Three-dimensional-cultured MSC-derived exosome with hydrogel for cerebral ischemia repair

Hydrogel-exosome system in tissue engineering: A promising therapeutic strategy

Characterized by their pivotal roles in cell-to-cell communication, cell proliferation, and immune regulation during tissue repair, exosomes have emerged as a promising avenue for "cell-free therapy" in clinical applications. Hydrogels, possessing commendable biocompatibility, degradability, adjustability, and physical properties akin to biological tissues, have also found extensive utility in tissue engineering and regenerative repair. The synergistic combination of exosomes and hydrogels holds the potential not only to enhance the efficiency of exosomes but also to collaboratively advance the tissue repair process. This review has summarized the advancements made over the past decade in the research of hydrogel-exosome systems for regenerating various tissues including skin, bone, cartilage, nerves and tendons, with a focus on the methods for encapsulating and releasing exosomes within the hydrogels. It has also critically examined the gaps and limitations in current research, whilst proposed future directions and potential applications of this innovative approach.

Advancing stroke therapy: innovative approaches with stem cell-derived extracellular vesicles

Stroke is a leading cause of mortality and long-term disability globally, with acute ischemic stroke (AIS) being the most common subtype. Despite significant advances in reperfusion therapies, their limited time window and associated risks underscore the necessity for novel treatment strategies. Stem cell-derived extracellular vesicles (EVs) have emerged as a promising therapeutic approach due to their ability to modulate the post-stroke microenvironment and facilitate neuroprotection and neurorestoration. This review synthesizes current research on the therapeutic potential of stem cell-derived EVs in AIS, focusing on their origin, biogenesis, mechanisms of action, and strategies for enhancing their targeting capacity and therapeutic efficacy. Additionally, we explore innovative combination therapies and discuss both the challenges and prospects of EV-based treatments. Our findings reveal that stem cell-derived EVs exhibit diverse therapeutic effects in AIS, such as promoting neuronal survival, diminishing neuroinflammation, protecting the blood-brain barrier, and enhancing angiogenesis and neurogenesis. Various strategies, including targeting modifications and cargo modifications, have been developed to improve the efficacy of EVs. Combining EVs with other treatments, such as reperfusion therapy, stem cell transplantation, nanomedicine, and gut microbiome modulation, holds great promise for improving stroke outcomes. However, challenges such as the heterogeneity of EVs and the need for standardized protocols for EV production and quality control remain to be addressed. Stem cell-derived EVs represent a novel therapeutic avenue for AIS, offering the potential to address the limitations of current treatments. Further research is needed to optimize EV-based therapies and translate their benefits to clinical practice, with an emphasis on ensuring safety, overcoming regulatory hurdles, and enhancing the specificity and efficacy of EV delivery to target tissues.

Direct and cell-mediated EV-ECM interplay

Extracellular vesicles (EV) are a heterogeneous group of lipid particles excreted by cells. They play an important role in regeneration, development, inflammation, and cancer progression, together with the extracellular matrix (ECM), which they constantly interact with. In this review, we discuss direct and indirect interactions of EVs and the ECM and their impact on different physiological processes. The ECM affects the secretion of EVs, and the properties of the ECM and EVs modulate EVs' diffusion and adhesion. On the other hand, EVs can affect the ECM both directly through enzymes and indirectly through the modulation of the ECM synthesis and remodeling by cells. This review emphasizes recently discovered types of EVs bound to the ECM and isolated by enzymatic digestion, including matrix-bound nanovesicles (MBV) and tissue-derived EV (TiEV). In addition to the experimental studies, computer models of the EV-ECM-cell interactions, from all-atom models to quantitative pharmacology models aiming to improve our understanding of the interaction mechanisms, are also considered. STATEMENT OF SIGNIFICANCE: Application of extracellular vesicles in tissue engineering is an actively developing area. Vesicles not only affect cells themselves but also interact with the matrix and change it. The matrix also influences both cells and vesicles. In this review, different possible types of interactions between vesicles, matrix, and cells are discussed. Furthermore, the united EV-ECM system and its regulation through the cellular activity are presented.

REVIEW: "ISCHEMIC STROKE: From Fibrinolysis to Functional Recovery" Nanomedicine: emerging approaches to treat ischemic stroke

Stroke is responsible for 11% of all deaths worldwide, the majority of which are caused by ischemic strokes, thus making the need to urgently find safe and effective therapies. Today, these can be cured either by mechanical thrombectomy when the thrombus is accessible, or by intravenous injection of fibrinolytics. However, the latter present several limitations, such as potential severe side effects, few eligible patients and low rate of partial and full recovery. To design safer and more effective treatments, nanomedicine appeared in this medical field a few decades ago. This review will explain why nanoparticle-based therapies and imaging techniques are relevant for ischemic stroke management. Then, it will present the different nanoparticle types that have been recently developed to treat this pathology. It will also study the various targeting strategies used to bring nanoparticles to the stroke site, thereby limiting side effects and improving the therapeutic efficacy. Finally, this review will present the few clinical studies testing nanomedicine on stroke and discuss potential causes for their scarcity.

Ultra-low content physio-chemically crosslinked gelatin hydrogel improves encapsulated 3D cell culture

Gelatin-based hydrogels are extensively used for 3D cell culture, bioprinting, and tissue engineering due to their cell-adhesive nature and tunable physio-chemical properties. Gelatin hydrogels for 3D cell culture are often developed using high-gelatin content (frequently 10-15 % w/v) to ensure fast gelation and improved stability. While highly stable, such matrices restrict the growth of encapsulated cells due to creating a dense, restrictive environment around the encapsulated cells. Hydrogels with lower polymer content are known to improve 3D cell growth, yet fabrication of ultra-low concentration gelatin hydrogels is challenging while ensuring fast gelation and stability. Here, we demonstrate that physical gelation and photo-crosslinking in gelatin results in a fast-gelling hydrogel at a remarkably low gelatin concentration of 1 % w/v (GelPhy/Photo). The GelPhy/Photo hydrogel was highly stable, allowed uniform 3D distribution of cells, and significantly improved the spreading of encapsulated 3T3 fibroblast cells. Moreover, human cholangiocarcinoma (HuCCT-1) cells encapsulated in 1 % GelPhy/Photo matrix grew and self-assembled into epithelial cysts with lumen, which could not be achieved in a traditional high-concentration gelatin hydrogel. These findings pave the way to significantly improve existing gelatin hydrogels for 3D cell culture applications.

Priming and Combined Strategies for the Application of Mesenchymal Stem Cells in Ischemic Stroke: A Promising Approach

Ischemic stroke (IS) is a leading cause of death and disability worldwide. Tissue plasminogen activator (tPA) administration and mechanical thrombectomy are the main treatments but have a narrow time window. Mesenchymal stem cells (MSCs), which are easily scalable in vitro and lack ethical concerns, possess the potential to differentiate into various types of cells and secrete a great number of growth factors for neuroprotection and regeneration. Moreover, MSCs have low immunogenicity and tumorigenic properties, showing safety and preliminary efficacy both in preclinical studies and clinical trials of IS. However, it is unlikely that MSC treatment alone will be sufficient to maximize recovery due to the low survival rate of transplanted cells and various mechanisms of ischemic brain damage in the different stages of IS. Preconditioning was used to facilitate the homing, survival, and secretion ability of the grafted MSCs in the ischemic region, while combination therapies are alternatives that can maximize the treatment effects, focusing on multiple therapeutic targets to promote stroke recovery. In this case, the combination therapy can yield a synergistic effect. In this review, we summarize the type of MSCs, preconditioning methods, and combined strategies as well as their therapeutic mechanism in the treatment of IS to accelerate the transformation from basic research to clinical application.

cGAS Deficiency Regulates the Phenotypic Polarization and Glycolysis of Microglia Through Lactylation in Hypoxic-Ischemic Encephalopathy Cell Model

Promoting the M2 phenotype polarization of microglia is of great significance in alleviating hypoxic-ischemic encephalopathy (HIE). The umbilical artery blood sample was collected to evaluate the expression of cGAS, and the aberrant expressed cGAS was verified in the oxygen glucose deprivation (OGD) microglia which was established to mimic HIE in vitro. Then the regulating role of cGAS on the transformation of microglia M2 phenotype polarization and glycolysis was investigated. Moreover, the lactylation of cGAS in OGD treated microglia was evaluated by western blot. cGAS was found to be highly expressed in umbilical artery blood of HIE group, and OGD treated microglia. OGD interference activated microglia into M1 phenotype by enhancing CD86 and suppressing CD206 levels; meanwhile, the microglia in OGD group highly expressed IL-1β, iNOS and TNF-α, and lowly expressed IL-4, IL-10, and Arg-1. Inhibition of cGAS promotes the transformation of microglia from M1 to M2 phenotype. Meanwhile, OGD increased ECAR and decreased OCR to regulate glycolysis, cGAS deficiency inhibits glycolysis in OGD treated microglia. Moreover, the pan lysine lactylation (Pan-Kla) levels and lactated cGAS levels in microglia were upregulated in the OGD group. Lactate reversed the effects of cGAS knockdown on microglia polarization and glycolysis. The present study reveals that the cGAS-mediated neuron injury is associated with high level of cGAS lactylation. Inhibition of cGAS promotes the M2 phenotype polarization of microglia and suppress glycolysis. Thereby, targeting cGAS provides a new strategy for the development of therapeutic agents against HIE.

Hydrogel-encapsulated extracellular vesicles for the regeneration of spinal cord injury

Spinal cord injury (SCI) is a critical neurological condition that may impair motor, sensory, and autonomous functions. At the cellular level, inflammation, impairment of axonal regeneration, and neuronal death are responsible for SCI-related complications. Regarding the high mortality and morbidity rates associated with SCI, there is a need for effective treatment. Despite advances in SCI repair, an optimal treatment for complete recovery after SCI has not been found so far. Therefore, an effective strategy is needed to promote neuronal regeneration and repair after SCI. In recent years, regenerative treatments have become a potential option for achieving improved functional recovery after SCI by promoting the growth of new neurons, protecting surviving neurons, and preventing additional damage to the spinal cord. Transplantation of cells and cells-derived extracellular vesicles (EVs) can be effective for SCI recovery. However, there are some limitations and challenges related to cell-based strategies. Ethical concerns and limited efficacy due to the low survival rate, immune rejection, and tumor formation are limitations of cell-based therapies. Using EVs is a helpful strategy to overcome these limitations. It should be considered that short half-life, poor accumulation, rapid clearance, and difficulty in targeting specific tissues are limitations of EVs-based therapies. Hydrogel-encapsulated exosomes have overcome these limitations by enhancing the efficacy of exosomes through maintaining their bioactivity, protecting EVs from rapid clearance, and facilitating the sustained release of EVs at the target site. These hydrogel-encapsulated EVs can promote neuroregeneration through improving functional recovery, reducing inflammation, and enhancing neuronal regeneration after SCI. This review aims to provide an overview of the current research status, challenges, and future clinical opportunities of hydrogel-encapsulated EVs in the treatment of SCI.

Engineered Extracellular Vesicles: A potential treatment for regeneration

Extracellular vesicles (EVs) play a critical role in various physiological and pathological processes. EVs have gained recognition in regenerative medicine due to their biocompatibility and low immunogenicity. However, the practical application of EVs faces challenges such as limited targeting ability, low yield, and inadequate therapeutic effects. To overcome these limitations, engineered EVs have emerged. This review aims to comprehensively analyze the engineering methods utilized for modifying donor cells and EVs, with a focus on comparing the therapeutic potential between engineered and natural EVs. Additionally, it aims to investigate the specific cell effects that play a crucial role in promoting repair and regeneration, while also exploring the underlying mechanisms involved in the field of regenerative medicine.

Synergistic Therapeutic Potential of Dual 3D Mesenchymal Stem Cell Therapy in an Ischemic Hind Limb Mouse Model

Three-dimensional (3D) culture systems have been widely used to promote the viability and metabolic activity of mesenchymal stem cells (MSCs). The aim of this study was to explore the synergistic benefits of using dual 3D MSC culture systems to promote vascular regeneration and enhance therapeutic potential. We used various experimental assays, including dual 3D cultures of human adipose MSCs (hASCs), quantitative reverse transcription polymerase chain reaction (qRT-PCR), in vitro cell migration, Matrigel tube network formation, Matrigel plug assay, therapeutic assays using an ischemic hind limb mouse model, and immunohistochemical analysis. Our qRT-PCR results revealed that fibroblast growth factor 2 (FGF-2), granulocyte chemotactic protein-2 (GCP-2), and vascular endothelial growth factor-A (VEGF-A) were highly upregulated in conventional 3D-cultured hASCs (ASC-3D) than in two-dimensional (2D)-cultured hASCs. Hepatocyte growth factor (HGF), insulin-like growth factor-1 (IGF-1), and stromal-cell-derived factor-1 (SDF-1) showed higher expression levels in cytokine-cocktail-based, 3D-cultured hASCs (ASC-3Dc). A conditioned medium (CM) mixture of dual 3D ASCs (D-3D; ASC-3D + ASC-3Dc) resulted in higher migration and Matrigel tube formation than the CM of single 3D ASCs (S-3D; ASC-3D). Matrigel plugs containing D-3D contained more red blood cells than those containing S-3D. D-3D transplantation into ischemic mouse hind limbs prevented limb loss and augmented blood perfusion when compared to S-3D transplantation. Transplanted D-3D also revealed a high capillary density and angiogenic cytokine levels and transdifferentiated into endothelial-like cells in the hind limb muscle. These findings highlight the benefits of using the dual 3D culture system to optimize stem-cell-based therapeutic strategies, thereby advancing the therapeutic strategy for ischemic vascular disease and tissue regeneration.

Exosomal miR-17-92 derived from human mesenchymal stem cells promotes wound healing by enhancing angiogenesis and inhibiting endothelial cell ferroptosis

BACKGROUND

Wound healing is a complex and dynamic process that involves a series of cellular and molecular events. Mesenchymal stem cells (MSCs) and their exosomes (MSC-Exos) have crucial functions in cutaneous wound healing. MiR-17-92 is a multifunctional microRNA (miRNA) cluster that plays vital roles in tissue development and tumor angiogenesis. This study aimed to explore the function of miR-17.92 in wound healing as a component of MSC-Exos.

METHODS

Human MSCs were cultured in serum-free medium, and exosomes were collected by ultracentrifugation. The levels of miR-17-92 in MSCs and MSC-Exos were determined by quantitative real-time polymerase chain reaction. MSC-Exos were topically applied to full-thickness excision wounds in the skin of miR-17-92 knockout (KO) and wild-type (WT) mice. The proangiogenic and antiferroptotic effects of MSC-Exos overexpressing miR-17-92 were assayed by evaluating the relative levels of angiogenic and ferroptotic markers.

RESULTS

MiRNA-17-92 was found to be highly expressed in MSCs and enriched in MSC-Exos. Moreover, MSC-Exos promoted the proliferation and migration of human umbilical vein endothelial cells in vitro. KO of miR-17-92 effectively attenuated the promotion of wound healing by MSC-Exos. Furthermore, exosomes derived from miR-17-92-overexpressing human umbilical cord-derived MSCs accelerated cell proliferation, migration, angiogenesis, and enhanced against erastin-induced ferroptosis in vitro. miR-17-92 plays a key role in the protective effects of MSC-Exos against erastin-induced ferroptosis in HUVECs CONCLUSION: These findings suggest that miR-17-92 participates in the repair ability of MSC-Exos and that miR-17-92-overexpressing exosomes may represent a new strategy for cutaneous wound repair.

Various Three-Dimensional Culture Methods and Cell Types for Exosome Production

Cell-based therapies have been used as promising treatments for several untreatable diseases. However, cell-based therapies have side effects such as tumorigenesis and immune responses. To overcome these side effects, therapeutic effects of exosomes have been researched as replacements for cell-based therapies. In addition, exosomes reduced the risk that can be induced by cell-based therapies. Exosomes contain biomolecules such as proteins, lipids, and nucleic acids that play an essential role in cell-cell and cell-matrix interactions during biological processes. Since the introduction of exosomes, those have been proven perpetually as one of the most effective and therapeutic methods for incurable diseases. Much research has been conducted to enhance the properties of exosomes, including immune regulation, tissue repair, and regeneration. However, yield rate of exosomes is the critical obstacle that should be overcome for practical cell-free therapy. Three-dimensional (3D) culture methods are introduced as a breakthrough to get higher production yields of exosomes. For example, hanging drop and microwell were well known 3D culture methods and easy to use without invasiveness. However, these methods have limitation in mass production of exosomes. Therefore, a scaffold, spinner flask, and fiber bioreactor were introduced for mass production of exosomes isolated from various cell types. Furthermore, exosomes treatments derived from 3D cultured cells showed enhanced cell proliferation, angiogenesis, and immunosuppressive properties. This review provides therapeutic applications of exosomes using 3D culture methods.

The Role of Mesenchymal Stromal Cells and Their Products in the Treatment of Injured Spinal Cords

Spinal cord injury (SCI) is a destructive condition that results in lasting neurological damage resulting in disruption of the connection between the central nervous system and the rest of the body. Currently, there are several approaches in the treatment of a damaged spinal cord; however, none of the methods allow the patient to return to the original full-featured state of life before the injury. Cell transplantation therapies show great potential in the treatment of damaged spinal cords. The most examined type of cells used in SCI research are mesenchymal stromal cells (MSCs). These cells are at the center of interest of scientists because of their unique properties. MSCs regenerate the injured tissue in two ways: (i) they are able to differentiate into some types of cells and so can replace the cells of injured tissue and (ii) they regenerate tissue through their powerful known paracrine effect. This review presents information about SCI and the treatments usually used, aiming at cell therapy using MSCs and their products, among which active biomolecules and extracellular vesicles predominate.