The hematopoietic stem cell: biology and clinical applications

The hematopoietic stem cells (HSCs) are defined as cells that are able of both self-renewal and multilineage reconstitution of the hematopoietic system. Their biological properties and, similarly, the gene regulation, the positive and negative factors of the hematopoietic progenitor cells and the models of the hematopoietic amplification in the murine system are described. The clinical relevance of HCS has been obtained by the characterization and function of the CD34 cell surface molecule. The methods of isolation, selection and purification of HCS, the clinical use (particularly the mobilization of peripheral CD34+ cells) are detailed. Finally the potential advantages and use of HCS in vivo expansion are described.     

Favorable outcome after infusion of coagulase-negative staphylococci-contaminated peripheral blood hematopoietic cells for autologous transplantation

Bacterial contamination of peripheral blood hematopoietic cells collected for autologous bone marrow transplantation occurs sporadically. Although transfusion of contaminated hematopoietic cells without adverse clinical sequelae has been reported, detailed guidelines for transfusing cells with contamination are not available. We report a case of autologous hematopoietic cell transplantation that necessitated using multiple aliquots of peripheral blood hematopoietic cells known to be contaminated with coagulase-negative Staphylococcus bacteria. Prophylactic intravenous antibiotic therapy was given with the infusion of contaminated hematopoietic cells. The patient had positive results on a blood culture, but engraftment was successful, and serious adverse effects did not occur. With appropriate microbial identification and prophylactic antibiotic therapy, contaminated hematopoietic products can be safely infused when necessary with a good clinical outcome.     

Optimizing the effectiveness of hematopoietic growth factors

Hematopoiesis is regulated in a very precise fashion by a balance between both positive and negative growth factor signals in the hematopoietic microenvironment. Many of these growth factor signals have been identified and are available as recombinant proteins. At the present time, the approved uses for hematopoietic growth factors involve their use to facilitate blood cell production in situations of hematopoietic suppression or in cases where endogenous growth factor production is inappropriately low. Recent studies with the hematopoietic growth factors are looking at innovative strategies for their use and new clinical situations in which to evaluate their effectiveness. This review looks at some of these new uses for hematopoietic growth factors.     

Ex vivo expanding hematopoietic stem cells by intracellular delivery of Cdx4 fusion proteins

Hematopoietic stem cells transplantation has been wildly used in clinical settings and has shown exciting results in treating a wide variety of diseases. However, the relative small number of hematopoietic stem cells in bone marrow, even lower in peripheral or umbilical cord blood limits its clinical utility. There are several protocols, which have been developed to expand hematopoietic stem cells to reach clinical goal. With the recent insights into the mechanisms of hematopoietic stem cells self-renewal, we postulate that Cdx4, which is coded by one of the caudal related homeobox genes and regulates the expression of hox genes, could fuse with protein transduction domains, thereby get the ability to cross cellular membrane. And the recombinant fusion proteins could be used in expanding hematopoietic stem cells. Meanwhile, Cdx4 fusion proteins would be more efficient than other methods that had been developed for it can up-regulate a cocktail of hox genes, which has been proved to be capable of amplifying hematopoietic stem cells. It would provide us an alternative protocol to amplify hematopoietic stem cells if the hypothesis proved to be practical.     

Hematopoietic growth factors. Biology and clinical applications

The hematopoietic growth factors are potent regulators of blood-cell proliferation and development. The first phase of clinical trials suggests that they may augment hematopoiesis in a number of different conditions of primary and secondary bone marrow dysfunction. Future clinical use is likely to include combinations of these growth factors, in order to stimulate early marrow progenitors and obtain multilineage effects. An improved understanding of the biologic and clinical effects of hematopoietic growth factors promises future clinical applications for conditions of impaired function and reduced numbers of blood cells.     

Tolerance induction for solid organ grafts with donor-derived hematopoietic reconstitution

Tolerance of transplanted tissue has been a focus of immunologists for decades. Indeed, to some the birth of immunology and the search for tolerance of the non-self are synonymous. One of the most powerful and reproducible methods of tolerance induction to allogeneic tissue has involved infusion of donor-specific hematopoietic cells. Under certain conditions, such infusion can result in hematopoietic reconstitution that can be experimentally accomplished at a variety of different time-points in the life of an organism from the in utero period through adulthood, reconstitution at each time-point involving consideration of a different set of immunological and physiological parameters. When high levels of donor-derived hematopoietic reconstitution are achieved, tolerance induction to donor-specific antigens is reproducible and long-lasting. Unfortunately, however, clinical efforts to achieve such high levels of hematopoietic reconstitution have historically been unsuccessful or fraught with complications. Transplantation efforts have been plagued by failure of engraftment, graft-vs-host disease (GVHD), or severe immunoincompetence of the recipient. Laboratory and clinical efforts during the last decade have resulted in a variety of developments that may overcome these barriers: (1) methods have been devised in which cells that cause GVHD can be depleted from the hematopoietic graft while hematopoietic reconstitution potential is preserved, (2) methods of harvesting large numbers of cells with multilineage reconstitution potential have been devised (an accomplishment that seems to allow the immunological barrier to be overwhelmed), and (3) capitalizing on the above two principles, minimally toxic preconditioning regimens have been designed that allow allogeneic engraftment. This review will focus on some of the experimental and clinical data of the past and the experimental and clinical issues that loom ahead.     

G-CSF、GM-CSF的临床应用现状

粒细胞集落刺激因子（Ｇｒａｎｕｌｏｃｙｔｅ ｃｏｌｏｎｙ－ｓｔｉｍｕｌａｔｉｎｇ ｆａｃｔｏｒ, Ｇ－ＣＳＦ）、粒巨噬细胞集落刺激因子（ Ｇｒａｎｕｌｏｃｙｔｅ ｍａｃｒｏｐｈａｇｅ ｃｏｌｏｎｙ－ｓｔｉｍｕｌａｔｉｎｇ ｆａｃｔｏｒ,ＧＭ－ＣＳＦ）分别是促粒系、粒－单系造血祖细胞增殖、分化及成熟,并增强其成熟细胞功能的特异造血调控生长因子。重组ＤＮＡ技术的发展,使得利用基因工程方法大量生产细胞因子成为可能。目前,Ｇ－ＣＳＦ、ＧＭ－ＣＳＦ基因重组产品已广泛应用于临床。在血液病的治疗,造血干细胞移植及恶…     

造血干/祖细胞体外扩增的最新研究进展

造血干/祖细胞体外扩增方法的快速发展为造血于/祖细胞广泛应用于临床开辟了广阔的前景,就造血干/祖细胞体外扩增的方法和培养系统的最新进展做一综述.     

造血干/祖细胞体外扩增的最新研究进展

造血干/祖细胞体外扩增方法的快速发展为造血干/祖细胞广泛应用于临床开辟了广阔的前景,就造血干/祖细胞体外扩增的方法和培养系统的最新进展做一综述。     

异基因造血干细胞移植后的相关并发症及危险因素

背景：有效预防和治疗异基因造血干细胞移植后并发症是提高患者存活率的重要因素。 目的：分析异基因造血干细胞移植后相关并发症的发生和危险因素。 方法：应用文献检索的方法获取异基因造血干细胞移植后相关并发症研究的文献,对符合研究标准的文献进行深入的数据分析,文章选取异基因造血干细胞移植后极易发生的并发症进行分析,如肺部并发症、真菌性败血症、巨细胞病毒感染以及中枢神经系统并发症等。 结果与结论：异基因造血干细胞移植后易出现肺部并发症,而且死亡率较高,肺部并发症的发病机制可能与移植物抗宿主病和巨细胞病毒抗原血症相关。异基因造血干细胞移植后真菌性败血症病原菌以假丝酵母菌属为主,死亡率较高,应二级预防性和早期经验性抗真菌治疗。更昔洛韦、膦甲酸钠对异基因造血干细胞移植后巨细胞病毒感染的治疗有效。中枢神经系统并发症在异基因造血干细胞移植后发生率较低,但在治疗过程也不容忽视。异基因造血干细胞移植后相关并发症的发生与多种危险因素有关,在临床治疗过程中要对相关因素采取预防措施,减少并发症的发生,提高患者的存活率。     

In Utero Hematopoietic Stem Cell Transplantation: Progress toward Clinical Application

In utero hematopoietic stem cell transplantation (IUHCT) is a potential therapeutic alternative to postnatal hematopoietic stem cell transplantation (HSCT) for congenital hematologic disorders that can be diagnosed early in gestation and can be cured by HSCT. The rationale is to take advantage of normal events during hematopoietic and immunologic ontogeny to facilitate allogeneic hematopoietic engraftment. Although the rationale remains compelling, IUHCT has not yet achieved its clinical potential. Achieving therapeutic levels of engraftment by IUHCT alone remains challenging. However, considerable experimental progress has been made toward the clinical strategy of using IUHCT to induce donor-specific tolerance to facilitate a relatively nontoxic postnatal HSCT. Because donor specific tolerance induction requires relatively minimal engraftment, this strategy may hold the key to broad clinical application of IUHCT in the near future.     

Non-myeloablative hematopoietic stem cell transplantation.

Conventional approaches to allogeneic stem cell transplantation have used toxic high-dose conditioning therapy in attempts to eradicate underlying diseases and achieve allogeneic engraftment. Preclinical studies and clinical observations have shown that to achieve engraftment conditioning regimens could be markedly reduced in intensity with reduction in treatment toxicities. The use of potent pre- and postgrafting immunosuppression facilitated stable mixed hematopoietic chimerism in a preclinical canine model. The initial clinical experiences with attenuated conditioning regimens have shown promise as a modality to achieve human stem cell transplantation with an improved safety profile. This may allow offering potentially curative hematopoietic stem cell transplantation (HSCT) to a more representative patient population (older and sicker) who are currently not eligible for such therapy. Obtaining a state of mixed hematopoietic chimerism could prove curative of the disease phenotype of various nonmalignant disturbances of the hematopoietic and immune systems. On the other hand, patients with hematopoietic malignancy will likely require conversion to full donor hematopoeisis by virtue of graft-versus-host (GVH) reactions directed against both recipient hematopoiesis and underlying malignancy. The infusion of additional donor lymphocytes has been proposed by many groups to augment graft versus tumor responses, but most likely more specific strategies will need to be developed to improve efficacy and avoid nonspecific GVH reactions.     

Retrovirus-mediated gene transfer into human hematopoietic stem cells

 Human hematopoietic stem cells genetically modified by retroviral-mediated gene transfer may offer new treatment options for patients with genetic disease. The potential of gene-modified hematopoietic stem cells as vehicles for gene delivery was first illustrated by the demonstration that hematopoietic systems of lethally irradiated mice can be reconstituted with retroviral vector transduced syngeneic bone marrow, and that these cells can in turn provide genetically marked progeny which persist in blood and marrow over extended time periods [1–4]. In contrast, hematopoietic stem cells from large animals prove difficult to transduce with retroviral vectors and are consequently less likely to function as vehicles for long-term gene therapy. Indeed, clinically relevant levels of gene transfer into large animal and human hematopoietic stem cells has not been widely achieved. The need for improved retroviral vector systems and for understanding the biology of hematopoietic stem cell gene transfer continue to fuel intense research activity. Preliminary results from human stem cell gene marking and gene therapy trials currently underway are encouraging. This contribution reviews the underlying concepts relevant to retroviral-mediated gene transfer into hematopoietic stem cells. We survey the evolution of approaches for gene transfer into hematopoietic stem cells, from murine and large animal models to the first human clinical trials. Finally, we discuss new strategies which are currently being pursued. Received: 12 March 1997 / Accepted: 21 July 1997     

Mesenchymal stem cell-organized bone marrow elements: an alternative hematopoietic progenitor resource

Bone marrow-derived mesenchymal stem cells (BMMSCs) are multipotent postnatal stem cells that have been used for the treatment of bone defects and graft-versus-host diseases in clinics. In this study, we found that subcutaneously transplanted human BMMSCs are capable of organizing hematopoietic progenitors of recipient origin. These hematopoietic cells expressed multiple lineages of hematopoietic cell associated markers and were able to rescue lethally irradiated mice, with successful engraftment in the recipient, suggesting a potential bone marrow (BM) resource for stem cell therapies. Furthermore, we found that platelet-derived growth factor (PDGF) promotes the formation of BMMSC-generated BM niches through upregulation of beta-catenin, implying that the PDGF pathway contributes to the formation of ectopic BM. These results indicate that the BMMSC-organized BM niche system represents a unique hematopoietic progenitor resource possessing potential clinical value.     

Hematopoietic stem and progenitor cell trafficking

Migration of hematopoietic stem cells (HSCs) is essential during embryonic development and throughout adult life. During embryogenesis, trafficking of HSCs is responsible for the sequential colonization of different hematopoietic organs by blood-producing cells. In adulthood, circulation of HSCs maintains homeostasis of the hematopoietic system and participates in innate immune responses. HSC trafficking is also crucial in clinical settings such as bone marrow (BM) and stem cell transplantation. This review provides an overview of the molecular and cellular signals that control and fine-tune trafficking of HSCs and hematopoietic progenitor cells in embryogenesis and during postnatal life. We also discuss the potential clinical utility of therapeutic approaches to modulate HSC trafficking in patients.     

Application of xenogeneic stem cells for induction of transplantation tolerance: present state and future directions

Xenotransplantation using pig organs provides a possible solution to the severe shortage of allogeneic organ donors, one of the major limiting factors in clinical transplantation. However, because of the greater antigenic differences that exist between different species than within a species, the immune response to xenografts is much more vigorous than to allografts. Thus, tolerance induction is essential to the success of clinical xenotransplantation. Tolerance induced by mixed hematopoietic chimerism across the MHC barrier is remarkably robust, but its ability to induce tolerance across highly disparate xenogeneic barriers remains poorly studied. None of the current available regimens of host conditioning, which permit hematopoietic stem cell engraftment and chimerism induction in allogeneic or closely related (concordant) xenogeneic combinations, has been demonstrated to be effective in establishing porcine hematopoietic chimerism in a discordant xenogeneic species. Unlike bone marrow transplantation within the same species, the innate immune system and the species specificity of cytokines and adhesion molecules essential to hematopoiesis pose formidable obstacles to the establishment of donor hematopoiesis across discordant xenogeneic barriers. The genetic incompatibility between species may also impede xenograft tolerance induction by mixed chimerism. While we remain far from achieving tolerance in clinical xenotransplantation, recent studies using a transgenic mouse model have proven the principle that mixed hematopoietic chimerism may induce mouse and human T cell tolerance to porcine xenografts. This review article focuses on the barriers to porcine hematopoietic engraftment in highly disparate xenogeneic species and the possible application of mixed hematopoietic chimerism to xenograft tolerance induction.     

Hematopoietic stem cell antigen CD34: role in adhesion or homing

CD34 is highly glycosylated surface antigen of enormous clinical utility in the identification, enumeration, and purification of engraftable lymphohematopoietic progenitors for transplantation. However, recently its importance in the specific marking of most immature hematopoietic stem/progenitor cells have been questioned by addressing long-term reconstitution capability of CD34(-) hematopoietic cellular fractions. These controversies have stimulated a demand for elucidation of the structure, function, and molecular interactions of CD34 to define exactly its biological significance in clinical regimens. There is accumulating data showing the participation of CD34 in adhesion or perhaps homing of lymphohematopoietic progenitors. On the other hand, CD34 has been demonstrated to down-regulate cytokine-induced differentiation and proliferation of CD34(+) cells. Studies in CD34 knockout mice revealed normal hematopoiesis but a profound delay in hematopoietic reconstitution after sublethal irradiation of the mice. In short, CD34 expression is likely to represent a specific state of hematopoietic development that may have altered adhering properties with expanding and differentiating capabilities in both in vitro and in vivo conditions. This article focuses on the adhesive properties of CD34 and its potential role in homing, which are likely to mimic lymphocyte homing to the inflammatory sites.     

In vitro effects and possible clinical relevance of interleukin 3

Cytokines are mainly produced by monocytes and lymphocytes and influence a broad spectrum of physiological processes within the hematopoietic and the immune system. Clinical trials have mainly been initiated with a subgroup of cytokines namely the hematopoietic growth factors. Interleukin 3 (IL-3) was recently introduced into phase I and II trials. This factor was also termed "multipoietin" because of its ability to stimulate in vitro the hematopoietic stem cell and thus all three hematopoietic cell lines. The latest in vivo data, however, demonstrate that IL-3 stimulates leukopoiesis and megakaryopoieis with only marginal effects on erythropoiesis. In large clinical trials the therapeutic effect of this factor is investigated in patients with myelodysplastic syndromes. Further indications will be other primary bone marrow failures and aplasia caused by bone marrow transplantation, aggressive chemotherapy and radiation. Potential applications offered by combinations with other cytokines can hardly be foreseen.     

Depletion of Naïve Lymphocytes with Fas Ligand Ex Vivo Prevents Graft-versus-Host Disease without Impairing T Cell Support of Engraftment or Graft-versus-Tumor Activity

Graft-versus-host disease (GVHD) can be prevented by Fas-mediated selective depletion of host-sensitized donor lymphocytes ex vivo. We tested the hypothesis that Fas-mediated depletion of lymphocytes in the absence of host-specific antigenic stimulation can alleviate GVHD. Brief exposure (24 hours) of unstimulated donor lymphocytes to Fas ligand (FasL) ex vivo results in balanced apoptosis of CD8⁺ and CD4⁺ subsets with preferential depletion of CD62L and CD69, increased T regulatory fractions, and sustained responses to stimulation. This procedure ameliorates weight loss and improves the clinical and histologic score of skin and gastrointestinal GVHD with and without concurrent transplantation of hematopoietic progenitors and irrespective of conditioning-induced tissue injury. Although FasL-resistant donor T cells are less potent effectors of GVHD, they facilitate hematopoietic progenitor engraftment when infused with or after the graft and retain the potential to elaborate graft-versus-tumor reactions. These findings in a preclinical model together with the known trophic effects of FasL on primitive hematopoietic progenitors suggest that brief ex vivo incubation of hematopoietic grafts with FasL may improve the outcome and safety of clinical T cell–replete allogeneic and haploidentical transplants.