A strategy for enhancing the engraftment of human hematopoietic stem cells in NOD/SCID mice

To overcome the limitations of allogeneic hematopoietic stem cell transplantation (HSCT), we conducted a study to identify a strategy for enhancing hematopoietic stem cell (HSC) engraftment during HSCT. Co-transplantation experiments with mesenchymal stem cells (MSCs) derived from adult human tissues including bone marrow (BM), adipose tissue (AT), and umbilical cord blood (CB) were conducted. We showed that AT-MSCs and CB-MSCs enhanced the engraftment of HSCs as effectively as BM-MSCs in NOD/SCID mice, suggesting that AT-MSCs and CB-MSCs can be used as alternative stem cell sources for enhancing the engraftment and homing of HSCs. CB-MSCs derived from different donors showed different degrees of efficacy in enhancing the engraftment of HSCs. The most effective CB-MSCs showed higher proliferation rates and secreted more MCP-1, RANTES, EGF, and VEGF. Our results suggest that AT-MSCs and CB-MSCs could be alternative stem cell sources for co-transplantation in HSCT. Furthermore, in terms of MSCs’ heterogeneity, characteristics of each population of MSCs are considerable factors for selecting MSCs suitable for co-transplantation with HSC.     

SSEA-4 identifies mesenchymal stem cells from bone marrow

Adult bone marrow (BM) contains hematopoietic stem cells (HSCs) as well as a nonhematopoietic, stromal cell population. Within this stromal population are mesenchymal stem cells (MSCs), which not only support hematopoiesis but also differentiate into multiple lineages, including fat, bone, and cartilage. Because of this multipotentiality, the MSC is an attractive candidate for clinical applications to repair or regenerate damaged tissues of mesenchymal origin. However, research progress has been hampered by the limited existing knowledge of the biology of these cells, particularly by the lack of a suitable marker for their prospective isolation. Here, we report that SSEA-4, an early embryonic glycolipid antigen commonly used as a marker for undifferentiated pluripotent human embryonic stem cells and cleavage to blastocyst stage embryos, also identifies the adult mesenchymal stem cell population.     

Mesenchymal stem cell therapy for cirrhosis: Present and future perspectives

Cirrhosis occurs as a result of various chronic liver injuries, which may be caused by viral infections, alcohol abuse and the administration of drugs and chemicals. Recently, bone marrow cells (BMCs), hematopoietic stem cells (HSCs) and mesenchymal stem cells (MSCs) have been used for developing treatments for cirrhosis. Clinical trials have investigated the therapeutic potential of BMCs, HSCs and MSCs for the treatment of cirrhosis based on their potential to differentiate into hepatocytes. Although the therapeutic mechanisms of BMC, HSC and MSC treatments are still not fully characterized, the evidence thus far has indicated that the potential therapeutic mechanisms of MSCs are clearer than those of BMCs or HSCs with respect to liver regenerative medicine. MSCs suppress inflammatory responses, reduce hepatocyte apoptosis, increase hepatocyte regeneration, reverse liver fibrosis and enhance liver functionality. This paper summarizes the clinical studies that have used BMCs, HSCs and MSCs in patients with liver failure or cirrhosis. We also present the potential therapeutic mechanisms of BMCs, HSCs and MSCs for the improvement of liver function.     

Plasticity of marrow-derived stem cells

Bone marrow (BM) contains hematopoietic stem cells (HSCs), which differentiate into every type of mature blood cell; endothelial cell progenitors; and marrow stromal cells, also called mesenchymal stem cells (MSCs), which can differentiate into mature cells of multiple mesenchymal tissues including fat, bone, and cartilage. Recent findings indicate that adult BM also contains cells that can differentiate into additional mature, nonhematopoietic cells of multiple tissues including epithelial cells of the liver, kidney, lung, skin, gastrointestinal (GI) tract, and myocytes of heart and skeletal muscle. Experimental results obtained in vitro and in vivo are the subject of this review. The emphasis is on how these experiments were performed and under what conditions differentiation from bone marrow to epithelial and neural cells occurs. Questions arise regarding whether tissue injury is necessary for this differentiation and the mechanisms by which it occurs. We also consider which bone marrow subpopulations are capable of this differentiation. Only after we have a better understanding of the mechanisms involved and of the cells required for this differentiation will we be able to fully harness adult stem cell plasticity for clinical purposes.     

Human umbilical cord is a unique and safe source of various types of stem cells suitable for treatment of hematological diseases and for regenerative medicine

Cord blood (CB) is a rich source of hematopoietic stem cells (HSCs) and for this reason CB transplantation has been used successfully for the treatment of some malignant and nonmalignant diseases. However, this technique is limited by the relatively low number of HSCs present in each CB unit and by the delayed engraftment of platelets and neutrophils. To bypass these obstacles efforts have been made to develop strategies to expand CB HSCs in vitro for transplantation. CB is also an important source of other stem cells, including endothelial progenitors, mesenchymal stem cells (MSCs), very small embryonic/epiblast-like (VSEL) stem cells, and unrestricted somatic stem cells (USSC), potentially suitable for use in regenerative medicine. For some of these stem cell populations, such as MSCs, clinical studies have been started and for other stem cell populations potential clinical applications have been identified and clinical studies will follow. In addition to CB, other parts of umbilical cord, such as the Wharton's jelly, or tissues strictly linked such as the placenta are also rich sources of stem cells.     

Targeting the Molecular and Cellular Interactions of the Bone Marrow Niche in Immunologic Disease

Recent investigations have expanded our knowledge of the regulatory bone marrow (BM) niche, which is critical in maintaining and directing hematopoietic stem cell (HSC) self-renewal and differentiation. Osteoblasts, mesenchymal stem cells (MSCs), and CXCL12-abundant reticular (CAR) cells are niche components in close association with HSCs and have been more clearly defined in immune cell function and homeostasis. Importantly, cellular inhabitants of the BM niche signal through G protein-coupled surface receptors (GPCRs) for various appropriate immune functions. In this article, recent literature on BM niche inhabitants (HSCs, osteoblasts, MSCs, CAR cells) and their GPCR mechanistic interactions are reviewed for better understanding of the BM cells involved in immune development, immunologic disease, and current immune reconstitution therapies.     

A novel BMT technique for treatment of various currently intractable diseases

A recently-developed BMT method combines a "Perfusion Method" (PM) for collecting bone marrow cells (BMCs) with the Intra-Bone Marrow (IBM) injection of BMCs (IBM-BMT). As distinct from the conventional aspiration method (AM), the PM allows rapid (within 1?h) collection of BMCs without T cell contamination (T cells?相似文献   

Hierarchical organization and regulation of the hematopoietic stem cell osteoblastic niche

Hematopoietic stem cells (HSCs) are characterized with long-term self-renewal and multi-lineage differentiation. HSCs preferentially reside in osteoblastic niche that is hierarchically organized so as to exactly regulate HSCs properties and maintain organism hematopoietic homeostasis. Hematopoietic stem cell–mesenchymal stem cell pairings share stem cell niches in adult bone marrow under immune–humoral–neural regulation. Here, we review the hierarchical HSC osteoblastic niche in terms of its localization, composition, function, and multi-layer regulation systems.     

The influence of extracellular matrix proteins and mesenchymal stem cells on erythropoietic cell maturation

Background and Objectives As part of the bone marrow niche, cellular and acellular components like mesenchymal stem cells (MSCs) and extracellular matrix (ECM) proteins influence human haematopoiesis. To identify factors able to improve the in vitro generation of red blood cells (RBCs), we investigated the effect of these factors on proliferation and differentiation of human haematopoietic stem cells (HSCs) into erythroid cells. Material and Methods Granulocyte colony‐stimulating factor–mobilized CD34⁺ HSCs were cultured for 16 days using an in vitro erythropoiesis assay as described previously (by our group). The HSCs were co‐cultured with MSCs in either direct or indirect contact and with different ECM proteins (fibronectin, laminin, collagen and a mixture of ECM proteins, called ECM gel). Results Co‐culturing of HSCs with ECM gel improved cell viability, and the presence of laminin slightly increased the maturation into enucleated RBCs. HSC expansion could not be improved by addition of any of the ECM proteins investigated. In contrast, fibronectin inhibited erythroid formation. Co‐culturing of HSCs with MSCs generally stimulated cell viability and HSC proliferation, however, in favour of the myeloid lineage. In summary, of all investigated factors, only laminin and ECM gel had a supportive effect on RBC development under the described in vitro culture conditions.     

Dual origin of mesenchymal stem cells contributing to organ growth and repair

In many adult tissues, mesenchymal stem cells (MSCs) are closely associated with perivascular niches and coexpress many markers in common with pericytes. The ability of pericytes to act as MSCs, however, remains controversial. By using genetic lineage tracing, we show that some pericytes differentiate into specialized tooth mesenchyme-derived cells--odontoblasts--during tooth growth and in response to damage in vivo. As the pericyte-derived mesenchymal cell contribution to odontoblast differentiation does not account for all cell differentiation, we identify an additional source of cells with MSC-like properties that are stimulated to migrate toward areas of tissue damage and differentiate into odontoblasts. Thus, although pericytes are capable of acting as a source of MSCs and differentiating into cells of mesenchymal origin, they do so alongside other MSCs of a nonpericyte origin. This study identifies a dual origin of MSCs in a single tissue and suggests that the pericyte contribution to MSC-derived mesenchymal cells in any given tissue is variable and possibly dependent on the extent of the vascularity.     

The emergence of definitive hematopoietic stem cells in the mammal

PURPOSE OF REVIEW: Hematopoietic stem cells (HSC) are the basis for blood formation during adult life. The amazing potency of HSCs has been exploited for over 30 years in regenerative therapies for patients with blood-related genetic disease and leukemia. As clinically important cells and also as the most widely studied cell differentiation system, they have been the focus of intense fundamental research. Indeed, HSC research has established many paradigms in the more general field of stem cells. Recently, the study of the embryonic origins of HSCs and their genetic program is beginning to provide unique insights into how these stem cells are formed, maintained, and expanded, and how they contribute to the complex adult hematopoietic system. Although many short-lived hematopoietic progenitors are present in early stage mammalian embryos, this review will focus on the events leading to emergence of the most potent cells of the hematopoietic system, HSCs and on their developmental lineage relationships. RECENT FINDINGS: Developmental and genetic studies further our understanding of the fate determination events occurring in several embryonic tissues leading to the generation of potent HSCs--those cells with the ability to long-term, high-level repopulate all hematopoietic lineages of the adult. SUMMARY: Several mammalian embryonic tissues contribute to the growth and/or generation of potent HSCs that are the source of blood cells throughout the lifespan of the individual. Insight into how mammalian HSC fate is determined has been provided through functional, phenotypic, and genetic studies at early developmental stages.     

PTH and stem cells

At least 2 different types of cells, hematopoietic and mesenchymal, are present in the adult bone marrow, in addition to endothelial cells. Hematopoietic and mesenchymal cells are believed to originate from hematopoietic stem cells (HSC) and mesenchymal stem cells (MSC), respectively. The bone marrow stroma, a cellular microenvironment that supports HSC, is composed of non-hematopoietic cells and contains MSC. A unique expansion of the bone marrow stroma, also known as marrow fibrosis, is the hallmark of a variety of disorders including hyperparathyroidism and fibrous dysplasia. PTH is the first bone anabolic agent approved by US Food and Drug Administration for the treatment of osteoporosis. Recent studies have suggested that PTH treatment may affect the number of hematopoietic stem cells in the bone marrow and their mobilization into the bloodstream. In addition, cells with classical features of mesenchymal stem cells/progenitors have been shown to express receptors for PTH, and to increase in number and undergo redistribution in the adult bone marrow upon PTH treatment. In this review, we will summarize the up-to-date knowledge on PTH and its relation to stem cells. We will also discuss the contribution of different cell types to the development of marrow fibrosis and the involvement of PTH signaling in this pathology.     

Bone marrow-derived mesenchymal stem cells remain host-derived despite successful hematopoietic engraftment after allogeneic transplantation in patients with lysosomal and peroxisomal storage diseases

Human bone marrow contains mesenchymal stem cells (MSCs) that can differentiate into various cells of mesenchymal origin. We developed an efficient method of isolating and culture expanding a homogenous population of MSCs from bone marrow and determined that MSCs express alpha-L-iduronidase, arylsulfatase-A and B, glucocerebrosidase, and adrenoleukodystrophy protein. These findings raised the possibility that MSCs may be useful in the treatment of storage disorders. To determine if donor derived MSCs are transferred to the recipients with lysosomal or peroxisomal storage diseases by allogeneic hematopoietic stem cell (HSC) transplantation, we investigated bone marrow derived MSCs of 13 patients 1-14 years after allogeneic transplantation. Highly purified MSCs were genotyped either by fluorescence in situ hybridization using probes for X and Y-chromosomes in gender mis-matched recipients or by radiolabeled PCR amplification of polymorphic simple sequence repeats. Phenotype was determined by the measurement of disease specific protein/enzyme activity in purified MSCs. We found that MSCs isolated from recipients of allogeneic HSC transplantation are not of donor genotype and have persistent phenotypic defects despite successful donor type hematopoietic engraftment. Whether culture expanded normal MSCs can be successfully transplanted into patients with storage diseases and provide therapeutic benefit needs to be determined.     

Hepatic stellate cell progenitor cells

Hepatic stellate cells (HSCs) are recognized as a major player in liver fibrogenesis. Upon liver injury, HSCs differentiate into myofibroblasts and participate in progression of fibrosis and cirrhosis. Additional cell types such as resident liver fibroblasts/myofibroblasts or bone marrow cells are also known to generate myofibroblasts. One of the major obstacles to understanding the mechanism of liver fibrogenesis is the lack of knowledge regarding the developmental origin of HSCs and other liver mesenchymal cells. Recent cell lineage analyses demonstrate that HSCs are derived from mesoderm during liver development. MesP1-expressing mesoderm gives rise to the septum transversum mesenchyme before liver formation and then to the liver mesothelium and mesenchymal cells, including HSCs and perivascular mesenchymal cells around the veins during liver development. During the growth of embryonic liver, the mesothelium, consisting of mesothelial cells and submesothelial cells, migrates inward from the liver surface and gives rise to HSCs and perivascular mesenchymal cells, including portal fibroblasts, smooth muscle cells around the portal vein, and fibroblasts around the central vein. Cell lineage analyses indicate that mesothelial cells are HSC progenitor cells capable of differentiating into HSCs and other liver mesenchymal cells during liver development.     

Stem cell heterogeneity: implications for aging and regenerative medicine

For decades, hematopoietic stem cells (HSCs) were thought to be a homogeneous population of cells with flexible behavior. Now a new picture has emerged: The HSC compartment consists of several subpopulations of HSCs each with distinct, preprogrammed differentiation and proliferation behaviors. These programs are epigenetically fixed and are stably bequeathed to all daughter HSCs on self-renewal. HSCs within each subset are remarkably similar in their self- renewal and differentiation behaviors, to the point where their life span can be predicted with mathematical certainty. Three subsets can be distinguished when HSCs are classified by their differentiation capacity: myeloid-biased, balanced, and lymphoid-biased HSCs. The relative number of the HSC subsets is developmentally regulated. Lymphoid-biased HSCs are found predominantly early in the life of an organism, whereas myeloid-biased HSCs accumulate in aged mice and humans. Thus, the discovery of distinct subpopulations of HSCs has led to a new understanding of HCS aging. This finding has implications for other aspects of HSC biology and applications in re-generative medicine. The possibility that other adult tissue stem cells show similar heterogeneity and mechanisms of aging is discussed.     

Hematopoietic origin of fibroblasts/myofibroblasts: Its pathophysiologic implications

Tissue fibroblasts/myofibroblasts play a key role in growth factor secretion, matrix deposition, and matrix degradation, and therefore are important in many pathologic processes. Regarding the origin of tissue fibroblasts/myofibroblasts, a number of recent in vivo transplantation studies have suggested the bone marrow as the source of fibroblasts/myofibroblasts in liver, intestine, skin, and lung. Because bone marrow cells are thought to contain 2 types of stem cells (ie, hematopoietic stem cells [HSCs] and mesenchymal stem cells), it is important to determine which type of stem cells is the source of fibroblasts/myofibroblasts. To address this issue, we have carried out a series of studies of tissue reconstitution by single HSCs. By transplanting clones derived from single HSCs expressing transgenic enhanced green fluorescent protein, we found that fibroblasts/myofibroblasts in many organs and tissues are derived from HSCs. This brief note summarizes these findings and discusses clinical and experimental perspectives generated by this newly identified differentiation pathway of HSCs.     

Highly potent human haemopoietic stem cells first emerge in the intraembryonic aorta-gonad-mesonephros region

BackgroundHaemopoietic stem cells (HSCs) are used in the clinic to treat various haematological disorders. These cells emerge during early embryogenesis and maintain haemopoiesis in the adult organism. In the vertebrate embryo, HSCs develop in multiple locations. Little is known about the embryonic development of human HSCs.MethodsHuman embryonic and fetal tissues were obtained after elective termination of pregnancy. Preconditioned immunodeficient mice were used as recipients for human HSCs. Transplanted mice were bled every 1–2 months to assess human HSC contribution.FindingsWe have found that human HSCs emerge first in the aorta-gonad-mesonephros (AGM) region and only later appear in the yolk sac, liver, and placenta. Transplantation of human AGM region cells into immunodeficient mice provides long-term high-level multilineage haemopoietic repopulation. We have shown that, despite the low number of HSCs in the human AGM region, their self-renewal potential is enormous. A single HSC derived from the AGM region generates around 600 daughter HSCs in primary recipients, which disseminate throughout the entire recipient bone marrow and are retransplantable.InterpretationWe provide a systematic spatiotemporal analysis of HSC emergence in the early human embryo and identify the AGM region as the primary source of powerful HSCs with enormous self-renewal capacity. This high potency of the first HSCs sets a new standard for in-vitro generation of HSCs from pluripotent stem cells for the purpose of regenerative medicine.FundingUK Medical Research Council.     

Hepatic differentiation capability of rat bone marrow-derived mesenchymal stem cells and hematopoietic stem cells

AIM: To investigate the different effects of mesenchymal stem cells (MSCs) and hematopoietic stem cells (HSCs) on hepatic differentiation. METHODS: MSCs from rat bone marrow were isolated and cultured by standard methods. HSCs from rat bone marrow were isolated and purified by magnetic activated cell sorting. Both cell subsets were induced. Morphology, RT-PCR and immunocytochemistry were used to identify the hepatic differentiation grade. RESULTS: MSCs exhibited round in shape after differentiation, instead of fibroblast-like morphology before differentiation. Albumin mRNA and protein were expressed positively in MSCs, without detection of alpha-fetoprotein (AFP). HSCs were polygonal in shape after differentiation. The expression of albumin signal decreased and AFP signal increased. The expression of CK18 was continuous in MSCs and HSCs both before and after induction. CONCLUSION: Both MSCs and HSCs have hepatic differentiation capabilities. However, their capabilities are not the same. MSCs can differentiate into mature hepatocyte-like cells, never expressing early hepatic specific genes, while Thy-1.1(+) cells are inclined to differentiate into hepatic stem cell-like cells, with an increasing AFP expression and a decreasing albumin signal. CK18 mRNA is positive in Thy-1.1(+) cells and MSCs, negative in Thy-1.1(-) cells. It seems that CK18 has some relationship with Thy-1.1 antigen, and CK18 may be a predictive marker of hepatic differentiation capability.     

Mesenchymal stem cells: harnessing cell plasticity to tissue and organ repair

Plastic behavior of cells is a hallmark of embryonic development. The emergence of primary mesenchyme from within the inner cell mass entails the first epithelial-mesenchymal transition step that is then followed by sequential transitions; the formation of new tissues and organs requires transitions from mesenchyme into epithelium and vice versa. Although it is currently believed that in the adult such transitions do not persist, the frequent occurrence of mesenchymal stem cells (MSCs) in various tissues of the adult organisms, and the reported plasticity of such adult mesenchymal cells, raises the question as to whether the frequency of mesenchymal epithelial transitions in the adult have been underestimated. Indeed, adult mesenchymal stem cells have been reported to differentiate in culture into a multitude of mature cell types including epithelial cells. This opens the way to the use of these stem cells for the construction of new tissues and organs for therapeutic purposes, but the question is still open as to whether mesenchymal stem cells transdifferentiate also in vivo. The molecular mechanism that underlies the plasticity of mesenchymal stem cells and their capacity to transdifferentiate is unresolved. We found that these cells have a promiscuous gene expression pattern; mesenchymal cells, whether primary or cloned cell lines, express T cell receptor (TCR) beta and alpha genes, along with other components of the TCR complex. These cells may therefore be in a standby state, in which many gene families are expressed at a low level thereby making the cell readily capable of shifting fates.