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.     

Mesenchymal stem cells,the secretome and biomaterials: Regenerative medicine application

Mesenchymal stem cells (MSCs) are multipotent cells usually isolated from bone marrow, endometrium, adipose tissues, skin, and dental pulp. MSCs played a crucial role in regenerative therapy and have been introduced as an interdisciplinary field between cell biology and material science. Recently, MSCs have been widely explored for their application in regenerative medicine and COVID-19 treatment. Different approaches to evaluate the future of biomaterials and stem cell properties have been developed. However, misconceptions and ethical issues still exist, such as MSCs being non-angiogenic, anti-apoptotic, and immunoregulatory competencies. Embryonic stem cells isolation primarily requires the consent of donors and can include the killing of fertilized eggs. These issues generate questions related to ethical and moral issues. However, MSCs have gained considerable attention for tissue regeneration owing to their differentiation ability with immunomodulatory effects. They are capable of secreting a broad range of biomolecules such as proteins, nucleic acids, exosomes, microRNAs, and membrane vesicles, collectively known as secretomes. Secretomes are released in response to the surrounding microenvironment. In this article, we briefly address topics related to the therapeutic potential of MSCs as an advanced approach in the field of regenerative medicine and various perspectives.     

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.     

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.     

Prospects for tooth regeneration in the 21st century: a perspective

The prospects for tooth regeneration in the 21st century are compelling. Using the foundations of experimental embryology, developmental and molecular biology, the principles of biomimetics (the mimicking of biological processes), tooth regeneration is becoming a realistic possibility within the next few decades. The cellular, molecular, and developmental "rules" for tooth morphogenesis are rapidly being discovered. The knowledge gained from adult stem cell biology, especially associated with dentin, cartilage, and bone tissue regeneration, provides additional opportunities for eventual tooth organogenesis. The centuries of tooth development using xenotransplantation, allotransplantation, and autotransplantation have resulted in many important insights that can enhance tooth regeneration. In considering the future, several lines of evidence need to be considered: (1) enamel organ epithelia and dental papilla mesenchyme tissues contain stem cells during postnatal stages of life; (2) late cap stage and bell stage tooth organs contain stem cells; (3) odontogenic adult stem cells respond to mechanical as well as chemical "signals"; (4) presumably adult bone marrow as well as dental pulp tissues contain "odontogenic" stem cells; and (5) epithelial-mesenchymal interactions are pre-requisite for tooth regeneration. The authors express "guarded enthusiasm," yet there should be little doubt that adult stem cell-mediated tooth regeneration will be realized in the not too distant future. The prospects for tooth regeneration could be realized in the next few decades and could be rapidly utilized to improve the quality of human life in many nations around the world.     

Mesenchymal stem cell-derived exosome: The likely game-changer in stem cell research

Stem cell research is a promising area of transplantation and regenerative medicine with tremendous potential for improving the clinical treatment and diagnostic options across a variety of conditions and enhancing understanding of human development. Over the past few decades, mesenchymal stem cell (MSCs) studies have exponentially increased with a promising outcome. However, regardless of the huge investment and the research attention given to stem cell research, FDA approval for clinical use is still lacking. Amid the challenges confronting stem cell research as a cell-based product, there appears to be evidence of superior effect and heightened potential success in its expressed vesicles, exosomes, as cell-free products. In addition to their highly desirable intrinsic biologically unique structural, compositional, and morphological characteristics, as well as predominant physiochemical stability and biocompatibility properties, exosomes can also be altered to enhance their therapeutic capability or diagnostic imaging potential via physical, chemical, and biological modification approaches. More importantly, the powerful therapeutic potential and superior biological functions of exosomes, particularly, regarding engineered exosomes as cell-free products, and their utilization in a new generation of nanomedicine treatment, vaccination, and diagnosis platforms, brings hope of a change in the near future. This viewpoint discusses the trend of stem cell research and why stem cell-derived exosomes could be the game-changer.     

Production of mesenchymal stem cell derived-secretome as cell-free regenerative therapy and immunomodulation: A biomanufacturing perspective

The potential of mesenchymal stem cells (MSCs) in regenerative medicine has been largely known due to their capability to induce tissue regeneration in vivo with minimum inflammation during implantation. This adult stem cell type exhibit unique features of tissue repair mechanism and immune modulation mediated by their secreted factors, called secretome. Recently, the utilization of secretome as a therapeutic agent provided new insight into cell-free therapy. Nevertheless, a sufficient amount of secretome is necessary to realize their applications for translational medicine which required a proper biomanufacturing process. Several factors related to their production need to be considered to produce a clinical-grade secretome as a biological therapeutic agent. This viewpoint highlights the current challenges and considerations during the biomanufacturing process of MSCs secretome.     

M1 macrophage-derived exosomes moderate the differentiation of bone marrow mesenchymal stem cells

Differentiated macrophages have been proven to participate in the development of mesenchymal stem cells in different tissues. However, the regulatory processes remain obscure. Exosomes, which are key secretions of macrophages, have attracted increasing attention. Therefore, macrophage-derived exosomes may modulate the development of Bone marrow mesenchymal stem cells (BMMSCs). Different culture conditions were used to induce M1 polarization in THP1 cells. Subsequently, exosomes derived from unpolarized (M0) and polarized (M1) macrophages were isolated, BMMSCs were cultured with normal complete medium or inductive medium supplemented with M0 or M1 derived exosomes, and the osteogenic capacity of the BMMSCs was measured and analyzed. Finally, molecular mechanism associated with Akt and RUNX2 was investigated. Alizarin red staining and WB experiments showed that M1 macrophages could promote the osteogenic differentiation of BMMSCs better than M0 macrophages. Then, exosomes derived from M0 and M1 macrophages were successfully isolated and analyzed by electron microscopy and WB experiments. We concluded that media containing M1-derived exosomes promoted the osteogenic differentiation of BMMSCs better than media containing M0-derived exosomes. In addition, M1-derived exosomes could activate Akt and increase RUNX2 levels to promote osteogenesis. Our data demonstrated that exosomes derived from M1 macrophages induced osteogenesis by activating Akt and increasing RUNX2 level.     

Microenvironmental regulation of stem cells injected in the area at risk of neurodegenerative diseases

The complex mechanism of degenerative diseases and the non-specific modulation of regenerative targets are topics that need to be elucidated in order to advance the use of stem cells in improvement of neurodegenerative diseases. From pre-transplantation through post-transplantation, there are many changes in the conditions, both inside and outside of the stem cells that have not been carefully considered. This has hindered development in the field of cell therapy and regeneration. This viewpoint highlights the potential implications of intracellular and extracellular alterations of stem cells in transplanted areas at risk of neurodegenerative disease.     

Immunoregulatory effects of human amniotic mesenchymal stem cells and their exosomes on human peripheral blood mononuclear cells

Background: The immunomodulatory effects of mesenchymal stem cells (MSCs) and their exosomes have been receiving increasing attention. This study investigated the immunoregulatory effects of human amniotic mesenchymal stem cells (hAMSCs) and their exosomes on phytohemagglutinin (PHA)-induced peripheral blood mononuclear cells (PBMCs). Methods: The hAMSCs used in the experiment were identified by light microscopy and flow cytometry, and the differentiation ability of the cells was determined by Oil Red O and Alizarin Red staining. The expressions of transforming growth factor (TGF)-β, indoleamine 2,3-dioxygenase (IDO), cyclooxygenase-2 (COX-2), hepatocyte growth factor (HGF), and interleukin (IL)-6 were detected by quantitative real-time polymerase chain reaction and western blotting. PBMCs, hAMSCs, and their exosomes were collected for in vitro group culture. Then the immunoregulatory ability of hAMSCs and their exosomes were analyzed by flow cytometry and Enzyme-linked immunosorbent assay. Results: The hAMSCs and exosomes were successfully extracted from the human amniotic membrane. TGF-β, IDO, COX-2, HGF, and IL-6 were significantly expressed in hAMSCs. In vitro co-culture showed that hAMSCs promoted the proliferation of Th2 cells in PHA-induced PBMCs, while hAMSCs and exosomes inhibited the secretion of TNF-α in PHA-induced PBMCs, and promoted the secretion of IL-4 and IL-10, and hAMSCs had more significant effects than exosomes. Conclusions: hAMSCs or exosomes could exert immunoregulatory effects on PHA-induced PBMCs by affecting Th2 cell proliferation and cytokine secretion.     

Adipose-derived mesenchymal stem/stromal cells: from the lab bench to the basic concepts for clinical translation

In the last years, much work has shown that the most effective repair system of the body is represented by stem cells, which are defined as undifferentiated precursors that own unlimited or prolonged self-renewal ability, which also have the potential to transform themselves into various cell types through differentiation.All tissues that form the body contain many different types of somatic cells, along with stem cells that are called ‘mesenchymal stem (or stromal) cells’ (MSC). In certain circumstances, some of these MSC migrate to injured tissues to replace dead cells or to undergo differentiation to repair it.The discovery of MSC has been an important step in regenerative medicine because of their high versatility. Moreover, the finding of a method to isolate MSC from adipose tissue, so called ‘adipose-derived mesenchymal stem cells’ (ASC), which share similar differentiation capabilities and isolation yield that is greater than other MSC, and less bioethical concerns compared to embryonic stem cells, have created self-praised publicity to procure almost any treatment with them. Here, we review the current techniques for isolation, culture and differentiation of human ASC (hASC), and describe them in detail. We also compile some advantages of the hASC over other stem cells, and provide some concepts that could help finding strategies to promote their therapeutic efficiency.     

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.     

Exosomes: Key tools for cancer liquid biopsy

Precision medicine is based on the identification of biomarkers of tumor development and progression. Liquid biopsy is at the forefront of the ability to gather diagnostic and prognostic information on tumors, as it can be noninvasively performed prior or during treatment. Liquid biopsy mostly utilizes circulating tumor cells, or free DNA, but also exosomes. The latter are nanovesicles secreted by most cell types, found in any body fluid that deliver proteins, nucleic acids and lipids to nearby and distant cells with a unique homing ability. Exosomes function in signalling between the tumor microenvironment and the rest of the body, promoting metastasis, immune remodelling and drug resistance. Exosomes are emerging as a key tool in precision medicine for cancer liquid biopsy, as they efficiently preserve their biomarker cargo. Moreover, exosomes strongly resemble the parental cell, which can help in assessing the oxidative and metabolic state of the donor cell. In this respect, exosomes represent one of the most promising new tools to fight cancer. This review will discuss the clinical applications of profiling exosomal proteins and lipids by high-throughput proteomics and metabolomics, and nucleic acids by next generation sequencing, as well as how this may allow cancer diagnosis, therapy response monitoring and recurrence detection.     

The effect of exosomes in transferring TET signaling alterations

Ten eleven translocation (TET) enzymes are composed of three representatives: TET1/2/3 which are involved in the hydroxymethylation of methylated cytosines. Because of the wide array of processes that are governed by these epigenetic marks, there have been a wide range of clinical effects associated with TET alterations. Even though many research groups have focused on analyzing the effect of TET alterations within certain cells, few have taken into consideration the effect of TET in the context of intercellular communication. One important entity through which intercellular communication occurs is represented by exosomes. Thus, in the current viewpoint we discussed the direct transfer of TET by exosomes, its alterations in the cell targeted by exosomes and the effect of TET alterations on exosome secretion.     

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.     

Precise tissue bioengineering and niches of mesenchymal stem cells: Their size and hierarchy matter

Stem cell microterritories (niches), as a specialized part of the extracellular matrix (ECM), are considered an important target and tool for the development of new materials, medical implants, and devices. However, tissue bioengineering products that have stem cell niches of known size on the surface or in the bulk structure of artificial materials are practically unknown. This brief review attempts to draw attention to the problematic aspects of niches as specific parts of the ECM, such as their hierarchy and size for mesenchymal stromal/stem cells (MSCs). These parameters arise directly from numerous definitions of stem cell niches as specialized morphological microterritories found in various tissues. The authors of this review analyze the known information on the hierarchy of MSC microterritories by analogy with that of hematopoietic stem cells. Occasional reports on the size of artificial MSC niches compared to natural niche candidates are summarized. A consensus on a hierarchy and optimal range of niche sizes for MSCs and other stem cells is needed to accelerate the development of prototyping technologies and additive manufacturing in applications to precise tissue bioengineering and regenerative medicine.     

The fate of implanted autologous chondrocytes in regenerated articular cartilage

Autologous chondrocyte implantation (ACI) is used to treat some articular cartilage defects. However, the fate of the cultured chondrocytes after in-vivo transplantation and their role in cartilage regeneration remains unclear. To monitor the survival and fate of such cells in vivo, the chondrocytes were labelled with a lipophilic dye and the resultant regenerated tissue in dogs examined. It was found that, 4 weeks after implantation, the osteochondral defects were filled with regenerative tissue that resembled hyaline cartilage. Fluorescence microscopy of frozen sections of the regenerated tissue revealed that the majority of cells were derived from the DiI-labelled implanted chondrocytes. From these results, it was concluded that a large population of implanted autologous chondrocytes can survive at least 4 weeks after implantation and play a direct role in cartilage regeneration. However, it remains unknown whether other cells, such as periosteal cells or bone marrow stromal stem cells, are involved in the regeneration of cartilage after ACI.