TL;DR: The results suggest that exosomal transfer of pro-angiogenic miRs plays an important role in MSC mediated angiogenesis and stem cell-to-endothelial cell communication.
Abstract: Mesenchymal stem cells (MSCs) have been found to benefit patients with a variety of ischemic diseases via promoting angiogenesis. It is also well established that exosomes secreted from MSCs deliver bioactive molecules, including microRNAs (miRs) to recipient cells. Therefore, we hypothesized that exosomes secreted from MSCs deliver miRs into endothelial cells and mediate angiogenesis. The pro-angiogenic stimulatory capacity of exosomes was investigated using tube-like structure formation and spheroid-based sprouting of human umbilical vein endothelial cells (HUVECs), and in vivo Matrigel plug assay. The secretion of pro-angiogenic miRs (pro-angiomiRs) from MSCs into culture medium and transfer of the miRs to HUVECs were confirmed using real-time quantitative PCR. Supplementation of the exosome secretion blocker GW4869 (10 μM) reduced the pro-angiomiRs in the MSC-derived conditioned medium (CdMMSC). Addition of exosomes isolated from CdMMSC could directly 1) promote HUVEC tube-like structure formation in vitro; 2) mobilize endothelial cells into Matrigel plug subcutaneously transplanted into mice; and 3) increase blood flow inside Matrigel plug. Fluorescence tracking showed that the exosomes were internalized rapidly by HUVECs causing an upregulated expression of pro-angiomiRs in HUVECs. Loss-and-gain function of the pro-angiomiRs (e.g., miR-30b) in MSCs significantly altered the pro-angiogenic properties of these MSC-derived exosomes, which could be associated with the regulation of their targets in HUVECs. These results suggest that exosomal transfer of pro-angiogenic miRs plays an important role in MSC mediated angiogenesis and stem cell-to-endothelial cell communication.
TL;DR: The history of MSC research from the initial discovery of their multipotency to the more recent recognition of their perivascular identity in vivo and their extraordinary capacity for immunomodulation and angiogenic signaling is summarized.
Abstract: As a result of over five decades of investigation, mesenchymal stromal/stem cells (MSCs) have emerged as a versatile and frequently utilized cell source in the fields of regenerative medicine and tissue engineering. In this review, we summarize the history of MSC research from the initial discovery of their multipotency to the more recent recognition of their perivascular identity in vivo and their extraordinary capacity for immunomodulation and angiogenic signaling. As well, we discuss long-standing questions regarding their developmental origins and their capacity for differentiation toward a range of cell lineages. We also highlight important considerations and potential risks involved with their isolation, ex vivo expansion, and clinical use. Overall, this review aims to serve as an overview of the breadth of research that has demonstrated the utility of MSCs in a wide range of clinical contexts and continues to unravel the mechanisms by which these cells exert their therapeutic effects.
231 citations
Cites background from "Mesenchymal stem cells release exos..."
...Similarly, recent qPCR screening of exosomes derived from murine MSC-like cells revealed they contain a number of known proangiogenic microRNAs, several of which were found to be preferentially internalized by endothelial cells, including miR-424, miR-30c, miR-30b, and let-7f [101]....
TL;DR: It is proposed that MSC exosomes most probably work through the protein rather than the RNA, and this rationale beyond a physical presence to include biologically relevant concentration, biochemical functionality and the potential to elicit an appropriate timely biochemical response is expanded.
Abstract: Mesenchymal stem cell (MSC) exosome specifically defines the 50–200 nm vesicles that are secreted into the extracellular space when multivesicular bodies in the MSC fuse with the plasma membrane. However, the exosome is just one of several 50–200 nm extracellular vesicles (EVs) known to be secreted by cells. Nevertheless, the term ‘MSC exosome’ is often used to describe populations of 50–200 nm EVs that are prepared from culture medium conditioned by MSCs on the basis that these populations collectively exhibited typical exosome-associated proteins such as endosomal proteins, TSG101 and Alix, and tetraspanin proteins, CD9, CD63 and CD81. They also carry a rich diverse RNA cargo. MSC exosomes are increasingly implicated as the mediator of many of the MSC-associated therapeutic potencies. They elicit therapeutic activity by delivering their cargo of potentially therapeutic proteins and RNAs to the recipient cells. The therapeutic potency of MSC exosomes is usually rationalized on the presence of a biologically relevant protein or RNA in the MSC exosome. In the present paper, we expanded this rationale beyond a physical presence to include biologically relevant concentration, biochemical functionality and the potential to elicit an appropriate timely biochemical response. Based on these, we propose that MSC exosomes most probably work through the protein rather than the RNA.
TL;DR: The different actors of the osteosarcoma microenvironment are described and an overview of the past, current, and future strategies of therapy targeting this complex ecosystem is given, with a focus on the role of extracellular vesicles and on the emergence of multi-kinase inhibitors.
Abstract: Osteosarcomas are the most frequent primary bone sarcomas, affecting mainly children, adolescents, and young adults, and with a second peak of incidence in elderly individuals. The current therapeutic management, a combined regimen of poly-chemotherapy and surgery, still remains largely insufficient, as patient survival has not improved in recent decades. Osteosarcomas are very heterogeneous tumors, both at the intra- and inter-tumor level, with no identified driver mutation. Consequently, efforts to improve treatments using targeted therapies have faced this lack of specific osteosarcoma targets. Nevertheless, these tumors are inextricably linked to their local microenvironment, composed of bone, stromal, vascular and immune cells and the osteosarcoma microenvironment is now considered to be essential and supportive for growth and dissemination. This review describes the different actors of the osteosarcoma microenvironment and gives an overview of the past, current, and future strategies of therapy targeting this complex ecosystem, with a focus on the role of extracellular vesicles and on the emergence of multi-kinase inhibitors.
212 citations
Cites background from "Mesenchymal stem cells release exos..."
...EVs from MSCs have been described as able to act on endothelial cells to deliver angiogenic signals [81], especially in hypoxic and ischemic conditions [82,83]....
TL;DR: It is demonstrated that when given intranasally, exosomes derived from mesenchymal stem cells could pass the blood brain barrier, and migrate to the injured spinal cord area, and MSC-Exo loaded with phosphatase and tensin homolog small interfering RNA (ExoPTEN) could attenuate the expression of PTEN in thejured spinal cord region followingintranasal administrations.
Abstract: Individuals with spinal cord injury (SCI) usually suffer from permanent neurological deficits, while spontaneous recovery and therapeutic efficacy are limited. Here, we demonstrate that when given intranasally, exosomes derived from mesenchymal stem cells (MSC-Exo) could pass the blood brain barrier and migrate to the injured spinal cord area. Furthermore, MSC-Exo loaded with phosphatase and tensin homolog small interfering RNA (ExoPTEN) could attenuate the expression of PTEN in the injured spinal cord region following intranasal administrations. In addition, the loaded MSC-Exo considerably enhanced axonal growth and neovascularization, while reducing microgliosis and astrogliosis. The intranasal ExoPTEN therapy could also partly improve structural and electrophysiological function and, most importantly, significantly elicited functional recovery in rats with complete SCI. The results imply that intranasal ExoPTEN may be used clinically to promote recovery for SCI individuals.
TL;DR: Although MSCs have a potential to exert anti-tumor activities, they largely provide service to the tumor using the multidirectional communication system established by exosomes in the TME.
TL;DR: It is shown that exosomes contain both mRNA and microRNA, which can be delivered to another cell, and can be functional in this new location, and it is proposed that this RNA is called “exosomal shuttle RNA” (esRNA).
Abstract: Exosomes are 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" (esRNA).
10,484 citations
"Mesenchymal stem cells release exos..." refers background in this paper
...Exosomes shuttle mRNAs, miRs, and other molecular constituents to achieve cell-to-cell communication, and modulate the function of recipient cells [20]....
TL;DR: The physical properties that define exosomes as a specific population of secreted vesicles are described, their biological effects, particularly on the immune system, are summarized, and the potential roles that secretedvesicles could have as intercellular messengers are discussed.
Abstract: Exosomes are small membrane vesicles of endocytic origin that are secreted by most cells in culture. Interest in exosomes has intensified after their recent description in antigen-presenting cells and the observation that they can stimulate immune responses in vivo. In the past few years, several groups have reported the secretion of exosomes by various cell types, and have discussed their potential biological functions. Here, we describe the physical properties that define exosomes as a specific population of secreted vesicles, we summarize their biological effects, particularly on the immune system, and we discuss the potential roles that secreted vesicles could have as intercellular messengers.
4,380 citations
"Mesenchymal stem cells release exos..." refers background in this paper
...They are initially formed by fusion of a multi-vesicular body with a plasma membrane, or released directly from the plasma membrane [17, 19]....
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...Exosomes are cell-derived vesicles (diameter 30–100 nm) that exist in almost all biological fluids including blood, urine, saliva, cerebrospinal fluid, and cell preconditioned medium [17, 18]....
TL;DR: This work has shown that the regulation of miRNA metabolism and function by a range of mechanisms involving numerous protein–protein and protein–RNA interactions has an important role in the context-specific functions of miRNAs.
Abstract: MicroRNAs (miRNAs) are a large family of post-transcriptional regulators of gene expression that are ~21 nucleotides in length and control many developmental and cellular processes in eukaryotic organisms. Research during the past decade has identified major factors participating in miRNA biogenesis and has established basic principles of miRNA function. More recently, it has become apparent that miRNA regulators themselves are subject to sophisticated control. Many reports over the past few years have reported the regulation of miRNA metabolism and function by a range of mechanisms involving numerous protein-protein and protein-RNA interactions. Such regulation has an important role in the context-specific functions of miRNAs.
4,123 citations
"Mesenchymal stem cells release exos..." refers background in this paper
...MiRs, a class of small non-coding RNAs (containing about 18–22 nucleotides), regulate gene expression on the posttranscriptional level by binding to specific mRNA and inducing their degradation and/or translational inhibition [27]....
TL;DR: Recent progress in understanding extracellular vesicle biology and the role of extrace cellular vesicles in disease is reviewed, emerging therapeutic opportunities are discussed and the associated challenges are considered.
Abstract: Within the past decade, extracellular vesicles have emerged as important mediators of intercellular communication, being involved in the transmission of biological signals between cells in both prokaryotes and higher eukaryotes to regulate a diverse range of biological processes. In addition, pathophysiological roles for extracellular vesicles are beginning to be recognized in diseases including cancer, infectious diseases and neurodegenerative disorders, highlighting potential novel targets for therapeutic intervention. Moreover, both unmodified and engineered extracellular vesicles are likely to have applications in macromolecular drug delivery. Here, we review recent progress in understanding extracellular vesicle biology and the role of extracellular vesicles in disease, discuss emerging therapeutic opportunities and consider the associated challenges.
TL;DR: This review focuses on various strategies for purifying exosomes and discusses their biophysical and biochemical properties, and an update on proteomic analysis of exosome from various cell types and body fluids is provided and host-cell specific proteomic signatures are discussed.
2,093 citations
"Mesenchymal stem cells release exos..." refers background in this paper
...They are initially formed by fusion of a multi-vesicular body with a plasma membrane, or released directly from the plasma membrane [17, 19]....