using the binary logistic toll on SPSS considering the experimental group as the dependent variable and the different tested miRNAs as covariates. The area under the curve (AUC) measures of the ability of each miRNA or the miRNA panel to distinguish between both groups, and the p-value tests the null hypothesis that the AUC equals 0.5. [0056] In an embodiment, ROC analysis is performed to evaluate the ability of the differently expressed miRNAs to distinguish between depression patients and healthy controls, individually or in combination. The area under the curve (AUC) for miR-342, miR-146a and miR-155 when tested individually is 0.667 (CI=0.53-0.80, p=0.0164), 0.736 (0=0.62-0.85, p=0.0007) and 0.691 (CI=0.57-0.81, p=0.006) respectively. When tested as a miRNA panel, sensitivity increases significantly and the use of the three miRNAs in combination is the best classifier (AUC=0.842, 0=0.75-0.93, p<0.0001; Figure 4 and Table 2).

Table 2. ROC analysis of the differently expressed miRNAs, individually or combined. AUC - area under the curve; Cl - confidence interval. miR-146a 0.7363 0.06018 0.62-0.85 0.0007 miR-155 0.6911 0.06257 0.57-0.81 0.006

A miR-342 + miR-146a 0.8065 0.05234 0.70-090 <0.0001

B miR-342 + miR-155 0.7629 0.05876 0.65-0.88 0.0002

C miR-146a + iR-155 0.7411 0.05797 0.63-0.85 0.0005

D miR-342 + miR-146a + miR-155 0.8419 0.04679 0.75-0.93 <0.0001

[0057] The term "comprising" whenever used in this document is intended to indicate the presence of stated features, integers, steps, components, but not to preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0058] The disclosure should not be seen in any way restricted to the embodiments described and a person with ordinary skill in the art will foresee many possibilities to modifications thereof. The above-described embodiments are combinable.

[0059] The following claims further set out particular embodiments of the disclosure.

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Claims

C L A I M S An in vitro or ex vivo use of miR-342-3p miRNA as a biomarker of depression or major depressive disorder. The use according to any of the previous claims further comprising the use of miR- 155-5p as biomarkers of depression or major depressive disorder. The use according to the previous claim 1 further comprising the use of miR-155-5p and miR-146a-5p as biomarkers of depression or major depressive disorder. The use according to any of the previous claims wherein a measured level of expression of miR-342-3p into an isolated biological sample is compared to a control reference value, and wherein an increase of said measured level relative to said control reference value is indicative of depression. The use according to any of the previous claims comprising the measured levels of expression of a biomarker combination, wherein said biomarker combination miR- 342-3p and miR-146a-5p into the isolated biological sample are compared to a control reference value, and wherein an increase of miR-342-3p measured level and decrease of miR-146a-5p measured level relative to said control reference value is indicative of depression. The use according to any of the previous claims comprising the measured levels of expression of a biomarker combination, wherein said biomarker combination miR- 342-3p and miR-155-5p into the isolated biological sample are compared to a control reference value, and wherein an increase of miR-342-3p measured level and decrease of miR-155-5p measured level relative to said control reference value is indicative of depression. The use according to any of the previous claims comprising the measured levels of expression of a biomarker combination, wherein said biomarker combination miR- 342-3p, miR-146a-5p and miR-155-5p into the isolated biological sample are compared to a control reference value, and wherein an increase of miR-342-3p measured level and decrease of miR-146a-5p and miR-155-5p measured levels relative to said control reference value is indicative of depression. The use according to any of the previous claims wherein the biological sample is blood. The use according to the previous claim wherein the biological sample is peripheral blood mononuclear cells. An in vitro or ex vivo method for diagnosis or prognosis of depression or major depressive disorder in a subject, comprising the following the steps: measuring a presence oran expression level of miR-342-3p miRNA, in a biological sample previously obtained from said subject; and comparing said presence or expression level to a control reference value, wherein an increased presence or level of expression of said miRNA relative to said control reference value is indicative of depression. The method according to the previous claim further comprising the following steps: measuring a presence or an expression level of miR-146a-5p and/or miR-155-5p in a biological sample previously obtained from said subject; and comparing said presence or expression level to a control reference value, wherein a decreased presence or level of expression of said miRNA relative to said control reference value is indicative of depression. The method according to any of previous claims 10 - 11 wherein the biological sample is blood. The method according to any of previous claims 10 - 12 wherein the biological sample is peripheral blood mononuclear cells. A biomarker for use in vitro or ex vivo diagnostic of depression or major depressive disorder, wherein said biomarker is miR-342-3p, preferably combined with miR- 146a-5p and/or miR-155-5p. The biomarker for use according to the previous claim 14, wherein said biomarker is the combination of miR-342-3p and miR-155-5p; or miR-342-3p and miR-146a-5p. The biomarker for use according to the previous claim 14 further comprising miR- 342-3p, miR-155-5p and miR-146a-5p. A kit for use in vitro or ex vivo diagnostic of depression comprising the biomarker described in any of the claims 14-16.

16