Mesenchymal stem cell transplantation is undergoing extensive evaluation as a cellular therapy in human clinical trials. Because MSCs are easily isolated and amenable to culture expansion in vitro there is a natural desire to test MSCs in many diverse clinical indications. This is exemplified by the rapidly expanding literature base that includes many in vivo animal models. More recently, MSC-derived extracellular vesicles (EVs), which include exosomes and microvesicles (MV), are being examined for their role in MSC-based cellular therapy. These vesicles are involved in cell-to-cell communication, cell signaling, and altering cell or tissue metabolism at short or long distances in the body. The exosomes and MVs can influence tissue responses to injury, infection, and disease. MSC-derived exosomes have a content that includes cytokines and growth factors, signaling lipids, mRNAs, and regulatory miRNAs. To the extent that MSC exosomes can be used for cell-free regenerative medicine, much will depend on the quality, reproducibility, and potency of their production, in the same manner that these parameters dictate the development of cell-based MSC therapies. However, the MSC exosome's contents are not static, but rather a product of the MSC tissue origin, its activities and the immediate intercellular neighbors of the MSCs. As such, the exosome content produced by MSCs appears to be altered when MSCs are cultured with tumor cells or in the in vivo tumor microenvironment. Therefore, careful attention to detail in producing MSC exosomes may provide a new therapeutic paradigm for cell-free MSC-based therapies with decreased risk. Stem Cells 2017;35:851-858.

https://stemcellsjournals.onlinelibrary.wiley.com/doi/epdf/10.1002/stem.2575

Concise Review: MSC-Derived Exosomes for Cell-Free Therapy

Rationale: Chronic nonhealing diabetic wound therapy and complete skin regeneration remains a critical clinical challenge. The controlled release of bioactive factors from a multifunctional hydrogel was a promising strategy to repair chronic wounds. Methods: Herein, for the first time, we developed an injectable, self-healing and antibacterial polypeptide-based FHE hydrogel (F127/OHA-EPL) with stimuli-responsive adipose-derived mesenchymal stem cells exosomes (AMSCs-exo) release for synergistically enhancing chronic wound healing and complete skin regeneration. The materials characterization, antibacterial activity, stimulated cellular behavior and in vivo full-thickness diabetic wound healing ability of the hydrogels were performed and analyzed. Results: The FHE hydrogel possessed multifunctional properties including fast self-healing process, shear-thinning injectable ability, efficient antibacterial activity, and long term pH-responsive bioactive exosomes release behavior. In vitro, the FHE@exosomes (FHE@exo) hydrogel significantly promoted the proliferation, migration and tube formation ability of human umbilical vein endothelial cells (HUVECs). In vivo, the FHE@exo hydrogel significantly enhanced the healing efficiency of diabetic full-thickness cutaneous wounds, characterized with enhanced wound closure rates, fast angiogenesis, re-epithelization and collagen deposition within the wound site. Moreover, the FHE@exo hydrogel displayed better healing outcomes than those of exosomes or FHE hydrogel alone, suggesting that the sustained release of exosomes and FHE hydrogel can synergistically facilitate diabetic wound healing. Skin appendages and less scar tissue also appeared in FHE@exo hydrogel treated wounds, indicating its potent ability to achieve complete skin regeneration. Conclusion: This work offers a new approach for repairing chronic wounds completely through a multifunctional hydrogel with controlled exosomes release.

Engineering Bioactive Self-Healing Antibacterial Exosomes Hydrogel for Promoting Chronic Diabetic Wound Healing and Complete Skin Regeneration.

Exosomes, extracellular vesicles with diameters ranging from 30 to 150 nm, are widely present in various body fluids. Recently, microRNAs (miRNAs) have been identified in exosomes, the biogenesis, release, and uptake of which may involve the endosomal sorting complex required for transport (ESCRT complex) and relevant proteins. After release, exosomes are taken up by neighboring or distant cells, and the miRNAs contained within modulate such processes as interfering with tumor immunity and the microenvironment, possibly facilitating tumor growth, invasion, metastasis, angiogenesis and drug resistance. Therefore, exosomal miRNAs have a significant function in regulating cancer progression. Here, we briefly review recent findings regarding tumor-derived exosomes, including RNA sorting and delivering mechanism. We then describe the intercommunication occurring between different cells via exosomal miRNAs in tumor microenvironmnt, with impacts on tumor proliferation, vascularization, metastasis and other biological characteristics. Finally, we highlight the potential role of these molecules as biomarkers in cancer diagnosis and prognosis and tumor resistance to therapeutics.

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Effect of exosomal miRNA on cancer biology and clinical applications.

During the past decade, extracellular vesicles (EVs), which include apoptotic bodies, microvesicles, and exosomes, have emerged as important players in cell-to-cell communication in normal physiology and pathological conditions. EVs encapsulate and convey various bioactive molecules that are further transmitted to neighboring or more distant cells, where they induce various signaling cascades. The message delivered to the target cells is dependent on EV composition, which, in turn, is determined by the cell of origin and the surrounding microenvironment during EV biogenesis. Among their multifaceted role in the modulation of biological responses, the involvement of EVs in vascular development, growth, and maturation has been widely documented and their potential therapeutic application in regenerative medicine or angiogenesis-related diseases is drawing increasing interest. EVs derived from various cell types have the potential to deliver complex information to endothelial cells and to induce either pro- or antiangiogenic signaling. As dynamic systems, in response to changes in the microenvironment, EVs adapt their cargo composition to fine-tune the process of blood vessel formation. This article reviews the current knowledge on the role of microvesicles and exosomes from various cellular origins in angiogenesis, with a particular emphasis on the underlying mechanisms, and discusses the main challenges and prerequisites for their therapeutic applications.

Extracellular Vesicles in Angiogenesis.

Exosomes are nano-sized small extracellular vesicles secreted by cells, carrying nucleic acids, proteins, lipids and other bioactive substances to play a role in the body's physiological and pathological processes. Compared to synthetic carriers such as liposomes and nanoparticles, the endogeneity and heterogeneity of exosomes give them extensive and unique advantages in the field of disease diagnosis and treatment. However, the storage stability, low yield, low purity, and weak targeting of exosomes limit its clinical application. For this reason, further exploration is needed to optimize the above problems and facilitate future functional studies of exosomes. In this paper, the origin, classification, preparation and characterization, storage stability and applications of exosome delivery system are summarized and discussed by searching a large number of literatures.

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Exosome: A Review of Its Classification, Isolation Techniques, Storage, Diagnostic and Targeted Therapy Applications

Angiogenesis plays crucial roles in various physiological processes including wound healing and tissue repair. It requires a tight interaction between endothelial cells and their surrounding environment. Mesenchymal stem cells (MSCs), one of the non-endothelial cell types present in the perivascular environment, have been shown to secret exosomes to modulate intercellular communications between MSCs and their target cells. In this study, we initially isolated exosomes secreted by human adipose-derived MSCs (adMSC-Exo) and examined their roles in angiogenesis. We found that adMSC-Exo could be taken up by endothelial cells and significantly promote angiogenesis in vitro and in vivo Further study showed that miR-125a was enriched in adMSC-Exo, and repressed the expression of the angiogenic inhibitor delta-like 4 (DLL4) by targeting its 3' untranslated region. Additionally, adMSC-Exo and its exosomal transferred miR-125a could repress DLL4 expression and modulate endothelial cell angiogenesis through promoting formation of endothelial tip cells. In conclusion, our study indicates that adMSC-Exo can transfer miR-125a to endothelial cells and promote angiogenesis by repressing DLL4. adMSC-Exo, as a pro-angiogenic factor, might be a promising candidate for therapeutical tissue repair.

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Exosomes secreted by mesenchymal stem cells promote endothelial cell angiogenesis by transferring miR-125a

Podocyte depletion is a key event in the progression of end-stage kidney disease (ESKD) resulting in nephrotic proteinuria and renal failure, but the treatment options are limited to dialysis and renal transplantation. So there is an urgent need for renal regenerative therapies. Generation of podocytes from human stem cells is regarded as a promising therapeutic strategy to repair or regenerate the damaged kidneys; however, the reliable induction system remains a challenge. In this study, we established a two-stage induction protocol for podocyte generation from human adipose-derived mesenchymal stem cells (hAD-MSCs). We initially established a condition that induces hAD-MSCs toward intermediate mesoderm cells with activin A and high concentration of retinoic acid (RA). Subsequently, by using the combination of activin A and low concentration of RA and BMP7, we generated podocyte-like cells expressing multiple podocyte-specific markers and able to integrate into a developing nephron of embryonic kidney explant culture and ameliorate proteinuria and kidney injure in adriamycin-treated mice. Furthermore, we identified that miRNA-498 inhibitor has potential to improve the differentiation of hAD-MSCs into podocyte-like cells and established a robust induction protocol. Thereby, our study advocated an efficient method for the induction of kidney podocyte-like (iPod) cells from hAD-MSCs and provided an ideal candidate for regenerative therapies of the kidney.

MicroRNA-498 Inhibition Enhances the Differentiation of Human Adipose-Derived Mesenchymal Stem Cells into Podocyte-Like Cells

AIMS
This study aimed to explore the mechanism of ferroptosis (an iron-dependent form of nonapoptotic cell death) resistance in senescent chondrocytes.


RESULTS
In this study, by utilizing metabolomics and single-cell RNA sequencing, we found that hyperactivation of ferroptosis metabolism was one of the most prominent metabolic features in Senescent chondrocytes (SenChos). Interestingly, however, SenChos were able to survive in this state and were resistant to ferroptosis induced cell death. Next, we elucidated that this survival mechanism of SenChos could be primarily attributed to overexpression of the membrane protein excitatory amino acid transporter protein 1 (EAAT1), which can increase intracellular glutamate levels and activate the glutathione system to counteract ferroptosis. In addition, UCPH-101 (a specific inhibitor of EAAT1) and siRNA-EAAT1 were able to substantially increase the sensitivity of SenChos to ferroptosis and to induce cell death, with no apparent effects on the normal cells. Administration of intra-articular injection of UCPH-101, caused inhibition of EAAT1 selectively, cleared SenChos from cartilage, improved the cartilage homeostasis and significantly delayed the progression of OA.


INNOVATION
This work supports a relevant role for EAAT1 in ferroptosis resistance mechanism for SenChos, revealing a potential OA therapeutic target.


CONCLUSIONS
EAAT1-glutamate-GPX4 anti-ferroptosis axis is a key survival mechanism for SenChos and EAAT1 is an effective and specific target for anti-senescence therapy in OA.

Selective clearance of senescent chondrocytes in osteoarthritis by targeting EAAT1 to induce ferroptosis.

Background Osteosarcoma remains to be the most devastating malignant tumor in children and teenagers. Mitochondria have also been proven to play critical roles in osteosarcoma. However, a mitochondria-related signature has been established in osteosarcoma to comprehensively evaluate the pathogenic roles and regulatory roles of mitochondria in osteosarcoma. Methods In this study, osteosarcoma samples' transcriptome data and clinical information were collected from Therapeutically Applicable Research to Generate Effective Treatments (TARGET) and Gene Expression Omnibus (GEO) databases. A comprehensive bioinformatics analysis was performed on the samples at the bulk RNA sequencing level and single-cell RNA sequencing (scRNA-seq) level. EdU, Transwell, and immunohistochemistry (IHC) were performed on PCCB. Results A mitochondria-related signature was constructed in osteosarcoma patients. The prognostic value of the mitochondria-related signature was explored. The predictive value of the mitochondria-related signature in the immune microenvironment and chemotherapy agents was explored. The association between mitochondria and immunity in the tumor microenvironment of osteosarcoma at the scRNA-seq level was investigated. The tumorigenic role of the critical mitochondria-related gene, PCCB, was verified by in vitro validation. Conclusion In conclusion, a mitochondria-related signature was developed in osteosarcoma with solid predictive values in the immune microenvironment, chemotherapy agents, and prognosis.

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A mitochondria-related signature for predicting immune microenvironment and therapeutic response in osteosarcoma

Background The role of ferroptosis in tumor progression and immune microenvironment is extensively investigated. However, the potential value of ferroptosis regulators in predicting prognosis and therapeutic strategies for osteosarcoma (OS) patients remains to be elucidated. Methods Here, we extracted transcriptomic and survival data from Therapeutically Applicable Research to Generate Effective Treatments (TARGET) and Gene Expression Omnibus (GEO) to investigate the expression and prognostic value of ferroptosis regulators in OS patients. After comprehensive analyses, including Gene set variation analysis (GSVA), single-sample gene-set enrichment analysis (ssGSEA), Estimated Stromal and Immune cells in Malignant Tumor tissues using Expression (ESTIMATE), single-cell RNA sequencing, and biological experiments, our constructed 8-ferroptosis-regulators prognostic signature effectively predicted the immune landscape, prognosis, and chemoradiotherapy strategies for OS patients. Results We constructed an 8-ferroptosis-regulators signature that could predict the survival outcome of OS. The signature algorithm scored samples, and high-scoring patients were more prone to worse prognoses. The tumor immune landscape suggested the positive relevance between risk score and immunosuppression. Interfering HILPDA and MUC1 expression would inhibit tumor cell proliferation and migration, and MUC1 might improve the ferroptosis resistance of OS cells. Moreover, we predicted chemoradiotherapy strategies of cancer patients following ferroptosis-risk-score groups. Conclusion Dysregulated ferroptosis gene expression can affect OS progression by affecting the tumor immune landscape and ferroptosis resistance. Our risk model can predict OS survival outcomes, and we propose that HILPDA and MUC1 are potential targets for cancer therapy.

https://www.frontiersin.org/articles/10.3389/fonc.2022.1024915/pdf

Lina Zhang

Papers

Exosomes secreted by mesenchymal stem cells promote endothelial cell angiogenesis by transferring miR-125a

MicroRNA-498 Inhibition Enhances the Differentiation of Human Adipose-Derived Mesenchymal Stem Cells into Podocyte-Like Cells

Selective clearance of senescent chondrocytes in osteoarthritis by targeting EAAT1 to induce ferroptosis.

A mitochondria-related signature for predicting immune microenvironment and therapeutic response in osteosarcoma

A ferroptosis-related gene signature associated with immune landscape and therapeutic response in osteosarcoma