Rejuvenation of mesenchymal stem cells by extracellular vesicles inhibits the elevation of reactive oxygen species

Chemical Hypoxic Preconditioning Improves Survival and Proliferation of Mesenchymal Stem Cells

Increasing evidence has demonstrated that mesenchymal stem cells (MSCs) have been linked to tissue regeneration both in vitro and in vivo. However, poor engraftment and low survival rate of transplanted MSCs are still a major concern. It has been found that the proliferation, survival, and migration of MSCs are all increased by hypoxic preconditioning. However, the molecular mechanism through which hypoxic preconditioning enhances these beneficial properties of MSCs remains to be fully investigated. Therefore, the present study is aimed to investigate the mechanism by which hypoxic preconditioning enhances the survival of MSCs. We used proteomic analysis to explore the molecules that may contribute to the survival and proliferation of hypoxic preconditioned (HP) MSCs. The analysis revealed a higher expression of prelamin A/C (Lmna), glutamate dehydrogenase 1(Glud1), Actin, cytoplasmic 1(Actb), Alpha-enolase (Eno1), Glucose-6-phosphate 1-dehydrogenase (G6pd), Protein disulfide-isomerase A3 (Pdia3), Malate dehydrogenase (Mdh1), Peroxiredoxin-6 (Prdx6), Superoxide dismutase (Sod1), and Annexin A2 (Anxa2) in HP-MSCs. These proteins are possibly involved in cellular survival and proliferation through various cellular pathways. This research could aid in understanding the processes involved in hypoxic preconditioning of MSCs and designing of cell-based therapeutic strategies for tissue regeneration.

Mechanical Rejuvenation of Mesenchymal Stem Cells from Aged Patients

Mesenchymal stem cells (MSC) are an appealing therapeutic cell type for many diseases. However, patients with poor health or advanced age often have MSCs with poor regenerative properties. A major limiter of MSC therapies is cellular senescence, which is marked by limited proliferation capability, diminished multipotency, and reduced regenerative properties. In this work, we explored the ability of applied mechanical forces to reduce cellular senescence in MSCs. Our studies revealed that mechanical conditioning caused a lasting enhancement in proliferation, overall cell culture expansion potential, multipotency, and a reduction of senescence in MSCs from aged donors. Mechanistic studies suggested that these functional enhancements were mediated by oxidative stress and DNA damage repair signaling with mechanical load altering the expression of proteins of the sirtuin pathway, the DNA damage repair protein ATM, and antioxidant proteins. In addition, our results suggest a biophysical mechanism in which mechanical stretch leads to improved recognition of damaged DNA in the nucleus. Analysis of the cells through RNA-seq and ATAC-seq, demonstrated that mechanical loading alters the cell's genetic landscape to cause broad shifts in transcriptomic patterns that related to senescence. Overall, our results demonstrate that mechanical conditioning can rejuvenate mesenchymal stem cells derived from aged patients and improve their potential as a therapeutic cell type.

GRAPHICAL ABSTRACT

Extracellular Vesicles Derived from Type 2 Diabetic Mesenchymal Stem Cells Induce Endothelial Mesenchymal Transition under High Glucose Conditions Through the TGFβ/Smad3 Signaling Pathway

Type 2 diabetes mellitus (T2DM) is associated with endothelial dysfunction, which results in delayed wound healing. Mesenchymal stem cells (MSCs) play a vital role in supporting endothelial cells (ECs) and promoting wound healing by paracrine effects through their secretome-containing extracellular vesicles. We previously reported the impaired wound healing ability of adipose tissue-derived MSC from T2DM donors; however, whether extracellular vesicles isolated from T2DM adipose tissue-derived MSCs (dEVs) exhibit altered functions in comparison to those derived from healthy donors (nEVs) is still unclear. In this study, we found that nEVs induced EC survival and angiogenesis, whereas dEVs lost these abilities. In addition, under high glucose conditions, nEV protected ECs from endothelial-mesenchymal transition (EndMT), whereas dEV significantly induced EndMT by activating the transforming growth factor-β/Smad3 signaling pathway, which impaired the tube formation and in vivo wound healing abilities of ECs. Interestingly, the treatment of dEV-internalized ECs with nEVs rescued the induced EndMT effects. Of note, the internalization of nEV into T2DM adipose tissue-derived MSC resulted in the production of an altered n-dEV, which inhibited EndMT and supported the survival of T2DM db/db mice from severe wounds. Taken together, our findings suggest the role of dEV in endothelial dysfunction and delayed wound healing in T2DM by the promotion of EndMT. Moreover, nEV treatment can be considered a promising candidate for cell-free therapy to protect ECs in T2DM.

Adsorption effects of acetone and acetonitrile on defected penta-PdSe2 nanoribbons: a DFT study

Using DFT calculations, the structural and electronic properties of the ZZ7 p-PdSe2 nanoribbons (ZZ7) with the four kinds of vacancy defects, including ZZ7-VPd, ZZ7-VSe, ZZ7-VPd+Se, and ZZ7-V2Se are studied, in which their stability, diverse geometries, and altered electronic properties are determined through the formation energies, optimal structural parameters, electronic band structures, and DOSs. Specifically, the formation energies of all studied systems show significant negative values around -3.9 eV, evidencing their good thermal stability. The geometries of four defective structures exhibit different diversification, whereas only the ZZ7-V2Se structure possesses the highly enhanced feature, identified as the most effective substrate for the acetone and acetonitrile adsorption. On the electronic behaviors, the ZZ7 band structure displays the nonmagnetic metallic characteristics that become the ferromagnetic half-metallic band structures for the ZZ7-VPd and ZZ7-VSe and the ferromagnetic semi-metallic band structures for the ZZ7-VPd+Se and ZZ7-V2Se. For adsorption of the acetone and acetonitrile on the ZZ7-V2Se structure, the energetic stability, adsorption sites, adsorption distances, charge transfers, and electronic characteristics of the adsorbed systems are determined by the adsorption energies, optimal adsorption sites, adsorption distances, Mulliken populations, and DOSs. The adsorption energies of the acetone- and acetonitrile-adsorbed ZZ7-V2Se systems display significant values at -1.2 eV and -0.86 eV at the preferable sites of 8 and 11, respectively, indicating their great adsorption ability. The adsorption mechanism of the acetone- and acetonitrile-adsorbed systems belongs to the physisorption owing to absence of chemical bonds, in which the bond lengths of the ZZ7-V2Se substrate show a very small deviation. Under the acetone and acetonitrile adsorptions, the ferromagnetic semi-metallic DOSs of the ZZ7-V2Se become the ferromagnetic half-metallic DOSs for the ZZ7-V2Se-acetone-8 and the ferromagnetic semiconducting DOSs for the ZZ7-V2Se-acetonitrile-11. Our systematic results can provide a complete understanding of the acetone- and acetonitrile adsorptions on the potential ZZ7-V2Se structure, which is very useful for nanosensor application.

Stem Cell and Regenerative Therapies for the Treatment of Osteoporotic Vertebral Compression Fractures

Osteoporotic vertebral compression fractures (OVCFs) significantly increase morbidity and mortality, presenting a formidable challenge in healthcare. Traditional interventions such as vertebroplasty and kyphoplasty, despite their widespread use, are limited in addressing the secondary effects of vertebral fractures in adjacent areas and do not facilitate bone regeneration. This review paper explores the emerging domain of regenerative therapies, spotlighting stem cell therapy's transformative potential in OVCF treatment. It thoroughly describes the therapeutic possibilities and mechanisms of action of mesenchymal stem cells against OVCFs, relying on recent clinical trials and preclinical studies for efficacy assessment. Our findings reveal that stem cell therapy, particularly in combination with scaffolding materials, holds substantial promise for bone regeneration, spinal stability improvement, and pain mitigation. This integration of stem cell-based methods with conventional treatments may herald a new era in OVCF management, potentially improving patient outcomes. This review advocates for accelerated research and collaborative efforts to translate laboratory breakthroughs into clinical practice, emphasizing the revolutionary impact of regenerative therapies on OVCF management. In summary, this paper positions stem cell therapy at the forefront of innovation for OVCF treatment, stressing the importance of ongoing research and cross-disciplinary collaboration to unlock its full clinical potential.

Rejuvenating aged stem cells: therapeutic strategies to extend health and lifespan

Aging is associated with a global decline in stem cell function. To date, several strategies have been proposed to rejuvenate aged stem cells: most of these result in functional improvement of the tissue where the stem cells reside, but the impact on the lifespan of the whole organism has been less clearly established. Here, we review some of the most recent work dealing with interventions that improve the regenerative capacity of aged somatic stem cells in mammals and that might have important translational possibilities. Overall, we underscore that somatic stem cell rejuvenation represents a strategy to improve tissue homeostasis upon aging and present some recent approaches with the potential to affect health span and lifespan of the whole organism.

Utilizing Extracellular Vesicles for Eliminating 'Unwanted Molecules': Harnessing Nature's Structures in Modern Therapeutic Strategies

Extracellular vesicles (EVs) are small phospholipid bilayer-bond structures released by diverse cell types into the extracellular environment, maintaining homeostasis of the cell by balancing cellular stress. This article provides a comprehensive overview of extracellular vesicles, their heterogeneity, and diversified roles in cellular processes, emphasizing their importance in the elimination of unwanted molecules. They play a role in regulating oxidative stress, particularly by discarding oxidized toxic molecules. Furthermore, endoplasmic reticulum stress induces the release of EVs, contributing to distinct results, including autophagy or ER stress transmission to following cells. ER stress-induced autophagy is a part of unfolded protein response (UPR) and protects cells from ER stress-related apoptosis. Mitochondrial-derived vesicles (MDVs) also play a role in maintaining homeostasis, as they carry damaged mitochondrial components, thereby preventing inflammation. Moreover, EVs partake in regulating aging-related processes, and therefore they can potentially play a crucial role in anti-aging therapies, including the treatment of age-related diseases such as Alzheimer's disease or cardiovascular conditions. Overall, the purpose of this article is to provide a better understanding of EVs as significant mediators in both physiological and pathological processes, and to shed light on their potential for therapeutic interventions targeting EV-mediated pathways in various pathological conditions, with an emphasis on age-related diseases.

Phytic acid improves osteogenesis and inhibits the senescence of human bone marrow mesenchymal stem cells under high-glucose conditions via the ERK pathway

Hyperglycaemia causes impairment of osteogenic differentiation and accelerates stem cell senescence, resulting in weakened osteogenesis and disordered bone metabolism. Phytic acid (PA) is an antioxidant that is reportedly beneficial to bone homeostasis. The present study aims to clarify how PA affects the osteogenic capacity and cellular senescence of bone marrow mesenchymal stem cells (BMSCs) exposed to high-glucose environments, as well as the potential molecular mechanisms. Our results indicate that osteogenic differentiation in BMSCs cultivated in high-glucose conditions is enhanced by PA, as evidenced by increased alkaline phosphatase activity and staining, Alizarin Red S staining, osteogenic marker in in vitro studies, and increased osteogenesis in animal experiments. PA also prevented high-glucose-induced senescence of BMSCs, as evidenced by the repression of reactive oxygen species production, senescence-associated β-galactosidase staining, and P21 and P53 expression. Furthermore, it was found that PA rescued the high-glucose-inhibited expression of phosphorylated extracellular regulated protein kinases (p-ERK). The inhibition of ERK pathway by the specific inhibitor PD98059 blocked the PA-enhanced osteogenesis of BMSCs and promoted cell senescence. Our results revealed that PA enhances osteogenic differentiation and inhibits BMSC senescence in a high-glucose environment. In addition, the activation of the ERK pathway seems to mediate the beneficial effects of PA. The findings provide novel insights that could facilitate bone regeneration in patients with diabetes.

Extracellular Vesicles Derived from Osteogenic-Differentiated Human Bone Marrow-Derived Mesenchymal Cells Rescue Osteogenic Ability of Bone Marrow-Derived Mesenchymal Cells Impaired by Hypoxia

In orthopedics, musculoskeletal disorders, i.e., non-union of bone fractures or osteoporosis, can have common histories and symptoms related to pathological hypoxic conditions induced by aging, trauma or metabolic disorders. Here, we observed that hypoxic conditions (2% O2) suppressed the osteogenic differentiation of human bone marrow-derived mesenchymal cells (hBMSC) in vitro and simultaneously increased reactive oxygen species (ROS) production. We assumed that cellular origin and cargo of extracellular vesicles (EVs) affect the osteogenic differentiation capacity of hBMSCs cultured under different oxygen pressures. Proteomic analysis revealed that EVs isolated from osteogenic differentiated hBMSC cultured under hypoxia (hypo-osteo EVs) or under normoxia (norm-osteo EVs) contained distinct protein profiles. Extracellular matrix (ECM) components, antioxidants and pro-osteogenic proteins were decreased in hypo-osteo EVs. The proteomic analysis in our previous study revealed that under normoxic culture conditions, pro-osteogenic proteins and ECM components have higher concentrations in norm-osteo EVs than in EVs derived from naïve hBMSCs (norm-naïve EVs). When selected for further analysis, five anti-hypoxic proteins were significantly upregulated (response to hypoxia) in norm-osteo EVs. Three of them are characterized as antioxidant proteins. We performed qRT-PCR to verify the corresponding gene expression levels in the norm-osteo EVs' and norm-naïve EVs' parent cells cultured under normoxia. Moreover, we observed that norm-osteo EVs rescued the osteogenic ability of naïve hBMSCs cultured under hypoxia and reduced hypoxia-induced elevation of ROS production in osteogenic differentiated hBMSCs, presumably by inducing expression of anti-hypoxic/ antioxidant and pro-osteogenic genes.

Mesenchymal Stem Cell Senescence during Aging:From Mechanisms to Rejuvenation Strategies

In cell transplantation therapy, mesenchymal stem cells(MSCs)are ideal seed cells due to their easy acquisition and cultivation, strong regenerative capacity, multi-directional differentiation abilities, and immunomodulatory effects. Autologous MSCs are better applicable compared with allogeneic MSCs in clinical practice. The elderly are the main population for cell transplantation therapy, but as donor aging, MSCs in the tissue show aging-related changes. When the number of generations of in vitro expansion is increased, MSCs will also exhibit replicative senescence. The quantity and quality of MSCs decline during aging, which limits the efficacy of autologous MSCs transplantation therapy. In this review, we examine the changes in MSC senescence as a result of aging, discuss the progress of research on mechanisms and signalling pathways of MSC senescence, and discuss possible rejuvenation strategies of aged MSCs to combat senescence and enhance the health and therapeutic potential of MSCs.

Effect of stem cell secretome in skin rejuvenation: a narrative review

PURPOSE

Cutaneous aging is an inevitable biological process that develops over time due to cumulative cellular and molecular changes caused by exposure to intrinsic (chronological aging) and extrinsic (photo-aging) factors on the skin. Skin aging is characterized by a decline in the body's capability to sustain senescence, dermal cell apoptosis, and homeostasis. Stem cell secretions (secretome) are defined as the total set of dynamically overlapping paracrine soluble growth factors, cytokines, chemokines, angiogenic factors, extracellular matrix proteins, and antimicrobial peptides known to be responsible for tissue rejuvenation, regeneration, homeostasis, and immunomodulation.

METHODS

In this review, we summarized the molecular and regulatory mechanism of the secretome in preventing the skin aging process, as well as its capacity in inducing skin rejuvenation. Furthermore, we illustrated secretome efficiency as an anti-aging therapeutic strategy based on in vitro and in vivo published studies.

RESULTS

In all reviewed publications, the secretome has been proven to be the most effective treatment for aged skin, capable of reversing the aging process through the action of cytokines, growth factors, and collagen, which are its primary components. The reported mechanism of action involves modulating the signaling pathways of aging and replenishing the skin with collagen, fibronectin, and elastin, ultimately resulting in skin renewal and rejuvenation.

CONCLUSION

In conclusion, compared to available treatments, the secretome shows great promise as an anti-aging therapy.

Research progress of extracellular vesicles and exosomes derived from mesenchymal stem cells in the treatment of oxidative stress-related diseases

There is growing evidence that mesenchymal stem cell-derived extracellular vesicles and exosomes can significantly improve the curative effect of oxidative stress-related diseases. Mesenchymal stem cell extracellular vesicles and exosomes (MSC-EVs and MSC-Exos) are rich in bioactive molecules and have many biological regulatory functions. In this review, we describe how MSC-EVs and MSC-Exos reduce the related markers of oxidative stress and inflammation in various systemic diseases, and the molecular mechanism of MSC-EVs and MSC-Exos in treating apoptosis and vascular injury induced by oxidative stress. The results of a large number of experimental studies have shown that both local and systemic administration can effectively inhibit the oxidative stress response in diseases and promote the survival and regeneration of damaged parenchymal cells. The mRNA and miRNAs in MSC-EVs and MSC-Exos are the most important bioactive molecules in disease treatment, which can inhibit the apoptosis, necrosis and oxidative stress of lung, heart, kidney, liver, bone, skin and other cells, and promote their survive and regenerate.

Cerebral-Organoid-Derived Exosomes Alleviate Oxidative Stress and Promote LMX1A-Dependent Dopaminergic Differentiation

The remarkable advancements related to cerebral organoids have provided unprecedented opportunities to model human brain development and diseases. However, despite their potential significance in neurodegenerative diseases such as Parkinson's disease (PD), the role of exosomes from cerebral organoids (OExo) has been largely unknown. In this study, we compared the effects of OExo to those of mesenchymal stem cell (MSC)-derived exosomes (CExo) and found that OExo shared similar neuroprotective effects to CExo. Our findings showed that OExo mitigated H₂O₂-induced oxidative stress and apoptosis in rat midbrain astrocytes by reducing excess ROS production, antioxidant depletion, lipid peroxidation, mitochondrial dysfunction, and the expression of pro-apoptotic genes. Notably, OExo demonstrated superiority over CExo in promoting the differentiation of human-induced pluripotent stem cells (iPSCs) into dopaminergic (DA) neurons. This was attributed to the higher abundance of neurotrophic factors, including neurotrophin-4 (NT-4) and glial-cell-derived neurotrophic factor (GDNF), in OExo, which facilitated the iPSCs' differentiation into DA neurons in an LIM homeobox transcription factor 1 alpha (LMX1A)-dependent manner. Our study provides novel insight into the biological properties of cerebral organoids and highlights the potential of OExo in the treatment of neurodegenerative diseases such as PD.

Protective roles of mesenchymal stem cells on skin photoaging: A narrative review

Skin is a natural barrier of human body and a visual indicator of aging process. Exposure to ultraviolet (UV) radiation in the sunlight may injure the skin tissues and cause local damage. Besides, it is reported that repetitive or long-term exposure to UV radiation may reduce the collagen production, change the normal skin structure and cause premature skin aging. This is termed "photoaging". The classical symptoms of photoaging include increased roughness, wrinkle formation, mottled pigmentation or even precancerous changes. Mesenchymal stem cells (MSCs) are a kind of cells with the ability of self-renewal and multidirectional differentiation into many types of cells, like adipocytes, osteoblasts and chondrocytes. Researchers have explored diverse pharmacological actions of MSCs because of their migratory activity, paracrine actions and immunoregulation effects. In recent years, the huge potential of MSCs in preventing skin from photoaging has gained wide attention. MSCs exert their beneficial effects on skin photoaging via antioxidant effect, anti-apoptotic/anti-inflammatory effect, reduction of matrix metalloproteinases (MMPs) and activation of dermal fibroblasts proliferation. MSCs and MSC related products have demonstrated huge potential in the treatment of skin photoaging. This narrative review concisely sums up the recent research developments on the roles of MSCs in protection against photoaging and highlights the enormous potential of MSCs in skin photoaging treatment.

SOD3 Suppresses the Expression of MMP-1 and Increases the Integrity of Extracellular Matrix in Fibroblasts

The superoxide dismutase (SOD) family functions as a reactive oxygen species (ROS)-scavenging system by converting superoxide anions into hydrogen peroxide in the cytosol (SOD1), mitochondria (SOD2), and extracellular matrix (SOD3). In this study, we examined the potential roles of SOD family members in skin aging. We found that SOD3 expression levels were significantly more reduced in the skin tissues of old mice and humans than in young counterparts, but SOD1 and SOD2 expression levels remained unchanged with aging. Accordingly, we analyzed the effects of SOD3 on intracellular ROS levels and the integrity of the extracellular matrix in fibroblasts. The treatment of foreskin fibroblasts with recombinant SOD3 reduced the intracellular ROS levels and secretion of MMP-1 while increasing the secretion of type I collagen. The effects of SOD3 were greater in fibroblasts treated with the TNF-α. SOD3 treatment also decreased the mRNA levels and promoter activity of MMP-1 while increasing the mRNA levels and promoter activities of COL1A1 and COL1A2. SOD3 treatment reduced the phosphorylation of NF-κB, p38 MAPK, ERK, and JNK, which are essential for MMP-1 transactivation. In a three-dimensional culture of fibroblasts, SOD3 decreased the amount of type I collagen fragments produced by MMP-1 and increased the amount of nascent type I procollagen. These results demonstrate that SOD3 reduces intracellular ROS levels, suppresses MMP-1 expression, and induces type I collagen expression in fibroblasts. Therefore, SOD3 may play a role in delaying or preventing skin aging.

Aging and “rejuvenation” of resident stem cells — a new way to active longevity?

This review presents the current data on the methodology for assessing the biological and epigenetic age, describes the concept of the epigenetic clock, and characterizes the main types of resident stem cells and the specifics of their aging. It has been shown that age-related changes in organs and tissues, as well as age-related diseases, are largely due to the aging of resident stem cells. The latter represent an attractive target for cell rejuvenation, as they can be isolated, cultured ex vivo, modified, and re-introduced into the resident niches. Two main methodologies for the cellular rejuvenation are presented: genetic reprogramming with zeroing the age of a cell using transient expression of transcription factors, and various approaches to epigenetic rejuvenation. The close relationship between aging, regeneration, and oncogenesis, and between these factors and the functioning of resident stem cell niches requires further precision studies, which, we are sure, can result in the creation of an effective anti-aging strategy and prolongation of human active life.

Potential pre-activation strategies for improving therapeutic efficacy of mesenchymal stem cells: current status and future prospects

Mesenchymal stem cell (MSC)-based therapy has been considered as a promising approach targeting a variety of intractable diseases due to remarkable multiple effect of MSCs, such as multilineage differentiation, immunomodulatory property, and pro-regenerative capacity. However, poor engraftment, low survival rate of transplanted MSC, and impaired donor-MSC potency under host age/disease result in unsatisfactory therapeutic outcomes. Enhancement strategies, including genetic manipulation, pre-activation, and modification of culture method, have been investigated to generate highly functional MSC, and approaches for MSC pre-activation are highlighted. In this review, we summarized the current approaches of MSC pre-activation and further classified, analysed the scientific principles and main characteristics of these manipulations, and described the pros and cons of individual pre-activation strategies. We also discuss the specialized tactics to solve the challenges in this promising field so that it improves MSC therapeutic functions to serve patients better.

Tumorigenic Aspects of MSC Senescence-Implication in Cancer Development and Therapy

As an organism ages, many physiological processes change, including the immune system. This process, called immunosenescence, characterized by abnormal activation and imbalance of innate and adaptive immunity, leads to a state of chronic low-grade systemic inflammation, termed inflammaging. Aging and inflammaging are considered to be the root of many diseases of the elderly, as infections, autoimmune and chronic inflammatory diseases, degenerative diseases, and cancer. The role of mesenchymal stromal/stem cells (MSCs) in the inflammaging process and the age-related diseases is not completely established, although numerous features of aging MSCs, including altered immunomodulatory properties, impeded MSC niche supporting functions, and senescent MSC secretory repertoire are consistent with inflammaging development. Although senescence has its physiological function and can represent a mechanism of tumor prevention, in most cases it eventually transforms into a deleterious (para-)inflammatory process that promotes tumor growth. In this review we are going through current literature, trying to explore the role of senescent MSCs in making and/or sustaining a microenvironment permissive to tumor development and to analyze the therapeutic options that could target this process.

Epigenetic Clock and Circadian Rhythms in Stem Cell Aging and Rejuvenation

This review summarizes the current understanding of the interaction between circadian rhythms of gene expression and epigenetic clocks characterized by the specific profile of DNA methylation in CpG-islands which mirror the senescence of all somatic cells and stem cells in particular. Basic mechanisms of regulation for circadian genes CLOCK-BMAL1 as well as downstream clock-controlled genes (ССG) are also discussed here. It has been shown that circadian rhythms operate by the finely tuned regulation of transcription and rely on various epigenetic mechanisms including the activation of enhancers/suppressors, acetylation/deacetylation of histones and other proteins as well as DNA methylation. Overall, up to 20% of all genes expressed by the cell are subject to expression oscillations associated with circadian rhythms. Additionally included in the review is a brief list of genes involved in the regulation of circadian rhythms, along with genes important for cell aging, and oncogenesis. Eliminating some of them (for example, Sirt1) accelerates the aging process, while the overexpression of Sirt1, on the contrary, protects against age-related changes. Circadian regulators control a number of genes that activate the cell cycle (Wee1, c-Myc, p20, p21, and Cyclin D1) and regulate histone modification and DNA methylation. Approaches for determining the epigenetic age from methylation profiles across CpG islands in individual cells are described. DNA methylation, which characterizes the function of the epigenetic clock, appears to link together such key biological processes as regeneration and functioning of stem cells, aging and malignant transformation. Finally, the main features of adult stem cell aging in stem cell niches and current possibilities for modulating the epigenetic clock and stem cells rejuvenation as part of antiaging therapy are discussed.

Human Induced Pluripotent Stem Cell-Derived Mesenchymal Stem Cells Acquire Rejuvenation and Reduced Heterogeneity

Despite the uniform selection criteria for the isolation of human mesenchymal stem cells (MSCs), considerable heterogeneity exists which reflects the distinct tissue origins and differences between individuals with respect to their genetic background and age. This heterogeneity is manifested by the variabilities seen in the transcriptomes, proteomes, secretomes, and epigenomes of tissue-specific MSCs. Here, we review literature on different aspects of MSC heterogeneity including the role of epigenetics and the impact of MSC heterogeneity on therapies. We then combine this with a meta-analysis of transcriptome data from distinct MSC subpopulations derived from bone marrow, adipose tissue, cruciate, tonsil, kidney, umbilical cord, fetus, and induced pluripotent stem cells derived MSCs (iMSCs). Beyond that, we investigate transcriptome differences between tissue-specific MSCs and pluripotent stem cells. Our meta-analysis of numerous MSC-related data sets revealed markers and associated biological processes characterizing the heterogeneity and the common features of MSCs from various tissues. We found that this heterogeneity is mainly related to the origin of the MSCs and infer that microenvironment and epigenetics are key drivers. The epigenomes of MSCs alter with age and this has a profound impact on their differentiation capabilities. Epigenetic modifications of MSCs are propagated during cell divisions and manifest in differentiated cells, thus contributing to diseased or healthy phenotypes of the respective tissue. An approach used to reduce heterogeneity caused by age- and tissue-related epigenetic and microenvironmental patterns is the iMSC concept: iMSCs are MSCs generated from induced pluripotent stem cells (iPSCs). During iMSC generation epigenetic and chromatin remodeling result in a gene expression pattern associated with rejuvenation thus allowing to overcome age-related shortcomings (e.g., limited differentiation and proliferation capacity). The importance of the iMSC concept is underlined by multiple clinical trials. In conclusion, we propose the use of rejuvenated iMSCs to bypass tissue- and age-related heterogeneity which are associated with native MSCs.

The Immunomodulatory Effect of Triptolide on Mesenchymal Stromal Cells

Mesenchymal stromal cells (MSCs) are known to have immunosuppressive ability and have been used in clinical treatment of acute graft-versus-host disease, one of severe complications of the hematopoietic stem cell transplantation. However, MSCs are activated to suppress the immune system only after encountering an inflammatory stimulation. Thus, it will be ideal if MSCs are primed to be activated and ready to suppress the immune reaction before being administered. Triptolide (TPL) is a diterpene triepoxide purified from a Chinese herb-Tripterygium wilfordii Hook.f. It has been shown to possess anti-inflammatory and immunosuppressive properties in vitro. In this study, we aimed to use TPL to prime umbilical cord-derived MSCs (TPL-primed UC-MSCs) to enter a stronger immunosuppressive status. UC-MSCs were primed with TPL, which was washed out thoroughly, and the TPL-primed UC-MSCs were resuspended in fresh medium. Although TPL inhibited the proliferation of UC-MSCs, 0.01 μM TPL for 24 h was tolerable. The surface markers of TPL-primed UC-MSCs were identical to those of non-primed UC-MSCs. TPL-primed UC-MSCs exhibited stronger anti-proliferative effect for activated CD4+ and CD8+ T cells in the allogeneic mixed lymphocyte reaction assay than the non-primed UC-MSCs. TPL-primed UC-MSCs promoted the expression of IDO-1 in the presence of IFN-γ, but TPL alone was not sufficient. Furthermore, TPL-primed UC-MSCs showed increased expression of PD-L1. Conclusively, upregulation of IDO-1 in the presence of IFN-γ and induction of PD-L1 enhances the immunosuppressive potency of TPL-primed UC-MSCs on the proliferation of activated T cells. Thus, TPL- primed MSCs may provide a novel immunosuppressive cell therapy.

Extracellular Vesicles in Premature Aging and Diseases in Adulthood Due to Developmental Exposures

The developmental origins of health and disease (DOHaD) is a paradigm that links prenatal and early life exposures that occur during crucial periods of development to health outcome and risk of disease later in life. Maternal exposures to stress, some psychoactive drugs and alcohol, and environmental chemicals, among others, may result in functional changes in developing fetal tissues, creating a predisposition for disease in the individual as they age. Extracellular vesicles (EVs) may be mediators of both the immediate effects of exposure during development and early childhood as well as the long-term consequences of exposure that lead to increased risk and disease severity later in life. Given the prevalence of diseases with developmental origins, such as cardiovascular disease, neurodegenerative disorders, osteoporosis, metabolic dysfunction, and cancer, it is important to identify persistent mediators of disease risk. In this review, we take this approach, viewing diseases typically associated with aging in light of early life exposures and discuss the potential role of EVs as mediators of lasting consequences.

Extracellular vesicles from mesenchymal stromal cells: Therapeutic perspectives for targeting senescence in osteoarthritis

Osteoarthritis (OA) is a common age-related disease that correlates with a high number of senescent cells in joint tissues. Senescence has been reported to be one of the main drivers of OA pathogenesis, in particular via the release of senescence-associated secretory phenotype (SASP) factors. SASP factors are secreted as single molecules and/or packaged within extracellular vesicles (EVs), thereby contributing to senescent phenotype dissemination. Targeting senescent cells using senolytics or senomorphics has therefore been tested and improvement of OA-associated features has been reported in murine models. Mesenchymal stromal cells (MSCs) and their derived EVs (MSC-EVs) are promising treatments for OA, exerting pleiotropic functions by producing a variety of factors. However, functions of MSCs and MSC-EVs are affected by aging. In this review, we discuss on the impact of the senescent environment on functions of aged MSC-EVs and on the anti-aging properties of MSC-EVs in the context of OA.

Extracellular Vesicles of Mesenchymal Stem Cells: Therapeutic Properties Discovered with Extraordinary Success

Mesenchymal stem cells (MSCs), the cells distributed in the stromas of the body, are known for various properties including replication, the potential of various differentiations, the immune-related processes including inflammation. About two decades ago, these cells were shown to play relevant roles in the therapy of numerous diseases, dependent on their immune regulation and their release of cytokines and growth factors, with ensuing activation of favorable enzymes and processes. Such discovery induced great increase of their investigation. Soon thereafter, however, it became clear that therapeutic actions of MSCs are risky, accompanied by serious drawbacks and defects. MSC therapy has been therefore reduced to a few diseases, replaced for the others by their extracellular vesicles, the MSC-EVs. The latter vesicles recapitulate most therapeutic actions of MSCs, with equal or even better efficacies and without the serious drawbacks of the parent cells. In addition, MSC-EVs are characterized by many advantages, among which are their heterogeneities dependent on the stromas of origin, the alleviation of cell aging, the regulation of immune responses and inflammation. Here we illustrate the MSC-EV therapeutic effects, largely mediated by specific miRNAs, covering various diseases and pathological processes occurring in the bones, heart and vessels, kidney, and brain. MSC-EVs operate also on the development of cancers and on COVID-19, where they alleviate the organ lesions induced by the virus. Therapy by MSC-EVs can be improved by combination of their innate potential to engineering processes inducing precise targeting and transfer of drugs. The unique properties of MSC-EVs explain their intense studies, carried out with extraordinary success. Although not yet developed to clinical practice, the perspectives for proximal future are encouraging.

Cell therapy for the treatment of heart disease: Renovation work on the broken heart is still in progress

Cardiovascular disease (CVD) continues to be the number one killer in the aging population. Heart failure (HF) is also an important cause of morbidity and mortality in patients with congenital heart disease (CHD). Novel therapeutic approaches that could restore stable heart function are much needed in both paediatric and adult patients. Regenerative medicine holds promises to provide definitive solutions for correction of congenital and acquired cardiac defects. In this review article, we recap some important aspects of cardiovascular cell therapy. First, we report quantifiable data regarding the scientific advancements in the field and how this has been translated into tangible outcomes according clinical studies and related meta-analyses. We then comment on emerging trends and technologies, such as the use of second-generation cell products, including pericyte-like vascular progenitors, and reprogramming of cells by different approaches including modulation of oxidative stress. The more affordable and feasible strategy of repurposing clinically available drugs to awaken the intrinsic healing potential of the heart will be discussed in the light of current social, financial, and ethical context. Cell therapy remains a work in progress field. Uncertainty in the ability of the experts and policy makers to solve urgent medical problems is growing in a world that is significantly influenced by them. This is particularly true in the field of regenerative medicine, due to great public expectations, polarization of leadership and funding, and insufficient translational vision. Cardiovascular regenerative medicine should be contextualized in a holistic program with defined priorities to allow a complete realization. Reshaping the notion of medical expertise is fundamental to fill the current gap in translation.

Novel and Converging Ways of NOX2 and SOD3 in Trafficking and Redox Signaling in Macrophages

Macrophages and related tissue macrophage populations use the classical NADPH oxidase (NOX2) for the regulated production of superoxide and derived oxidants for pathogen combat and redox signaling. With an emphasis on macrophages, we discuss how sorting into secretory storage vesicles, agonist-responsive membrane trafficking, and segregation into sphingolipid and cholesterol-enriched microdomains (lipid rafts) determine the subcellular distribution and spatial organization of NOX2 and superoxide dismutase-3 (SOD3). We discuss how inflammatory activation of macrophages, in part through small GTPase Rab27A/B regulation of the secretory compartments, mediates the coalescence of these two proteins on the cell surface to deliver a focalized hydrogen peroxide output. In interplay with membrane-embedded oxidant transporters and redox sensitive target proteins, this arrangement allows for the autocrine and paracrine signaling, which govern macrophage activation states and transcriptional programs. By discussing examples of autocrine and paracrine redox signaling, we highlight why formation of spatiotemporal microenvironments where produced superoxide is rapidly converted to hydrogen peroxide and conveyed immediately to reach redox targets in proximal vicinity is required for efficient redox signaling. Finally, we discuss the recent discovery of macrophage-derived exosomes as vehicles of NOX2 holoenzyme export to other cells.