Proteomic analysis of the secretome of adipose tissue-derived murine mesenchymal cells overexpressing telomerase and myocardin

Analysis and Characterization of the Extracellular Vesicles Released in Non-Cancer Diseases Using Matrix-Assisted Laser Desorption Ionization/Mass Spectrometry

The extracellular vesicles (EVs) released by cells play a crucial role in intercellular communications and interactions. The direct shedding of EVs from the plasma membrane represents a fundamental pathway for the transfer of properties and information between cells. These vesicles are classified based on their origin, biogenesis, size, content, surface markers, and functional features, encompassing a variety of bioactive molecules that reflect the physiological state and cell type of origin. Such molecules include lipids, nucleic acids, and proteins. Research efforts aimed at comprehending EVs, including the development of strategies for their isolation, purification, and characterization, have led to the discovery of new biomarkers. These biomarkers are proving invaluable for diagnosing diseases, monitoring disease progression, understanding treatment responses, especially in oncology, and addressing metabolic, neurological, infectious disorders, as well as advancing vaccine development. Matrix-Assisted Laser Desorption Ionization (MALDI)/Mass Spectrometry (MS) stands out as a leading tool for the analysis and characterization of EVs and their cargo. This technique offers inherent advantages such as a high throughput, minimal sample consumption, rapid and cost-effective analysis, and user-friendly operation. This review is mainly focused on the primary applications of MALDI-time-of-flight (TOF)/MS in the analysis and characterization of extracellular vesicles associated with non-cancerous diseases and pathogens that infect humans, animals, and plants.

Endothelial heterogeneity and their relevance in cardiac development and coronary artery disease

Micro- and macrovascular endothelial cells (ECs) are characterized by structural and functional heterogeneity, which is also reflected in their secretory activity. The root of this heterogeneity and related regulatory mechanisms are still poorly understood. During embryogenesis, microvascular ECs participate in organogenesis prior to the development of the fetal circulation, suggesting that ECs are capable of releasing paracrine trophogens, termed angiocrine factors (AFs). These are angiocrine growth factors, adhesion molecules, and chemokines, which are intended to promote morphogenesis and repair of the adjacent parenchyma/stroma where the vessels are located. There is a tissue and organ-specificity of AFs that traces the heterogeneity of ECs. This AF heterogeneity also traces how ECs respond to pathological conditions or exposure to cardiovascular risk factors. The study of the mechanisms that regulate endothelial and paracrine heterogeneity and that contribute to endotheliopathy represents a broad and as yet understudied area of research. A better understanding of the cellular and molecular mechanisms that regulate this heterogeneity, leading to endotheliopathy is an exciting challenge. In this brief review we will discuss experimental advances in the heterogeneity of ECs and their AF, with a focus on their involvement in the pathogenesis of coronary artery disease.

Human retinal secretome: A cross-link between mesenchymal and retinal cells

In recent years, mesenchymal stem cells (MSC) have been considered the most effective source for regenerative medicine, especially due to released soluble paracrine bioactive components and extracellular vesicles. These factors, collectively called the secretome, play crucial roles in immunomodulation and in improving survival and regeneration capabilities of injured tissue. Recently, there has been a growing interest in the secretome released by retinal cytotypes, especially retinal pigment epithelium and Müller glia cells. The latter trophic factors represent the key to preserving morphofunctional integrity of the retina, regulating biological pathways involved in survival, function and responding to injury. Furthermore, these factors can play a pivotal role in onset and progression of retinal diseases after damage of cell secretory function. In this review, we delineated the importance of cross-talk between MSCs and retinal cells, focusing on common/induced secreted factors, during experimental therapy for retinal diseases. The cross-link between the MSC and retinal cell secretomes suggests that the MSC secretome can modulate the retinal cell secretome and vice versa. For example, the MSC secretome can protect retinal cells from degeneration by reducing oxidative stress, autophagy and programmed cell death. Conversely, the retinal cell secretome can influence the MSC secretome by inducing changes in MSC gene expression and phenotype.

Delivery of Stem Cell Secretome for Therapeutic Applications

Intensive studies on stem cell therapy reveal that benefits of stem cells attribute to the paracrine effects. Hence, direct delivery of stem cell secretome to the injured site shows the comparative therapeutic efficacy of living cells while avoiding the potential limitations. However, conventional systemic administration of stem cell secretome often leads to rapid clearance in vivo. Therefore, a variety of different biomaterials are developed for sustained and controllable delivery of stem cell secretome to improve therapeutic efficiency. In this review, we first introduce current approaches for the preparation and characterization of stem cell secretome as well as strategies to improve their therapeutic efficacy and production. The up-to-date delivery platforms are also summarized, including nanoparticles, injectable hydrogels, microneedles, and scaffold patches. Meanwhile, we discuss the underlying therapeutic mechanism of stem cell secretome for the treatment of various diseases. In the end, future opportunities and challenges are proposed.

Bone marrow- or adipose-mesenchymal stromal cell secretome preserves myocardial transcriptome profile and ameliorates cardiac damage following ex vivo cold storage

BACKGROUND

Heart transplantation, a life-saving approach for patients with end-stage heart disease, is limited by shortage of donor organs. While prolonged storage provides more organs, it increases the extent of ischemia. Therefore, we seek to understand molecular mechanisms underlying pathophysiological changes of donor hearts during prolonged storage. Additionally, considering mesenchymal stromal cell (MSC)-derived paracrine protection, we aim to test if MSC secretome preserves myocardial transcriptome profile and whether MSC secretome from a certain source provides the optimal protection in donor hearts during cold storage.

METHODS AND RESULTS

Isolated mouse hearts were divided into: no cold storage (control), 6 h cold storage (6 h-I), 6 h-I + conditioned media from bone marrow MSCs (BM-MSC CM), and 6 h-I + adipose-MSC CM (Ad-MSC CM). Deep RNA sequencing analysis revealed that compared to control, 6 h-I led to 266 differentially expressed genes, many of which were implicated in modulating mitochondrial performance, oxidative stress response, myocardial function, and apoptosis. BM-MSC CM and Ad-MSC CM restored these gene expression towards control. They also improved 6 h-I-induced myocardial functional depression, reduced inflammatory cytokine production, decreased apoptosis, and reduced myocardial H₂O₂. However, neither MSC-exosomes nor exosome-depleted CM recapitulated MSC CM-ameliorated apoptosis and CM-improved mitochondrial preservation during cold ischemia. Knockdown of Per2 by specific siRNA abolished MSC CM-mediated these protective effects in cardiomyocytes following 6 h cold storage.

CONCLUSIONS

Our results demonstrated that using MSC secretome (BM-MSCs and Ad-MSCs) during prolonged cold storage confers preservation of the normal transcriptional "fingerprint", and reduces donor heart damage. MSC-released soluble factors and exosomes may synergistically act for donor heart protection.

HATMSC Secreted Factors in the Hydrogel as a Potential Treatment for Chronic Wounds-In Vitro Study

Mesenchymal stem cells (MSCs) can improve chronic wound healing; however, recent studies suggest that the therapeutic effect of MSCs is mediated mainly through the growth factors and cytokines secreted by these cells, referred to as the MSC secretome. To overcome difficulties related to the translation of cell therapy into clinical use such as efficacy, safety and cost, we propose a hydrogel loaded with a secretome from the recently established human adipose tissue mesenchymal stem cell line (HATMSC2) as a potential treatment for chronic wounds. Biocompatibility and biological activity of hydrogel-released HATMSC2 supernatant were investigated in vitro by assessing the proliferation and metabolic activity of human fibroblast, endothelial cells and keratinocytes. Hydrogel degradation was measured using hydroxyproline assay while protein released from the hydrogel was assessed by interleukin-8 (IL-8) and macrophage chemoattractant protein-1 (MCP-1) ELISAs. Pro-angiogenic activity of the developed treatment was assessed by tube formation assay while the presence of pro-angiogenic miRNAs in the HATMSC2 supernatant was investigated using real-time RT-PCR. The results demonstrated that the therapeutic effect of the HATMSC2-produced factors is maintained following incorporation into collagen hydrogel as confirmed by increased proliferation of skin-origin cells and improved angiogenic properties of endothelial cells. In addition, HATMSC2 supernatant revealed antimicrobial activity, and which therefore, in combination with the hydrogel has a potential to be used as advanced wound-healing dressing.

Telomerase/myocardin expressing mesenchymal cells induce survival and cardiovascular markers in cardiac stromal cells undergoing ischaemia/reperfusion

Cardiac stromal cells (CSCs) contain a pool of cells with supportive and paracrine functions. Various types of mesenchymal stromal cells (MSCs) can influence CSCs in the cardiac niche through their paracrine activity. Ischaemia/reperfusion (I/R) leads to cell death and reduction of the paracrine activity of CSCs. The forced co‐expression of telomerase reverse transcriptase (TERT) and myocardin (MYOCD), known to potentiate anti‐apoptotic, pro‐survival and pro‐angiogenic activities of MSCs isolated from the adipose tissue (AT‐MSCs), may increase CSC survival, favouring their paracrine activities. We aimed at investigating the hypothesis that CSCs feature improved resistance to simulated I/R (SI/R) and increased commitment towards the cardiovascular lineage when preconditioned with conditioned media (CM) or extracellular vesicles (EV) released from AT‐MSCs overexpressing TERT and MYOCD (T/M AT‐MSCs). Murine CSCs were isolated with the cardiosphere (CSps) isolation technique. T/M AT‐MSCs and their secretome improved spontaneous intracellular calcium changes and ryanodine receptor expression in aged CSps. The cytoprotective effect of AT‐MSCs was tested in CSCs subjected to SI/R. SI/R induced cell death as compared to normoxia (28 ± 4 vs 10 ± 3%, P = .02). Pre‐treatment with CM (15 ± 2, P = .02) or with the EV‐enriched fraction (10 ± 1%, P = .02) obtained from mock‐transduced AT‐MSCs in normoxia reduced cell death after SI/R. The effect was more pronounced with CM (7 ± 1%, P = .01) or the EV‐enriched fraction (2 ± 1%, P = .01) obtained from T/M AT‐MSCs subjected to SI/R. In parallel, we observed lower expression of the apoptosis marker cleaved caspase‐3 and higher expression of cardiac and vascular markers eNOS, sarcomeric α‐actinin and cardiac actin. The T/M AT‐MSCs secretome exerts a cytoprotective effect and promotes development of CSCs undergoing SI/R towards a cardiovascular phenotype.

Mitochondrial ROS and mitochondria-targeted antioxidants in the aged heart

Excessive mitochondrial ROS production has been causally linked to the pathophysiology of aging in the heart and other organs, and plays a deleterious role in several age-related cardiac pathologies, including myocardial ischemia-reperfusion injury and heart failure, the two worldwide leading causes of death and disability in the elderly. However, ROS generation is also a fundamental mitochondrial function that orchestrates several signaling pathways, some of them exerting cardioprotective effects. In cardiac myocytes, mitochondria are particularly abundant and are specialized in subcellular populations, in part determined by their relationships with other organelles and their cyclic calcium handling activity necessary for adequate myocardial contraction/relaxation and redox balance. Depending on their subcellular location, mitochondria can themselves be differentially targeted by ROS and display distinct age-dependent functional decline. Thus, precise mitochondria-targeted therapies aimed at counteracting unregulated ROS production are expected to have therapeutic benefits in certain aging-related heart conditions. However, for an adequate design of such therapies, it is necessary to unravel the complex and dynamic interactions between mitochondria and other cellular processes.

Transplantation of telomerase/myocardin-co-expressing mesenchymal cells in the mouse promotes myocardial revascularization and tissue repair

AIM

Cell therapies are hampered by poor survival and growth of grafts. We tested whether forced co-expression of telomerase reverse transcriptase (TERT) and myocardin (MYOCD) improves post-infarct revascularization and tissue repair by adipose tissue-derived mesenchymal stromal cells (AT-MSCs).

METHODS AND RESULTS

We transplanted AT-MSCs overexpressing MYOCD and TERT in a murine model of acute myocardial infarction (AMI). We characterized paracrine effects of AT-MSCs. When transplanted into infarcted hearts of C57BL/6 mice, AT-MSCs overexpressing TERT and MYOCD decreased scar tissue and the intra-scar CD3 and B220 lymphocyte infiltration; and increased arteriolar density as well as ejection fraction compared with saline or mock-transduced AT-MSCs. These effects were accompanied by higher persistence of the injected cells in the heart, increased numbers of Ki-67⁺ and CD117⁺ cells, and the expression of cardiac actin and β-myosin heavy chain. Intramyocardial delivery of the secretome and its extracellular vesicle (EV)-enriched fraction also decreased scar tissue formation and increased arteriolar density in the murine AMI model. Proteomic analysis of AT-MSCs-EV-enriched fraction predicted the activation of vascular development and the inhibition of immune cell trafficking. Elevated concentrations of miR-320a, miR-150-5p and miR-126-3p associated with regulation of apoptosis and vasculogenesis were confirmed in the AT-MSCs-EV-enriched fraction.

CONCLUSIONS

AT-MSCs overexpressing TERT and MYOCD promote persistence of transplanted aged AT-MSCs and enhance arteriolar density in a murine model of AMI. EV-enriched fraction is the component of the paracrine secretion by AT-MSCs with pro-angiogenic and anti-fibrotic activities.

Exosomal Secretion of Adipose Tissue during Various Physiological States

Exosomes are secreted extracellular vesicles containing a wide array of biologically active components. Recent studies have demonstrated that exosomes serve as an important vehicle for extracellular communication and exert systemic effects on the physiology of organisms. Adipose tissues (ATs) play a key role in balancing systemic energy homeostasis as a central hub for fatty acid metabolism. At the same time, proper endocrine function of ATs has also been shown to be crucial for regulating physiological and metabolic health. The endocrine function of ATs is partially mediated by AT-derived exosomes that regulate metabolic homeostasis, such as insulin signaling, lipolysis, and inflammation. During the pathogenesis of obesity, metabolic syndrome, and cancer, exosomes shed by the resident cells in ATs may also have a role in regulating the progression of these diseases along with associated pathologies. In this review, we summarize the contents of AT-derived exosomes and their effects on various cell populations along with possible underlying molecular mechanisms. We further discuss the potential applications of exosomes as a drug delivery tool and therapeutic target.

Senescent mesenchymal stem/stromal cells and restoring their cellular functions

Mesenchymal stem/stromal cells (MSCs) have various properties that make them promising candidates for stem cell-based therapies in clinical settings. These include self-renewal, multilineage differentiation, and immunoregulation. However, recent studies have confirmed that aging is a vital factor that limits their function and therapeutic properties as standardized clinical products. Understanding the features of senescence and exploration of cell rejuvenation methods are necessary to develop effective strategies that can overcome the shortage and instability of MSCs. This review will summarize the current knowledge on characteristics and functional changes of aged MSCs. Additionally, it will highlight cell rejuvenation strategies such as molecular regulation, non-coding RNA modifications, and microenvironment controls that may enhance the therapeutic potential of MSCs in clinical settings.

Genetic Engineering as a Strategy to Improve the Therapeutic Efficacy of Mesenchymal Stem/Stromal Cells in Regenerative Medicine

Mesenchymal stem/stromal cells (MSCs) have been widely studied in the field of regenerative medicine for applications in the treatment of several disease settings. The therapeutic potential of MSCs has been evaluated in studies in vitro and in vivo, especially based on their anti-inflammatory and pro-regenerative action, through the secretion of soluble mediators. In many cases, however, insufficient engraftment and limited beneficial effects of MSCs indicate the need of approaches to enhance their survival, migration and therapeutic potential. Genetic engineering emerges as a means to induce the expression of different proteins and soluble factors with a wide range of applications, such as growth factors, cytokines, chemokines, transcription factors, enzymes and microRNAs. Distinct strategies have been applied to induce genetic modifications with the goal to enhance the potential of MCSs. This review aims to contribute to the update of the different genetically engineered tools employed for MSCs modification, as well as the factors investigated in different fields in which genetically engineered MSCs have been tested.

Stimulating pro-reparative immune responses to prevent adverse cardiac remodelling: consensus document from the joint 2019 meeting of the ESC Working Groups of cellular biology of the heart and myocardial function

Cardiac injury may have multiple causes, including ischaemic, non-ischaemic, autoimmune, and infectious triggers. Independent of the underlying pathophysiology, cardiac tissue damage induces an inflammatory response to initiate repair processes. Immune cells are recruited to the heart to remove dead cardiomyocytes, which is essential for cardiac healing. Insufficient clearance of dying cardiomyocytes after myocardial infarction (MI) has been shown to promote unfavourable cardiac remodelling, which may result in heart failure (HF). Although immune cells are integral key players of cardiac healing, an unbalanced or unresolved immune reaction aggravates tissue damage that triggers maladaptive remodelling and HF. Neutrophils and macrophages are involved in both, inflammatory as well as reparative processes. Stimulating the resolution of cardiac inflammation seems to be an attractive therapeutic strategy to prevent adverse remodelling. Along with numerous experimental studies, the promising outcomes from recent clinical trials testing canakinumab or colchicine in patients with MI are boosting the interest in novel therapies targeting inflammation in cardiovascular disease patients. The aim of this review is to discuss recent experimental studies that provide new insights into the signalling pathways and local regulators within the cardiac microenvironment promoting the resolution of inflammation and tissue regeneration. We will cover ischaemia- and non-ischaemic-induced as well as infection-related cardiac remodelling and address potential targets to prevent adverse cardiac remodelling.

Macrophage M2 polarization induced by exosomes from adipose-derived stem cells contributes to the exosomal proangiogenic effect on mouse ischemic hindlimb

BACKGROUND

M2 macrophages and exosomes from adipose-derived stem cells (ASCs) are both reported to promote angiogenesis. However, the possible synergistic effects between exogenous exosomes and endogenous M2 macrophages are poorly understood.

METHODS

Exosomes were isolated from conditioned medium of normoxic and hypoxic ASCs using the combined techniques of ultrafiltration and size-exclusion chromatography and were identified with nanoparticle tracking analysis and immunoblotting for exosomal markers. Macrophages were collected from the mouse peritoneal cavity. M1 and M2 macrophages were detected by immunoblotting for the intracellular markers inducible nitric oxide synthase (iNOS) and arginase-1 (Arg-1) and by flow cytometry for the surface markers F4/80, CD86, and CD206. Murine models of Matrigel plug and hindlimb ischemia were employed as in vivo angiogenic assays.

RESULTS

When M1 macrophages were treated with exosomes from normoxic ASCs (Nor/Exo), and particularly from hypoxic ASCs (Hyp/Exo), the expression of the M1 marker iNOS decreased, and the M2 marker Arg-1 increased in a time- and dose-dependent manner. Additionally, a decrease in the M1 surface marker CD86 and an increase in the M2 surface marker CD206 were observed, which suggested that M1 macrophages were polarized to an M2-like phenotype. Conditioned medium from these M2-like macrophages presented lower levels of proinflammatory cytokines and higher levels of proangiogenic factors and promoted endothelial cell proliferation, migration, and tube formation. Furthermore, M2 polarization and angiogenesis were induced upon the administration of exosomes in mouse Matrigel plug and hindlimb ischemia (HLI) models. Interestingly, these exosomal effects were attenuated by using a colony stimulating factor 1 receptor (CSF-1R) inhibitor, BLZ945, in vitro and in vivo. Downregulation of microRNA-21 (miR-21) in hypoxic ASCs reduced the exosomal effects on M2 polarization, Akt phosphorylation, and CSF-1 secretion. A similar reduction in exosomal activity was also observed when exosomes were administered along with BLZ945.

CONCLUSION

Our findings provide evidence that exosomes from ASCs polarize macrophages toward an M2-like phenotype, which further enhances the exosomal proangiogenic effects. Exosomal delivery of miR-21 and positive feedback of secreted CSF-1 may be involved in macrophage polarization.