Comprehensive Proteomic Analysis of Mesenchymal Stem Cell Exosomes Reveals Modulation of Angiogenesis via Nuclear Factor-KappaB Signaling

Role of mesenchymal stromal cell-derived extracellular vesicles in tumour microenvironment

Stromal cells, deriving from mesenchymal stromal cells (MSCs), are crucial component of tumour microenvironment and represent key regulators of tumour processes. MSCs can be recruited to the tumour environment and interact with many cellular elements, thus influencing tumour biology. Cell-to-cell communication is in part mediated by the release of extracellular vesicle (EVs). EVs can induce significant molecular changes in recipient cells, delivering bioactive molecules. In this review, we describe the MSC-derived EVs content and discuss their role in different processes related to cancer biology. Furthermore, we summarize chemical or biological EVs modifications aiming to develop more efficient antitumor therapies.

Stem Cell Extracellular Vesicles in Skin Repair

Stem cell extracellular vesicles (EVs) have been widely studied because of their excellent therapeutic potential. EVs from different types of stem cell can improve vascularization as well as aid in the treatment of cancer and neurodegenerative diseases. The skin is a complex organ that is susceptible to various types of injury. Strategies designed to restore epithelial tissues’ integrity with stem cell EVs have shown promising results. Different populations of stem cell EVs are able to control inflammation, accelerate skin cell migration and proliferation, control wound scarring, improve angiogenesis, and even ameliorate signs of skin aging. However, large-scale production of such stem cell EVs for human therapy is still a challenge. This review focuses on recent studies that explore the potential of stem cell EVs in skin wound healing and skin rejuvenation, as well as challenges of their use in therapy.

Secretomes from Mesenchymal Stem Cells against Acute Kidney Injury: Possible Heterogeneity

A kidney has the ability to regenerate itself after a variety of renal injuries. Mesenchymal stem cells (MSCs) have been shown to ameliorate tissue damages during renal injuries and diseases. The regenerations induced by MSCs are primarily mediated by the paracrine release of soluble factors and extracellular vesicles, including exosomes and microvesicles. Extracellular vesicles contain proteins, microRNAs, and mRNAs that are transferred into recipient cells to induce several repair signaling pathways. Over the past few decades, many studies identified trophic factors from MSCs, which attenuate renal injury in a variety of animal acute kidney injury models, including renal ischemia-reperfusion injury and drug-induced renal injury, using microarray and proteomic analysis. Nevertheless, these studies have revealed the heterogeneity of trophic factors from MSCs that depend on the cell origins and different stimuli including hypoxia, inflammatory stimuli, and aging. In this review article, we summarize the secretomes and regenerative mechanisms induced by MSCs and highlight the possible heterogeneity of trophic factors from different types of MSC and different circumstances for renal regeneration.

Exosomes-the enigmatic regulators of bone homeostasis

Exosomes are a heterogeneous group of cell-derived membranous structures, which mediate crosstalk interaction between cells. Recent studies have revealed a close relationship between exosomes and bone homeostasis. It is suggested that bone cells can spontaneously secret exosomes containing proteins, lipids and nucleic acids, which then to regulate osteoclastogenesis and osteogenesis. However, the network of regulatory activities of exosomes in bone homeostasis as well as their therapeutic potential in bone injury remain largely unknown. This review will detail and discuss the characteristics of exosomes, the regulatory activities of exosomes in bone homeostasis as well as the clinical potential of exosomes in bone injury.

Vesicles known as exosomes may prove to be valuable clinical tools once their function is clarified. Exosomes were discovered in the 1980s but not observed in bone tissue until 2003. Minghao Zheng of the University of Western Australia, together with colleagues elsewhere, has reviewed the biology of exosomes, their role in maintaining bones, and their potential clinical uses. Exosomes carry lipids, proteins, and nucleic acids between cells. They are released by every type of bone cell, with the role of each exosome determined by its specific contents. Exosome-mediated crosstalk is involved in regulating bone remodeling, and exosomes have also been implicated in myelomas. Recent work has shown that exosome treatment can improve fracture healing. The authors conclude that a better understanding of the role of exosomes in bone homeostasis will unlock their significant clinical potential.

Data driven mathematical modeling reveals the dynamic mechanism of MSC-induced neovascularization

Coculture of mesenchymal stem cells (MSCs) and vascular endothelial cells (ECs) in vitro leads to the formation of a capillary-like reticular structure by ECs, which has great potential as a better substitute for artificial blood vessels in terms of stability and functionality. To investigate the mechanisms of the early neovascularization induced by MSCs, we analyzed the kinematic features of the motion of ECs and concluded that the dynamic interaction between cells and the extracellular matrix would reveal the capillary-like structure formation. Based on this hypothesis, we proposed a mathematical model to simulate the vascular-like migration pattern of ECs in silico, which was confirmed by in vitro studies. These in vitro studies validated that the dynamic secretion and degradation of collagen I is the critical factor for capillary structure formation. The model proposed based on cell tracking, single cell sequencing, and mathematical simulation provides a better understanding of the neovascularization process induced by MSCs and a possible simple explanation guiding this important cellular behavior.-Yu, Y., Situ, Q., Jia, W., Li, J., Wu, Q., Lei, J. Data driven mathematical modeling reveals the dynamic mechanism of MSC-induced neovascularization.

Mesenchymal Stromal Cell Secretome: Influencing Therapeutic Potential by Cellular Pre-conditioning

Mesenchymal stromal cells (MSCs) are self-renewing, culture-expandable adult stem cells that have been isolated from a variety of tissues, and possess multipotent differentiation capacity, immunomodulatory properties, and are relatively non-immunogenic. Due to this unique set of characteristics, these cells have attracted great interest in the field of regenerative medicine and have been shown to possess pronounced therapeutic potential in many different pathologies. MSCs' mode of action involves a strong paracrine component resulting from the high levels of bioactive molecules they secrete in response to the local microenvironment. For this reason, MSCs' secretome is currently being explored in several clinical contexts, either using MSC-conditioned media (CM) or purified MSC-derived extracellular vesicles (EVs) to modulate tissue response to a wide array of injuries. Rather than being a constant mixture of molecular factors, MSCs' secretome is known to be dependent on the diverse stimuli present in the microenvironment that MSCs encounter. As such, the composition of the MSCs' secretome can be modulated by preconditioning the MSCs during in vitro culture. This manuscript reviews the existent literature on how preconditioning of MSCs affects the therapeutic potential of their secretome, focusing on MSCs' immunomodulatory and regenerative features, thereby providing new insights for the therapeutic use of MSCs' secretome.

Hypoxia-elicited mesenchymal stem cell-derived exosomes facilitates cardiac repair through miR-125b-mediated prevention of cell death in myocardial infarction

Exosomes (Exo) secreted from hypoxia-conditioned bone marrow mesenchymal stem cells (BM-MSCs) were found to be protective for ischemic disease. However, the role of exosomal miRNA in the protective effect of hypoxia-conditioned BM-MSCs-derived Exo (Hypo-Exo) remains largely uncharacterized and the poor specificity of tissue targeting of Exo limits their clinical applications. Therefore, the objective of this study was to examine the effect of miRNA in Hypo-Exo on the repair of ischemic myocardium and its underlying mechanisms. We further developed modified Hypo-Exo with high specificity to the myocardium and evaluate its therapeutic effects.

Methods: Murine BM-MSCs were subjected to hypoxia or normoxia culture and Exo were subsequently collected. Hypo-Exo or normoxia-conditioned BM-MSC-derived Exo (Nor-Exo) were administered to mice with permanent condition of myocardial infarction (MI). After 28 days, to evaluate the therapeutic effects of Hypo-Exo, infarction area and cardio output in Hypo-Exo and Nor-Exo treated MI mice were compared through Masson's trichrome staining and echocardiography respectively. We utilized the miRNA array to identify the significantly differentially expressed miRNAs between Nor-Exo and Hypo-Exo. One of the most enriched miRNA in Hypo-Exo was knockdown by applying antimiR in Hypoxia-conditioned BM-MSCs. Then we performed intramyocardial injection of candidate miRNA-knockdown-Hypo-Exo in a murine MI model, changes in the candidate miRNA's targets expression of cardiomyocytes and the cardiac function were characterized. We conjugated Hypo-Exo with an ischemic myocardium-targeted (IMT) peptide by bio-orthogonal chemistry, and tested its targeting specificity and therapeutic efficiency via systemic administration in the MI mice.

Results: The miRNA array revealed significant enrichment of miR-125b-5p in Hypo-Exo compared with Nor-Exo. Administration of miR-125b knockdown Hypo-Exo significantly increased the infarction area and suppressed cardiomyocyte survival post-MI. Mechanistically, miR-125b knockdown Hypo-Exo lost the capability to suppress the expression of the proapoptotic genes p53 and BAK1 in cardiomyocytes. Intravenous administration of IMT-conjugated Hypo-Exo (IMT-Exo) showed specific targeting to the ischemic lesions in the injured heart and exerted a marked cardioprotective function post-MI.

Conclusion: Our results illustrate a new mechanism by which Hypo-Exo-derived miR125b-5p facilitates ischemic cardiac repair by ameliorating cardiomyocyte apoptosis. Furthermore, our IMT- Exo may serve as a novel drug carrier that enhances the specificity of drug delivery for ischemic disease.

Stem Cell-Mediated Angiogenesis in Tissue Engineering Constructs

Angiogenesis has always been a concern in the field of tissue engineering. Poor vascularization of engineered constructs is a problem for the clinical success of these structures. Among the various methods employed to induce angiogenesis, stem cells provide a promising tool for the future. The present review aims to present the application of stem cells in the induction of angiogenesis. Additionally, it summarizes recent advancements in stem cell-mediated angiogenesis of different tissue engineering constructs.

To Protect and to Preserve: Novel Preservation Strategies for Extracellular Vesicles

Extracellular vesicles (EVs)-based therapeutics are based on the premise that EVs shed by stem cells exert similar therapeutic effects and these have been proposed as an alternative to cell therapies. EV-mediated delivery is an effective and efficient system of cell-to-cell communication which can confer therapeutic benefits to their target cells. EVs have been shown to promote tissue repair and regeneration in various animal models such as, wound healing, cardiac ischemia, diabetes, lung fibrosis, kidney injury, and many others. Given the unique attributes of EVs, considerable thought must be given to the preservation, formulation and cold chain strategies in order to effectively translate exciting preclinical observations to clinical and commercial success. This review summarizes current understanding around EV preservation, challenges in maintaining EV quality, and also bioengineering advances aimed at enhancing the long-term stability of EVs.

Extracellular vesicles from human liver stem cells inhibit tumor angiogenesis

Human liver stem-like cells (HLSC) and derived extracellular vesicles (EVs) were previously shown to exhibit anti-tumor activity. In our study, we investigated whether HLSC-derived EVs (HLSC-EVs) were able to inhibit tumor angiogenesis in vitro and in vivo, in comparison with EVs derived from mesenchymal stem cells (MSC-EVs). The results obtained indicated that HLSC-EVs, but not MSC-EVs, inhibited the angiogenic properties of tumor-derived endothelial cells (TEC) both in vitro and in vivo in a model of subcutaneous implantation in Matrigel. Treatment of TEC with HLSC-EVs led to the down-regulation of pro-angiogenic genes. Since HLSC-EVs carry a specific set of microRNAs (miRNAs) that could target these genes, we investigated their potential role by transfecting TEC with HLSC-EV specific miRNAs. We observed that four miRNAs, namely miR-15a, miR-181b, miR-320c and miR-874, significantly inhibited the angiogenic properties of TEC in vitro, and decreased the expression of some predicted target genes (ITGB3, FGF1, EPHB4 and PLAU). In parallel, TEC treated with HLSC-EVs significantly enhanced expression of miR-15a, miR-181b, miR-320c and miR-874 associated with the down-regulation of FGF1 and PLAU. In summary, HLSC-EVs possess an anti-tumorigenic effect, based on their ability to inhibit tumor angiogenesis.

Mesenchymal stem cells are attracted to latent HIV-1-infected cells and enable virus reactivation via a non-canonical PI3K-NFκB signaling pathway

Persistence of latent HIV-1 in macrophages (MACs) and T-helper lymphocytes (THLs) remain a major therapeutic challenge. Currently available latency reversing agents (LRAs) are not very effective in vivo. Therefore, understanding of physiologic mechanisms that dictate HIV-1 latency/reactivation in reservoirs is clearly needed. Mesenchymal stromal/stem cells (MSCs) regulate the function of immune cells; however, their role in regulating virus production from latently-infected MACs & THLs is not known. We documented that exposure to MSCs or their conditioned media (MSC-CM) rapidly increased HIV-1 p24 production from the latently-infected U1 (MAC) & ACH2 (THL) cell lines. Exposure to MSCs also increased HIV-1 long terminal repeat (LTR) directed gene expression in the MAC and THL reporter lines, U937-VRX and J-Lat (9.2), respectively. MSCs exposed to CM from U1 cells (U1-CM) showed enhanced migratory ability towards latently-infected cells and retained their latency-reactivation potential. Molecular studies showed that MSC-mediated latency-reactivation was dependent upon both the phosphatidyl inositol-3-kinase (PI3K) and nuclear factor-κB (NFκB) signaling pathways. The pre-clinically tested inhibitors of PI3K (PX-866) and NFκB (CDDO-Me) suppressed MSC-mediated HIV-1 reactivation. Furthermore, coexposure to MSC-CM enhanced the latency-reactivation efficacy of the approved LRAs, vorinostat and panobinostat. Our findings on MSC-mediated latency-reactivation may provide novel strategies against persistent HIV-1 reservoirs.

Mesenchymal Stromal Cells Based Therapy in Systemic Sclerosis: Rational and Challenges

Systemic Sclerosis (SSc) is a rare chronic disease, related to autoimmune connective tissue diseases such as Systemic Lupus Erythematosus and Sjögren's Syndrome. Although its clinical heterogeneity, main features of the disease are: extensive tissue fibrosis with increase matrix deposition in skin and internal organ, microvascular alterations and activation of the immune system with autoantibodies against various cellular antigens. In the diffuse cutaneous scleroderma subtype, the disease is rapidly progressive with a poor prognosis, leading to failure of almost any internal organ, especially lung which is the leading cause of death. Primary trigger is unknown but may involve an immune process against mesenchymal cells in a genetically receptive host. Pathophysiology reveals a pivotal role of fibrosis and inflammation alterations implicating different cell subtypes, cytokines and growth factors, autoantibodies and reactive oxygen species. Despite improvement, the overall survival of SSc patients is still lower than that of other inflammatory diseases. Recommended drugs are agents capable of modulating fibrotic and inflammatory pathways. Cellular therapy has recently emerged as a credible option. Besides autologous hematopoietic stem cell transplantation which demonstrated remarkable improvement, mesenchymal stromal cells (MSCs) represent promising therapeutic candidates. Indeed, these cells possess anti-inflammatory, antiproliferative, antifibrotic, and immunomodulary properties especially by secreting a large panel of bioactive molecules, addressing the most important key points of the SSc. In addition, these cells are very sensitive to their environment and are able to modulate their activity according to the pathophysiological context in which they are located. Autologous or allogeneic MSCs from various sources have been tested in many trials in different auto-immune diseases such as multiple sclerosis, Crohn's disease or systemic lupus erythematosus. They are characterized by a broad availability and no or low acute toxicity. However, few randomized prospective clinical trials were published and their production under ATMP regulatory procedures is complex and time-consuming. Many aspects have still to be addressed to ascertain their potential as well as the potential of their derived products in the management of SSc, probably in association with other therapies.

Enhanced Therapeutic Effects of Mesenchymal Stem Cell-Derived Exosomes with an Injectable Hydrogel for Hindlimb Ischemia Treatment

Mesenchymal stem cell (MSC)-derived exosomes have been recognized as new candidates for cell-free treatment of various diseases. However, maintaining the retention and stability of exosomes over time in vivo after transplantation is a major challenge in the clinical application of MSC-derived exosomes. Here, we investigated if human placenta-derived MSC-derived exosomes incorporated with chitosan hydrogel could boost the retention and stability of exosomes and further enhance their therapeutic effects. Our results demonstrated that chitosan hydrogel notably increased the stability of proteins and microRNAs in exosomes, as well as augmented the retention of exosomes in vivo as confirmed by Gaussia luciferase imaging. In addition, we assessed endothelium-protective and proangiogenesis abilities of hydrogel-incorporated exosomes in vitro. Meanwhile, we evaluated the therapeutic function of hydrogel-incorporated exosomes in a murine model of hindlimb ischemia. Our data demonstrated that chitosan hydrogel could enhance the retention and stability of exosomes and further augment the therapeutic effects for hindlimb ischemia as revealed by firefly luciferase imaging of angiogenesis. The strategy used in this study may facilitate the development of easy and effective approaches for assessing and enhancing the therapeutic effects of stem cell-derived exosomes.

Bioprocessing of Mesenchymal Stem Cells and Their Derivatives: Toward Cell-Free Therapeutics

Mesenchymal stem cells (MSCs) have attracted tremendous research interest due to their ability to repair tissues and reduce inflammation when implanted into a damaged or diseased site. These therapeutic effects have been largely attributed to the collection of biomolecules they secrete (i.e., their secretome). Recent studies have provided evidence that similar effects may be produced by utilizing only the secretome fraction containing extracellular vesicles (EVs). EVs are cell-derived, membrane-bound vesicles that contain various biomolecules. Due to their small size and relative mobility, they provide a stable mechanism to deliver biomolecules (i.e., biological signals) throughout an organism. The use of the MSC secretome, or its components, has advantages over the implantation of the MSCs themselves: (i) signals can be bioengineered and scaled to specific dosages, and (ii) the nonliving nature of the secretome enables it to be efficiently stored and transported. However, since the composition and therapeutic benefit of the secretome can be influenced by cell source, culture conditions, isolation methods, and storage conditions, there is a need for standardization of bioprocessing parameters. This review focuses on key parameters within the MSC culture environment that affect the nature and functionality of the secretome. This information is pertinent to the development of bioprocesses aimed at scaling up the production of secretome-derived products for their use as therapeutics.

New Insights into the Role of Exosomes in the Heart After Myocardial Infarction

Intercellular communications play a pivotal role in several cardiac pathophysiological processes. One subtype of extracellular vesicles, so-called exosomes, became known as important intercellular communication mediators in the heart. Exosomes are lipid bilayer biological nanovesicles loaded with diverse proteins, lipids, and mRNAs/microRNAs. All major cardiac cell types can modulate recipient cellular function via the release of exosomes. After myocardial infarction (MI), exosomes, especially those secreted by different cardiac stem cells, have been shown to confer cardioprotective effects, activate regenerative signals, and participate into cardiac repair. In this review, we rapidly recall the biology of exosomes at the beginning. Then we summarize the exosomes secreted by different myocardial cells and their function in cardiac intercellular communication. At last, we discuss the role of these vesicles in cardiac repair after MI.

Exosomes and Their MicroRNA Cargo: New Players in Peripheral Nerve Regeneration

Peripheral nerve injury is a major clinical problem and often results in a poor functional recovery. Despite obvious clinical need, treatment strategies have been largely suboptimal. In the nervous system, exosomes, which are nanosized extracellular vesicles, play a critical role in mediating intercellular communication. More specifically, microRNA carried by exosomes are involved in various key processes such as nerve and vascular regeneration, and exosomes originating from Schwann cells, macrophages, and mesenchymal stem cells can promote peripheral nerve regeneration. In this review, the current knowledge of exosomes' and their miRNA cargo's role in peripheral nerve regeneration are summarized. The possible future roles of exosomes in therapy and the potential for microRNA-containing exosomes to treat peripheral nerve injuries are also discussed.

Extracellular vesicles, exosomes and shedding vesicles in regenerative medicine - a new paradigm for tissue repair

Tissue regeneration by stem cells is driven by the paracrine activity of shedding vesicles and exosomes, which deliver specific cargoes to the recipient cells. Proteins, RNA, cytokines and subsequent gene expression, orchestrate the regeneration process by improving the microenvironment to promote cell survival, controlling inflammation, repairing injury and enhancing the healing process. The action of microRNA is widely accepted as an essential driver of the regenerative process through its impact on multiple downstream biological pathways, and its ability to regulate the host immune response. Here, we present an overview of the recent potential uses of exosomes for regenerative medicine and tissue engineering. We also highlight the differences in composition between shedding vesicles and exosomes that depend on the various types of stem cells from which they are derived. The conditions that affect the production of exosomes in different cell types are deliberated. This review also presents the current status of candidate exosomal microRNAs for potential therapeutic use in regenerative medicine, and in applications involving widely studied organs and tissues such as heart, lung, cartilage and bone.

Mesenchymal Stromal/Stem Cells in Regenerative Medicine and Tissue Engineering

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.

Therapeutic Efficacy-Potentiated and Diseased Organ-Targeting Nanovesicles Derived from Mesenchymal Stem Cells for Spinal Cord Injury Treatment

Human mesenchymal stem cell (hMSC)-derived exosomes have been spotlighted as a promising therapeutic agent for cell-free regenerative medicine. However, poor organ-targeting ability and insufficient therapeutic efficacy of systemically injected hMSC-exosomes were identified as critical limitations for their further applications. Therefore, in this study we fabricated iron oxide nanoparticle (IONP)-incorporated exosome-mimetic nanovesicles (NV-IONP) from IONP-treated hMSCs and evaluated their therapeutic efficacy in a clinically relevant model for spinal cord injury. Compared to exosome-mimetic nanovesicles (NV) prepared from untreated hMSCs, NV-IONP not only contained IONPs which act as a magnet-guided navigation tool but also carried greater amounts of therapeutic growth factors that can be delivered to the target cells. The increased amounts of therapeutic growth factors inside NV-IONP were attributed to IONPs that are slowly ionized to iron ions which activate the JNK and c-Jun signaling cascades in hMSCs. In vivo systemic injection of NV-IONP with magnetic guidance significantly increased the amount of NV-IONP accumulating in the injured spinal cord. Accumulated NV-IONP enhanced blood vessel formation, attenuated inflammation and apoptosis in the injured spinal cord, and consequently improved spinal cord function. Taken together, these findings highlight the development of therapeutic efficacy-potentiated extracellular nanovesicles and demonstrate their feasibility for repairing injured spinal cord.

Mesenchymal Stem Cell-Derived Small Extracellular Vesicles Promote Neuroprotection in Rodent Models of Glaucoma

Purpose

To investigate the benefit of bone marrow mesenchymal stem cell (BMSC)-derived small extracellular vesicles (sEV) as an intravitreal (ivit) therapy in two rat models of glaucoma and to determine and identify candidate miRNA involved in the mechanism.

Methods

sEV were isolated from human BMSC and fibroblasts and ivit injected into adult rats after induction of elevated IOP. IOP was elevated using either intracameral injection of microbeads or laser photocoagulation of circumferential limbal vessels and the trabecular meshwork. Retinal nerve fiber layer (RNFL) thickness was measured using optical coherence tomography, positive scotopic threshold response (pSTR) recorded using ERG, and RNA binding protein with multiple splicing (RBPMS⁺) retinal ganglion cell (RGC) counted using retinal wholemounts. sEV miRNA were sequenced using RNAseq.

Results

sEV isolated from BMSC promoted significant neuroprotection of RGC while preventing RNFL degenerative thinning and loss of pSTR. sEV proved therapeutically efficacious when ivit injected every week or every month, but ineffective with longer delays between treatments. Knockdown of Argonaute2 (AGO2), a protein critical for miRNA function and packing into sEV prior to sEV isolation, significantly attenuated the above effects. Addition of BMSC sEV (but not fibroblast sEV) reduced death of cultured purified RGC. RNAseq identified 43 miRNA upregulated in BMSC sEV in comparison to fibroblast sEV, which yielded no neuroprotective effects.

Conclusions

Injection of BMSC-derived sEV into the vitreous provided significant therapeutic benefit to glaucomatous eyes. The neuroprotective effect of sEV, at least partially, may be explained by direct action on RGC through miRNA-dependent mechanisms.

Novel Multiomics Profiling of Human Carotid Atherosclerotic Plaques and Plasma Reveals Biliverdin Reductase B as a Marker of Intraplaque Hemorrhage

Clinical tools to identify individuals with unstable atherosclerotic lesions are required to improve prevention of myocardial infarction and ischemic stroke. Here, a systems-based analysis of atherosclerotic plaques and plasma from patients undergoing carotid endarterectomy for stroke prevention was used to identify molecular signatures with a causal relationship to disease. Local plasma collected in the lesion proximity following clamping prior to arteriotomy was profiled together with matched peripheral plasma. This translational workflow identified biliverdin reductase B as a novel marker of intraplaque hemorrhage and unstable carotid atherosclerosis, which should be investigated as a potential predictive biomarker for cardiovascular events in larger cohorts.

Cartilage Regeneration in Humans with Adipose Tissue-Derived Stem Cells and Adipose Stromal Vascular Fraction Cells: Updated Status

Adipose tissue-derived stem cells (ASCs) in the form of stromal vascular fraction (SVF) and cultured expansion have been applied in clinical settings in some countries to treat osteoarthritis (OA) of knees, one of the most common debilitating, incurable disorders. Since the first report of successful cartilage-like tissue regeneration with autologous adipose SVF containing ASCs, there has been a gradual increase in the number of publications confirming such results. Thus far, most of the reports have been limited to treatments of OA of knees. Recently, successful applications of adipose SVF in treating OA of ankles and hips have been reported. In addition, several groups have reported modified methods of applying adipose SVF, such as combining bone marrow stimulation with adipose SVF or adding additional extracellular matrix (ECM) in treating OA. Here, we present an updated, systematic review of clinical effectiveness and safety in treating OA of knees, ankles, and one hip since 2016 using ASCs in the form of adipose SVF or in cultured expansion, along with a description and suggestion of potential biological mechanisms of cartilage regeneration.

MSC exosome works through a protein-based mechanism of action

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.

Mesenchymal Stem Cell-Macrophage Choreography Supporting Spinal Cord Repair

Spinal cord injury results in destructive events that lead to tissue loss and functional impairments. A hallmark of spinal cord injury is the robust and persistent presence of inflammatory macrophages. Mesenchymal stem cells (MSCs) are known to benefit repair of the damaged spinal cord often associated with improved functional recovery. Transplanted MSCs immediately encounter the abundance of inflammatory macrophages in the injury site. It is known that MSCs interact closely and reciprocally with macrophages during tissue healing. Here, we will review the roles of (transplanted) MSCs and macrophages in spinal cord injury and repair. Molecular interactions between MSCs and macrophages and the deficiencies in our knowledge about the underlying mechanisms will be reviewed. We will discuss possible ways to benefit from the MSC-macrophage choreography for developing repair strategies for the spinal cord.

Mesenchymal stromal cell-derived extracellular vesicles: regenerative and immunomodulatory effects and potential applications in sepsis

Mesenchymal stromal (stem) cells (MSCs) have multipotent differentiation capacity and exist in nearly all forms of post-natal organs and tissues. The immunosuppressive and anti-inflammatory properties of MSCs have made them an ideal candidate in the treatment of diseases, such as sepsis, in which inflammation plays a critical role. One of the key mechanisms of MSCs appears to derive from their paracrine activity. Recent studies have demonstrated that MSC-derived extracellular vesicles (MSC-EVs) are at least partially responsible for the paracrine effect. MSC-EVs transfer molecules (such as proteins/peptides, mRNA, microRNA and lipids) with immunoregulatory properties to recipient cells. MSC-EVs have been shown to mimic MSCs in alleviating sepsis and may serve as an alternative to whole cell therapy. Compared with MSCs, MSC-EVs may offer specific advantages due to lower immunogenicity and higher safety profile. The first two sections of the review discuss the preclinical and clinical findings of MSCs in sepsis. Next, we review the characteristics of EVs and MSC-EVs. Then, we summarize the mechanisms of MSC-EVs, including tissue regeneration and immunomodulation. Finally, our review presents the evidences that MSC-EVs are effective in treating models of sepsis. In conclusion, MSC-EVs may have the potential to become a novel therapeutic strategy for sepsis.

Dynamic Cultivation of Mesenchymal Stem Cell Aggregates

Mesenchymal stem cells (MSCs) are considered as primary candidates for cell-based therapies due to their multiple effects in regenerative medicine. Pre-conditioning of MSCs under physiological conditions—such as hypoxia, three-dimensional environments, and dynamic cultivation—prior to transplantation proved to optimize their therapeutic efficiency. When cultivated as three-dimensional aggregates or spheroids, MSCs display increased angiogenic, anti-inflammatory, and immunomodulatory effects as well as improved stemness and survival rates after transplantation, and cultivation under dynamic conditions can increase their viability, proliferation, and paracrine effects, alike. Only few studies reported to date, however, have utilized dynamic conditions for three-dimensional aggregate cultivation of MSCs. Still, the integration of dynamic bioreactor systems, such as spinner flasks or stirred tank reactors might pave the way for a robust, scalable bulk expansion of MSC aggregates or MSC-derived extracellular vesicles. This review summarizes recent insights into the therapeutic potential of MSC aggregate cultivation and focuses on dynamic generation and cultivation techniques of MSC aggregates.

Exosomes Derived from Human Induced Pluripotent Stem Cells Ameliorate the Aging of Skin Fibroblasts

Stem cells and their paracrine factors have emerged as a resource for regenerative medicine. Many studies have shown the beneficial effects of paracrine factors secreted from adult stem cells, such as exosomes, on skin aging. However, to date, few reports have demonstrated the use of exosomes derived from human pluripotent stem cells for the treatment of skin aging. In this study, we collected exosomes from the conditioned medium of human induced pluripotent stem cells (iPSCs) and investigated the effect on aged human dermal fibroblasts (HDFs). Cell proliferation and viability were determined by an MTT assay and cell migration capacity was shown by a scratch wound assay and a transwell migration assay. To induce photoaging and natural senescence, HDFs were irradiated by UVB (315 nm) and subcultured for over 30 passages, respectively. The expression level of certain mRNAs was evaluated by quantitative real-time PCR (qPCR). Senescence-associated-β-galactosidase (SA-β-Gal) activity was assessed as a marker of natural senescence. As a result, we found that exosomes derived from human iPSCs (iPSCs-Exo) stimulated the proliferation and migration of HDFs under normal conditions. Pretreatment with iPSCs-Exo inhibited the damages of HDFs and overexpression of matrix-degrading enzymes (MMP-1/3) caused by UVB irradiation. The iPSCs-Exo also increased the expression level of collagen type I in the photo-aged HDFs. In addition, we demonstrated that iPSCs-Exo significantly reduced the expression level of SA-β-Gal and MMP-1/3 and restored the collagen type I expression in senescent HDFs. Taken together, it is anticipated that these results suggest a therapeutic potential of iPSCs-Exo for the treatment of skin aging.

Extracellular Vesicles: A New Prospective in Crosstalk between Microenvironment and Stem Cells in Hematological Malignancies

The bone marrow (BM) microenvironment in hematological malignancies (HMs) comprises heterogeneous populations of neoplastic and nonneoplastic cells. Cancer stem cells (CSCs), neoplastic cells, hematopoietic stem cells (HSCs), and mesenchymal stromal/stem cells (MSCs) are all components of this microenvironment. CSCs are the HM initiators and are associated with neoplastic growth and drug resistance, while HSCs are able to reconstitute the entire hematopoietic system; finally, MSCs actively support hematopoiesis. In some HMs, CSCs and neoplastic cells compromise the normal development of HSCs and perturb BM-MSCs. In response, "reprogrammed" MSCs generate a favorable environment to support neoplastic cells. Extracellular vesicles (EVs) are an important cell-to-cell communication type in physiological and pathological conditions. In particular, in HMs, EV secretion participates to unidirectional and bidirectional interactions between neoplastic cells and BM cells. The transfer of EV molecular cargo triggers different responses in target cells; in particular, malignant EVs modify the BM environment in favor of neoplastic cells at the expense of normal HSCs, by interfering with antineoplastic immunity and participating in resistance to treatment. Here, we review the role of EVs in BM cell communication in physiological conditions and in HMs, focusing on the effects of BM niche EVs on HSCs and MSCs.

Lipid, Protein, and MicroRNA Composition Within Mesenchymal Stem Cell-Derived Exosomes

Mesenchymal stem cells (MSCs) were regarded as one of the most promising type of seed cells in tissue engineering due to its easy accessibility and multipotent feature of being able to differentiate into adipocyte, osteoblast, cardiomyocytes, and neurons. For years, MSCs have been applied in treating cardiovascular disease, reconstructing kidney injury, and remodeling immune system with remarkable achievements. Basic researches revealed that its clinic effects are not only due to their pluripotent ability but also through their paracrine function that they synthesize and secrete a broad spectrum of growth factors and cytokines. Recent studies show that exosomes is the main paracrine executor of MSCs. The lipid bilayer of exosome maintains its stability and integrity and keeps biological potency of biological substance within it. MSC-derived exosomes were shown to be successful in treating many diseases, including tumor and cardiovascular diseases. However, the exact composition of MSC-derived exosomes is not known yet. In this review, we will discuss the lipid, protein, and microRNA contents within MSC-derived exosomes based on current studies to guide further research and clinical applications of MSC-derived exosomes.

Exosomes Secreted by Adipose-Derived Stem Cells Contribute to Angiogenesis of Brain Microvascular Endothelial Cells Following Oxygen-Glucose Deprivation In Vitro Through MicroRNA-181b/TRPM7 Axis

Adipose-derived stem cells (ADSCs) have been demonstrated to promote cerebral vascular remodeling processes after stroke. However, the exact molecular mechanism by which ADSCs exert protective roles in ischemic stroke is still poorly understood. In this study, we identified the role of exosomal microRNA-181b-5p (181b-Exos) in regulating post-stroke angiogenesis. The results of migration assay and capillary network formation assay showed that exosomes secreted by ADSCs (ADSCs-Exos) promoted the mobility and angiogenesis of brain microvascular endothelial cells (BMECs) after oxygen-glucose deprivation (OGD). Quantitative real-time polymerase chain reaction (qRT-PCR) showed that microRNA-212-5p (miR-212-5p) and miR-181b-5p were upregulated in BMECs subjected to the brain extract of the middle cerebral artery occlusion rats. The migration distance and tube length were increased in BMECs cultured with 181b-Exos. Furthermore, we identified that transient receptor potential melastatin 7 (TRPM7) was a direct target of miR-181b-5p. TRPM7 mRNA and protein levels were declined in BMECs cultured with 181b-Exos, but not in BMECs cultured with 212-Exos. Overexpression of TRPM7 reversed the effects of 181b-Exos on migration and tube formation of BMECs. In addition, 181b-Exos upregulated the protein expression of hypoxia-inducible factor 1α and vascular endothelial cell growth factor, and downregulated the protein expression of tissue inhibitor of metalloproteinase 3. The regulatory effect of 181b-Exos was attenuated by overexpressing TRPM7. Altogether, ADSCs-Exos promote the angiogenesis of BMECs after OGD via miR-181b-5p/TRPM7 axis, suggesting that ADSCs-Exos may represent a novel therapeutic approach for stroke recovery.

Tissue Engineering and Regenerative Medicine 2017: A Year in Review

In 2017, a new paradigm change caused by artificial intelligence and big data analysis resulted in innovation in each field of science and technology, and also significantly influenced progress in tissue engineering and regenerative medicine (TERM). TERM has continued to make technological advances based on interdisciplinary approaches and has contributed to the overall field of biomedical technology, including cancer biology, personalized medicine, development biology, and cell-based therapeutics. While researchers are aware that there is still a long way to go until TERM reaches the ultimate goal of patient treatment through clinical translation, the rapid progress in convergence studies led by technological improvements in TERM has been encouraging. In this review, we highlighted the significant advances made in TERM in 2017 (with an overlap of 5 months in 2016). We identified major progress in TERM in a manner similar to previous reviews published in the last few years. In addition, we carefully considered all four previous reviews during the selection process and chose main themes that minimize the duplication of the topics. Therefore, we have identified three areas that have been the focus of most journal publications in the TERM community in 2017: (i) advanced biomaterials and three-dimensional (3D) cell printing, (ii) exosomes as bioactive agents for regenerative medicine, and (iii) 3D culture in regenerative medicine.

Harnessing extracellular vesicles to direct endochondral repair of large bone defects

Large bone defects remain a tremendous clinical challenge. There is growing evidence in support of treatment strategies that direct defect repair through an endochondral route, involving a cartilage intermediate. While culture-expanded stem/progenitor cells are being evaluated for this purpose, these cells would compete with endogenous repair cells for limited oxygen and nutrients within ischaemic defects. Alternatively, it may be possible to employ extracellular vesicles (EVs) secreted by culture-expanded cells for overcoming key bottlenecks to endochondral repair, such as defect vascularization, chondrogenesis, and osseous remodelling. While mesenchymal stromal/stem cells are a promising source of therapeutic EVs, other donor cells should also be considered. The efficacy of an EV-based therapeutic will likely depend on the design of companion scaffolds for controlled delivery to specific target cells. Ultimately, the knowledge gained from studies of EVs could one day inform the long-term development of synthetic, engineered nanovesicles. In the meantime, EVs harnessed from in vitro cell culture have near-term promise for use in bone regenerative medicine. This narrative review presents a rationale for using EVs to improve the repair of large bone defects, highlights promising cell sources and likely therapeutic targets for directing repair through an endochondral pathway, and discusses current barriers to clinical translation. Cite this article: E. Ferreira, R. M. Porter. Harnessing extracellular vesicles to direct endochondral repair of large bone defects. Bone Joint Res 2018;7:263-273. DOI: 10.1302/2046-3758.74.BJR-2018-0006.

Safety and efficacy of the mesenchymal stem cell in feline eosinophilic keratitis treatment

Background

Feline eosinophilic keratitis (FEK) is a chronic keratopathy caused by a suspected immune mediated response to an unknown antigenic stimulus. The purpose of this study was to investigate the safety and therapeutic effects of allogeneic feline adipose-derived mesenchymal stromal cells (fAd-MSCs) implanted subconjunctival around the ocular surface lesion in five cats with FEK refractory to current available treatments.

Results

FEK was diagnosed by clinical appearance and evidence of eosinophil and/or mast cells in corneal cytology. Each animal was treated with two applications of 2 × 10⁶ million of fAd-MSCs 2 months apart. Ocular surface integrity was assessed before treatment and at 1, 3, 6 and 11 months after treatment. Clinical signs showed a significant change during the follow-up with resolution of the corneal and conjunctiva lesions and there were no signs of regression or worsening.

Conclusions

Implanted cells were well-tolerated and effective reducing clinical signs of FEK with a sustained effect during the study period. None of the animals showed systemic or local complications during the study. To our knowledge, this is the first time in literature that local implantation of allogeneic fAd-MSCs has been found as an effective therapeutic alternative to treat cats with FEK.

Therapeutic Potential of Engineered Extracellular Vesicles

Extracellular vesicles (EVs) comprise a heterogeneous group of small membrane vesicles, including exosomes, which play a critical role in intracellular communication and regulation of numerous physiological processes in health and disease. Naturally released from virtually all cells, these vesicles contain an array of nucleic acids, lipids and proteins which they transfer to target cells within their local milieu and systemically. They have been proposed as a means of “cell-free, cell therapy” for cancer, immune disorders, and more recently cardiovascular disease. In addition, their unique properties of stability, biocompatibility, and low immunogenicity have prompted research into their potential as therapeutic delivery agents for drugs and small molecules. In this review, we aim to provide a comprehensive overview of the current understanding of extracellular vesicle biology as well as engineering strategies in play to improve their therapeutic potential.

Long-term regeneration and remodeling of the pig esophagus after circumferential resection using a retrievable synthetic scaffold carrying autologous cells

Treatment of esophageal disease can necessitate resection and reconstruction of the esophagus. Current reconstruction approaches are limited to utilization of an autologous conduit such as stomach, small bowel, or colon. A tissue engineered construct providing an alternative for esophageal replacement in circumferential, full thickness resection would have significant clinical applications. In the current study, we demonstrate that regeneration of esophageal tissue is feasible and reproducible in a large animal model using synthetic polyurethane electro-spun grafts seeded with autologous adipose-derived mesenchymal stem cells (aMSCs) and a disposable bioreactor. The scaffolds were not incorporated into the regrown esophageal tissue and were retrieved endoscopically. Animals underwent adipose tissue biopsy to harvest and expand autologous aMSCs for seeding on electro-spun polyurethane conduits in a bioreactor. Anesthetized pigs underwent full thickness circumferential resection of the mid-lower thoracic esophagus followed by implantation of the cell seeded scaffold. Results from these animals showed gradual structural regrowth of endogenous esophageal tissue, including squamous esophageal mucosa, submucosa, and smooth muscle layers with blood vessel formation. Scaffolds carrying autologous adipose-derived mesenchymal stem cells may provide an alternative to the use of a gastro-intestinal conduit for some patients following resection of the esophagus.

Amniotic fluid stem cell exosomes: Therapeutic perspective

It is widely accepted that the therapeutic potential of stem cells can be largely mediated by paracrine factors, also included into exosomes. Thus, stem cell-derived exosomes represent a major therapeutic option in regenerative medicine avoiding, if compared to stem cells graft, abnormal differentiation and tumor formation. Exosomes derived from mesenchymal stem cells (MSC) induce damaged tissue repair, and can also exert immunomodulatory effects on the differentiation, activation and function of different lymphocytes. Therefore, MSC exosomes can be considered as a potential treatment for inflammatory diseases and also an ideal candidate for allogeneic therapy due to their low immunogenicity. Amniotic fluid stem cells (AFSCs) are broadly multipotent, can be expanded in culture, and can be easily cryopreserved in cellular banks. In this study, morphology, phenotype, and protein content of exosomes released into amniotic fluid in vivo and from AFSC during in vitro culture (conditioned medium) were examined. We found that AFSC-derived exosomes present different molecules than amniotic fluid ones, some of them involved in immunomodulation, such transforming growth factor beta and hepatic growth factors. The immunomodulatory effect of AFSC's exosomes on peripheral blood mononuclear cells stimulated with phytohemagglutinin was compared to that of the supernatant produced by such conditioned media deprived of exosomes. We present evidence that the principal effect of AFSC conditioned media (without exosomes) is the induction of apoptosis in lymphocytes, whereas exposure to AFSC-derived exosomes decreases the lymphocyte's proliferation, supporting the hypothesis that the entire secretome of stem cells differently affects immune-response. © 2017 BioFactors, 44(2):158-167, 2018.

Exosomes: Nanocarriers of Biological Messages

Cell-cell communication is crucial to maintain homeostasis in multicellular organism. Cells communicate each other by direct contact or by releasing factors that, soluble or packaged in membrane vesicles, can reach different regions of the organism. To date numerous studies highlighted the existence of several types of extracellular vesicles that, differing for dimension, origin and contents, play a role in physiological and/or pathological processes. Among extracellular vesicles, exosomes are emerging as efficient players to modulate target cells phenotype and as new non-invasive diagnostic and prognostic tools in multiple diseases. They, in fact, strictly reflect the type and functional status of the producing cells and are able to deliver their contents even over a long distance. The results accumulated in the last two decades and collected in this chapter, indicated that exosomes, can carry RNAs, microRNAs, long non-coding RNAs, DNA, lipids, metabolites and proteins; a deeper understanding of their contents is therefore needed to get the most from this incredible cell product.

Mesenchymal Stem Cells as Endogenous Regulators of Inflammation

This chapter discusses the regulatory role of endogenous mesenchymal stem cells (MSC) during an inflammatory response. MSC are a heterogeneous population of multipotent cells that normally contribute towards tissue maintenance and repair but have garnered significant scientific interest for their potent immunomodulatory potential. It is through these physicochemical interactions that MSC are able to exert an anti-inflammatory response on neighbouring stromal and haematopoietic cells. However, the impact of the chronic inflammatory environment on MSC function remains to be determined. Understanding the relationship of MSC between resolution of inflammation and autoimmunity will both offer new insights in the use of MSC as a therapeutic, and also their involvement in the pathogenesis of inflammatory disorders.

Extracellular vesicles and cardiovascular disease therapy

Cardiovascular disease (CVD) constitutes one of the leading causes of mortality worldwide, therefore representing a major public health concern. Despite recent advances in the treatment of patients with acute myocardial infarction (AMI), such as bypass surgery or percutaneous coronary intervention, pathological cardiac remodeling often predisposes survivors to fatal heart failure. In this context, the proven efficacy of stem cell-regenerative therapies constitutes a promising therapeutic perspective with is nevertheless slow down by safety and ethical concerns. Recent studies have underscored the capacity of stem cell-derived extracellular vesicles (EV) to recapitulate the regenerative properties of their parental cells therefore offering a therapeutic alternative to cell therapy in cardiovascular regenerative medicine. In this article, we review the functional relevance of using stem cell-derived EV as therapeutically agents and detail the identified molecular pathways that they used to exert their effects. We also discuss the advantages of using such an acellular regenerative therapy, in regard with parental stem cells, and address the limitations, which would need to be resolved, before their clinical translation.

Exosome and mesenchymal stem cell cross-talk in the tumor microenvironment

Mesenchymal stem cells (MSCs) are a major component of the tumor microenvironment (TME) and play a key role in promoting tumor progression. The tumor uses exosomes to co-opt MSCs and re-program their functional profile from normally trophic to pro-tumorigenic. These tumor-derived small vesicles called "TEX" carry and deliver a cargo rich in proteins and nucleic acids to MSCs. Upon interactions with surface receptors on MSCs and uptake of the exosome cargo by MSCs, molecular, transcriptional and translational changes occur that convert MSCs into producers of factors that are necessary for tumor growth and that also alter functions of non-tumor cells in the TME. The MSCs re-programmed by TEX become avid producers of their own exosomes that carry and deliver mRNA and miRNA species as well as molecular signals not only back to tumor cells, directly enhancing their growth, but also horizontally to fibroblasts, endothelial cells and immune cells in the TME, indirectly enhancing their pro-tumor functions. TEX-driven cross-talk of MSCs with immune cells blocks their anti-tumor activity and/or converts them into suppressor cells. MSCs re-programmed by TEX mediate pro-angiogenic activity and convert stromal cells into cancer-associated fibroblasts (CAFs). 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. Future therapeutic options consider disruption of this complex vicious cycle by either molecular or gene-regulated silencing of pro-tumor effects mediated by MSCs in the TME.

Neural Stem Cells and Its Derivatives as a New Material for Melanin Inhibition

The pigment molecule, melanin, is produced from melanosomes of melanocytes through melanogenesis, which is a complex process involving a combination of chemical and enzymatically catalyzed reactions. The synthesis of melanin is primarily influenced by tyrosinase (TYR), which has attracted interest as a target molecule for the regulation of pigmentation or depigmentation in skin. Thus, direct inhibitors of TYR activity have been sought from various natural and synthetic materials. However, due to issues with these inhibitors, such as weak or permanent ability for depigmentation, allergy, irritant dermatitis and rapid oxidation, in vitro and in vivo, the development of new materials that inhibit melanin production is essential. A conditioned medium (CM) derived from stem cells contains many cell-secreted factors, such as cytokines, chemokines, growth factors and extracellular vesicles including exosomes. In addition, the secreted factors could negatively regulate melanin production through stimulation of a microenvironment of skin tissue in a paracrine manner, which allows the neural stem cell CM to be explored as a new material for skin depigmentation. In this review, we will summarize the current knowledge regulating depigmentation, and discuss the potential of neural stem cells and their derivatives, as a new material for skin depigmentation.

Stem cell extracellular vesicles and kidney injury

Extracellular vesicles (EVs) appear as a new promising cell-free therapy for acute and chronic renal diseases. EVs retain characteristics of the cell of origin and those derived from stem cells may mimic their regenerative properties per se. In fact, EVs contain many active molecules such as proteins and RNA species that act on target cells through different mechanisms, stimulating proliferation and angiogenesis and reducing apoptosis and inflammation. There are several reports that demonstrate a general regenerative potential of EVs derived from mesenchymal stromal cells (MSCs) of different sources in kidney injury models. In addition, a promising new approach is the use of EVs in the graft perfusion solution for kidney conditioning before transplant. Here we summarize the application of EVs released by stem cells in preclinical models of acute and chronic renal damage, comparing animal models, use of EVs of different cell origin and of their sub-fractions, doses, route of administration and efficacy of treatment.

The Protein Content of Extracellular Vesicles Derived from Expanded Human Umbilical Cord Blood-Derived CD133+ and Human Bone Marrow-Derived Mesenchymal Stem Cells Partially Explains Why both Sources are Advantageous for Regenerative Medicine

Adult stem cells have beneficial effects when exposed to damaged tissue due, at least in part, to their paracrine activity, which includes soluble factors and extracellular vesicles (EVs). Given the multiplicity of signals carried by these vesicles through the horizontal transfer of functional molecules, human mesenchymal stem cell (hMSCs) and CD133⁺ cell-derived EVs have been tested in various disease models and shown to recover damaged tissues. In this study, we profiled the protein content of EVs derived from expanded human CD133⁺ cells and bone marrow-derived hMSCs with the intention of better understanding the functions performed by these vesicles/cells and delineating the most appropriate use of each EV in future therapeutic procedures. Using LC-MS/MS analysis, we identified 623 proteins for expanded CD133⁺-EVs and 797 proteins for hMSCs-EVs. Although the EVs from both origins were qualitatively similar, when protein abundance was considered, hMSCs-EVs and CD133⁺-EVs were different. Gene Ontology (GO) enrichment analysis in CD133⁺-EVs revealed proteins involved in a variety of angiogenesis-related functions as well proteins related to the cytoskeleton and highly implicated in cell motility and cellular activation. In contrast, when overrepresented proteins in hMSCs-EVs were analyzed, a GO cluster of immune response-related genes involved with immune response-regulating factors acting on phagocytosis and innate immunity was identified. Together our data demonstrate that from the point of view of protein content, expanded CD133⁺-EVs and hMSCs-EVs are in part similar but also sufficiently different to reflect the main beneficial paracrine effects widely reported in pre-clinical studies using expanded CD133⁺ cells and/or hBM-MSCs.

Regenerative Therapies in Dry Eye Disease: From Growth Factors to Cell Therapy

Dry eye syndrome is a complex and insidious pathology with a high level of prevalence among the human population and with a consequently high impact on quality of life and economic cost. Currently, its treatment is symptomatic, mainly based on the control of lubrication and inflammation, with significant limitations. Therefore, the latest research is focused on the development of new biological strategies, with the aim of regenerating affected tissues, or at least restricting the progression of the disease, reducing scar tissue, and maintaining corneal transparency. Therapies range from growth factors and cytokines to the use of different cell sources, in particular mesenchymal stem cells, due to their multipotentiality, trophic, and immunomodulatory properties. We will review the state of the art and the latest advances and results of these promising treatments in this pathology.