Analysis of the Secretome of Apoptotic Peripheral Blood Mononuclear Cells: Impact of Released Proteins and Exosomes for Tissue Regeneration

Novel Electrochemically Switchable, Flexible, Microporous Cloth that Selectively Captures, Releases, and Concentrates Intact Extracellular Vesicles

There is a significant and growing research interest in the isolation of extracellular vesicles (EVs) from large volumes of biological samples and their subsequent concentration into clean and small volumes of buffers, especially for applications in medical diagnostics. Materials that are easily incorporated into simple sampling devices and which allow the release of EVs without the need for auxiliary and hence contaminating reagents are particularly in demand. Herein, we report on the design and fabrication of a flexible, microporous, electrochemically switchable cloth that addresses the key challenges in diagnostic applications of EVs. We demonstrate the utility of our electrochemically switchable substrate for the fast, selective, nondestructive, and efficient capture and subsequent release of EVs. The substrate consists of an electrospun cloth, infused with a conducting polymer and decorated with gold particles. Utilizing gold-sulfur covalent bonding, the electrospun substrates may be functionalized with SH-terminated aptamer probes selective to EV surface proteins. We demonstrate that EVs derived from primary human dermal fibroblast (HDFa) and breast cancer (MCF-7) cell lines are selectively captured with low nonspecific adsorption using an aptamer specific to the CD63 protein expressed on the EV membranes. The specific aptamer-EV interactions enable easy removal of the nonspecifically bound material through washing steps. The conducting polymer component of the cloth provides a means for efficient (>92%) and fast (<5 min) electrochemical release of clean and intact captured EVs by cathodic cleavage of the Au-S bond. We demonstrate successful capture of diluted EVs from a large volume sample and their release into a small volume of clean phosphate-buffered saline buffer. The developed cloth can easily be incorporated into different designs for separation systems and would be adaptable to other biological entities including cells and other EVs. Furthermore, the capture/release capability holds great promise for liquid biopsies if used to targeted disease-specific markers.

Optimized method for extraction of exosomes from human primary muscle cells

Skeletal muscle is increasingly considered an endocrine organ secreting myokines and extracellular vesicles (exosomes and microvesicles), which can affect physiological changes with an impact on different pathological conditions, including regenerative processes, aging, and myopathies. Primary human myoblasts are an essential tool to study the muscle vesicle secretome. Since their differentiation in conditioned media does not induce any signs of cell death or cell stress, artefactual effects from those processes are unlikely. However, adult human primary myoblasts senesce in long-term tissue culture, so a major technical challenge is posed by the need to avoid artefactual effects resulting from pre-senescent changes. Since these cells should be studied within a strictly controlled pre-senescent division count (<21 divisions), and yields of myoblasts per muscle biopsy are low, it is difficult or impossible to amplify sufficiently large cell numbers (some 250 × 10⁶ myoblasts) to obtain sufficient conditioned medium for the standard ultracentrifugation approach to exosome isolation.

Thus, an optimized strategy to extract and study secretory muscle vesicles is needed. In this study, conditions are optimized for the in vitro cultivation of human myoblasts, and the quality and yield of exosomes extracted using an ultracentrifugation protocol are compared with a modified polymer-based precipitation strategy combined with extra washing steps. Both vesicle extraction methods successfully enriched exosomes, as vesicles were positive for CD63, CD82, CD81, floated at identical density (1.15-1.27 g.ml⁻¹), and exhibited similar size and cup-shape using electron microscopy and NanoSight tracking. However, the modified polymer-based precipitation was a more efficient strategy to extract exosomes, allowing their extraction in sufficient quantities to explore their content or to isolate a specific subpopulation, while requiring >30 times fewer differentiated myoblasts than what is required for the ultracentrifugation method. In addition, exosomes could still be integrated into recipient cells such as human myotubes or iPSC-derived motor neurons.

Modified polymer-based precipitation combined with extra washing steps optimizes exosome yield from a lower number of differentiated myoblasts and less conditioned medium, avoiding senescence and allowing the execution of multiple experiments without exhausting the proliferative capacity of the myoblasts.

Role for Lipids Secreted by Irradiated Peripheral Blood Mononuclear Cells in Inflammatory Resolution in Vitro

Periodontal inflammation is associated with dying cells that potentially release metabolites helping to promote inflammatory resolution. We had shown earlier that the secretome of irradiated, dying peripheral blood mononuclear cells support in vitro angiogenesis. However, the ability of the secretome to promote inflammatory resolution remains unknown. Here, we determined the expression changes of inflammatory cytokines in murine bone marrow macrophages, RAW264.7 cells, and gingival fibroblasts exposed to the secretome obtained from γ-irradiated peripheral blood mononuclear cells in vitro by RT-PCR and immunoassays. Nuclear translocation of p65 was detected by immunofluorescence staining. Phosphorylation of p65 and degradation of IκB was determined by Western blot. The secretome of irradiated peripheral blood mononuclear cells significantly decreased the expression of IL1 and IL6 in primary macrophages and RAW264.7 cells when exposed to LPS or saliva, and of IL1, IL6, and IL8 in gingival fibroblasts when exposed to IL-1β and TNFα. These changes were associated with decreased phosphorylation and nuclear translocation of p65 but not degradation of IκB in macrophages. We also show that the lipid fraction of the secretome lowered the inflammatory response of macrophages exposed to the inflammatory cues. These results demonstrate that the secretome of irradiated peripheral blood mononuclear cells can lower an in vitro simulated inflammatory response, supporting the overall concept that the secretome of dying cells promotes inflammatory resolution.

Exosome-Containing Preparations From Postirradiated Mouse Melanoma Cells Delay Melanoma Growth In Vivo by a Natural Killer Cell-Dependent Mechanism

PURPOSE

To investigate the ability of radiation to stimulate exosome release from melanoma cells and to characterize the resulting exosome-containing vesicle preparations for their ability to promote a host antitumor immune response.

MATERIALS AND METHODS

Cultured B16F10 murine melanoma cells or tumors were irradiated, and secreted extracellular vesicles were isolated and characterized. The exosome-containing vesicle preparations were injected into fresh tumors in syngeneic mice, and tumor growth and infiltrating T cells and natural killer (NK) cells were characterized.

RESULTS

Irradiation stimulated exosome release from B16F10 murine melanoma cells. Exosome preparations from irradiated cell culture supernatants were biologically active, as demonstrated by uptake into recipient cells and by the ability to induce dendritic cell maturation and activation in vitro. Intratumoral injection significantly delayed tumor growth in vivo, whereas injection of similar preparations from non irradiated cells had no effect. The antitumor effect was correlated to an increase in interferon gamma-producing tumor-infiltrating NK cells. Pretreatment of the host mice with anti-NK cell antibodies abolished the effect, whereas pretreatment with anti-CD8⁺ T-cell antibodies did not.

CONCLUSION

Exosomes from irradiated cells, or synthetic mimics, might provide an effective strategy for potentiation of NK cell-mediated host antitumor immunity.

Methods for the Determination of the Purity of Exosomes

BACKGROUND

Exosomes open exciting new opportunities for advanced drug transport and targeted release. Furthermore, exosomes may be used for vaccination, immunosuppression or wound healing. To fully utilize their potential as drug carriers or immune-modulatory agents, the optimal purity of exosome preparations is of crucial importance.

METHODS

Articles describing the isolation and purification of exosomes were retrieved from the PubMed database.

RESULTS

Exosomes are often separated from biological fluids containing high concentrations of proteins, lipids and other molecules that keep vesicle purification challenging. A great number of purification protocols have been published, however, their outcome is difficult to compare because the assessment of purity has not been standardized. In this review, we first give an overview of the generation and composition of exosomes, as well as their multifaceted biological functions that stimulated various medical applications. Finally, we describe various methods that have been used to purify small vesicles and to assess the purity of exosome preparations and critically compare the quality of these evaluation protocols.

CONCLUSION

Combinations of various techniques have to be applied to reach the required purity and quality control of exosome preparations.

Quantitative Hybrid Cardiac [18F]FDG-PET-MRI Images for Assessment of Cardiac Repair by Preconditioned Cardiosphere-Derived Cells

Cardiosphere-derived cells (CDCs) are progenitor cells derived from heart tissue and have shown promising results in preclinical models. APOSEC, the secretome of irradiated peripheral blood mononuclear cells, has decreased infarct size in acute and chronic experimental myocardial infarction (MI). We enhanced the effect of CDCs with APOSEC preconditioning (apoCDC) and investigated the reparative effect in a translational pig model of reperfused MI. Supernatants of CDCs, assessed by proteomic analysis, revealed reduced production of extracellular matrix proteins after in vitro APOSEC preconditioning. In a porcine model of catheter-based reperfused anterior acute MI (AMI), CDCs with (apoCDC, n = 8) or without APOSEC preconditioning (CDC, n = 6) were infused intracoronary, 15 min after the start of reperfusion. Untreated AMI animals (n = 7) and sham procedures (n = 5) functioned as controls. 2-deoxy-2-(18 F)-fluoro-D-glucose-positron emission tomography-magnetic resonance imaging ([¹⁸F]FDG-PET-MRI), with late enhancement after 1 month, showed reduced scar volume and lower transmurality of the infarcted area in CDC and apoCDC compared to AMI controls. Segmental quantitative PET images displayed indicated more residual viability in apoCDC. The left-ventricle (LV) ejection fraction was improved nonsignificantly to 45.8% ± 8.6% for apoCDC and 43.5% ± 7.1% for CDCs compared to 38.5% ± 4.4% for untreated AMI. Quantitative hybrid [¹⁸F]FDG-PET-MRI demonstrated improved metabolic and functional recovery after CDC administration, whereas apoCDCs induced preservation of viability of the infarcted area.

Shedding Light on the Role of Extracellular Vesicles in HIV Infection and Wound Healing

Extracellular vesicles (EVs) play an important role in intercellular communication. They are naturally released from cells into the extracellular environment. Based on their biogenesis, release pathways, size, content, and function, EVs are classified into exosomes, microvesicles (MVs), and apoptotic bodies (ApoBDs). Previous research has documented that EVs, specifically exosomes and MVs, play an important role in HIV infection, either by promoting HIV infection and pathogenesis or by inhibiting HIV-1 to a certain extent. We have also previously reported that EVs (particularly exosomes) from vaginal fluids inhibit HIV at the post-entry step (i.e., reverse transcription, integration). Besides the role that EVs play in HIV, they are also known to regulate the process of wound healing by regulating both the immune and inflammatory responses. It is noted that during the advanced stages of HIV infection, patients are at greater risk of wound-healing and wound-related complications. Despite ongoing research, the data on the actual effects of EVs in HIV infection and wound healing are still premature. This review aimed to update the current knowledge about the roles of EVs in regulating HIV pathogenesis and wound healing. Additionally, we highlighted several avenues of EV involvement in the process of wound healing, including coagulation, inflammation, proliferation, and extracellular matrix remodeling. Understanding the role of EVs in HIV infection and wound healing could significantly contribute to the development of new and potent antiviral therapeutic strategies and approaches to resolve impaired wounds in HIV patients.

Therapeutic potential of lipids obtained from γ-irradiated PBMCs in dendritic cell-mediated skin inflammation

BACKGROUND

Since numerous pathological conditions are evoked by unwanted dendritic cell (DC) activity, therapeutic agents modulating DC functions are of great medical interest. In regenerative medicine, cellular secretomes have gained increasing attention and valuable immunomodulatory properties have been attributed to the secretome of γ-irradiated peripheral blood mononuclear cells (PBMCs). Potential effects of the PBMC secretome (PBMCsec) on key DC functions have not been elucidated so far.

METHODS

We used a hapten-mediated murine model of contact hypersensitivity (CH) to study the effects of PBMCsec on DCs in vivo. Effects of PBMCsec on human DCs were investigated in monocyte-derived DCs (MoDC) and ex vivo skin cultures. DCs were phenotypically characterised by transcriptomics analyses and flow cytometry. DC function was evaluated by cytokine secretion, antigen uptake, PBMC proliferation and T-cell priming.

FINDINGS

PBMCsec significantly alleviated tissue inflammation and cellular infiltration in hapten-sensitized mice. We found that PBMCsec abrogated differentiation of MoDCs, indicated by lower expression of classical DC markers CD1a, CD11c and MHC class II molecules. Furthermore, PBMCsec reduced DC maturation, antigen uptake, lipopolysaccharides-induced cytokine secretion, and DC-mediated immune cell proliferation. Moreover, MoDCs differentiated with PBMCsec displayed diminished ability to prime naïve CD4+T-cells into TH1 and TH2 cells. Furthermore, PBMCsec modulated the phenotype of DCs present in the skin in situ. Mechanistically, we identified lipids as the main biomolecule accountable for the observed immunomodulatory effects.

INTERPRETATION

Together, our data describe DC-modulatory actions of lipids secreted by stressed PBMCs and suggest PBMCsec as a therapeutic option for treatment of DC-mediated inflammatory skin conditions.

FUNDING

This research project was supported by the Austrian Research Promotion Agency (Vienna, Austria; grant "APOSEC" 862068; 2015-2019) and the Vienna Business Agency (Vienna, Austria; grant "APOSEC to clinic" 2343727).

Blood Gene Expression Profile Study Revealed the Activation of Apoptosis and p53 Signaling Pathway May Be the Potential Molecular Mechanisms of Ionizing Radiation Damage and Radiation-Induced Bystander Effects

Radiotherapy is an effective treatment for local solid tumors, but the mechanism of damage to human body caused by radiation therapy needs further study. In this study, gene expression profiles of human peripheral blood samples exposed to different doses and rates of ionizing radiation (IR) were used for bioinformatics analysis to investigate the mechanism of IR damage and radiation-induced bystander effect (RIBE). Differentially expressed genes analysis, weighted gene correlation network analysis, functional enrichment analysis, hypergeometric test, gene set enrichment analysis, and gene set variation analysis were applied to analyze the data. Moreover, receiver operating characteristic curve analysis was performed to identify core genes of IR damage. Weighted gene correlation network analysis identified 3 modules associated with IR damage, 2 were positively correlated and 1 was negatively correlated. The analysis showed that the positively correlated modules were significantly involved in apoptosis and p53 signaling pathway, and ESR1, ATM, and MYC were potential transcription factors regulating these modules. Thus, the study suggested that apoptosis and p53 signaling pathway may be the potential molecular mechanisms of IR damage and RIBE, which could be driven by ESR1, ATM, and MYC.

Mesenchymal Stem Cell Derived Extracellular Vesicles in Aging

Aging is associated with high prevalence of chronic degenerative diseases that take a large part of the increasing burden of morbidities in a growing demographic of elderly people. Aging is a complex process that involves cell autonomous and cell non-autonomous mechanisms where senescence plays an important role. Senescence is characterized by the loss of proliferative potential, resistance to cell death by apoptosis and expression of a senescence-associated secretory phenotype (SASP). SASP includes pro-inflammatory cytokines and chemokines, tissue-damaging proteases, growth factors; all contributing to tissue microenvironment alteration and loss of tissue homeostasis. Emerging evidence suggests that the changes in the number and composition of extracellular vesicles (EVs) released by senescent cells contribute to the adverse effects of senescence in aging. In addition, age-related alterations in mesenchymal stem/stromal cells (MSCs) have been associated to dysregulated functions. The loss of functional stem cells necessary to maintain tissue homeostasis likely directly contributes to aging. In this review, we will focus on the characteristics and role of EVs isolated from senescent MSCs, the potential effect of MSC-derived EVs in aging and discuss their therapeutic potential to improve age-related diseases.

Reproducibility of GMP-compliant production of therapeutic stressed peripheral blood mononuclear cell-derived secretomes, a novel class of biological medicinal products

BACKGROUND

The recent concept of secretome-based tissue regeneration has profoundly altered the field of regenerative medicine and offers promising novel therapeutic options. In contrast to medicinal products with a single active substance, cell-derived secretomes comprise pleiotropic bioactive ingredients, representing a major obstacle for reproducible drug product efficacy and warranting patient safety. Good manufacturing practice (GMP)-compliant production guarantees high batch-to-batch consistency and reproducible efficacy of biological medicinal products, but different batches of cellular secretomes produced under GMP have not been compared yet, and suitable quality control parameters have not been established. To this end, we analyzed diverse biological and functional parameters of different batches produced under GMP of the secretome obtained from γ-irradiated peripheral blood mononuclear cells with proven tissue regenerative properties in infarcted myocardium, stroke, spinal cord injury, and skin wounds.

METHODS

We quantified key secretome ingredients, including cytokines, lipids, and extracellular vesicles, and functionally assessed potency in tube formation assay, ex vivo aortic ring sprouting assay, and cell-based protein and reporter gene assays. Furthermore, we determined secretome stability in different batches after 6 months of storage at various ambient temperatures.

RESULTS

We observed that inter-batch differences in the bioactive components and secretome properties were small despite considerable differences in protein concentrations and potencies between individual donor secretomes. Stability tests showed that the analytical and functional properties of the secretomes remained stable when lyophilisates were stored at temperatures up to + 5 °C for 6 months.

CONCLUSIONS

We are the first to demonstrate the consistent production of cell-derived, yet cell-free secretome as a biological medicinal product. The results from this study provide the basis for selecting appropriate quality control parameters for GMP-compliant production of therapeutic cell secretomes and pave the way for future clinical trials employing secretomes in tissue regenerative medicine.

Viral safety of APOSECTM: a novel peripheral blood mononuclear cell derived-biological for regenerative medicine

BACKGROUND

Viral reduction and inactivation of cell-derived biologicals is paramount for patients' safety and so viral reduction needs to be demonstrated to regulatory bodies in order to obtain marketing authorisation. Allogeneic human blood-derived biological medicinal products require special attention. APOSECTM, the secretome harvested from selected human blood cells, is a new biological with promising regenerative capabilities. We evaluated the effectiveness of inactivation of model viruses by methylene blue/light treatment, lyophilisation, and gamma irradiation during the manufacturing process of APOSECTM.

MATERIALS AND METHODS

Samples of intermediates of APOSECTM were acquired during the manufacturing process and spiked with bovine viral diarrhoea virus (BVDV), human immunodeficiency virus type 1 (HIV-1), pseudorabies virus (PRV), hepatitis A virus (HAV), and porcine parvovirus (PPV). Viral titres were assessed with suitable cell lines.

RESULTS

Methylene blue-assisted viral reduction is mainly effective against enveloped viruses: the minimum log10 reduction factors for BVDV, HIV-1, and PRV were ≥6.42, ≥6.88, and ≥6.18, respectively, with no observed residual infectivity. Viral titres of both HAV and PPV were not significantly reduced, indicating minor inactivation of non-enveloped viruses. Lyophilisation had minor effects on the viability of several enveloped model viruses. Gamma irradiation contributes to the viral safety by reduction of enveloped viruses (BVDV: ≥2.42; HIV-1: 4.53; PRV: ≥4.61) and to some degree of non-enveloped viruses as seen for HAV with a minimum log10 reduction factor of 2.92. No significant reduction could be measured for the non-enveloped virus PPV (2.60).

DISCUSSION

Three manufacturing steps of APOSECTM were evaluated under Good Laboratory Practice conditions for their efficacy at reducing and inactivating potentially present viruses. It could be demonstrated that all three steps contribute to the viral safety of APOSECTM.

Ca2+ Flux: Searching for a Role in Efferocytosis of Apoptotic Cells in Atherosclerosis

In atherosclerosis, macrophages in the arterial wall ingest plasma lipoprotein-derived lipids and become lipid-filled foam cells with a limited lifespan. Thus, efficient removal of apoptotic foam cells by efferocytic macrophages is vital to preventing the dying foam cells from forming a large necrotic lipid core, which, otherwise, would render the atherosclerotic plaque vulnerable to rupture and would cause clinical complications. Ca2+ plays a role in macrophage migration, survival, and foam cell generation. Importantly, in efferocytic macrophages, Ca2+ induces actin polymerization, thereby promoting the formation of a phagocytic cup necessary for efferocytosis. Moreover, in the efferocytic macrophages, Ca2+ enhances the secretion of anti-inflammatory cytokines. Various Ca2+ antagonists have been seminal for the demonstration of the role of Ca2+ in the multiple steps of efferocytosis by macrophages. Moreover, in vitro and in vivo experiments and clinical investigations have revealed the capability of Ca2+ antagonists in attenuating the development of atherosclerotic plaques by interfering with the deposition of lipids in macrophages and by reducing plaque calcification. However, the regulation of cellular Ca2+ fluxes in the processes of efferocytic clearance of apoptotic foam cells and in the extracellular calcification in atherosclerosis remains unknown. Here, we attempted to unravel the molecular links between Ca2+ and efferocytosis in atherosclerosis and to evaluate cellular Ca2+ fluxes as potential treatment targets in atherosclerotic cardiovascular diseases.

Extracellular Vesicles in Modifying the Effects of Ionizing Radiation

Extracellular vesicles (EVs) are membrane-coated nanovesicles actively secreted by almost all cell types. EVs can travel long distances within the body, being finally taken up by the target cells, transferring information from one cell to another, thus influencing their behavior. The cargo of EVs comprises of nucleic acids, lipids, and proteins derived from the cell of origin, thereby it is cell-type specific; moreover, it differs between diseased and normal cells. Several studies have shown that EVs have a role in tumor formation and prognosis. It was also demonstrated that ionizing radiation can alter the cargo of EVs. EVs, in turn can modulate radiation responses and they play a role in radiation-induced bystander effects. Due to their biocompatibility and selective targeting, EVs are suitable nanocarrier candidates of drugs in various diseases, including cancer. Furthermore, the cargo of EVs can be engineered, and in this way they can be designed to carry certain genes or even drugs, similar to synthetic nanoparticles. In this review, we describe the biological characteristics of EVs, focusing on the recent efforts to use EVs as nanocarriers in oncology, the effects of EVs in radiation therapy, highlighting the possibilities to use EVs as nanocarriers to modulate radiation effects in clinical applications.

Tissue-regenerative potential of the secretome of γ-irradiated peripheral blood mononuclear cells is mediated via TNFRSF1B-induced necroptosis

Peripheral blood mononuclear cells (PBMCs) have been shown to produce and release a plethora of pro-angiogenetic factors in response to γ-irradiation, partially accounting for their tissue-regenerative capacity. Here, we investigated whether a certain cell subtype of PBMCs is responsible for this effect, and whether the type of cell death affects the pro-angiogenic potential of bioactive molecules released by γ-irradiated PBMCs. PBMCs and PBMC subpopulations, including CD4⁺ and CD8⁺ T cells, B cells, monocytes, and natural killer cells, were isolated and subjected to high-dose γ-irradiation. Transcriptome analysis revealed subpopulation-specific responses to γ-irradiation with distinct activation of pro-angiogenic pathways, cytokine production, and death receptor signalling. Analysis of the proteins released showed that interactions of the subsets are important for the generation of a pro-angiogenic secretome. This result was confirmed at the functional level by the finding that the secretome of γ-irradiated PBMCs displayed higher pro-angiogenic activity in an aortic ring assay. Scanning electron microscopy and image stream analysis of γ-irradiated PBMCs revealed distinct morphological changes, indicative for apoptotic and necroptotic cell death. While inhibition of apoptosis had no effect on the pro-angiogenic activity of the secretome, inhibiting necroptosis in stressed PBMCs abolished blood vessel sprouting. Mechanistically, we identified tumor necrosis factor (TNF) receptor superfamily member 1B as the main driver of necroptosis in response to γ-irradiation in PBMCs, which was most likely mediated via membrane-bound TNF-α. In conclusion, our study demonstrates that the pro-angiogenic activity of the secretome of γ-irradiated PBMCs requires interplay of different PBMC subpopulations. Furthermore, we show that TNF-dependent necroptosis is an indispensable molecular process for conferring tissue-regenerative activity and for the pro-angiogenic potential of the PBMC secretome. These findings contribute to a better understanding of secretome-based therapies in regenerative medicine.

Generation of GLA-Knockout Human Embryonic Stem Cell Lines to Model Autophagic Dysfunction and Exosome Secretion in Fabry Disease-Associated Hypertrophic Cardiomyopathy

Fabry disease (FD) is a rare inherited disorder characterized by a wide range of systemic symptoms; it is particularly associated with cardiovascular and renal problems. Enzyme replacement therapy and pharmacological chaperone migalastat are the only approved and effective treatment strategies for FD patients. It is well documented that alpha-galactosidase A (GLA) enzyme activity deficiency causes globotriaosylceramide (Gb3) accumulation, which plays a crucial role in the etiology of FD. However, the detailed mechanisms remain unclear, and the lack of a reliable and powerful disease model is an obstacle. In this study, we created such a model by using CRISPR/Cas9-mediated editing of GLA gene to knockout its expression in human embryonic stem cells (hESCs). The cardiomyocytes differentiated from these hESCs (GLA-null CMs) were characterized by the accumulation of Gb3 and significant increases of cell surface area, the landmarks of FD-associated cardiomyopathy. Furthermore, we used mass spectrometry to compare the proteomes of GLA-null CMs and parental wild type CMs and found that the Rab GTPases involved in exocytotic vesicle release were significantly downregulated. This caused impairment of autophagic flux and protein turnover, resulting in an increase of reactive oxygen species and apoptosis. To summarize, we established a FD model which can be used as a promising tool to study human hypertrophic cardiomyopathy in a physiologically and pathologically relevant manner and to develop new therapies by targeting Rab GTPases signaling-related exosomal vesicles transportation.

Toxicological testing of allogeneic secretome derived from peripheral mononuclear cells (APOSEC): a novel cell-free therapeutic agent in skin disease

A cell-free approach using secretomes derived from stem cells or peripheral blood mononuclear cells is an active area of regenerative medicine that holds promise for therapies. Regulatory authorities classify these secretomes as biological medicinal products, and non- clinical safety assessment thus falls under the scope of ICH S6. A secretome of stressed peripheral blood mononuclear cells (APOSEC) was successfully tested in a toxicology program, supporting clinical use of the new drug candidate. Here, to allow for topical, dermal treatment of patients with diabetic foot ulcer, several non-clinical safety studies were performed. Acute toxicity (single dose) and neuropharmacological screening were tested intravenously in a rat model. Risk for skin sensitisation was tested in mice. A 4-week intravenous toxicity study in mice and a 4-week subcutaneous toxicity study in minipigs were conducted to cover the clinical setting and application in a rodent and a non-rodent model. Acute and repeated-dose toxicity studies show that APOSEC administered intravenously and subcutaneously does not involve major toxicities or signs of local intolerance at levels above the intended total human maximal dose of 3.3 U/kg/treatment, 200 U/wound/treatment, and 100 U/cm²/treatment. The non-clinical data support the safe topical use of APOSEC in skin diseases related to deficient wound healing.

Enhancing the pro-inflammatory anti-cancer T cell response via biomanufactured, secretome-based, immunotherapeutics

T lymphocytes play a critical role in the pro-inflammatory anti-cancer response; hence, significant pharmacologic efforts have been made to enhance the endogenous T cell response. Unfortunately, significant toxicity arises consequent to pan T cell activation. In contrast, the less robust T cell alloresponse has also demonstrated an anti-cancer effect, but poses an inherent risk of GvHD. To overcome the GvHD risk, an acellular pro-inflammatory agent (IA1) has been biomanufactured from the secretome of the allorecognition response. To assess IA1's immunomodulatory activity, T cell proliferation and differentiation were determined in vitro. The pro-inflammatory properties of the IA1 therapeutic were mediated by the miRNA-enriched fractions. Moreover, cross-species efficacy was observed consequent to the evolutionary conservation of miRNA. IA1 exerted no toxicity to resting PBMC but induced significant proliferation of resting CD3⁺ (CD4⁺ and CD8⁺) T cells and skewed the response towards a pro-inflammatory state (i.e., increased Teff:Treg ratio). Crucially, IA1-activated PBMC demonstrated a potent inhibition of cancer cell (HeLa and SH-4 melanoma) proliferation relative to the resting PBMC. The anti-proliferation effect of IA1-activated PBMC was noted within ˜12 h versus 4-5 days for resting cells. A second biomanufactured therapeutic (IA2; produced using HeLa cells) surprisingly demonstrated direct toxicity to cancer cells but was less effective than IA1 in inducing a cell-mediated response. This study demonstrates that miRNA-enriched therapeutics can be biomanufactured from the secretome and can induce a potent pro-inflammatory, anti-cancer, effect on resting lymphocytes.

Different pro-angiogenic potential of γ-irradiated PBMC-derived secretome and its subfractions

Secretomes from various cell sources exert strong regenerative activities on numerous organs, including the skin. Although secretomes consist of many diverse components, a growing body of evidence suggests that small extracellular vesicles (EVs) account for their regenerative capacity. We previously demonstrated that the secretome of γ-irradiated peripheral blood mononuclear cells (PBMCs) exhibits wound healing capacity. Therefore, we sought to dissect the molecular composition of EVs present in the secretome and compared wound healing-related activities of these EVs to other subfractions of the secretome and the fully supplemented secretome (MNC^aposec). Compared to EVs derived from non-irradiated PBMCs, γ-irradiation significantly increased the size and number and changed the composition of released EVs. Detailed characterization of the molecular components of EVs, i.e. miRNA, proteins, and lipids, derived from irradiated PBMCs revealed a strong association with regenerative processes. Reporter gene assays and aortic ring sprouting assays revealed diminished activity of the subfractions compared to MNC^aposec. In addition, we showed that MNC^aposec accelerated wound closure in a diabetic mouse model. Taken together, our results suggest that secretome-based wound healing represents a promising new therapeutic avenue, and strongly recommend using the complete secretome instead of purified subfractions, such as EVs, to exploit its full regenerative capacity.

VEGFR-2 Inhibitor Apatinib Hinders Endothelial Cells Progression Triggered by Irradiated Gastric Cancer Cells-derived Exosomes

Background: Radiotherapy is a standard treatment for a significant fraction of cancer patients. Nonetheless, to this day radiation resistance is a key impediment in gastric cancer (GC) treatment. Moreover, GC is characterized by its substantial neo-angiogenesis, driven by high levels of vascular endothelial growth factor (VEGF) correlated with the presence of stomach cancer. The aim of our study was to address if VEGFR inhibitors treatments impact the negative effect of radiotherapy regiments of gastric cancer.

Materials and methods: Isolation of exosomes released by SGC-7901 and BGC-823 lines after irradiation at 0 Gy or 6 Gy was performed by differential ultra-centrifugation. Incubation of Human Umbilical Vein Endothelial Cells (HUVEC) was carried out with different concentrations of exosomes from non- or irradiated GC cells to address their proliferation and survival fraction (SF) by MTS. 6 Gy irradiated cells exosomes at concentration of 20 µg/ml were compared to EC incubated with the same exosome concentration from non-irradiated human GC cells over 72-hour time course. Wound-healing and Transwell assays were performed in a migration buffer consisting of exosomes released by non- or irradiated SGC-7901 and BGC-823 cells over 24-hour time course. HUVEC cells stained with DAPI that have passed through a gluten gel were counted in order to monitor their invasion capacity. Employing IC50, 60 µg/ml was determined as the optimal Apatinib (YN968D1) concentration for the half-life of HUVEC, and incubated with exosomes from irradiated GC cells. The aforementioned assays were performed in the background of the same conditions in order to analyse the effect of Apatinib on HUVEC progression.

Results: We show that proliferation, motility and invasive capacity of HUVEC are enhanced upon incubation with exosomes released by irradiated GC cell lines. Importantly, the latter is counteracted by the VEGFR-2 inhibitor Apatinib which hinders ECs progression.

Conclusion / Significance: Combining radiotherapy and VEGFR inhibitors treatment can provide potentially a substantial impact in decreasing cancer death rates by averting the negative effect of radiotherapy regiments and provide better standard for cancer patients.

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.

Exosomal lipid composition and the role of ether lipids and phosphoinositides in exosome biology

Exosomes are a type of extracellular vesicle released from cells after fusion of multivesicular bodies with the plasma membrane. These vesicles are often enriched in cholesterol, SM, glycosphingolipids, and phosphatidylserine. Lipids not only have a structural role in exosomal membranes but also are essential players in exosome formation and release to the extracellular environment. Our knowledge about the importance of lipids in exosome biology is increasing due to recent technological developments in lipidomics and a stronger focus on the biological functions of these molecules. Here, we review the available information about the lipid composition of exosomes. Special attention is given to ether lipids, a relatively unexplored type of lipids involved in membrane trafficking and abundant in some exosomes. Moreover, we discuss how the lipid composition of exosome preparations may provide useful information about their purity. Finally, we discuss the role of phosphoinositides, membrane phospholipids that help to regulate membrane dynamics, in exosome release and how this process may be linked to secretory autophagy. Knowledge about exosome lipid composition is important to understand the biology of these vesicles and to investigate possible medical applications.

Secretome of Differentiated PC12 Cells Restores the Monocrotophos-Induced Damages in Human Mesenchymal Stem Cells and SHSY-5Y Cells: Role of Autophagy and Mitochondrial Dynamics

A perturbed cellular homeostasis is a key factor associated with xenobiotic exposure resulting in various ailments. The local cellular microenvironment enriched with secretory components aids in cell-cell communication that restores this homeostasis. Deciphering the underlying mechanism behind this restorative potential of secretome could serve as a possible solution to many health hazards. We, therefore, explored the protective efficacy of the secretome of differentiated PC12 cells with emphasis on induction of autophagy and mitochondrial biogenesis. Monocrotophos (MCP), a widely used neurotoxic organophosphate, was used as the test compound at sublethal concentration. The conditioned medium (CM) of differentiated PC12 cells comprising of their secretome restored the cell viability, oxidative stress and apoptotic cell death in MCP-challenged human mesenchymal stem cells and SHSY-5Y, a human neuroblastoma cell line. Delving further to identify the underlying mechanism of this restorative effect we observed a marked increase in the expression of autophagy markers LC3, Beclin-1, Atg5 and Atg7. Exposure to autophagy inhibitor, 3-methyladenine, led to a reduced expression of these markers with a concomitant increase in the expression of pro-apoptotic caspase-3. Besides that, the increased mitochondrial fission in MCP-exposed cells was balanced with increased fusion in the presence of CM facilitated by AMPK/SIRT1/PGC-1α signaling cascade. Mitochondrial dysfunctions are strongly associated with autophagy activation and as per our findings, cellular secretome too induces autophagy. Therefore, connecting these three potential apices can be a major breakthrough in repair and rescue of xenobiotic-damaged tissues and cells.

Comparative Proteomic Analysis of Liver Steatosis and Fibrosis after Oral Hepatotoxicant Administration in Sprague-Dawley Rats

The past decade has seen an increase in the development and clinical use of biomarkers associated with histological features of liver disease. Here, we conduct a comparative histological and global proteomics analysis to identify coregulated modules of proteins in the progression of hepatic steatosis or fibrosis. We orally administered the reference chemicals bromobenzene (BB) or 4,4'-methylenedianiline (4,4'-MDA) to male Sprague-Dawley rats for either 1 single administration or 5 consecutive daily doses. Livers were preserved for histopathology and global proteomics assessment. Analysis of liver sections confirmed a dose- and time-dependent increase in frequency and severity of histopathological features indicative of lipid accumulation after BB or fibrosis after 4,4'-MDA. BB administration resulted in a dose-dependent increase in the frequency and severity of inflammation and vacuolation. 4,4'-MDA administration resulted in a dose-dependent increase in the frequency and severity of periportal collagen accumulation and inflammation. Pathway analysis identified a time-dependent enrichment of biological processes associated with steatogenic or fibrogenic initiating events, cellular functions, and toxicological states. Differentially expressed protein modules were consistent with the observed histology, placing physiologically linked protein networks into context of the disease process. This study demonstrates the potential for protein modules to provide mechanistic links between initiating events and histopathological outcomes.

Serum miR-375-3p increase in mice exposed to a high dose of ionizing radiation

Exposure to high-doses of ionizing radiation (IR) leads to development of a strong acute radiation syndrome (ARS) in mammals. ARS manifests after a latency period and it is important to develop fast prognostic biomarkers for its early detection and assessment. Analysis of chromosomal aberrations in peripheral blood lymphocytes is the gold standard of biological dosimetry, but it fails after high doses of IR. Therefore, it is important to establish novel biomarkers of exposure that are fast and reliable also in the high dose range. Here, we investigated the applicability of miRNA levels in mouse serum. We found significantly increased levels of miR-375-3p following whole body exposure to 7 Gy of X-rays. In addition, we analyzed their levels in various organs of control mice and found them to be especially abundant in the pancreas and the intestine. Following a dose of 7 Gy, extensive cell death occurred in these tissues and this correlated negatively with the levels of miR-375-3p in the organs. We conclude that high expressing tissues of miR-375-3p may secrete this miRNA in serum following exposure to 7 Gy. Therefore, elevated miR-375-3p in serum may be a predictor of tissue damage induced by exposure to a high radiation dose.

Current knowledge on exosome biogenesis and release

Exosomes are nanosized membrane vesicles released by fusion of an organelle of the endocytic pathway, the multivesicular body, with the plasma membrane. This process was discovered more than 30 years ago, and during these years, exosomes have gone from being considered as cellular waste disposal to mediate a novel mechanism of cell-to-cell communication. The exponential interest in exosomes experienced during recent years is due to their important roles in health and disease and to their potential clinical application in therapy and diagnosis. However, important aspects of the biology of exosomes remain unknown. To explore the use of exosomes in the clinic, it is essential that the basic molecular mechanisms behind the transport and function of these vesicles are better understood. We have here summarized what is presently known about how exosomes are formed and released by cells. Moreover, other cellular processes related to exosome biogenesis and release, such as autophagy and lysosomal exocytosis are presented. Finally, methodological aspects related to exosome release studies are discussed.

Characterization of extracellular vesicles derived from cardiac cells in an in vitro model of preconditioning

Preconditioning is a promising technique to protect the heart from ischaemia-reperfusion injury. In this context, the crosstalk between different cardiac cell types and especially the exchange of cardioprotective mediators has come into the focus of current research. Recently, extracellular vesicles (EVs), nano-sized structures, emerged as possible communication mediators. They are taken up by recipient cells and can alter gene expression or activate intracellular signal cascades. It has been shown that all cardiac cell types are able to secrete EVs, but so far the influence of an in vitro preconditioning stimulus on EV concentration and composition has not been investigated. Therefore, we stimulated primary cardiac myocytes and fibroblasts from neonatal rats, as well as H9c2 cells, with two known in vitro preconditioning stimuli: hypoxia or isoflurane. EVs were isolated from cell culture supernatants 48 h after stimulation by differential centrifugation and size exclusion chromatography. They were characterized by transmission electron microscopy, tunable resistive pulse sensing, miRNA array and Western blot analysis. The detected EVs had the typical cup-shaped morphology and a size of about 150 nm. No significant differences in EV concentration were observed between the different groups. The protein and miRNA load was affected by in vitro preconditioning with isoflurane or hypoxia. EV markers like Alix, CD63, flotillin-1 and especially heat shock protein 70 were significantly up-regulated by the treatments. Several miRNAs like miR-92b-3p, miR-761 and miR-101a-5p were also significantly affected. A migration assay confirmed the physiological benefit of these EVs. Taken together, our findings show that a model of in vitro preconditioning of cardiac cells does not influence EV concentration but strongly regulates the EV cargo and affects migration. This might indicate a role for EV-mediated communication in isoflurane- and hypoxia-induced in vitro preconditioning.

Comparison and functional characterisation of peripheral blood mononuclear cells isolated from filarial lymphoedema and endemic normals of a South Indian population

OBJECTIVE

The underlying problem in lymphatic filariasis is irreversible swelling of the limbs (lymphoedema), which is a unique feature of lymphatic insufficiency. It is still unclear whether the natural ability of lymphatics to form functional lymphatic vasculature is achieved or attenuated in the lymphoedemal pathology. Clinical studies have clearly shown that circulating lymphatic progenitors (CLPs), a subset of bone marrow-derived mononuclear cells (PBMCs), contribute to post-natal lymph vasculogenesis. CLP-based revascularisation could be a promising strategy to bypass the endothelial disruption and damage incurred by the filarial parasites. Thus our aim was to compare and characterise the functional prowess of PBMCs in physiological and lymphoedemal pathology.

METHODS

PBMCs were isolated from venous blood sample from drug-naive endemic normals (EN) and drug-deprived filarial lymphoedema (FL) individuals using density gradient centrifugation. Adhesion, transwell migration and in vitro matrigel assays were employed to characterise the lymphvasculogenic potential of PBMCs. CLPs were phenotypically characterised using flow cytometry; expression levels of lymphatic markers and inflammatory cytokines were quantified using qRT-PCR and ELISA, respectively.

RESULTS

PBMCs from FL group display poor adherence to fibronectin (P = 0.040), reduced migration towards SDF-1α (P = 0.035), impaired tubular network (P = 0.004) and branching point (P = 0.048) formation. The PBMC mRNA expression of VEGFR3 (P = 0.039) and podoplanin (P = 0.050) was elevated, whereas integrin α9 (P = 0.046) was inhibited in FL individuals; additionally, the surface expression of CD34 (P = 0.048) was significantly reduced in the FL group compared to the EN group.

CONCLUSION

PBMCs from filarial lymphoedema show defective and dysregulated lymphvasculogenic function compared to endemic normals.

Extracellular Vesicles as Biomarkers and Therapeutics in Dermatology: A Focus on Exosomes

Extracellular vesicles (exosomes, microvesicles, and apoptotic bodies) are ubiquitous in human tissues, circulation, and body fluids. Of these vesicles, exosomes are of growing interest among investigators across multiple fields, including dermatology. The characteristics of exosomes, their associated cargo (nucleic acids, proteins, and lipids), and downstream functions are vastly different, depending on the cell origin. Here, we review concepts in extracellular vesicle biology, with a focus on exosomes, highlighting recent studies in the field of dermatology. Furthermore, we highlight emerging technical issues associated with isolating and measuring exosomes. Extracellular vesicles, including exosomes, have immediate potential for serving as biomarkers and therapeutics in dermatology over the next decade.

Safety and tolerability of topically administered autologous, apoptotic PBMC secretome (APOSEC) in dermal wounds: a randomized Phase 1 trial (MARSYAS I)

Developing effective therapies against chronic wound healing deficiencies is a global priority. Thus we evaluated the safety of two different doses of topically administered autologous APOSEC, the secretome of apoptotic peripheral blood mononuclear cells (PBMCs), in healthy male volunteers with artificial dermal wounds. Ten healthy men were enrolled in a single-center, randomized, double-blinded, placebo-controlled phase 1 trial. Two artificial wounds at the upper arm were generated using a 4-mm punch biopsy. Each participant was treated with both topically applied APOSEC and placebo in NuGel for 7 consecutive days. The volunteers were randomized into two groups: a low-dose group (A) receiving the supernatant of 12.5 × 10⁶ PBMCs and a high-dose group (B) receiving an equivalent of 25 × 10⁶ PBMCs resuspended in NuGel Hydrogel. Irradiated medium served as placebo. The primary outcome was the tolerability of the topical application of APOSEC. All adverse events were recorded until 17 days after the biopsy. Local tolerability assessment was measured on a 4-point scale. Secondary outcomes were wound closure and epithelization at day 7. No therapy-related serious adverse events occurred in any of the participants, and both low- and high-dose treatments were well tolerated. Wound closure was not affected by APOSEC therapy.

Exosomes and Exosomal MicroRNAs in Prostate Cancer Radiation Therapy

Despite current risk stratification systems using traditional clinicopathologic factors, many localized and locally advanced prostate cancers fail radical treatment (ie, radical prostatectomy, radiation therapy with or without androgen deprivation therapy). Therefore, a pressing need exists for enhanced methods of disease stratification through novel prognostic and predictive tools that can reliably be applied in clinical practice. Exosomes are 50- to 150-nm small vesicles released by cancer cells that reflect the genetic and nongenetic materials of parent cancer cells. Cancer cells can contain distinct sets of microRNA profiles, the expression of which can change owing to stress such as radiation therapy. These alterations or distinctions in contents allow exosomes to be used as prognostic and/or predictive biomarkers and to monitor the treatment response. Additionally, microRNAs have been shown to influence multiple processes in prostate tumorigenesis, including cell proliferation, induction of apoptosis, migration, oncogene inhibition, and radioresistance. Thus, comparative exosomal microRNA profiling at different levels could help portray tumor aggressiveness and response to radiation therapy. Although technical challenges persist in exosome isolation and characterization, recent improvements in microRNA profiling have evolved toward in-depth analyses of the exosomal cargo and its functions. We have reviewed the role of exosomes and exosomal microRNAs in biologic processes of prostate cancer progression and radiation therapy response, with a particular focus on the development of clinical assays for treatment personalization.

Inflammaging and 'Garb-aging'

'Inflammaging' refers to the chronic, low-grade inflammation that characterizes aging. Inflammaging is macrophage centered, involves several tissues and organs, including the gut microbiota, and is characterized by a complex balance between pro- and anti-inflammatory responses. Based on literature data, we argue that the major source of inflammatory stimuli is represented by endogenous/self, misplaced, or altered molecules resulting from damaged and/or dead cells and organelles (cell debris), recognized by receptors of the innate immune system. While their production is physiological and increases with age, their disposal by the proteasome via autophagy and/or mitophagy progressively declines. This 'autoreactive/autoimmune' process fuels the onset or progression of chronic diseases that can accelerate and propagate the aging process locally and systemically. Consequently, inflammaging can be considered a major target for antiaging strategies.

Ionizing radiation regulates long non-coding RNAs in human peripheral blood mononuclear cells

Long non-coding RNAs (lncRNAs) are non-protein coding transcripts that modulate mRNA and microRNA (miRNA) expression, thereby controlling multiple cellular processes, including transcriptional regulation of gene expression, cell differentiation and apoptosis. Ionizing radiation (IR), a strong cellular stressor, is known to influence gene expression of irradiated cells, mainly by activation of oxidative processes. Whether and how IR also affects lncRNA expression in human peripheral blood mononuclear cells (PBMCs) is still poorly understood. Exposure of PBMCs to IR dose-dependently activated p53 and its downstream target p21, ultimately leading to cell-cycle arrest and/or apoptosis. Cleavage of caspase-3, a specific process during apoptotic cell death, was detectable at doses as low as 30 Gy. Transcriptome analysis of 60 Gy-irradiated PBMCs revealed a strong time-dependent regulation of a variety of lncRNAs. Among many unknown lncRNAs we also identified a significant upregulation of Trp53cor1, MEG3 and TUG1, which have been shown to be involved in the regulation of cell cycle and apoptotic processes mediated by p53. In addition, we found 177 miRNAs regulated in the same samples, including several miRNAs that are known targets of upregulated lncRNAs. Our data show that IR dose-dependently regulates the expression of a wide spectrum of lncRNAs in PBMCs, suggesting a crucial role for lncRNAs in the complex regulatory machinery activated in response to IR.

Peripheral blood mononuclear cell secretome for tissue repair

For almost two decades, cell-based therapies have been tested in modern regenerative medicine to either replace or regenerate human cells, tissues, or organs and restore normal function. Secreted paracrine factors are increasingly accepted to exert beneficial biological effects that promote tissue regeneration. These factors are called the cell secretome and include a variety of proteins, lipids, microRNAs, and extracellular vesicles, such as exosomes and microparticles. The stem cell secretome has most commonly been investigated in pre-clinical settings. However, a growing body of evidence indicates that other cell types, such as peripheral blood mononuclear cells (PBMCs), are capable of releasing significant amounts of biologically active paracrine factors that exert beneficial regenerative effects. The apoptotic PBMC secretome has been successfully used pre-clinically for the treatment of acute myocardial infarction, chronic heart failure, spinal cord injury, stroke, and wound healing. In this review we describe the benefits of choosing PBMCs instead of stem cells in regenerative medicine and characterize the factors released from apoptotic PBMCs. We also discuss pre-clinical studies with apoptotic cell-based therapies and regulatory issues that have to be considered when conducting clinical trials using cell secretome-based products. This should allow the reader to envision PBMC secretome-based therapies as alternatives to all other forms of cell-based therapies.

Dying blood mononuclear cell secretome exerts antimicrobial activity

BACKGROUND

Several activities are attributed to antimicrobial peptides (AMPs), including bacterial killing, leucocyte recruitment and angiogenesis. Despite promises of advanced cellular therapies for treatment of diabetic foot ulcer, it is currently accepted that paracrine factors rather than cellular components are causative for the observed effects. Whether AMPs are present in the mononuclear cell (MNC) secretome (MNC-sec) of white blood cells that are beneficial in experimental wound healing is not known.

MATERIALS AND METHODS

Antimicrobial activity of the secretomes of nonirradiated (MNC-sec) and γ-irradiated MNCs (MNC-sec rad) was analysed by microdilution assay. AMPs were determined by quantitative real-time PCR (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). Whether human MNC-sec rad causes AMP secretion in vivo was examined in an experimental rat model. Image flow cytometry was used to determine the type of cell death induced in MNCs after exposure to γ-radiation.

RESULTS

The antimicrobial activity assay revealed a bactericidal activity of MNC-sec rad and to a lesser degree also of MNC-sec. Image flow cytometry showed that γ-irradiation of MNCs induced early apoptosis followed mainly by necroptosis. RT-PCR and ELISA revealed a high abundance of different AMPs in the secretome of MNCs. In addition, human MNC-sec elicited an increase in de novo endogenous AMP production in rats in vivo.

CONCLUSION

We provide evidence that the secretome of MNCs has direct and indirect positive effects on the immune defence system, including augmentation of antibacterial properties. Our data further suggest that necroptosis could play a key role for the release of paracrine factors and the therapeutic action of MNC-sec rad.

Extracellular Vesicles as New Players in Cellular Senescence

Cell senescence is associated with the secretion of many factors, the so-called "senescence-associated secretory phenotype", which may alter tissue microenvironment, stimulating the organism to clean up senescent cells and replace them with newly divided ones. Therefore, although no longer dividing, these cells are still metabolically active and influence the surrounding tissue. Much attention has been recently focused not only on soluble factors released by senescent cells, but also on extracellular vesicles as conveyors of senescence signals outside the cell. Here, we give an overview of the role of extracellular vesicles in biological processes and signaling pathways related to senescence and aging.

Stem Cell Therapy for the Heart: Blind Alley or Magic Bullet?

When stressed by ageing or disease, the adult human heart is unable to regenerate, leading to scarring and hypertrophy and eventually heart failure. As a result, stem cell therapy has been proposed as an ultimate therapeutic strategy, as stem cells could limit adverse remodelling and give rise to new cardiomyocytes and vasculature. Unfortunately, the results from clinical trials to date have been largely disappointing. In this review, we discuss the current status of the field and describe various limitations and how future work may attempt to resolve these to make way to successful clinical translation.

Defective quorum sensing of acute lymphoblastic leukemic cells: evidence of collective behavior of leukemic populations as semi-autonomous aberrant ecosystems

Quorum sensing (QS) is a generic term used to describe cell-cell communication and collective decision making by bacterial and social insects to regulate the expression of specific genes in controlling cell density and other properties of the populations in response to nutrient supply or changes in the environment. QS mechanisms also have a role in higher organisms in maintaining homeostasis, regulation of the immune system and collective behavior of cancer cell populations. In the present study, we used a p190(BCR-ABL) driven pre-B acute lymphoblastic leukemia (ALL3) cell line derived from the pleural fluid of a terminally ill patient with ALL to test the QS hypothesis in leukemia. ALL3 cells don't grow at low density (LD) in liquid media but grow progressively faster at increasingly high cell densities (HD) in contrast to other established leukemic cell lines that grow well at very low starting cell densities. The ALL3 cells at LD are poised to grow but shortly die without additional stimulation. Supernates of ALL3 cells (HDSN) and some other primary cells grown at HD stimulate the growth of the LD ALL3 cells without which they won't survive. To get further insight into the activation processes we performed microarray analysis of the LD ALL3 cells after stimulation with ALL3 HDSN at days 1, 3, and 6. This screen identified several candidate genes, and we linked them to signaling networks and their functions. We observed that genes involved in lipid, cholesterol, fatty acid metabolism, and B cell activation are most up- or down-regulated upon stimulation of the LD ALL3 cells using HDSN. We also discuss other pathways that are differentially expressed upon stimulation of the LD ALL3 cells. Our findings suggest that the Ph+ ALL population achieves dominance by functioning as a collective aberrant ecosystem subject to defective quorum-sensing regulatory mechanisms.

Paracrine Factors from Irradiated Peripheral Blood Mononuclear Cells Improve Skin Regeneration and Angiogenesis in a Porcine Burn Model

Burn wounds pose a serious threat to patients and often require surgical treatment. Skin grafting aims to achieve wound closure but requires a well-vascularized wound bed. The secretome of peripheral blood mononuclear cells (PBMCs) has been shown to improve wound healing and angiogenesis. We hypothesized that topical application of the PBMC secretome would improve the quality of regenerating skin, increase angiogenesis, and reduce scar formation after burn injury and skin grafting in a porcine model. Full-thickness burn injuries were created on the back of female pigs. Necrotic areas were excised and the wounds were covered with split-thickness mesh skin grafts. Wounds were treated repeatedly with either the secretome of cultured PBMCs (Sec(PBMC)), apoptotic PBMCs (Apo-Sec(PBMC)), or controls. The wounds treated with Apo-Sec(PBMC) had an increased epidermal thickness, higher number of rete ridges, and more advanced epidermal differentiation than controls. The samples treated with Apo-Sec(PBMC) had a two-fold increase in CD31+ cells, indicating more angiogenesis. These data suggest that the repeated application of Apo-Sec(PBMC) significantly improves epidermal thickness, angiogenesis, and skin quality in a porcine model of burn injury and skin grafting.

Concise Review: Apoptotic Cell-Based Therapies-Rationale, Preclinical Results and Future Clinical Developments

The objectives of this review are to summarize the experimental data obtained using apoptotic cell-based therapies, and then to discuss future clinical developments. Indeed, apoptotic cells exhibit immunomodulatory properties that are reviewed here by focusing on more recent mechanisms. These immunomodulatory mechanisms are in particular linked to the clearance of apoptotic cells (called also efferocytosis) by phagocytes, such as macrophages, and the induction of regulatory T cells. Thus, apoptotic cell-based therapies have been used to prevent or treat experimental inflammatory diseases. Based on these studies, we have identified critical steps to design future clinical trials. This includes: the administration route, the number and schedule of administration, the appropriate apoptotic cell type to be used, as well as the apoptotic signal. We also have analyzed the clinical relevancy of apoptotic-cell-based therapies in experimental models. Additional experimental data are required concerning the treatment of inflammatory diseases (excepted for sepsis) before considering future clinical trials. In contrast, apoptotic cells have been shown to favor engraftment and to reduce acute graft-versus-host disease (GvHD) in different relevant models of transplantation. This has led to the conduct of a phase 1/2a clinical trial to alleviate GvHD. The absence of toxic effects obtained in this trial may support the development of other clinical studies based on this new cell therapy. Stem Cells 2016;34:1464-1473.