Blood contains circulating cell-free respiratory competent mitochondria.

Mitochondria are considered as the power-generating units of the cell due to their key role in energy metabolism and cell signaling. However, mitochondrial components could be found in the extracellular space, as fragments or encapsulated in vesicles. In addition, this intact organelle has been recently reported to be released by platelets exclusively in specific conditions. Here, we demonstrate for the first time, that blood preparation with resting platelets, contains whole functional mitochondria in normal physiological state. Likewise, we show, that normal and tumor cultured cells are able to secrete their mitochondria. Using serial centrifugation or filtration followed by polymerase chain reaction-based methods, and Whole Genome Sequencing, we detect extracellular full-length mitochondrial DNA in particles over 0.22 µm holding specific mitochondrial membrane proteins. We identify these particles as intact cell-free mitochondria using fluorescence-activated cell sorting analysis, fluorescence microscopy, and transmission electron microscopy. Oxygen consumption analysis revealed that these mitochondria are respiratory competent. In view of previously described mitochondrial potential in intercellular transfer, this discovery could greatly widen the scope of cell-cell communication biology. Further steps should be developed to investigate the potential role of mitochondria as a signaling organelle outside the cell and to determine whether these circulating units could be relevant for early detection and prognosis of various diseases

Study of the structure of extracellular mitochonrial DNA

Le plasma transporte des cellules sanguines avec un mélange de composés, y compris les nutriments, déchets, anticorps, et messagers chimiques... dans tout l'organisme. Des facteurs non solubles tels que l’ADN circulant et les vésicules extracellulaires ont récemment été ajoutés à la liste de ces composants et ont fait l'objet d'études approfondies en raison de leur rôle dans la communication intercellulaire. Or, l’ADN circulant (ADNcir) est composé de fragments d’ADN libres ou associés à d’autres particules, libérés par tous les types cellulaires. Cet ADN est non seulement de l'ADN génomique mais aussi de l'ADN mitochondrial extra-chromosomique. De nombreux travaux réalisés au cours des dernières années indiquent que l’analyse quantitative et qualitative de l’ADNcir représente une avancée dans les applications cliniques en tant que biomarqueur non invasif de diagnostic, de pronostic et de suivi thérapeutique. Cependant, malgré l'avenir prometteur de cet ADNcir dans les applications cliniques, notamment en oncologie, les connaissances sur ses origines, sa composition et ses fonctions qui pourraient pourtant permettre d’optimiser considérablement sa valeur diagnostique, font encore défaut. Le principal objectif de ma thèse a été d’identifier et de caractériser les propriétés structurales de l’ADN extracellulaire d’origine mitochondrial. En examinant l'intégrité de cet ADN, ainsi que la taille et la densité des structures associées, ce travail a révélé la présence de particules denses d’une taille supérieure à 0,2 µm contenant des génomes mitochondriaux complets et non fragmentés. Nous avons caractérisé ces structures notamment par microscopie électronique et cytométrie en flux et nous avons identifié des mitochondries intactes dans le milieu extracellulaire in vitro et ex-vivo (dans des échantillons de plasma d’individus sains). Une consommation d'oxygène par ces mitochondries a été détectée par la technique du Seahorse, suggérant qu'au moins une partie de ces mitochondries extracellulaires intactes pourraient être fonctionnelles. Par ailleurs, j’ai participé à d’autres travaux réalisées dans l’équipe, dont (1) une étude visant à évaluer l’influence des paramètres pré-analytiques et démographiques sur la quantification d’ADNcir d’origine nucléaire et mitochondrial sur une cohorte composée de 104 individus sains et 118 patients atteints de cancer colorectal métastatique, (2) une étude dont l’objectif était d’évaluer l’influence de l’hypoxie sur le relargage de l’ADN circulant in vitro et in vivo, et (3) une étude visant à évaluer le potentiel de l’analyse de l’ADN circulant dans le dépistage et la détection précoce du cancer. Ce manuscrit présente une synthèse récente de la littérature sur l’ADNcir, ses différents mécanismes de relargage, qui vont de pair avec la caractérisation structurelle de cet ADN, ses aspects fonctionnels et ses différentes applications en cliniques. De plus, cette thèse apporte des connaissances nouvelles sur la structure de l’ADN mitochondrial extracellulaire tout en ouvrant de nouvelles pistes de réflexion notamment sur l’impact que pourrait avoir la présence de ces structures circulantes sur la communication cellulaire, l’inflammation et des applications en clinique.Plasma transports blood cells with a mixture of compounds, including nutrients, waste, antibodies, and chemical messengers...throughout the body. Non-soluble factors such as circulating DNA and extracellular vesicles have recently been added to the list of these components and have been the subject of extensive research due to their role in intercellular communication. Circulating DNA (cirDNA) is composed of cell-free and particle-associated DNA fragments, which can be released by all cell types. cirDNA is derived not only from genomic DNA but also from extrachromosomal mitochondrial DNA. Numerous studies carried out lately indicate that the quantitative and qualitative analysis of cirDNA represents a breakthrough in clinical applications as a non-invasive biomarker for diagnosis, prognosis and therapeutic follow-up. However, despite the promising future of cirDNA in clinical applications, particularly in oncology, knowledge regarding its origins, composition and functions, that could considerably optimize its diagnostic value, is still lacking.The main goal of my thesis was to identify and characterize the structural properties of extracellular DNA of mitochondrial origin. By examining the integrity of this DNA, as well as the size and density of associated structures, this work revealed the presence of dense particles larger than 0.2 µm containing whole mitochondrial genomes. We characterized these structures by electron microscopy and flow cytometry and identified intact mitochondria in the extracellular medium in vitro and ex vivo (in plasma samples from healthy individuals). Oxygen consumption by these mitochondria was detected by the Seahorse technology, suggesting that at least some of these intact extracellular mitochondria may be functional.In addition, I contributed to other studies carried out in the team, such as studies aiming at evaluating (1) the influence of pre-analytical and demographic parameters on the quantification of nuclear and mitochondrial cirDNA on a cohort of 104 healthy individuals and 118 patients with metastatic colorectal cancer, (2) the influence of hypoxia on the release of cirDNA in vitro and in vivo, and (3) the potential of cirDNA analysis in the early detection and screening of cancer.This manuscript present a recent review on cirDNA and its different mechanisms of release, which go hand in hand with the structural characterization of this DNA, its functional aspects and its clinical applications. In addition, this thesis provides new knowledge on the structure of extracellular mitochondrial DNA and opens up new avenues for reflection, particularly on the potential impact that could have those circulating mitochondria on cell-cell communication, inflammation and clinical applications

Étude de la structure de l'ADN circulant d'origine mitochondriale

Plasma transports blood cells with a mixture of compounds, including nutrients, waste, antibodies, and chemical messengers...throughout the body. Non-soluble factors such as circulating DNA and extracellular vesicles have recently been added to the list of these components and have been the subject of extensive research due to their role in intercellular communication. Circulating DNA (cirDNA) is composed of cell-free and particle-associated DNA fragments, which can be released by all cell types. cirDNA is derived not only from genomic DNA but also from extrachromosomal mitochondrial DNA. Numerous studies carried out lately indicate that the quantitative and qualitative analysis of cirDNA represents a breakthrough in clinical applications as a non-invasive biomarker for diagnosis, prognosis and therapeutic follow-up. However, despite the promising future of cirDNA in clinical applications, particularly in oncology, knowledge regarding its origins, composition and functions, that could considerably optimize its diagnostic value, is still lacking.The main goal of my thesis was to identify and characterize the structural properties of extracellular DNA of mitochondrial origin. By examining the integrity of this DNA, as well as the size and density of associated structures, this work revealed the presence of dense particles larger than 0.2 µm containing whole mitochondrial genomes. We characterized these structures by electron microscopy and flow cytometry and identified intact mitochondria in the extracellular medium in vitro and ex vivo (in plasma samples from healthy individuals). Oxygen consumption by these mitochondria was detected by the Seahorse technology, suggesting that at least some of these intact extracellular mitochondria may be functional.In addition, I contributed to other studies carried out in the team, such as studies aiming at evaluating (1) the influence of pre-analytical and demographic parameters on the quantification of nuclear and mitochondrial cirDNA on a cohort of 104 healthy individuals and 118 patients with metastatic colorectal cancer, (2) the influence of hypoxia on the release of cirDNA in vitro and in vivo, and (3) the potential of cirDNA analysis in the early detection and screening of cancer.This manuscript present a recent review on cirDNA and its different mechanisms of release, which go hand in hand with the structural characterization of this DNA, its functional aspects and its clinical applications. In addition, this thesis provides new knowledge on the structure of extracellular mitochondrial DNA and opens up new avenues for reflection, particularly on the potential impact that could have those circulating mitochondria on cell-cell communication, inflammation and clinical applications.Le plasma transporte des cellules sanguines avec un mélange de composés, y compris les nutriments, déchets, anticorps, et messagers chimiques... dans tout l'organisme. Des facteurs non solubles tels que l’ADN circulant et les vésicules extracellulaires ont récemment été ajoutés à la liste de ces composants et ont fait l'objet d'études approfondies en raison de leur rôle dans la communication intercellulaire. Or, l’ADN circulant (ADNcir) est composé de fragments d’ADN libres ou associés à d’autres particules, libérés par tous les types cellulaires. Cet ADN est non seulement de l'ADN génomique mais aussi de l'ADN mitochondrial extra-chromosomique. De nombreux travaux réalisés au cours des dernières années indiquent que l’analyse quantitative et qualitative de l’ADNcir représente une avancée dans les applications cliniques en tant que biomarqueur non invasif de diagnostic, de pronostic et de suivi thérapeutique. Cependant, malgré l'avenir prometteur de cet ADNcir dans les applications cliniques, notamment en oncologie, les connaissances sur ses origines, sa composition et ses fonctions qui pourraient pourtant permettre d’optimiser considérablement sa valeur diagnostique, font encore défaut. Le principal objectif de ma thèse a été d’identifier et de caractériser les propriétés structurales de l’ADN extracellulaire d’origine mitochondrial. En examinant l'intégrité de cet ADN, ainsi que la taille et la densité des structures associées, ce travail a révélé la présence de particules denses d’une taille supérieure à 0,2 µm contenant des génomes mitochondriaux complets et non fragmentés. Nous avons caractérisé ces structures notamment par microscopie électronique et cytométrie en flux et nous avons identifié des mitochondries intactes dans le milieu extracellulaire in vitro et ex-vivo (dans des échantillons de plasma d’individus sains). Une consommation d'oxygène par ces mitochondries a été détectée par la technique du Seahorse, suggérant qu'au moins une partie de ces mitochondries extracellulaires intactes pourraient être fonctionnelles. Par ailleurs, j’ai participé à d’autres travaux réalisées dans l’équipe, dont (1) une étude visant à évaluer l’influence des paramètres pré-analytiques et démographiques sur la quantification d’ADNcir d’origine nucléaire et mitochondrial sur une cohorte composée de 104 individus sains et 118 patients atteints de cancer colorectal métastatique, (2) une étude dont l’objectif était d’évaluer l’influence de l’hypoxie sur le relargage de l’ADN circulant in vitro et in vivo, et (3) une étude visant à évaluer le potentiel de l’analyse de l’ADN circulant dans le dépistage et la détection précoce du cancer. Ce manuscrit présente une synthèse récente de la littérature sur l’ADNcir, ses différents mécanismes de relargage, qui vont de pair avec la caractérisation structurelle de cet ADN, ses aspects fonctionnels et ses différentes applications en cliniques. De plus, cette thèse apporte des connaissances nouvelles sur la structure de l’ADN mitochondrial extracellulaire tout en ouvrant de nouvelles pistes de réflexion notamment sur l’impact que pourrait avoir la présence de ces structures circulantes sur la communication cellulaire, l’inflammation et des applications en clinique

Assessment of Dendrigrafts of Poly-L-Lysine Cytotoxicity and Cell Penetration in Cancer Cells

International audienceThis work provides an in vitro methodology to assess the cytotoxicity and cell penetration of Dendrigrafts of poly-L-Lysine (DGL) in order to select the best molecules to be further tested in preclinical models as nanoscale drug carriers for cancer treatment. The data obtained indicate that, despite their higher molecular weight, DGL cause cytotoxicity close to that published for other dendrimers (IC50 > 100nM up to 1.5μM depending on the DGL generation and the colon cancer cell line). Besides, uptake of DGL by cancer cells was observed within 5 minutes through a clathrin-dependent process. At a concentration at least 10-fold lower than the IC50 (10nM), 60-80% of colon cancer cells internalized DGL-G3,-G4 and-G5 within 4 hours, while a cell penetration efficiency of 20-60% was observed for DGL-G2. Finally, DGL cytotoxicity was significantly decreased by serum components. This methodology provides robust data to guide DGL functionalization to further reduce DGL cytotoxicity and safely address anti-cancer drugs to cancer cells, and represents a standardized and easy-to-use approach to characterize nanovectors for biological applications

Circulating nuclear DNA structural features, origins, and complete size profile revealed by fragmentomics

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Hypoxia differently modulates the release of mitochondrial and nuclear DNA

International audienceBackgroundWe investigated the influence of hypoxia on the concentration of mitochondrial and nuclear cell-free DNA (McfDNA and NcfDNA, respectively).MethodBy an ultra-sensitive quantitative PCR-based assay, McfDNA and NcfDNA were measured in the supernatants of different colorectal cell lines, and in the plasma of C57/Bl6 mice engrafted with TC1 tumour cells, in normoxic or hypoxic conditions.ResultsOur data when setting cell culture conditions highlighted the higher stability of McfDNA as compared to NcfDNA and revealed that cancer cells released amounts of nuclear DNA equivalent to the mass of a chromosome over a 6-h duration of incubation. In cell model, hypoxia induced a great increase in NcfDNA and McfDNA concentrations within the first 24 h. After this period, cfDNA total concentrations remained stable in hypoxia consecutive to a decrease of nuclear DNA release, and noteworthy, to a complete inhibition of daily mitochondrial DNA release. In TC1-engrafted mice submitted to intermittent hypoxia, plasma NcfDNA levels are much higher than in mice bred in normoxia, unlike plasma McfDNA concentration that is not impacted by hypoxia.ConclusionThis study suggests that hypoxia negatively modulates nuclear and, particularly, mitochondrial DNA releases in long-term hypoxia, and revealed that the underlying mechanisms are differently regulated

Recent advances in circulating nucleic acids in oncology

International audienceCirculating cell-free DNA (cfDNA) is one of the fastest growing and most exciting areas in oncology in recent years. Its potential clinical uses cover now each phase of cancer patient management care (predictive information, detection of the minimal residual disease, early detection of resistance, treatment monitoring, recurrence surveillance, and cancer early detection/screening). This review relates the recent advances in the application of circulating DNA or RNA in oncology building on unpublished or initial findings/work presented at the 10th international symposium on circulating nucleic acids in plasma and serum held in Montpellier from the 20th to the 22nd of September 2017. This year, presenters revealed their latest data and crucial observations notably in relation to (i) the circulating cell-free (cfDNA) structure and implications regarding their optimal detection; (ii) their role in the metastatic or immunological processes; (iii) evaluation of miRNA panels for cancer patient follow up; (iv) the detection of the minimal residual disease; (v) the evaluation of a screening tests for cancer using cfDNA analysis; and (vi) elements of preanalytical guidelines. This work reviews the recent progresses in the field brought to light in the meeting, as well as in the most important reports from the literature, past and present. It proposes a broader picture of the basic research and its potential, and of the implementation and current challenges in the use of circulating nucleic acids in oncology

Blood contains circulating cell free respiratory competent mitochondria: Blood contains extracellular mitochondria

International audienceMitochondria are considered as the power-generating units of the cell due to their key role in energy metabolism and cell signaling. However, mitochondrial components could be found in the extracellular space, as fragments or encapsulated in vesicles. In addition, this intact organelle has been recently reported to be released by platelets exclusively in specific conditions. Here, we demonstrate for the first time, that blood preparation with resting platelets, contains whole functional mitochondria in normal physiological state. Likewise, we show, that normal and tumor cultured cells are able to secrete their mitochondria. Using serial centrifugation or filtration followed by polymerase chain reaction-based methods, and Whole Genome Sequencing, we detect extracellular full-length mitochondrial DNA in particles over 0.22 µm holding specific mitochondrial membrane proteins. We identify these particles as intact cell-free mitochondria using fluorescence-activated cell sorting analysis, fluorescence microscopy, and transmission electron microscopy. Oxygen consumption analysis revealed that these mitochondria are respiratory competent. In view of previously described mitochondrial potential in intercellular transfer, this discovery could greatly widen the scope of cell-cell communication biology. Further steps should be developed to investigate the potential role of mitochondria as a signaling organelle outside the cell and to determine whether these circulating units could be relevant for early detection and prognosis of various diseases

Quantifying circulating cell-free DNA in humans

Abstract To our knowledge, this is the first comprehensive study on the influence of several pre-analytical and demographic parameters that could be a source of variability in the quantification of nuclear and mitochondrial circulating DNA (NcirDNA and McirDNA). We report data from a total of 222 subjects, 104 healthy individuals and 118 metastatic colorectal cancer (mCRC) patients. Approximately 50,000 and 3,000-fold more mitochondrial than nuclear genome copies were found in the plasma of healthy individuals and mCRC patients, respectively. In healthy individuals, NcirDNA concentration was statistically influenced by age (p = 0.009) and gender (p = 0.048). Multivariate analysis with logistic regression specified that age over 47 years-old was predictive to have higher NcirDNA concentration (OR = 2.41; p = 0.033). McirDNA concentration was independent of age and gender in healthy individuals. In mCRC patients, NcirDNA and McirDNA levels were independent of age, gender, delay between food intake and blood collection, and plasma aspect, either with univariate or multivariate analysis. Nonetheless, ad hoc study suggested that menopause and blood collection time might have tendency to influence cirDNA quantification. In addition, high significant statistical differences were found between mCRC patients and healthy individuals for NcirDNA (p < 0.0001), McirDNA (p < 0.0001) and McirDNA/NcirDNA ratio (p < 0.0001). NcirDNA and McirDNA levels do not vary in the same way with regards to cancer vs healthy status, pre-analytical and demographic factors