Controversies in therapeutic application of mesenchymal stem cell-derived secretome

Though mesenchymal stem cells (MSCs) are considered as an important pillar of regenerative medicine, their regenerative potential has been shown to be limited in several pathological conditions. The adverse properties of MSC-based cell therapy have drawn attention to the therapeutic use of MSC-derived secretome. However, MSC-originated exosomes and microvesicles can also possess a significant impact on disease development, including cancer. By interchanging secretome, MSCs can interact with tumor cells and promote mutual exchange/induction of cellular markers. In addition, enzymes secreted into and activated within exosomes can result in the acquisition of new tumor cell properties. Therefore, therapeutic applications of MSC-derived secretome require much caution.     

Mesenchymal stem cells,secretome and biomaterials in <i>in-vivo</i> animal models: Regenerative medicine application in cutaneous wound healing

The treatment of nonhealing and chronic cutaneous wounds still needs a clinical advancement to be effective. Both mesenchymal stem cells (MSCs), obtained from different sources, and their secretome derived thereof (especially exosomes) can activate signaling pathways related to promotion of cell migration, vascularization, collagen deposition, and inflammatory response demonstrating prohealing, angiogenetic and anti-scarring capacities. On the other hand, biodegradable biomimetic scaffolds can facilitate endogenous cell attachment and proliferation as well as extracellular matrix production. In this Review, we revise the complex composites made by biomimetic scaffolds, mainly hydrogels, and MSC-derived exosomes constructed for cutaneous wound healing. Studies demonstrate that there exists a synergistic action of scaffolds with encapsulated exosomes, displaying a sustained release profiles to facilitate longlasting healing effects. It can be envisioned that dressings made by biomimetic hydrogels and MSC-derived exosomes will be clinically applied in the near future for the effective treatment of nonhealing and chronic wounds.     

Mesenchymal stem cells-derived extracellular vesicles as ‘natural’ drug delivery system for tissue regeneration

Mesenchymal stem cells (MSCs) have abilities to mediate tissue protection through mechanisms of anti-apoptosis, anti-oxidative stress and anti-fibrosis as well as tissue regeneration through mechanisms of cell proliferation, differentiation and angiogenesis. These effects by MSCs are mediated by a variety of factors, including growth factors, cytokines and extracellular vesicles (EVs). Among these factors, EVs, containing proteins, mRNA and microRNAs (miRNA), may carry their contents into distant tissues with high stability. Therefore, the treatment with MSC-derived EVs may be promising as ‘natural’ drug delivery systems (DDS). Especially, the treatment of MSC-derived EVs with the manipulation of specific miRNAs expression has been reported to be beneficial under a variety of diseases and tissue injuries. The overexpression of specific miRNAs in the EVs might be through pre-loading method using the gene editing system by plasmid vector or post-loading method to load miRNA mimics into EVs by electroporation or calcium chloride-mediated transfection. Despite current several challenges for clinical use, it should open the next era of regenerative medicine for a variety of diseases. In this article, we highlight the therapeutic potential of MSC-derived EVs as ‘natural’ DDS and current challenges.     

Mesenchymal stem cell-derived exosomes as new remedy for the treatment of inflammatory eye diseases

Detrimental immune response has a crucially important role in the development and progression of inflammatory eye diseases. Inflammatory mediators and proteolytic enzymes released by activated immune cells induce serious injury of corneal epithelial cells and retinal ganglion cell which may result in the vision loss. Mesenchymal stem cells (MSCs) are regulatory cells which produce various immunosuppressive factors that modulate phenotype and function of inflammatory immune cells. However, several safety issues, including undesired differentiation and emboli formation, limit clinical use of MSCs. MSC-derived exosomes (MSC-Exos) are nano-sized extracellular vesicles which contain all MSC-derived immunoregulatory factors. Intraocular administration of MSC-Exos efficiently attenuated eye inflammation and significantly improved visual acuity in experimental animals without causing any severe side effects. As cell-free product, MSC-Exos addressed all safety issues related to the transplantation of MSCs. Therefore, MSC-Exos could be considered as potentially new remedy for the treatment of inflammatory eye diseases which efficacy should be explored in up-coming clinical trials.     

MSCs derived extracellular vesicles as a therapeutic paragon for neurodegenerative disorders: A viewpoint

Neurodegenerative disorders are a vicious woe to the public health and wellness. Uncertainty in their underlying causes, lack of effective biomarkers for their early detection, existence of only supportive therapy, and their ever rising incidence creates an unmatched need for targeted therapies. Mesenchymal Stem Cells (MSCs) have found to be promising candidates for regenerative and remedial therapy in neurodegenerative disorders, however several biological risks and practical issues impede in their translational utility. Deriving from MSCs are certain Extracellular Vesicles (EVs), which aid in the paracrine action of MSCs and have lately gained the scientific interest for their implacability in diverse set ups. Their cargo is of utmost importance and is being explored in various different diseases like heart diseases, neuronal diseases, respiratory diseases and hepatic diseases. They thereby hold the position of a likely prospective remedial candidate for therapy against neurodegenerative disorders.     

The RhoA nuclear localization changes in replicative senescence: New evidence from <i>in vitro</i> human mesenchymal stem cells studies

All non-immortalized mesenchymal stem cells have a limited proliferative potential, that is, replicative senescence (RS) is an integral characteristic of the life of all mesenchymal stem cells (MSCs). It is known that one of the important signs of RS is a decrease of cell motility, and that violations of migration processes contribute to the deterioration of tissue regeneration. Therefore, the characterization of the properties of the cell line associated with RS is a prerequisite for the effective use of MSCs in restorative medicine. One of the key proteins regulating cell motility is the small GTPase RhoA. The main purpose of this work was to study the nuclear-cytoplasmic redistribution of the RhoA protein during RS in MSC lines recently obtained and characterized in our laboratory. The study found that a comparative analysis of the intracellular localization of RhoA in three cell lines (MSCWJ-1, FetMSC, DF2) showed a decrease in the nuclear localization of RhoA during RS.     

The versatility of mesenchymal stem cells: From regenerative medicine to COVID,what is next?

Mesenchymal stem cells (MSCs) play key roles in regenerative medicine by promoting tissue healing. MSCs can be isolated from different adult tissues and they are able to differentiate into several lineages. Due to their anti-inflammatory, angiogenic and immune-modulatory properties, MSCs are suitable for tissue engineering applications and, when associated with biomaterials, their benefits can be improved. Moreover, recently, MSCs have been studied for new clinical applications, such as in the treatment of patients with COVID-19. MSCs regenerative potential has been attributed to their secretome, which comprises extracellular matrix, soluble proteins and several elements, including the release of extracellular vesicles. Even though, in order to explore all their therapeutic potential, it is still necessary to advance in the investigation of their basic cell biology characteristics.     

Investigation of the antioxidant defensive role of both AD-MSCs and BM-MSCs in modulating the alteration in the oxidative stress status in various STZ-diabetic rats’ tissues

Diabetes mellitus (DM) could negatively affect patients’ health via inducing a lot of serious functional hazards in many tissues’ cells at molecular levels. Recently, many scientists had proposed stem cell therapy being an appropriate alternative treatment protocol for numerous health threatening issues including diabetes. Therefore, the current study was designed to investigate the antioxidant potentiality of two MSCs types in alleviating tissues’ oxidative stress dramatic elevation resulting as a consequence of Type 1 DM induction. In our 4 weeks study, animals were divided into four groups: control group, STZ-diabetic group (D), D+AD-MSCs group and D+BM-MSCs group. Data reported that diabetic rats treated with either AD-MSCs or BM-MSCs exhibited a marvelous body tissues (Pancreas, Liver and Kidney) enhancing capabilities in attenuating the oxidative stress status; as evidenced by XO, ROS, and MDA levels down-regulation; with a general concomitant elevation in the antioxidants’ content; evidenced by many enzymatic and non-enzymatic antioxidants up-regulation; relative to the diabetic untreated group. Interestingly, comparing both treatments with each other and to control group, most of the measured parameters were reverted back to near normal levels after AD-MSCs injection; which clearly point out their stunning health benefits and superiority as anti-diabetic agent in overcoming different tissues’ complications; owing to their marked cytoprotective and regenerative potentialities.     

Mesenchymal stem cell secretome and nanotechnology: Combining therapeutic strategies

Mesenchymal stem cells (MSC) have pushed the field of stem cell-based therapies by inducing tissue regeneration, immunosuppression, and angiogenesis mainly through vesicles and soluble factors release (paracrine signaling). MSC-extracellular vesicles (MSC-EV) adaptable secretome and homing to injured sites allowed researchers to unlock a new era of cell-free based therapy. In parallel, nanoparticles (NP) have been explored in contributing to transport and drug delivery systems, giving drugs desired physical-chemical properties to exploit cell behavior. However, NPs can be quickly recognized by immune cells and cleared from circulation. In this viewpoint, we explore how combining both therapeutic strategies can improve efficacy and circumvent limitations of both therapies. MSCEV benefit from the potent MSC membrane composition, guiding chemotaxis to tumor sites, a very restricted microenvironment. MSC-EV has low immunogenicity, high stability, long half-life and can explore tissue targeting ligands as a precise drug carry, even across biological barriers. Those properties promote enhanced targeted drug delivery that can be combined with NP, exploring biological membrane production through: 1. direct cell therapy with NP-infused MSC; 2. NP-containing MSC-EV generated by NP-infused MSC; 3. by coating NP in MSC membrane (“MSC NanoGhosts”), allowing precise cargo definition without losing targeting. Therefore, nanotechnology combined with cell-based therapeutic resources can greatly improve targeted drug delivery, improving efficacy and opening a new venue of therapeutic possibilities.     

Future perspectives on cell therapy for autism spectrum disorder

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition characterized by impairments in social communication, abnormal to absent verbal communication, the presence of repetitive stereotypic verbal and non-verbal behaviors and restricted interests, with onset early in life. We showed cognitive and behavioral characteristics of ASD by impairment of communication, cognition, perception, motor skills, executive function, theory of mind and emotion control. Recently, pathogenesis of immune pathology in the brains of individuals with ASD has been focused. New therapeutic approaches in the viewpoints of immune modulation and microglial function are logical for novel treatments for individuals with ASD. Cell therapies such as umbilical cord blood cells and mesenchymal stromal cells for ASD will be a challenging and encouraging field in the future clinical study with progress of biotechnological science.     

Molecular approach to echinoderm regeneration.

Until very recently echinoderm regeneration research and indeed echinoderm research in general has suffered because of the lack of critical mass. In terms of molecular studies of regeneration, echinoderms in particular have lagged behind other groups in this respect. This is in sharp contrast to the major advances achieved with molecular and genetic techniques in the study of embryonic development in echinoderms. The aim of our studies has been to identify genes involved in the process of regeneration and in particular neural regeneration in different echinoderm species. Our survey included the asteroid Asterias rubens and provided evidence for the expression of Hox gene homologues in regenerating radial nerve cords. Present evidence suggests: 1) ArHox1 expression is maintained in intact radial nerve cord and may be upregulated during regeneration. 2) ArHox1 expression may contribute to the dedifferentiation and/or cell proliferation process during epimorphic regeneration. From the crinoid Antedon bifida, we have been successful in cloning a fragment of a BMP2/4 homologue (AnBMP2/4) and analysing its expression during arm regeneration. Here, we discuss the importance of this family of growth factors in several regulatory spheres, including maintaining the identity of pluripotent blastemal cells or as a classic skeletal morphogenic regulator. There is clearly substantial scope for future echinoderm research in the area of molecular biology and certain aspects are discussed in this review.     

Mesenchymal stem cells and cell-free preparations for treating atopic dermatitis

Atopic dermatitis (AD) is a chronic cutaneous inflammatory disease caused by an interaction between genetic, immune and epidermal barrier factors. Several treatments can be used to treat this disease but there are patients that do not respond to actual drugs. So, there is a need to develop effective therapies for AD. Mesenchymal stem cells (MSCs) are non-hematopoietic multipotent adult progenitor cells with immunomodulatory power and self-regenerating capacity to repair tissue damage, so they could be a potential effective treatment for AD. MSCs-Conditioned Medium (CM) and MSCs-exosomes are cell-free preparation with molecules secreted by stem cells that could be also beneficial for AD. This viewpoint reviews the actual development of MSCs, MSCs-CM and MSCs-exosomes for treating patients with AD.     

The antioxidant trolox inhibits aging and enhances prostaglandin E-2 secretion in mesenchymal stem cells

Mesenchymal stem cells (MSCs) have been widely used in regenerative medicine and clinical therapy due to their capabilities of proliferation, differentiation, and immune regulation. However, during in vitro expansion, MSCs are prone to aging, which largely limits their application. Prostaglandin E-2 (PGE-2) is a key effector secreted by MSCs to exert immunomodulatory effects. By screening the compound library for PGE-2 secretion, the antioxidant trolox was verified as a stimulator of MSCs to secrete PGE-2. The effect of antioxidant trolox on biological characteristics of MSCS, including aging, proliferation, and gene expression, was examined. The results demonstrated that trolox can resist aging, promote proliferation, and enhance PGE-2 secretion of MSCs without affecting their surface marker expression. Furthermore, trolox treatment up-regulates miR-17-92 clusters in MSCs and may contribute to its anti-aging effects. Thus, trolox addition might be beneficial for MSCs expansion and their application.     

Microscopic overview of crinoid regeneration.

Crinoids are well known for their striking regenerative potential and can rapidly and completely regenerate arms lost following self-induced or traumatic amputation. Thus they provide a valuable experimental model for investigation of the regenerative process from the macroscopic to the molecular level. In these last years we have studied in detail the overall process of arm regeneration in the comatulid Antedon mediterranea. This phenomenon can be described on the whole as a typical blastemal regeneration in which new structures develop from migratory pluripotential, actively proliferating cells in the presence of presumptive regulatory factors. The overall process can be subdivided into three main phases: a repair phase, an early regenerative phase, and an advanced regenerative phase, whose crucial aspects are related to common fundamental mechanisms such as cell migration and proliferation, intervention of stem cells and/or dedifferentiated cells, contribution of putative growth factors, particularly in terms of specific neurally derived factors, and mechanisms of pattern formation. This article focuses on the main aspects of the phenomenon and gives a brief account of the most recent and relevant results. Our approach employs classical methods of light (LM) and electron (TEM and SEM) microscopy, immunocytochemistry, and histofluorescence on experimentally induced arm regenerations of standard or abnormal type obtained in significantly different experimental conditions, including extreme mutilations (explants) or exposure to pseudo-estrogenic environmental contamination.     

Tuning mesenchymal stem cell secretome therapeutic potential through mechanotransduction

Mesenchymal stem cells (MSCs) and their byproducts have been widely validated as potential therapeutic products for regenerative medicine. The therapeutic effects result mainly from the paracrine activity of MSCs, which consists of the secretion of bioactive molecules, whether dispersed in medium conditioned by cell culture or encapsulated in extracellular vesicles. The composition of the MSC secretome, which represents the set of these secreted cellular products, is crucial for the performance of the desired therapeutic functions. Different cell culture strategies have been employed to adjust the secretome composition of MSCs to obtain the best therapeutic responses for different clinical contexts. However, the manipulation of culture conditions has focused mainly on the use of different biochemical elements for the preconditioning of MSCs and less on the physical conditions of the cell culture environment. Herein, we offer our point of view regarding the importance of the physical properties of cell culture substrates and their mechanotransduction responses in preconditioning the MSCs secretome. We highlight the relevance of studying mechanotransduction events associating cell morphology and the modulation of gene expression to customize and expand the use of MSCs secretomes.     

Poly(ADP-ribose), <i>adherens junctions</i>, vinculin and the actin cytoskeleton: Current evidence,future perspectives and implications

Poly(ADP-ribose) (PAR) is a highly negatively charged polymer. PAR is synthesized by poly(ADP-ribose)polymerases (PARPs) and is involved in the assembly and stabilization of macromolecular complexes. Here, the presence and putative roles of poly(ADP-ribosyl)ation (PARylation) associated to adherens junctions (AJ) and the actin cytoskeleton in epithelial and Schwann cells, is reviewed. The hypothesis generated by analogy, stating that PAR is associated to AJ in other cell types, is postulated. According to this hypothesis, PAR associated to puncta adherentia in chemical synapses would participate in plasticity, learning and memory. In turn, PAR associated to fascia adherens in cardiomyocytes, would affect heart beating. PARP inhibitors are currently under development and clinical testing. Basic research in different tissues will probably influence their clinical uses.     

Exosomes from adipose tissue-derived stem/stromal cells: A key to future regenerative medicine

Advances in regenerative medicine correlate strongly with progress in the use of adipose tissue-derived mesenchymal stem/stromal cells. The range of therapeutic indications has also expanded over recent years. Numerous recent studies have highlighted the primary importance of paracrine secretion by these cells. Though it is interesting to compare the different types of such secretions, we believe that exosomes (extra-cellular vesicles possessing the same properties as their source cells) will likely be the main key in tomorrow’s cell therapy. Exosomes also have many advantages compared to the direct use of cells, making these particles a major target in fundamental and translational research.     

Dental-derived stem cells and biowaste biomaterials: What’s next in bone regenerative medicine applications

The human teeth and oral cavity harbor various populations of mesenchymal stem cells (MSCs), so called dental-derived stem cells (D-dSCs) with self-renewing and multilineage differentiation capabilities. D-dSCs properties involves a strong paracrine component resulting from the high levels of bioactive molecules they secrete in response to the local microenvironment. Altogether, this viewpoint develops a general picture of current innovative strategies to employ D-dSCs combined with biomaterials and bioactive factors for regenerative medicine purposes, and offers information regarding the available scientific data and possible applications.