Inflammatory niche: Mesenchymal stromal cell priming by soluble mediators

Mesenchymal stromal/stem cells(MSCs) are adult stem cells of stromal origin that possess self-renewal capacity and the ability to differentiate into multiple mesodermal cell lineages. They play a critical role in tissue homeostasis and wound healing, as well as in regulating the inflammatory microenvironment through interactions with immune cells. Hence, MSCs have garnered great attention as promising candidates for tissue regeneration and cell therapy. Because the inflammatory niche plays a key role in triggering the reparative and immunomodulatory functions of MSCs, priming of MSCs with bioactive molecules has been proposed as a way to foster the therapeutic potential of these cells. In this paper, we review how soluble mediators of the inflammatory niche(cytokines and alarmins) influence the regenerative and immunomodulatory capacity of MSCs, highlighting the major advantages and concerns regarding the therapeutic potential of these inflammatory primed MSCs. The data summarized in this review may provide a significant starting point for future research on priming MSCs and establishing standardized methods for the application of preconditioned MSCs in cell therapy.     

Human mesenchymal stem cells - current trends and future prospective

Stem cells are cells specialized cell, capable of renewing themselves through cell division and can differentiate into multi-lineage cells. These cells are categorized as embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs) and adult stem cells. Mesenchymal stem cells (MSCs) are adult stem cells which can be isolated from human and animal sources. Human MSCs (hMSCs) are the non-haematopoietic, multipotent stem cells with the capacity to differentiate into mesodermal lineage such as osteocytes, adipocytes and chondrocytes as well ectodermal (neurocytes) and endodermal lineages (hepatocytes). MSCs express cell surface markers like cluster of differentiation (CD)29, CD44, CD73, CD90, CD105 and lack the expression of CD14, CD34, CD45 and HLA (human leucocyte antigen)-DR. hMSCs for the first time were reported in the bone marrow and till now they have been isolated from various tissues, including adipose tissue, amniotic fluid, endometrium, dental tissues, umbilical cord and Wharton''s jelly which harbours potential MSCs. hMSCs have been cultured long-term in specific media without any severe abnormalities. Furthermore, MSCs have immunomodulatory features, secrete cytokines and immune-receptors which regulate the microenvironment in the host tissue. Multilineage potential, immunomodulation and secretion of anti-inflammatory molecules makes MSCs an effective tool in the treatment of chronic diseases. In the present review, we have highlighted recent research findings in the area of hMSCs sources, expression of cell surface markers, long-term in vitro culturing, in vitro differentiation potential, immunomodulatory features, its homing capacity, banking and cryopreservation, its application in the treatment of chronic diseases and its use in clinical trials.     

Human mesenchymal stromal cell therapy for damaged cochlea repair in nod-scid mice deafened with kanamycin

Background

Kanamycin, mainly used in the treatment of drug-resistant-tuberculosis, is known to cause irreversible hearing loss. Using the xeno-transplant model, we compared both in vitro and in vivo characteristics of human mesenchymal stromal cells (MSCs) derived from adult tissues, bone marrow (BM-MSCs) and adipose tissue (ADSCs). These tissues were selected for their availability, in vitro multipotency and regenerative potential in vivo in kanamycin-deafened nod-scid mice.

Adult mesenchymal stem cells: potential for muscle and tendon regeneration and use in gene therapy

The expansion potential and plasticity of stem cells, adult or embryonic, offer great promise for their use in medical therapies. Recent provocative data suggest that the differentiation potential of adult stem cells may extend to lineages beyond those usually associated with the germ layer of origin. In this review, we describe recent developments related to adult stem cell research and in particular, in the arena of mesenchymal stem cell (MSC) research. Research demonstrates that transduced MSCs injected into skeletal muscle can persist and express secreted gene products. The ability of the MSC to differentiate into cardiomyocytes has been reported and their ability to engraft and modify the pathology in infarcted animal models is of great interest. Research using MSCs in tendon repair provides information on the effects of physical forces on phenotype and gene expression. In turn, MSCs produce changes in their matrix environment in response to those biomechanical forces. Recent data support the potential of MSCs to repair tendon, ligament, meniscus and other connective tissues. Therapeutic applications of adult stem cells are approaching clinical use in several fields, furthering the possibility to regenerate damaged and diseased tissue.     

Characteristics of stem cells derived from the degenerated human intervertebral disc cartilage endplate

Mesenchymal stem cells (MSCs) derived from adult tissues are an important candidate for cell-based therapies and regenerative medicine due to their multipotential differentiation capability. MSCs have been identified in many adult tissues but have not reported in the human intervertebral disc cartilage endplate (CEP). The initial purpose of this study was to determine whether MSCs exist in the degenerated human CEP. Next, the morphology, proliferation capacity, cell cycle, cell surface epitope profile and differentiation capacity of these CEP-derived stem cells (CESCs) were compared with bone-marrow MSCs (BM-MSCs). Lastly, whether CESCs are a suitable candidate for BM-MSCs was evaluated. Isolated cells from degenerated human CEP were seeded in an agarose suspension culture system to screen the proliferative cell clusters. Cell clusters were chosen and expanded in vitro and were compared with BM-MSCs derived from the same patient. The morphology, proliferation rate, cell cycle, immunophenotype and stem cell gene expression of the CESCs were similar to BM-MSCs. In addition, the CESCs could be induced into osteoblasts, adipocytes, chondrocytes, and are superior to BM-MSCs in terms of osteogenesis and chondrogenesis. This study is first to demonstrate the presence of stem cells in the human degenerated CEP. These results may improve our understanding of intervertebral disc (IVD) pathophysiology and the degeneration process, and could provide cell candidates for cell-based regenerative medicine and tissue engineering.     

Human adipose tissue is a source of multipotent stem cells

Much of the work conducted on adult stem cells has focused on mesenchymal stem cells (MSCs) found within the bone marrow stroma. Adipose tissue, like bone marrow, is derived from the embryonic mesenchyme and contains a stroma that is easily isolated. Preliminary studies have recently identified a putative stem cell population within the adipose stromal compartment. This cell population, termed processed lipoaspirate (PLA) cells, can be isolated from human lipoaspirates and, like MSCs, differentiate toward the osteogenic, adipogenic, myogenic, and chondrogenic lineages. To confirm whether adipose tissue contains stem cells, the PLA population and multiple clonal isolates were analyzed using several molecular and biochemical approaches. PLA cells expressed multiple CD marker antigens similar to those observed on MSCs. Mesodermal lineage induction of PLA cells and clones resulted in the expression of multiple lineage-specific genes and proteins. Furthermore, biochemical analysis also confirmed lineage-specific activity. In addition to mesodermal capacity, PLA cells and clones differentiated into putative neurogenic cells, exhibiting a neuronal-like morphology and expressing several proteins consistent with the neuronal phenotype. Finally, PLA cells exhibited unique characteristics distinct from those seen in MSCs, including differences in CD marker profile and gene expression.     

Intermolecular interactions of homologs of germ plasm components in mammalian germ cells

In some species such as flies, worms, frogs and fish, the key to forming and maintaining early germ cell populations is the assembly of germ plasm, microscopically distinct egg cytoplasm that is rich in RNAs, RNA-binding proteins and ribosomes. Cells which inherit germ plasm are destined for the germ cell lineage. In contrast, in mammals, germ cells are formed and maintained later in development as a result of inductive signaling from one embryonic cell type to another. Research advances, using complementary approaches, including identification of key signaling factors that act during the initial stages of germ cell development, differentiation of germ cells in vitro from mouse and human embryonic stem cells and the demonstration that homologs of germ plasm components are conserved in mammals, have shed light on key elements in the early development of mammalian germ cells. Here, we use FRET (Fluorescence Resonance Energy Transfer) to demonstrate that living mammalian germ cells possess specific RNA/protein complexes that contain germ plasm homologs, beginning in the earliest stages of development examined. Moreover, we demonstrate that, although both human and mouse germ cells and embryonic stem cells express the same proteins, germ cell-specific protein/protein interactions distinguish germ cells from precursor embryonic stem cells in vitro; interactions also determine sub-cellular localization of complex components. Finally, we suggest that assembly of similar protein complexes may be central to differentiation of diverse cell lineages and provide useful diagnostic tools for isolation of specific cell types from the assorted types differentiated from embryonic stem cells.     

Comparison of the Neural Differentiation Potential of Human Mesenchymal Stem Cells from Amniotic Fluid and Adult Bone Marrow

Human mesenchymal stem cells (MSCs) are considered a promising tool for cell-based therapies of nervous system diseases. Bone marrow (BM) has been the traditional source of MSCs (BM-MSCs). However, there are some limitations for their clinical use, such as the decline in cell number and differentiation potential with age. Recently, amniotic fluid (AF)-derived MSCs (AF-MSCs) have been shown to express embryonic and adult stem cell markers, and can differentiate into cells of all three germ layers. In this study, we isolated AF-MSCs from second-trimester AF by limiting dilution and compared their proliferative capacity, multipotency, neural differentiation ability, and secretion of neurotrophins to those of BM-MSCs. AF-MSCs showed a higher proliferative capacity and more rapidly formed and expanded neurospheres compared to those of BM-MSCs. Both immunocytochemical and quantitative real-time PCR analyses demonstrated that AF-MSCs showed higher expression of neural stemness markers than those of BM-MSCs following neural stem cell (NSC) differentiation. Furthermore, the levels of brain-derived growth factor and nerve growth factor secreted by AF-MSCs in the culture medium were higher than those of BM-MSCs. In addition, AF-MSCs maintained a normal karyotype in long-term cultures after NSC differentiation and were not tumorigenic in vivo. Our findings suggest that AF-MSCs are a promising and safe alternative to BM-MSCs for therapy of nervous system diseases.     

Development of the male germline stem cell niche in Drosophila

Stem cells are found in specialized microenvironments, or "niches", which regulate stem cell identity and behavior. The adult testis and ovary in Drosophila contain germline stem cells (GSCs) with well-defined niches, and are excellent models for studying niche development. Here, we investigate the formation of the testis GSC niche, or "hub", during the late stages of embryogenesis. By morphological and molecular criteria, we identify and follow the development of an embryonic hub that forms from a subset of anterior somatic gonadal precursors (SGPs) in the male gonad. Embryonic hub cells form a discrete cluster apart from other SGPs, express several molecular markers in common with the adult hub and organize anterior-most germ cells in a rosette pattern characteristic of GSCs in the adult. The sex determination genes transformer and doublesex ensure that hub formation occurs only in males. Interestingly, hub formation occurs in both XX and XY gonads mutant for doublesex, indicating that doublesex is required to repress hub formation in females. This work establishes the Drosophila male GSC niche as a model for understanding the mechanisms controlling niche formation and initial stem cell recruitment, as well as the development of sexual dimorphism in the gonad.     

Mesenchymal stem cells in tumor development: Emerging roles and concepts

Mesenchymal stem cells (MSCs) are multipotent progenitor cells that participate in the structural and functional maintenance of connective tissues under normal homeostasis. They also act as trophic mediators during tissue repair, generating bioactive molecules that help in tissue regeneration following injury. MSCs serve comparable roles in cases of malignancy and are becoming increasingly appreciated as critical components of the tumor microenvironment. MSCs home to developing tumors with great affinity, where they exacerbate cancer cell proliferation, motility, invasion and metastasis, foster angiogenesis, promote tumor desmoplasia and suppress anti-tumor immune responses. These multifaceted roles emerge as a product of reciprocal interactions occurring between MSCs and cancer cells and serve to alter the tumor milieu, setting into motion a dynamic co-evolution of both tumor and stromal tissues that favors tumor progression. Here, we summarize our current knowledge about the involvement of MSCs in cancer pathogenesis and review accumulating evidence that have placed them at the center of the pro-malignant tumor stroma.     

Mesenchymal stem cells in tumor development

Mesenchymal stem cells (MSCs) are multipotent progenitor cells that participate in the structural and functional maintenance of connective tissues under normal homeostasis. They also act as trophic mediators during tissue repair, generating bioactive molecules that help in tissue regeneration following injury. MSCs serve comparable roles in cases of malignancy and are becoming increasingly appreciated as critical components of the tumor microenvironment. MSCs home to developing tumors with great affinity, where they exacerbate cancer cell proliferation, motility, invasion and metastasis, foster angiogenesis, promote tumor desmoplasia and suppress anti-tumor immune responses. These multifaceted roles emerge as a product of reciprocal interactions occurring between MSCs and cancer cells and serve to alter the tumor milieu, setting into motion a dynamic co-evolution of both tumor and stromal tissues that favors tumor progression. Here, we summarize our current knowledge about the involvement of MSCs in cancer pathogenesis and review accumulating evidence that have placed them at the center of the pro-malignant tumor stroma.     

Expression of cardiac function genes in adult stem cells is increased by treatment with nitric oxide agents

Mesenchymal stem cells (MSCs) have received special attention for cardiomyoplasty because several studies have shown that they differentiate into cardiomyocytes both in vitro and in vivo. Nitric oxide (NO) is a free radical signaling molecule that regulates several differentiation processes including cardiomyogenesis. Here, we report an investigation of the effects of two NO agents (SNAP and DEA/NO), able to activate both cGMP-dependent and -independent pathways, on the cardiomyogenic potential of bone marrow-derived mesenchymal stem cells (BM-MSCs) and adipose tissue-derived stem cells (ADSCs). The cells were isolated, cultured and treated with NO agents. Cardiac- and muscle-specific gene expression was analyzed by indirect immunofluorescence, flow cytometry, RT-PCR and real-time PCR. We found that untreated (control) ADSCs and BM-MSCs expressed some muscle markers and NO-derived intermediates induce an increased expression of some cardiac function genes in BM-MSCs and ADSCs. Moreover, NO agents considerably increased the pro-angiogenic potential mostly of BM-MSCs as determined by VEGF mRNA levels.     

Novel aspects of parenchymal–mesenchymal interactions: from cell types to molecules and beyond

Mesenchymal stem or stromal cells (MSCs) were initially isolated from the bone marrow and received their name on the basis of their ability to differentiate into multiple lineages such as bone, cartilage, fat and muscle. However, more recent studies suggest that MSCs residing in perivascular compartments of the small and large blood vessels play a regulatory function supporting physiologic and pathologic responses of parenchymal cells, which define the functional representation of an organ or tissue. MSCs secrete or express factors that reach neighbouring parenchymal cells via either a paracrine effect or a direct cell‐to‐cell interaction promoting functional activity, survival and proliferation of the parenchymal cells. Previous concept of ‘epithelial–stromal’ interactions can now be widened. Given that MSC can also support hematopoietic, neuronal and other non‐epithelial parenchymal lineages, terms ‘parenchymal–stromal’ or ‘parenchymal–mesenchymal’ interactions may better describe the supportive or ‘trophic’ functions of MSC. Importantly, in many cases, MSCs specifically provide supportive microenvironment for the most primitive stem or progenitor populations and therefore can play a role as ‘stem/progenitor niche’ forming cells. So far, regulatory roles of MSCs have been reported in many tissues. In this review article, we summarize the latest studies that focused on the supportive function of MSC. This thread of research leads to a new perspective on the interactions between parenchymal and mesenchymal cells and justifies a principally novel approach for regenerative medicine based on co‐application of MSC and parenchymal cell for the most efficient tissue repair. Copyright © 2013 John Wiley & Sons, Ltd.     

IL-17 and FGF signaling involved in mouse mesenchymal stem cell proliferation

The mouse is a suitable experimental model to study the biology of mesenchymal stem cells (MSCs), as well as to be used in biocompatibility studies and tissue engineering models. However, the isolation and purification of murine MSCs is far more challenging than their counterparts from other species. In this study, we isolated, expanded and characterized mouse MSCs from bone marrow (BM-MSCs). Additionally, we analyzed the effects of two regulatory molecules, interleukin 17 (IL-17) and basic fibroblast growth factor (bFGF), on BM-MSCs growth and elucidated the signaling pathways involved. The results revealed that IL-17 increased the frequency of colony-forming units fibroblast (CFU-F) as well as the BM-MSCs proliferation in a dose-dependent manner, while bFGF supplementation had no significant effect on CFU-F frequency but induced an increase in cell proliferation. Their combined usage did not produce additive effects on BM-MSCs proliferation and even induced reduction in the number of CFU-F. Also, the involvement of both p38 and extracellular signal-regulated kinase (ERK) mitogen-activated protein kinases (MAPKs) signaling in proliferative activity of IL-17 and bFGF on murine BM-MSCs and, moreover, the increased co-activation of a common signaling molecule, p38 MAPK, were demonstrated. Together, the data presented highlighted the role of IL-17 and bFGF in murine BM-MSCs proliferation and pointed to the complexity and specificity of the signaling networks leading to MSCs proliferation in response to different regulatory molecules.     

Characterization of in vitro cultured bone marrow and adipose tissue‐derived mesenchymal stem cells and their ability to express neurotrophic factors

MSCs (mesenchymal stem cells) have attracted attention as a promising tool for regenerative medicine and transplantation therapy. MSCs exert neuroprotective effects by secreting a number of factors in vitro and in vivo. Similar characteristics are found in ADSCs (adipose‐derived stem cells) and BMSCs (bone marrow stromal cells). Multipotent capability, easy accessibility and rapid proliferation of ADSCs have been established. Our main objective was to compare cell viability, growth rate, expression of neurotrophic factors and nestin genes in ADSCs and BMSCs. Cell doubling time and proliferation rate indicate that ADSCs has a higher proliferation rate than BMSCs. ADSCs and BMSCs express a similar pattern of CD71 and CD90 markers. Nestin immunostaining showed that ADSCs and BMSCs are immunopositive. The expression of neurotrophic factors genes in ADSCs proved similar to that of BMSCs genes. Thus adipose tissue stem cells with a high proliferation rate can express nestin and neurotrophic factor genes. Therefore ADSCs may be useful in future cell replacement therapies and help improve neurodegenerative diseases.     

Increased Proliferation and Analysis of Differential Gene Expression in Human Wharton's Jelly-derived Mesenchymal Stromal Cells under Hypoxia

Multipotent mesenchymal stromal cells (MSCs) from Wharton''s jelly (WJ) of umbilical cord bear higher proliferation rate and self-renewal capacity than adult tissue-derived MSCs and are a primitive stromal cell population. Stem cell niche or physiological microenvironment plays a crucial role in maintenance of stem cell properties and oxygen concentration is an important component of the stem cell niche. Low oxygen tension or hypoxia is prevalent in the microenvironment of embryonic stem cells and many adult stem cells at early stages of development. Again, in vivo, MSCs are known to home specifically to hypoxic events following tissue injuries. Here we examined the effect of hypoxia on proliferation and in vitro differentiation potential of WJ-MSCs. Under hypoxia, WJ-MSCs exhibited improved proliferative potential while maintaining multi-lineage differentiation potential and surface marker expression. Hypoxic WJ-MSCs expressed higher mRNA levels of hypoxia inducible factors, notch receptors and notch downstream gene HES1. Gene expression profile of WJ-MSCs exposed to hypoxia and normoxia was compared and we identified a differential gene expression pattern where several stem cells markers and early mesodermal/endothelial genes such as DESMIN, CD34, ACTC were upregulated under hypoxia, suggesting that in vitro culturing of WJ-MSCs under hypoxic conditions leads to adoption of a mesodermal/endothelial fate. Thus, we demonstrate for the first time the effect of hypoxia on gene expression and growth kinetics of WJ-MSCs. Finally, although WJ-MSCs do not induce teratomas, under stressful and long-term culture conditions, MSCs can occasionally undergo transformation. Though there were no chromosomal abnormalities, certain transformation markers were upregulated in a few of the samples of WJ-MSCs under hypoxia.