Stem cells are a kind of specialized cell type with the ability of self-renewal and multilineage differentiation potential. They can proliferate and differentiate into many other cell types under a specific condition. However, proliferation and differentiation behaviors of stem cells depend on their located microenvironment, which is also named stem cell niche. An appropriate spatiotemporal dialog occurs between stem cells and niche to fulfill the balance of their self-renewal and differentiation. This review focused on several different stem cell niches and their relationship with proliferation and differentiation of stem cells.
Cell Differentiation ; Cell Proliferation ; Humans ; Stem Cell Niche ; physiology ; Stem Cells ; cytology ; physiology

The self-renewal and differentiation of adult stem cells are closely related to their niches. Naturally, spermatogonial stem cells (SSCs) are the only adult stem cells in the body, which can transfer genetic information into the offspring. An insight into the modulation of the self-renewal and differentiation of SSCs can help elucidate the mechanisms of spermatogenesis and investigate the proliferation and differentiation of other adult stem cells. Therefore, the SSC system provides an ideal model for researches on the adult stem cell niche. More and more evidence indicates that the self-renewal and differentiation of SSCs are regulated by their niches. Based on our previous work and other related findings recently reported, this article presents an overview on the biological properties of SSC niches and their relationship with the self-renewal and differentiation of SSCs, focusing on the basic properties and components of SSC niches and various regulatory factors they produce.
Animals ; Cell Differentiation ; Male ; Spermatogenesis ; Spermatogonia ; cytology ; Stem Cell Niche ; Stem Cells ; cytology

Hematopoietic stem cell transplantation (HSCT) is an important mean for clinical treatment to many of hematological diseases, malignant diseases, hereditary diseases and autoimmune diseases. Whether the implanted hematopoietic stem cells (HSC) can home to bone marrow (BM) smoothly and reconstitute the hematopoiesis is the key to successful HSCT. With the cognition of HSC homing mechanism, the visual observation of HSC homing to BM is attracting more and more attention and helps to clarify the micro-dialogue between HSC and BM microenvironment. In recent years, with the development of imaging technology, confocal laser scanning microscope (CLSM) and two-photon microscope are able to make 3D reconstruction and real-time observation of the tissue or cells. Researches on HSC homing process visibly become reality. In this article the methods of visual research and their application in HSC homing observation are reviewed.
Cell Movement ; Hematopoiesis ; physiology ; Hematopoietic Stem Cells ; cytology ; physiology ; Humans ; Stem Cell Niche ; physiology

Cancer stem cells represent a subpopulation of cells within tumor mass, endowed with self-renewal, survival, proliferation, and tumorigenic capacity. These cell populations are potentially associated with cancer prognosis. However, these cells do not play a part in isolation; instead, they are dependent on a variety of signals from their microenvironments. Cancer stem cells have two microenvironment niches: the first one is perivascular niche and the second is hypoxic regions where tumor stem cells locate. Bidirectional signal transduction is found between cancer stem cells and cancer stem cell niches. As a cancer stem cell-specific surface marker, CD133 plays a role in key molecular signaling pathways and high levels of drug-or radiation-resistance. Other molecules closely related to cancer stem cell signaling pathways include Wnt and Hh, which are also associated with cancer drug resistance. Further understanding the molecular mechanisms of pathological basis of cancer stem cells will facilitate the development of new therapeutic targets and new strategies for eradicating cancers. This paper summarizes the molecular mechanisms, and the possibilities and limitations of therapies targeting cancer stem cell.
Humans ; Neoplasms ; metabolism ; therapy ; Neoplastic Stem Cells ; metabolism ; Signal Transduction ; Stem Cell Niche ; Tumor Microenvironment

Hemopoietic stem cells(HSCs) are regulated by two niches: osteoblastic niche and vascular niche. Osteoblasts are the critical constitutive regulators of the osteoblastic niche. The significance of osteoblasts for hematopoietic disease has not escaped attention. This review attempts to capture the discoveries of the last few years regarding the role of osteoblasts in hematopoietic stem cell niche and relationship between osteoblasts and hematopoietic diseases.
Animals ; Hematologic Diseases ; Hematopoietic Stem Cells ; Humans ; Osteoblasts ; Stem Cell Niche

Bone marrow macrophage is an important component of bone marrow microenvironment, which is closely related to hematopoietic regulation and hematopoietic stem cell transplantation(HSCT). Recent studies have shown that bone marrow macrophage is an important part of hematopoietic stem cell niche, which can help regulate the mobilization and function of hematopoietic stem/progenitor cells. After HSCT, the microenvironment of bone marrow is damaged and a large number of macrophages infiltrate into the bone marrow. Regulating the macrophage-related signal pathways can promote the recovery of hematopoiesis and the reconstruction of hematopoietic function. Co-culture of macrophages and hematopoietic stem cells (HSC) in vitro significantly increased the number of HSCs and their ability of clone formation, which suggests that macrophages play an important role in the regulation of hematopoiesis in the hematopoietic microenvironment of bone marrow. This paper reviews the recent research progress on the role of macrophages in bone marrow hematopoietic microenvironment.
Humans ; Bone Marrow/metabolism* ; Hematopoietic Stem Cells/physiology* ; Hematopoiesis/physiology* ; Stem Cell Niche ; Macrophages/metabolism*

As pioneer of tumor stem cell research, leukemia stem cell research has not only important theoretical significance, but also clinical application potential. The survival and development of stem cells are directly impacted by their microenvironment. The research on leukemia stem cells and their microenvironment are now becoming a hot topic. The author presumes that stem cells are a population with heterogenecity and hierarchy; any single cell from the population is difficult to form a clone; the interaction between the leukemia stem cell and its microenvironment can be described by the concept of leukemia stem cell niche. In this article, the leukemia cell population with heterogenecity and hierarchy as well as leukemia stem cell niche were summarized and discussed.
Cell Line, Tumor ; Humans ; Leukemia ; genetics ; pathology ; Neoplastic Stem Cells ; metabolism ; pathology ; Stem Cell Niche ; cytology ; Stromal Cells ; cytology ; immunology

Myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) are clonal myeloid disorders characterized by hematopoietic insufficiency. As MDS and AML are considered to originate from genetic and molecular defects of hematopoietic stem and progenitor cells (HSPC), the main focus of research in this field has focused on the characterization of these cells. Recently, the contribution of BM microenvironment to the pathogenesis of myeloid malignancies, in particular MDS and AML has gained more interest. This is based on a better understanding of its physiological role in the regulation of hematopoiesis. Additionally, it was demonstrated as a ‘proof of principle’ that genetic disruption of cells of the mesenchymal or osteoblastic lineage can induce MDS, MPS or AML in mice. In this review, we summarize the current knowledge about the contribution of the BM microenvironment, in particular mesenchymal stromal cells (MSC) to the pathogenesis of AML and MDS. Furthermore, potential models integrating the BM microenvironment into the pathophysiology of these myeloid disorders are discussed. Finally, strategies to therapeutically exploit this knowledge and to interfere with the crosstalk between clonal hematopoietic cells and altered stem cell niches are introduced.
Animals ; Hematopoiesis ; Leukemia, Myeloid, Acute ; Mesenchymal Stromal Cells* ; Mice ; Myelodysplastic Syndromes ; Osteoblasts ; Stem Cell Niche ; Stem Cells

Self-renewal and differentiation are hallmarks of stem cells and controlled by various intrinsic and extrinsic factors. Increasing evidence indicates that estrogen (E2), the primary female sex hormone, is involved in regulating the proliferation and lineage commitment of adult and pluripotent stem cells as well as modulating the stem cell niche. Thus, a detailed understanding of the role of E2 in behavior of stem cells may help to improve their therapeutic potential. Recently, it has been reported that E2 promotes cell cycle activity of hematopoietic stem and progenitor cells and induces them to megakaryocyte-erythroid progenitors during pregnancy. This study paves the way towards a previously unexplored endocrine mechanism that controls stem cell behavior. In this review, we will focus on the scientific findings regarding the regulatory effects of E2 on the hematopoietic system including its microenvironment.
Adult ; Cell Cycle ; Estrogens* ; Female ; Hematopoiesis ; Hematopoietic Stem Cells* ; Hematopoietic System ; Humans ; Megakaryocyte-Erythroid Progenitor Cells ; Pluripotent Stem Cells ; Pregnancy ; Stem Cell Niche ; Stem Cells

PURPOSE: To investigate the minimal requirements of the limbal epithelium for successful limbal stem cell transplantation and the healing process. METHODS: Nine rabbits were divided into 4, 6, and 8 clock-hour transplantation groups. Limbal autografts from the healthy fellow eye were transplanted to the iatrogenic damaged eye. The amniotic membrane served as a stem cell niche. Experimental corneas were evaluated by slit lamp examination and immunohistochemistry. RESULTS: In the over 9 hours transplantation group, the healing process of the epithelium from the limbal stem cell was revealed and cornea-specific keratin k3, transcription factor p63, and connexin 43 were detected by immunohistochemistry. The normal corneal epithelium was regenerated after 60 days postoperatively in the fellow donor eye. CONCLUSIONS: Limbal cell transplantation of over 9 hours seems to be a safe and effective method in the treatment of severe ocular surface disorders. In addition, the donation of limbal epithelium for up to 8 hours did not affect the normal corneal regenerating capability.
Amnion ; Autografts ; Cell Transplantation* ; Connexin 43 ; Cornea* ; Epithelium* ; Epithelium, Corneal ; Humans ; Immunohistochemistry ; Rabbits ; Stem Cell Niche ; Stem Cell Transplantation ; Stem Cells ; Tissue Donors ; Transcription Factors ; Transplants*