Relationships among erythrocyte-derived microRNAs in serum of healthy donors

Human erythrocytes' perplexing behaviour: erythrocytic microRNAs

Erythrocytes have the potential role in erythropoiesis and disease diagnosis. Thought to have lacked nucleic acid content, mammalian erythrocytes are nevertheless able to function for 120-140 days, metabolize heme, maintain oxidative stress, and so on. Mysteriously, erythrocytes proved as largest repositories of microRNAs (miRNAs) some of which are selectively retained and function in mature erythrocytes. They have unique expression patterns and have been found to be linked to specific conditions such as sickle cell anaemia, high-altitude hypoxia, chronic mountain sickness, cardiovascular and metabolic conditions as well as host-parasite interactions. They also have been implicated in cell storage-related damage and the regulation of its survival. However, the mechanism by which miRNAs function in the cell remains unclear. Investigations into the molecular mechanism of miRNAs in erythrocytes via extracellular vesicles have provided important clues in research studies on Plasmodium infection. Erythrocytes are also the primary source of circulating miRNAs but, how they affect the plasma/serum miRNAs profiles are still poorly understood. Erythrocyte-derived exosomal miRNAs, can interact with various body cell types, and have easy access to all regions, making them potentially crucial in various pathophysiological conditions. Which can also improve our understanding to identify potential treatment options and discovery related to non-invasive diagnostic markers. This article emphasizes the importance of erythrocytic miRNAs while focusing on the enigmatic behaviour of erythrocytes. It also sheds light on how this knowledge may be applied in the future to enhance the state of erythrocyte translational research from the standpoint of erythrocytic miRNAs.

Differences in serum and plasma levels of microRNAs and their time-course changes after blood collection

Background

Serum and plasma are used for measurements of microRNAs (miRNAs) as biomarkers of various diseases. However, no consistent findings have been obtained regarding differences in serum and plasma levels of miRNAs. The purpose of this study was to clarify differences in serum and plasma levels of total miRNAs and their time-course changes after blood collection.

Methods

Venous blood was collected from healthy men, and samples were prepared at the time points of 0, 15, 30, 60 and 180 min after blood collection for plasma and after clot formation for serum. Levels of total miRNAs were analyzed by the hybridization method using the 3D-Gene miRNA Oligo chip.

Results

About one third of 2632 miRNAs tested showed levels high enough for comparison of serum and plasma levels and for investigation of their time-course changes. Levels of 299 miRNAs at time 0 were significantly different in serum and plasma. Levels of representative platelet-derived miRNAs including miR-185-5p, -22-3p and -320b were significantly higher in plasma than in serum, while levels of representative erythrocyte-derived miRNAs including miR-451a, -486-5p and -92a-3p were not significantly different in serum and plasma. Plasma levels of 173 miRNAs and 6 miRNAs showed significant decreasing and increasing tendencies, respectively, while there were no miRNAs in serum that showed significant time-course changes.

Conclusion

The results suggest that careful attention should be paid when comparing serum and plasma levels of miRNAs and that plasma samples should be prepared early after blood collection.

Exploring Optimal Biomarker Sources: A Comparative Analysis of Exosomes and Whole Plasma in Fasting and Non-Fasting Conditions for Liquid Biopsy Applications

The study of liquid biopsy with plasma samples is being conducted to identify biomarkers for clinical use. Exosomes, containing nucleic acids and metabolites, have emerged as possible sources for biomarkers. To evaluate the effectiveness of exosomes over plasma, we analyzed the small non-coding RNAs (sncRNAs) and metabolites extracted from exosomes in comparison to those directly extracted from whole plasma under both fasting and non-fasting conditions. We found that sncRNA profiles were not affected by fasting in either exosome or plasma samples. Our results showed that exosomal sncRNAs were found to have more consistent profiles. The plasma miRNA profiles contained high concentrations of cell-derived miRNAs that were likely due to hemolysis. We determined that certain metabolites in whole plasma exhibited noteworthy concentration shifts in relation to fasting status, while others did not. Here, we propose that (1) fasting is not required for a liquid biopsy study that involves both sncRNA and metabolomic profiling, as long as metabolites that are not influenced by fasting status are selected, and (2) the utilization of exosomal RNAs promotes robust and consistent findings in plasma samples, mitigating the impact of batch effects derived from hemolysis. These findings advance the optimization of liquid biopsy methodologies for clinical applications.

Differences in circulating obesity-related microRNAs in Austrian and Japanese men: A two-country cohort analysis

Background

The prevalence of obesity is higher in Western countries than in East Asian countries. It remains unknown whether microRNAs (miRNAs) are involved in the pathogenesis of the ethnic difference in obesity. The purpose of this study was to determine whether expression levels of circulating obesity-associated miRNAs are different in Europeans and Asians.

Methods

The subjects were middle-aged healthy male Austrians (n = 20, mean age of 49.9 years) and Japanese (n = 20, mean age of 48.7 years). Total miRNAs in serum from each subject were analyzed using the 3D-Gene miRNA Oligo chip. miRNAs that showed significant differences between the Austrian and Japanese groups were uploaded into Ingenuity Pathway Analysis (IPA).

Results

Among 16 miRNAs that were revealed to be associated with obesity in previous studies and showed expression levels that were high enough for a reasonable comparison, serum levels of 3 miRNAs displayed significant differences between the Austrian and Japanese groups: miR-125b-1-3p was significantly lower with a fold change of −2.94 and miR-20a-5p and miR-486–5p were significantly higher with fold changes of 1.73 and 2.38, respectively, in Austrians than in Japanese. In IPA including all 392 miRNAs that showed significant differences between Austrians and Japanese, three canonical pathways including leptin signaling in obesity, adipogenesis pathway and white adipose tissue browning pathway were identified as enriched pathways.

Conclusions

miRNAs are thought to be involved in the ethnic difference in the prevalence of obesity, which may in part be caused by different expression levels of miR-125b-1-3p, miR-20a-5p and miR-486–5p.

•

Ethnic difference in circulating obesity-related microRNAs (miRs) were investigated.

•

Levels of 2565 miRs in blood were compared between Austrians and Japanese.

•

miR-125b-1-3p, −20a-5p and -486–5p levels were significantly different between them.

•

Significant ethnic differences were found in blood levels of 392 miRs.

•

These miRs target the molecules comprising obesity-related three canonical pathways.

Circulating microRNAs: Challenges with their use as liquid biopsy biomarkers

Circulating microRNA (miRNA) is a major focus in liquid biopsy studies. The circulating levels of certain miRNAs have been suggested to reflect specific physiological conditions, and several studies have reported their potential use as biomarkers for the detection and prognosis of cancer, as well as for predicting responses to chemotherapy or radiotherapy. Alongside these biomarker studies, research into the effects of specific background factors on circulating miRNA levels is progressing. Indeed, several studies have shown that a number of factors, including blood sample collection and processing methods, as well as subject-specific factors such as age, sex, and other physiological conditions, can affect the normal levels of circulating miRNAs. Unfortunately, the evidence supporting these effects is not yet strong enough to support a definite conclusion and further research is warranted. Here, we summarize the findings of several studies that have addressed these concerns and identify important topics that should be considered when analyzing circulating miRNA levels in liquid biopsy studies.

Contribution of platelet-derived microRNAs to serum microRNAs in healthy men

Platelets are a major source of microRNAs (miRNAs) in blood. Relationships between circulating platelet-derived miRNAs were investigated to elucidate their significance as biomarkers. Total miRNAs in serum were analyzed using the 3D-Gene miRNA Oligo chip. Among 22 miRNAs that are included in platelets and play functional roles, sufficient miRNA levels for comparison were detected for 11 miRNAs (let-7b-5p, miR-16-5p, miR-17-5p, miR-24-3p, miR-107, miR-126-3p, miR-150-3p, miR-191-5p, miR-197-3p, miR-223-3p, and miR-326). Among 55 pairs prepared by these miRNAs, relatively strong correlations (Spearman's correlation coefficient >0.8) were shown between miRNAs of 7 pairs including let-7b-5p and miR-16-5p, let-7b-5p and miR-17-5p, let-7b-5p and miR-107, miR-16-5p and miR-17-5p, miR-16-5p and miR-107, miR-17-5p and miR-107, and miR-107 and miR-126-3p. In principal component analysis, the first principal component consisted of let-7b-5p, miR-16-5p, miR-17-5p, miR-107, miR-126-3p, and miR-191-5p. These six miRNAs may be useful biomarkers that reflect platelet condition and function.