Exosome and microRNA transfer
from a paracrine & endocrine communication to cross-kingdom
organisms, the cell-to-cell communication is of
particular importance for any physiological process, and the proper
organization of the entire organism. Numerous studies over the past
years suggest a horizontal transfer of cellular secreted microRNAs
between cells, tissues and organs. Hence extracellular RNAs (primarily
small non-coding RNAs) represent a novel
form of inter-cellular
communication by transferring genetic information from a donor cell to
a recipient cell. This points to an important new role for small
in inter-cellular communication on the paracrine- and endocrine-level.
Recent papers report a cell-to-cell microRNA exchange and communication
and endocrine communication
(primary microRNAs, piRNAs and other small RNA families) can
be exported out of the donor cells and transported as free circulating
DNA or RNA or by various carriers,
e.g. membrane-derived vesicles (exosomes, microvesicles, ectosomes,
apoptotic bodies, and more), microRNA-binding protein complexes (RBP),
or high density lipoproteins (HDL). Secreted microRNAs can be uptaken
into recipient cells where they function as endogenous microRNAs,
simultaneously regulating multiple target genes or signaling pathways.
this molecular signaling is typically referred to as
quorum sensing, whereas in eukaryotic cells, the molecular
communication occurs through hormones and cytokines. Recently various
publications report that microRNAs
can also be transmitted from one
species to another, inducing signal interference in distant
even in a cross-kingdom manner. This new mode of cross-species
communication might mediate symbiotic and pathogenic relationships
between various organisms.
This can be of
enormous importance in the inter-species communication
of microorganisms and their hosts or by diet-derived small RNAs. Higher
organisms are constantly under attack from pathogens, resulting in
severe consequences on global human or veterinary health. Recently also
the uptake of plant microRNA is discussed.
RNA mediated RNA interference (RNAi) is a
mechanism that is involved in almost all eukaryotic cellular processes,
including host immunity and pathogen virulence. Recent evidence
supports the significant contribution of small RNAs and RNAi to the
communication between hosts and some eukaryotic pathogens or symbiotic
microorganisms. Mobile silencing signals - most
likely small RNAs - are
capable of translocating from the host to its interacting organism, and
Basic Overview Papers
Cell-to-cell communication via Gap
Para- and endocrine communication
between tissue and organs:
between different organisms:
between plants and animals / humans:
|Exosome-mediated transfer of mRNAs and
microRNAs is a novel mechanism of genetic exchange between cells.
Valadi H, Ekström K, Bossios A, Sjöstrand M, Lee JJ,
Nat Cell Biol. 2007 (6): 654-659
vesicles of endocytic origin released by many cells. These vesicles can
mediate communication between cells, facilitating processes such as
antigen presentation. Here, we show that exosomes from a mouse and a
human mast cell line (MC/9 and HMC-1, respectively), as well as primary
bone marrow-derived mouse mast cells, contain RNA. Microarray
assessments revealed the presence of mRNA from approximately 1300
genes, many of which are not present in the cytoplasm of the donor
cell. In vitro translation proved that the exosome mRNAs were
functional. Quality control RNA analysis of total RNA derived from
exosomes also revealed presence of small RNAs, including microRNAs. The
RNA from mast cell exosomes is transferable to other mouse and human
mast cells. After transfer of mouse exosomal RNA to human mast cells,
new mouse proteins were found in the recipient cells, indicating that
transferred exosomal mRNA can be translated after entering another
cell. In summary, we show that exosomes contain both mRNA and microRNA,
which can be delivered to another cell, and can be functional in this
new location. We propose that this RNA is called "exosomal shuttle RNA"
|Secreted microRNAs -- a new form of
Chen X, Liang H, Zhang J, Zen K, Zhang CY.
Trends Cell Biol. 2012 22(3):125-32
organisms, cell-to-cell communication is of particular
importance for the proper development and function of the organism as a
whole. Intensive studies over the past three years suggesting
horizontal transfer of secreted microRNAs (miRNAs) between cells point
to a potentially novel role for these molecules in intercellular
communication. Using a microvesicle-dependent, or RNA-binding
protein-associated, active trafficking system, secreted miRNAs can be
delivered into recipient cells where they function as endogenous
miRNAs, simultaneously regulating multiple target genes or signaling
events. In this Opinion, we summarize recent literature on the
biogenesis and uptake of secreted miRNAs, propose a possible working
model for how secreted miRNAs might be sorted and transferred between
cells and speculate on their biological significance.
|Exosomes -- vesicular carriers for
Simons M and Raposo G.
Curr Opin Cell Biol. 2009 Aug;21(4): 575-581
different types of vesicular carriers of membrane and
cytosolic components into the extracellular space. These vesicles are
generated within the endosomal system or at the plasma membrane. Among
the various kinds of secreted membrane vesicles, exosomes are vesicles
with a diameter of 40-100 nm that are secreted upon fusion of
multivesicular endosomes with the cell surface. Exosomes transfer not
only membrane components but also nucleic acid between different cells,
emphasizing their role in intercellular communication. This ability is
likely to underlie the different physiological and pathological events,
in which exosomes from different cell origins have been implicated.
Only recently light have been shed on the subcellular compartments and
mechanisms involved in their biogenesis and secretion opening new
avenues to understand their functions.
|REVIEW -- New roles for microRNAs in
Liang H, Zen K, Zhang J, Zhang CY, Chen X.
RNA Biol. 2013 Mar;10(3): 367-370
between cells ensures coordinated behavior. In
prokaryotes, this signaling is typically referred to as quorum sensing,
whereas in eukaryotic cells, communication occurs through hormones. In
recent years, reports have shown that small noncoding RNAs, called
microRNAs (miRNAs), can be transmitted from one species to another,
inducing signal interference in distant species, even in a
cross-kingdom manner. This new mode of cross-species communication
might mediate symbiotic and pathogenic relationships between various
organisms (e.g., microorganisms and their hosts). Here, we discuss
several recent studies concerning miRNA-mediated cross-species gene
|Cardiovascular extracellular microRNAs:
emerging diagnostic markers and mechanisms of cell-to-cell RNA
Kinet V, Halkein J, Dirkx E, Windt LJ
Front Genet. 2013 Nov 12;4:214 - eCollection 2013
diseases are a leading cause of morbidity and mortality in Western
societies. It is now well established that microRNAs (miRNAs) are
determinant regulators in various medical conditions including
cardiovascular diseases. The recent discovery that miRNAs, while
associated with different carriers, can be exported out of the cell,
has triggered a renewed interest to analyze the potential to use
extracellular miRNAs as tools for diagnostic and therapeutic studies.
Circulating miRNAs in biological fluids present a technological
advantage compared to current diagnostic tools by virtue of their
remarkable stability and relative ease of detection rendering them
ideal tools for non-invasive and rapid diagnosis. Extracellular miRNAs
also represent a novel form of inter-cellular communication by
transferring genetic information from a donor cell to a recipient cell.
This review briefly summarizes recent insights in the origin, function
and diagnostic potential of extracellular miRNAs by focusing on a
select number of cardiovascular diseases.
FIGURE: Schematic representation of
cellular release (A) and inter-cellular communication (B) of miRNAs.
(A) In the nucleus,
miRNA genes are mainly transcribed by the RNA polymerase II (Pol II)
into primary miRNAs (pri-miRNAs) and processed to precursor miRNAs
(pre-miRNAs) by the Drosha complex. Pre-miRNAs are exported to the
cytoplasm and cleaved by Dicer to produce a double stranded miRNA
duplex. The duplex is separated and a mature miRNA is incorporated into
the RNA-induced silencing complex (RISC) while the other strand is
likely subject to degradation. Within the RISC complex, miRNAs bind to
their target messenger RNAs (mRNAs) to repress their translation or
induce their degradation. In addition, miRNAs can be exported out of
the cells and transported by various carriers, membrane-derived
vesicles (exosomes, microvesicles, apoptotic bodies), miRNA-binding
protein complexes (RBP), or high density lipoproteins (HDL).
miRNAs can be transferred to recipient cells where they alter gene
| Transfer via
Gap-Junctions from cell to cell
|Gap junctional shuttling of miRNA--A novel
pathway of intercellular gene regulation and its prospects in clinical
Lemcke H, Steinhoff G, David R
Cell Signal. 2015 Dec;27(12): 2506-2514
The gap junctional exchange of small molecules between adjacent cells
is crucial for maintaining tissue homeostasis and for a large number of
cellular processes, including differentiation and proliferation. miRNAs
represent a novel class of signalling molecules capable of crossing gap
junction (GJ) channels, thereby directly affecting gene expression in
the recipient cell. Here, we give an overview about the current
knowledge on the biological significance of miRNA shuttling in
different cell types (e.g. stem cells, cardiac cells, macrophages),
which indicates the GJ-dependent transfer of miRNA as a general
mechanism for intercellular gene regulation. Notably, shuttling via GJs
is superior to exosome-mediated intercellular transfer regarding
specificity and efficiency. We further elucidate this mechanism as a
promising approach for miRNA delivery in clinical applications. Using a
cell-based gap junctional dependent system, in vivo delivery of
therapeutic miRNAs might become more efficient compared to systemic
delivery methods. We will discuss the advantages of such a delivery
system and the challenges that have to be overcome for its successful
application in miRNA therapy.
mediated miRNA intercellular transfer and gene regulation: A novel
mechanism for intercellular genetic communication.
Zong L, Zhu Y, Liang R, Zhao HB
Sci Rep. 2016 6: 19884
genetic communication is an essential requirement for coordination of
cell proliferation and differentiation and has an important role in
many cellular processes. Gap junction channels possess large pore
allowing passage of ions and small molecules between cells. MicroRNAs
(miRNAs) are small regulatory RNAs that can regulate gene expression
broadly. Here, we report that miRNAs can pass through gap junction
channels in a connexin-dependent manner. Connexin43 (Cx43) had higher
permeability, whereas Cx30 showed little permeability to miRNAs. In the
tested connexin cell lines, the permeability to miRNAs demonstrated:
Cx43 > Cx26/30 > Cx26 > Cx31 > Cx30 = Cx-null. However,
consistent with a uniform structure of miRNAs, there was no significant
difference in permeability to different miRNAs. The passage is
efficient; the miRNA level in the recipient cells could be up to 30% of
the donor level. Moreover, the transferred miRNA is functional and
could regulate gene expression in neighboring cells. Connexin mutation
and gap junctional blockers could eliminate this miRNA intercellular
transfer and gene regulation. These data reveal a novel mechanism for
intercellular genetic communication. Given that connexin expression is
cell-specific, this connexin-dependent, miRNA intercellular genetic
communication may play an important role in synchronizing and
coordinating proliferation and differentiation of specific cell types
during multicellular organ development.
between tissues and organs
|Unraveling the Mystery of Cancer by
Secretory microRNA -- Horizontal microRNA Transfer between Living Cells.
Kosaka N and Ochiya T
Front Genet. 2012 2: 97
have been identified as a fine-tuner in a wide array of biological
processes, including development, organogenesis, metabolism, and
homeostasis. Deregulation of miRNAs causes diseases, especially cancer.
This occurs through a variety of mechanisms, such as genetic
alterations, epigenetic regulation, or altered expression of
transcription factors, which target miRNAs. Recently, it was discovered
that extracellular miRNAs circulate in the blood of both healthy and
diseased patients. Since RNase is abundant in the bloodstream, most of
the secretory miRNAs are contained in apoptotic bodies, microvesicles,
and exosomes or bound to the RNA-binding proteins. However, the
secretory mechanism and biological function, as well as the
significance of extracellular miRNAs, remain largely unclear. In this
article, we summarize the latest and most significant discoveries in
recent peer-reviewed research on secretory miRNA involvement in many
aspects of physiological and pathological conditions, with a special
focus on cancer. In addition, we discuss a new aspect of cancer
research that is revealed by the emergence of "secretory miRNA."
|Human saliva, plasma and breast milk
exosomes contain RNA: uptake by macrophages.
Lässer C, Alikhani VS, Ekström K, Eldh M, Paredes PT, Bossios
A, Sjöstrand M, Gabrielsson S, Lötvall J, Valadi H.
J Transl Med. 2011 Jan 14;9: 9
Exosomes are 30-100 nm membrane vesicles of endocytic origin produced
by numerous cells. They can mediate diverse biological functions,
including antigen presentation. Exosomes have recently been shown to
contain functional RNA, which can be delivered to other cells. Exosomes
may thus mediate biological functions either by surface-to-surface
interactions with cells, or by the delivery of functional RNA to cells.
Our aim was therefore to determine the presence of RNA in exosomes from
human saliva, plasma and breast milk and whether these exosomes can be
taken up by macrophages.
were purified from human saliva, plasma and breast milk using
ultracentrifugation and filtration steps. Exosomes were detected by
electron microscopy and examined by flow cytometry. Flow cytometry was
performed by capturing the exosomes on anti-MHC class II coated beads,
and further stain with anti-CD9, anti-CD63 or anti-CD81. Breast milk
exosomes were further analysed for the presence of Hsc70, CD81 and
calnexin by Western blot. Total RNA was detected with a Bioanalyzer and
mRNA was identified by the synthesis of cDNA using an oligo (dT) primer
and analysed with a Bioanalyzer. The uptake of PKH67-labelled saliva
and breast milk exosomes by macrophages was examined by measuring
fluorescence using flow cytometry and fluorescence microscopy.
RESULTS: RNA was
detected in exosomes from all three body fluids. A portion of the
detected RNA in plasma exosomes was characterised as mRNA. Our result
extends the characterisation of exosomes in healthy humans and confirms
the presence of RNA in human saliva and plasma exosomes and reports for
the first time the presence of RNA in breast milk exosomes. Our results
also show that the saliva and breast milk exosomes can be taken up by
Exosomes in saliva, plasma and breast milk all contain RNA, confirming
previous findings that exosomes from several sources contain RNA.
Furthermore, exosomes are readily taken up by macrophages, supporting
the notion that exosomal RNA can be shuttled between cells.
|The microRNA spectrum in 12 body fluids.
Weber JA, Baxter DH, Zhang S, Huang DY, Huang KH, Lee MJ, Galas DJ,
Clin Chem. 2010 56(11): 1733-1741
MicroRNAs (miRNAs) are small, noncoding RNAs that play an
important role in regulating various biological processes through their
interaction with cellular messenger RNAs. Extracellular miRNAs in
serum, plasma, saliva, and urine have recently been shown to be
associated with various pathological conditions including cancer.
METHODS: With the
goal of assessing the distribution
of miRNAs and
demonstrating the potential use of miRNAs as biomarkers, we examined
the presence of miRNAs in 12 human body fluids and urine samples from
women in different stages of pregnancy or patients with different
urothelial cancers. Using quantitative PCR, we conducted a global
survey of the miRNA distribution in these fluids.
were present in all fluids tested
and showed distinct
compositions in different fluid types. Several of the highly abundant
miRNAs in these fluids were common among multiple fluid types, and some
of the miRNAs were enriched in specific fluids. We also observed
distinct miRNA patterns in the urine samples obtained from individuals
with different physiopathological conditions.
MicroRNAs are ubiquitous in all the
body fluid types
tested. Fluid type-specific miRNAs may have functional roles associated
with the surrounding tissues. In addition, the changes in miRNA spectra
observed in the urine samples from patients with different urothelial
conditions demonstrates the potential for using concentrations of
specific miRNAs in body fluids as biomarkers for detecting and
monitoring various physiopathological conditions.
|Endogenous RNAs modulate microRNA sorting
to exosomes and transfer to acceptor cells.
Squadrito ML, Baer C, Burdet F, Maderna C, Gilfillan GD, Lyle R,
Ibberson M, De Palma M
Cell Rep. 2014 Sep 11;8(5): 1432-1446
transfer via exosomes may mediate cell-to-cell communication.
Interestingly, specific miRNAs are enriched in exosomes in a
cell-type-dependent fashion. However, the mechanisms whereby miRNAs are
sorted to exosomes and the significance of miRNA transfer to acceptor
cells are unclear. We used macrophages and endothelial cells (ECs) as a
model of heterotypic cell communication in order to investigate both
processes. RNA profiling of macrophages and their exosomes shows that
miRNA sorting to exosomes is modulated by cell-activation-dependent
changes of miRNA target levels in the producer cells. Genetically
perturbing the expression of individual miRNAs or their targeted
transcripts promotes bidirectional miRNA relocation from the cell
cytoplasm/P bodies (sites of miRNA activity) to multivesicular bodies
(sites of exosome biogenesis) and controls miRNA sorting to exosomes.
Furthermore, the use of Dicer-deficient cells and reporter lentiviral
vectors (LVs) for miRNA activity shows that exosomal miRNAs are
transferred from macrophages to ECs to detectably repress targeted
|MicroRNAs transported by exosomes in body
fluids as mediators of intercellular communication in cancer.
Salido-Guadarrama I, Romero-Cordoba S, Peralta-Zaragoza O,
Hidalgo-Miranda A, Rodríguez-Dorantes M
Onco Targets Ther. 2014 Jul 21;7: 1327-1338 eCollection 2014.
communication is an important and complex process, achieved through a
diversity of mechanisms that allows tumor cells to mold and influence
their environment. In recent years, evidence has accumulated indicating
that cells communicate via the release and delivery of microRNAs
(miRNAs) packed into tumor-released (TR) exosomes. Understanding the
role and mode of action of miRNAs from TR exosomes is of paramount
importance in the field of cancer biomarker discovery and for the
development of new biomedical applications for cancer therapeutics. In
this review, we focus on miRNAs secreted via TR exosomes, which by
acting in a paracrine or endocrine manner, facilitate a diversity of
signaling mechanisms between cancer cells. We address their
contribution as signaling molecules, to the establishment, maintenance,
and enhancement of the tumor microenvironment and the metastatic niche
in cancer. Finally, we address the potential role of these molecules as
biomarkers in cancer diagnosis and prognosis and their impact as a
biomedical tool in cancer therapeutics.
|Cross talk of combined gene and cell
therapy in ischemic heart disease -- role of exosomal microRNA transfer.
Ong SG, Lee WH, Huang M, Dey D, Kodo K, Sanchez-Freire V, Gold JD, Wu JC
Circulation. 2014 130 (11 Suppl 1): S60-69
Despite the promise shown by stem cells for restoration of cardiac
function after myocardial infarction, the poor survival of transplanted
cells has been a major issue. Hypoxia-inducible factor-1 (HIF1) is a
transcription factor that mediates adaptive responses to ischemia.
Here, we hypothesize that codelivery of cardiac progenitor cells (CPCs)
with a nonviral minicircle plasmid carrying HIF1 (MC-HIF1) into the
ischemic myocardium can improve the survival of transplanted CPCs.
RESULTS: After myocardial infarction, CPCs were codelivered
intramyocardially into adult NOD/SCID mice with saline, MC-green
fluorescent protein, or MC-HIF1 versus MC-HIF1 alone (n=10 per group).
Bioluminescence imaging demonstrated better survival when CPCs were
codelivered with MC-HIF1. Importantly, echocardiography showed mice
injected with CPCs+MC-HIF1 had the highest ejection fraction 6 weeks
after myocardial infarction (57.1±2.6%; P=0.002) followed by
MC-HIF1 alone (48.5±2.6%; P=0.04), with no significant
protection for CPCs+MC-green fluorescent protein (44.8±3.3%;
P=NS) when compared with saline control (38.7±3.2%). In vitro
mechanistic studies confirmed that cardiac endothelial cells produced
exosomes that were actively internalized by recipient CPCs. Exosomes
purified from endothelial cells overexpressing HIF1 had higher contents
of miR-126 and miR-210. These microRNAs activated prosurvival kinases
and induced a glycolytic switch in recipient CPCs, giving them
increased tolerance when subjected to in vitro hypoxic stress.
Inhibiting both of these miRs blocked the protective effects of the
summary, HIF1 can be used to modulate the host microenvironment for
improving survival of transplanted cells. The exosomal transfer of miRs
from host cells to transplanted cells represents a unique mechanism
that can be potentially targeted for improving survival of transplanted
|Transfer of microRNAs by extracellular
membrane microvesicles: a nascent crosstalk model in tumor
pathogenesis, especially tumor cell-microenvironment interactions.
Zhang L, Valencia CA, Dong B, Chen M, Guan PJ, Pan L
J Hematol Oncol. 2015 Feb 22;8(1): 14
treatments aiming at killing malignant cells have been applied for
decades but have been unsuccessful at curing the disease. The modern
concept of tumor microenvironment, especially angiogenesis, suggests
that the tumor is not only composed of malignant cells, but also
consists of other groups of cells that work together. Recently, genetic
message transfer has been revealed between tumor cells and their
microenvironment. The latest cell-derived vector, extracellular
membrane microvesicles (EMVs), has been found to provide membrane
protection and allowed to deliver genetic information beyond the cells.
Additionally, EMV-associated microRNAs are involved in a variety of
cellular pathways for tumor initiation and progression. Previous
published reviews have focused on miRNA that included EMVs as a
sensitive marker for tumor monitoring in clinical applications that are
based on the alteration of their expression levels in conjunction with
disease occurrence and progression. From the aspect of cellular
crosstalk, this article will review the role of EMV-mediated microRNA
transfer in tumor pathogenesis, including tumor treatment obstacles,
history and features, and current research in inflammatory/immune
pathologies, as well as in solid tumors and hematological malignancies.
This nascent crosstalk model will provide a novel insight into
complementing the classic mechanisms of intercellular communication and
contribute to the potential therapeutic strategy via small RNA
molecule-carrying EMVs for multimodality treatment of cancer.
|Regulation of mammalian gene expression by
Liang H, Huang L, Cao J, Zen K, Chen X, Zhang CY.
Wiley Interdiscip Rev RNA. 2012 Sep-Oct;3(5): 733-742
between cells ensures coordination of behavior. In prokaryotes, this
signaling is usually referred to as quorum sensing, while eukaryotic
cells communicate through hormones. In recent years, a growing number
of reports have shown that small signaling molecules produced by
organisms from different kingdoms of nature can facilitate cross-talk,
communication, or signal interference. This trans-kingdom communication
(also termed as trans-kingdom signaling or inter-kingdom signaling)
mediates symbiotic and pathogenic relationships between various
organisms (e.g., microorganisms and their hosts). Strikingly, it has
been discovered that microRNAs (miRNAs)--single-stranded noncoding RNAs
with an average length of 22 nt--can be transmitted from one species to
another, inducing posttranscriptional gene silencing in distant
species, even in a cross-kingdom fashion. Here, we discuss several
recent studies concerning miRNA-mediated cross-kingdom gene regulation.
|Interplay Between Exosomes, microRNAs and
Toll-Like Receptors in Brain Disorders.
Paschon V, Takada SH, Ikebara JM, Sousa E, Raeisossadati R, Ulrich H,
Mol Neurobiol. 2015 Apr 11
vesicles (EVs), including exosomes, microvesicles and apoptotic bodies,
participate in intercellular communication, and particularly, in
paracrine and endocrine signalling. The EVs and their specific contents
have been considered hallmarks of different diseases. It has been
recently discovered that EVs can co-transport nucleic acids such as
DNAs, ribosomal RNAs, circular RNAs (circRNAs), long noncoding RNAs
(lnRNAs) and microRNAs (miRNAs). miRNAs are important regulators of
gene expression at the post-transcriptional level, although they may
also play other roles. Recent evidence supports the hypothesis that
miRNAs can activate Toll-like receptors (TLRs) under certain
circumstances. TLRs belong to a multigene family of immune system
receptors and have been recently described in the nervous system. In
the immune system, TLRs are important for the recognition of the
invading microorganisms, whereas in the nervous system, they recognise
endogenous ligands released by undifferentiated or necrotic/injured
cells. In the neuronal disease field, TLRs activity has been associated
with amyotrophic lateral sclerosis (ALS), stroke, Alzheimer's and
Parkinson's disease. Herein, we reviewed the current knowledge of the
relationship between miRNA release by EVs and the inflammation
signalling triggered by TLRs in neighbouring cells or during
long-distance cell-to-cell communication. We highlight novel aspects of
this communication mechanism, offering a valuable insight into such
pathways in health and disease.
|Circulating free xeno-microRNAs - The new
kids on the block.
Fabris L & Calin GA
Mol Oncol. 2016 Mar;10(3): 503-508
The role of
circulating free microRNAs (cfmiRNAs) as promising tools for cancer
screening, prognosis and monitoring of anticancer therapies has been
widely studied in the past decades. cfmiRNAs have all the
characteristics of the perfect biomarkers owing high stability under
storage and handling conditions and being detectable not only in
plasma, but in almost all body fluids. Moreover, their levels in plasma
are likely to resemble ones in the primary tumor. Recently, viral and
plant miRNAs have been found in plasma of healthy individuals through
deep sequencing technique, and subsequently the same ones were
deregulated in patients. Growing body of literature is recently
focusing on understanding the potential cross-kingdom regulation of
human mRNAs by miRNAs most likely absorbed with food ingestion. In this
article we will review the literature concerning the xenomiRs detected
in plasma and their role in influencing cancer onset and progression.
XenomiRs could potentially be used not only as early screening tool,
but also for patients' prognosis.
between different organisms
|Horizontal transfer of microRNAs: molecular
mechanisms and clinical applications.
Chen X, Liang H, Zhang J, Zen K, Zhang CY.
Protein Cell. 2012 Jan;3(1): 28-37
A new class of RNA
regulatory genes known as microRNAs (miRNAs) has been found to
introduce a whole new layer of gene regulation in eukaryotes. The
intensive studies of the past several years have demonstrated that
miRNAs are not only found intracellularly, but are also detectable
outside cells, including in various body fluids (e.g. serum, plasma,
saliva, urine and milk). This phenomenon raises questions about the
biological function of such extracellular miRNAs. Substantial amounts
of extracellular miRNAs are enclosed in small membranous vesicles (e.g.
exosomes, shedding vesicles and apoptotic bodies) or packaged with
RNA-binding proteins (e.g. high-density lipoprotein, Argonaute 2 and
nucleophosmin 1). These miRNAs may function as secreted signaling
molecules to influence the recipient cell phenotypes. Furthermore,
secreted extracellular miRNAs may reflect molecular changes in the
cells from which they are derived and can therefore potentially serve
as diagnostic indicators of disease. Several studies also point to the
potential application of siRNA/miRNA delivery as a new therapeutic
strategy for treating diseases. In this review, we summarize what is
known about the mechanism of miRNA secretion. In addition, we describe
the pathophysiological roles of secreted miRNAs and their clinical
potential as diagnostic biomarkers and therapeutic drugs. We believe
that miRNA transfer between cells will have a significant impact on
biological research in the coming years.
|Wolbachia small noncoding RNAs and their
role in cross-kingdom communications.
Mayoral JG, Hussain M, Joubert DA, Iturbe-Ormaetxe I, O'Neill SL,
Proc Natl Acad Sci U S A. 2014 Dec 30;111(52): 18721-18726
small noncoding RNAs (snRNAs) of 50-500 nt are produced that are
important in bacterial virulence and response to environmental stimuli.
Here, we identified and characterized snRNAs from the endosymbiotic
bacteria, Wolbachia, which are widespread in invertebrates and cause
reproductive manipulations. Most importantly, some strains of Wolbachia
inhibit replication of several vector-borne pathogens in insects. We
demonstrate that two abundant snRNAs, WsnRNA-46 and WsnRNA-49, are
expressed in Wolbachia from noncoding RNA transcripts that contain
precursors with stem-loop structures. WsnRNAs were detected in Aedes
aegypti mosquitoes infected with the wMelPop-CLA strain of Wolbachia
and in Drosophila melanogaster and Drosophila simulans infected with
wMelPop and wAu strains, respectively, indicating that the WsnRNAs are
conserved across species and strains. In addition, we show that the
WsnRNAs may potentially regulate host genes and Wolbachia genes. Our
findings provide evidence for the production of functional snRNAs by
Wolbachia that play roles in cross-kingdom communication between the
endosymbiont and the host.
|Isolation of bovine milk-derived
microvesicles carrying mRNAs and microRNAs.
Hata T, Murakami K, Nakatani H, Yamamoto Y, Matsuda T, Aoki N.
Biochem Biophys Res Commun. 2010 May 28;396(2): 528-533
By a series of
centrifugation and ultracentrifugation, we could isolate microvesicles
with approximately 100 nm in diameter from bovine milk. We also found
that approximately 1700 and 1000 ng of total RNA, in which small RNAs
were major components, was contained inside the microvesicles isolated
from 6 ml of colostrum and mature milk, respectively, despite high
RNase activity in the milk. Polyadenylated gene transcripts for major
milk proteins and translation elongation factor-1alpha (EF-1alpha) were
present in the microvesicles, and integrity of some transcripts was
confirmed by real-time PCR targeting 5'- and 3'-ends of mRNA and by in
vitro translation analysis. Moreover, a considerable amount of mammary
gland and immune-related microRNAs were present in the milk-derived
microvesicles. Acidification of milk to mimic gastrointestinal tract
did not mostly affected RNA yield and quality. The milk related gene
transcripts were detected in cultured cells when incubated with
milk-derived microvesicles, suggesting cellular uptake of the
microvesicle contents including RNA. Our findings suggest that bovine
breast milk contains RNAs capable for being transferred to living cells
and involved in the development of calf's gastrointestinal and immune
microRNAs in exosomes - good things come in nano-packages.
Ouyang Y, Mouillet JF, Coyne CB, Sadovsky Y
Placenta. 2014 Feb;35 Suppl: S69-73
are small noncoding RNA gene products that commonly regulate mRNA
expression by repression of translation and/or transcript decay.
Whereas common and unique types of miRNAs are expressed by the placenta
during pregnancy, the functions of most placental miRNA species are
unknown. In addition to their intracellular silencing function, miRNAs
are also released to the extracellular space and systemic circulation,
where they can potentially target cells to regulate mRNA and protein
expression, providing a non-hormonal means of intercellular
communication that contributes to tissue homeostasis and disease
pathophysiology. This review centers on extracellular miRNAs that
originate in trophoblasts and that could mediate crosstalk between the
feto-placental unit and the mother during pregnancy. We specifically
detail the function of miRNAs from the primate-specific chromosome 19
miRNA cluster. These miRNAs are highly expressed in human placentas and
in the serum of pregnant women. They are also packaged into
extracellular vesicles of diverse sizes, including exosomes, and endow
non-trophoblastic cells with resistance to a variety of viruses.
|"Small Talk" in the Innate Immune System
via RNA-Containing Extracellular Vesicles.
van der Grein SG and Nolte-'t Hoen EN
Front Immunol. 2014 Oct 29;5: 542
A newly uncovered
means of communication between cells involves intercellular transfer of
nano-sized extracellular vesicles (EV), composed of lipids, proteins,
and genetic material. EV released by cells of the immune system can
play a regulatory role in the induction and suppression of immune
responses. These functions may be mediated not only by the bioactive
lipids and proteins present in EV but also by EV-associated RNAs. The
RNA in EV mainly consists of microRNAs and a large range of other small
non-coding RNA species. Since many of these small RNAs have the
potential to regulate gene expression, intercellular transfer of these
RNAs via EV may cause long-term changes in the function of EV-targeted
cells. Several types of innate immune cells release EV that affect
innate immune responses and other (patho)physiological processes.
Additionally, the innate immune system is influenced by EV released by
non-immune cells and EV found in body fluids. In this review, we focus
on how EV-associated RNAs contribute to these immune regulatory
between plants and animals / humans
|Conversations between kingdoms -- small
Weiberg A, Bellinger M, Jin H
Curr Opin Biotechnol. 2015 Apr;32:2207-215
and plants are constantly under attack from pathogens and pests,
resulting in severe consequences on global human health and crop
production. Small RNA (sRNA)-mediated RNA interference (RNAi) is a
conserved regulatory mechanism that is involved in almost all
eukaryotic cellular processes, including host immunity and pathogen
virulence. Recent evidence supports the significant contribution of
sRNAs and RNAi to the communication between hosts and some eukaryotic
pathogens, pests, parasites, or symbiotic microorganisms. Mobile
silencing signals—most likely sRNAs—are capable of translocating from
the host to its interacting organism, and vice versa. In this review,
we will provide an overview of sRNA communications between different
kingdoms, with a primary focus on the advances in plant-pathogen
|Exogenous plant MIR168a specifically
targets mammalian LDLRAP1: evidence of cross-kingdom regulation by
Zhang L, Hou D, Chen X, Li D, Zhu L, Zhang Y, Li J, Bian Z, Liang X,
Cai X, Yin Y, Wang C, Zhang T, Zhu D, Zhang D, Xu J, Chen Q, Ba Y, Liu
J, Wang Q, Chen J, Wang J, Wang M, Zhang Q, Zhang J, Zen K, Zhang CY.
Cell Res. 2012 Jan;22(1): 107-126
studies have demonstrated that stable microRNAs (miRNAs) in mammalian
serum and plasma are actively secreted from tissues and cells and can
serve as a novel class of biomarkers for diseases, and act as signaling
molecules in intercellular communication. Here, we report the
surprising finding that exogenous plant miRNAs are present in the sera
and tissues of various animals and that these exogenous plant miRNAs
are primarily acquired orally, through food intake. MIR168a is abundant
in rice and is one of the most highly enriched exogenous plant miRNAs
in the sera of Chinese subjects. Functional studies in vitro and in
vivo demonstrated that MIR168a could bind to the human/mouse
low-density lipoprotein receptor adapter protein 1 (LDLRAP1) mRNA,
inhibit LDLRAP1 expression in liver, and consequently decrease LDL
removal from mouse plasma. These findings demonstrate that exogenous
plant miRNAs in food can regulate the expression of target genes in
|Assessing the survival of exogenous plant
microRNA in mice.
Liang G, Zhu Y, Sun B, Shao Y, Jing A, Wang J, Xiao Z
Food Sci Nutr. 2014 Jul;2(4): 380-388
(miRNAs), a class of
small RNAs, are important molecules that influence several
developmental processes and regulate RNA interference (RNAi), and are
abundant in animals, plants, and plant tissues that are traditionally
consumed in the diet. The survival of plant small RNAs from the diet in
animals, however, remains unclear, and the persistence of miRNAs from
dietary plants in the animal gastrointestinal (GI) tract is still under
debate. In this study, ICR mice were fed plant total RNAs in quantities
of 10-50 μg, extracted from Brassica oleracea. Serum, feces, and
various tissues were collected from the mice after RNA consumption and
analyzed for several miRNAs. Exogenous plant miRNAs were present in the
sera, feces, and tissues of animals and these exogenous plant miRNAs
were primarily acquired orally. MiR-172, the most highly enriched
exogenous plant miRNA in B. oleracea, was found in the stomach,
intestine, serum, and feces of mice that were fed plant RNA extracts
including miR-172. The amount of miR-172 that survived passage through
the GI tract varied among individuals, with a maximum of 4.5% recovered
at the stomach of one individual, and had a range of 0.05-4.5% in
different organs. Furthermore, miR-172 was detected in the blood,
spleen, liver, and kidney of mice.
|Ineffective delivery of diet-derived
microRNAs to recipient animal organisms.
Snow JW, Hale AE, Isaacs SK, Baggish AL, Chan SY.
RNA Biol. 2013 Jul;10(7): 1107-1116
specific microRNAs to recipient organisms via food ingestion has been
reported recently. However, it is unclear if such delivery of microRNAs
occurs frequently in animal organisms after typical dietary intake. We
found substantial levels of specific microRNAs in diets commonly
consumed orally by humans, mice, and honey bees. Yet, after ingestion
of fruit replete with plant microRNAs (MIR156a, MIR159a, and MIR169a),
a cohort of healthy athletes did not carry detectable plasma levels of
those molecules. Similarly, despite consumption of a diet with animal
fat replete in endogenous miR-21, negligible expression of miR-21 in
plasma or organ tissue was observed in miR-21 -/- recipient mice.
Correspondingly, when fed vegetarian diets containing the above plant
microRNAs, wild-type recipient mice expressed insignificant levels of
these microRNAs. Finally, despite oral uptake of pollen containing
these plant microRNAs, negligible delivery of these molecules was
observed in recipient honeybees. Therefore, we conclude that horizontal
delivery of microRNAs via typical dietary ingestion is neither a robust
nor a frequent mechanism to maintain steady-state microRNA levels in a
variety of model animal organisms, thus defining the biological limits
of these molecules in vivo.
|Effective detection and quantification of
dietetically absorbed plant microRNAs in human plasma.
Liang H, Zhang S, Fu Z, Wang Y, Wang N, Liu Y, Zhao C, Wu J, Hu Y,
Zhang J, Chen X, Zen K, Zhang CY
J Nutr Biochem. 2015 May;26(5): 505-512
The detection of
exogenous plant microRNAs in human/animal plasma/sera lies at the
foundation of exploring their cross-kingdom regulatory functions. It is
necessary to establish a standard operation procedure to promote study
in this nascent field. In this study, 18 plant miRNAs were assessed in
watermelon juice and mixed fruits by quantitative reverse transcriptase
polymerase chain reaction (qRT-PCR). CT values, no-template controls
and standard curves for each miRNA were used to evaluate the
specificity and sensitivity of qRT-PCR and to obtain concentrations.
Sixteen miRNAs were selected and measured in human plasma from
volunteers after drinking juice. The CT values of 6 plant miRNAs in
human plasma fell outside the linear ranges of their standard curves.
The remaining 10 miRNAs were present at high basal levels, and 6 of
them showed a dynamic physiological pattern in plasma (absorption rates
of 0.04% to 1.31%). Northern blotting was used to confirm the qRT-PCR
results. Critical issues such as RNA extraction and internal controls
were also addressed.
|Real-time quantitative PCR and droplet
digital PCR for plant miRNAs in mammalian blood provide little evidence
for general uptake of dietary miRNAs -- Limited evidence for general
uptake of dietary plant xenomiRs.
Witwer KW, McAlexander MA, Queen SE, Adams RJ.
RNA Biol. 2013 Jul;10(7): 1080-1086
exogenous dietary miRNAs enter the bloodstream and tissues of ingesting
animals has been accompanied by an indication that at least one plant
miRNA, miR168, participates in "cross-kingdom" regulation of a
mammalian transcript. If confirmed, these findings would support
investigation of miRNA-based dietary interventions in disease. Here,
blood was obtained pre- and post-prandially (1, 4, 12 h) from pigtailed
macaques that received a miRNA-rich plant-based substance. Plant and
endogenous miRNAs were measured by RT-qPCR. Although low-level
amplification was observed for some plant miRNA assays, amplification
was variable and possibly non-specific, as suggested by droplet digital
PCR. A consistent response to dietary intake was not observed. While
our results do not support general and consistent uptake of dietary
plant miRNAs, additional studies are needed to establish whether or not
plant or animal xenomiRs are transferred across the gut in sufficient
quantity to regulate endogenous genes.
|Beyond nutrients: food-derived microRNAs
provide cross-kingdom regulation.
Jiang M, Sang X, Hong Z.
Bioessays. 2012 Apr;34(4): 280-284
Food turns out to
be not only the nutrient supplier for our body but also a carrier of
regulatory information. Interestingly, a recent study made the
discovery that some plant/food-derived microRNAs (miRNAs) accumulate in
the serum of humans or plant-feeding animals, and regulate mammalian
gene expression in a sequence-specific manner. The authors provided
striking evidence that miRNAs could function as active signaling
molecules to transport information across distinct species or even
kingdoms. Although the mechanism of how miRNAs are shuttled between
different organisms is still not well characterized, initial results
point to the involvement of microvesicles and specific
RNA-transporter-like proteins. These findings raise both speculation
about the potential impact that plants may have on animal physiology at
the molecular level, and an appealing possibility that food-derived
miRNAs may offer us another means to deliver necessary nutrients or
therapeutics to our bodies.
|Transfer and functional consequences of
dietary microRNAs in vertebrates: concepts in search of corroboration:
negative results challenge the hypothesis that dietary xenomiRs cross
the gut and regulate genes in ingesting vertebrates, but important
Witwer KW and Hirschi KD.
Bioessays. 2014 Apr;36(4):394-406
diet-derived foreign microRNA absorption and function in consuming
vertebrates would drastically alter our understanding of nutrition and
ecology. RNA interference (RNAi) mechanisms of Caenorhabditis elegans
are enhanced by uptake of environmental RNA and amplification and
systemic distribution of RNAi effectors. Therapeutic exploitation of
RNAi in treating human disease is difficult because these accessory
processes are absent or diminished in most animals. A recent report
challenged multiple paradigms, suggesting that ingested microRNAs
(miRNAs) are transferred to blood, accumulate in tissues, and exert
canonical regulation of endogenous transcripts. Independent replication
of these findings has been elusive, and multiple disconfirmatory
findings have been published. In the face of mounting negative results,
any additional positive reports must provide the proverbial
"extraordinary proof" to support such claims. In this article, we
review the evidence for and against a significant role for dietary
miRNAs in influencing gene expression, and make recommendations for
watch the Video Abstract.
|Diet-Derived MicroRNAs: Separating the
Dream from Reality.
Katherine Cottrill & Stephen Y. Chan
microRNA Diagn. Ther. 2014 (1): 46-57
and ubiquitous, microRNAs (miRNAs) exert control over a wide range of
cellular functions. They have been detected in virtually every
extracellular fluid in the mammalian body, and many circulate
substantial anatomical distances in plasma. Thus, secreted miRNAs are
valuable not only as diagnostic tools but also may serve as novel
biological effectors that can be transmitted between source and
review will discuss the possibility of delivering functional miRNAs
from exogenously derived dietary sources. We will examine prior
research interrogating the existence and relevance of such a mechanism.
Findings: Recent findings have reported cross-kingdom transfer of
specific plant-derived miRNAs to mammalian tissue following consumption
of plant-based foods. These exogenous miRNAs were reported to be active
in the recipient organisms, directing changes in gene expression at
distant organ sites. In spite of this, subsequent studies have been
unable to find evidence of substantial exogenous diet-derived miRNAs in
mammalian circulation or tissues, regardless of diet.
examination of diet-derived miRNA uptake is ongoing, but it does not
appear that horizontal delivery of miRNAs via normal dietary intake is
a generalizable or frequent process to maintain robust expression of
these miRNAs in most higher-order animal organisms.
|Role of plant MicroRNA in cross-species
regulatory networks of humans.
Zhang H, Li Y, Liu Y, Liu H, Wang H, Jin W, Zhang Y, Zhang C, Xu D
BMC Syst Biol. 2016 Aug 8;10(1): 60
BACKGROUND: It has
been found that microRNAs (miRNAs) can function as a regulatory factor
across species. For example, food-derived plant miRNAs may pass through
the gastrointestinal (GI) tract, enter into the plasma and serum of
mammals, and interact with endogenous RNAs to regulate their
expression. Although this new type of regulatory mechanism is not well
understood, it provides a fresh look at the relationship between food
consumption and physiology. To investigate this new type of mechanism,
we conducted a systematic computational study to analyze the potential
functions of these dietary miRNAs in the human body.
RESULTS: In this paper, we
predicted human and plant target genes using RNAhybrid and set some
criteria to further filter them. Then we built the cross-species
regulatory network according to the filtered targets, extracted central
nodes by PageRank algorithm and built core modules. We summarized the
functions of these modules to three major categories: ion transport,
metabolic process and stress response, and especially some target genes
are highly related to ion transport, polysaccharides and the lipid
metabolic process. Through functional analysis, we found that human and
plants have similar functions such as ion transport and stress
response, so our study also indicates the existence of a close link
between exogenous plant miRNA targets and digestive/urinary organs.
According to our analysis results, we suggest that the ingestion of
these plant miRNAs may have a functional impact on consuming organisms
in a cross-kingdom way, and the dietary habit may affect the
physiological condition at a genetic level. Our findings may be useful
for discovering cross-species regulatory mechanism in further study.
|Horizontal Transfer of Small RNAs to and
Han L & Luan YS
Front Plant Sci. 2015 Dec 10;6: 1113 -- eCollection 2015
information is traditionally thought to be transferred from parents to
offspring. However, there is evidence indicating that gene transfer can
also occur from microbes to higher species, such as plants,
invertebrates, and vertebrates. This horizontal transfer can be carried
out by small RNAs (sRNAs). sRNAs have been recently reported to move
across kingdoms as mobile signals, spreading silencing information
toward targeted genes. sRNAs, especially microRNAs (miRNAs) and small
interfering RNAs (siRNAs), are non-coding molecules that control gene
expression at the transcriptional or post-transcriptional level. Some
sRNAs act in a cross-kingdom manner between animals and their
parasites, but little is known about such sRNAs associated with plants.
In this report, we provide a brief introduction to miRNAs that are
transferred from plants to mammals/viruses and siRNAs that are
transferred from microbes to plants. Both miRNAs and siRNAs can exert
corresponding functions in the target organisms. Additionally, we
provide information concerning a host-induced gene silencing system as
a potential application that utilizes the transgenic trafficking of RNA
molecules to silence the genes of interacting organisms. Moreover, we
lay out the controversial views regarding cross-kingdom miRNAs and call
for better methodology and experimental design to confirm this unique
function of miRNAs.
|Nonfunctional ingestion of plant miRNAs in
silkworm revealed by digital droplet PCR and transcriptome analysis.
Jia L, Zhang D, Xiang Z, He N
Sci Rep. 2015 Jul 21;5: 12290
Since a plant
miRNA (miR168) cross-regulating a mammalian transcript was reported,
miRNA-mediated cross-kingdom communication has become one of the most
compelling but controversial topics. In the present study, we used
silkworm and mulberry, which is a model for studies on the interactions
between the insect and its host plant, to address whether
miRNA-mediated cross-kingdom communication is a common phenomenon. The
results of TA clone, Sanger sequencing and droplet digital PCR
demonstrated that several mulberry-derived miRNAs could enter to
silkworm hemolymph and multiple tested tissues. Synthetic miR166b was
also detected in hemolymph and fat body. However, the ingestion of
synthetic miR166b did not play roles in silkworm physiological
progress, which was revealed by RNA-seq analyses, RT-PCR, and
phenotypic investigations. Mulberry miRNAs are convincingly transferred
to the silkworm orally and no physiological process associated with the
miRNAs was demonstrable. The results provided a new aspect of
cross-kingdom miRNA transfer.
|Bioinformatics Prediction and Experimental
Validation of MicroRNAs Involved in Cross-Kingdom Interaction.
Pirrò S, Minutolo A, Galgani A, Potestà M, Colizzi V,
J Comput Biol. 2016 Jul 18.
are a class of small noncoding RNAs that act as efficient
post-transcriptional regulators of gene expression. In 2012, the first
cross-kingdom miRNA-based interaction had been evidenced, demonstrating
that exogenous miRNAs act in a manner of mammalian functional miRNAs.
Starting from this evidence, we defined the concept of cross-kingdom
functional homology between plant and mammalian miRNAs as a needful
requirement for vegetal miRNA to explicit a regulation mechanism into
the host mammalian cell, comparable to the endogenous one. Then, we
proposed a new dedicated algorithm to compare plant and mammalian
miRNAs, searching for functional sequence homologies between them, and
we developed a web software called MirCompare. We also predicted human
genes regulated by the selected plant miRNAs, and we determined the
role of exogenous miRNAs in the perturbation of intracellular
interaction networks. Finally, as already performed by Pirrò and
coworkers, the ability of MirCompare to select plant miRNAs with
functional homologies with mammalian ones has been experimentally
confirmed by evaluating the ability of mol-miR168a to downregulate the
protein expression of SIRT1, when its mimic is transfected into human
hepatoma cell line G2 (HEPG2) cells.
This tool is implemented into a user-friendly web
interface, and the access is free to public through the website http://22.214.171.124/MirCompare