What is the future for cord blood stem cells?

Stem and progenitor cells are present in cord blood at a high frequency making these cells a major target population for experimental and clinical studies. Over the past decade there has been considerable developments in cord blood research and transplantation but despite the rapid progress many problems remain. The initial hope that cord blood would be an alternative source of haemopoietic cells for transplantation has been tempered by the fact that there are insufficient cells in most cord blood collections to engraft an adult of average weight. In attempts to increase the cell number, a plethora of techniques for ex-vivo expansion have been developed.These techniques have also proved useful for gene therapy. As cord blood cells possess unique properties this allows them to be utilised as suitable vehicles for gene therapy and long-term engraftment of transduced cells has been achieved. Current work examining the nature of the stem cells present in this haematological source indicates that cord blood contains not only haemopoietic stem cells but also primitive non-haemopoietic cells with high proliferative and developmental potential. As attention focuses on stem cell biology and the controversies surrounding the potential use of embryonic stem cells in treatment of disease, the properties of stem cells from other sources including cord blood are being re-appraised. The purpose of this article is to review some of the current areas of work and highlight biological problems associated with the use of cord blood cells. This revised version was published online in July 2006 with corrections to the Cover Date.     

间充质干细胞促进脐带血干细胞体外扩增的研究进展

非亲缘脐带血移植是治疗造血系统疾病的重要移植方式之一,但脐带血移植面临的最大挑战是造血干细胞(HSCs)数量不足,特别是成人患者受到脐带血干细胞数量的限制,导致造血及免疫恢复延迟,非复发死亡率升高。体外扩增脐带血HSCs(UCB-HSCs)是解决该问题的途径之一。研究发现可以通过模拟骨髓造血龛(niche)这一生态位使HSCs在体外进行自我更新增殖,而间充质干细胞(MSCs)正是造血龛的重要的组成细胞之一。本文将探讨MSCs在UCB-HSCs体外扩增中的应用。重点以MSCs促造血的特点、机制,促进脐带血干细胞增殖的各种策略以及其临床应用和前景做一综述。     

Expansion of umbilical cord blood for clinical transplantation

Since the first successful cord blood transplant was performed in 1988 there has been a gradual increase in the use of cord blood for hemopoietic stem cell transplantation. Worldwide, over 8,000 unrelated cord blood transplants have been performed with the majority being for children with hemopoietic malignancies. Transplantation for adults has increased but is limited by the low number of nucleated cells and CD34(+) cells within a single cord blood collection. Cord blood hemopoietic stem cells are more primitive than their adult counterparts and have high proliferative potential. Cord blood ex vivo expansion is designed to improve transplant outcomes by increasing the number of hemopoietic stem cells with long term repopulating potential and their differentiated progeny. However, despite a large amount of research activity during the last decade, this aim has not been realized. Herein we discuss the rationale for this approach; culture methods for ex vivo expansion, ways to assess the functional capacity of ex vivo generated hemopoietic stem cells and clinical outcomes following transplantation with ex vivo expanded cord blood.     

小鼠脐血移植模型研究进展

脐血中含有丰富的原始造血干细胞,由于免疫细胞发育不成熟,抗原表达和功能活性低下,移植物抗宿主疾病发生率低。脐血来源丰富、不易受病毒及残留肿瘤细胞的污染,越来越多地作为造血干细胞的优质来源在临床上广泛应用。通过建立小鼠脐血移植模型,对临床多种疾病尤其是对恶性血液病的造血干细胞移植研究提供有效途径,可以对脐血的生物学功能、植入过程、移植疗效做进一步研究,不断优化的小鼠移植模型对我们解读人类疾病的发病机理、疾病进程起到推动作用,本文将从小鼠种属的选择、移植模型的构建及脐血移植模型新进展等方面对进行综述。     

Can Routine Commercial Cord Blood Banking Be Scientifically and Ethically Justified?

BACKGROUND TO THE DEBATE: Umbilical cord blood--the blood that remains in the placenta after birth--can be collected and stored frozen for years. A well-accepted use of cord blood is as an alternative to bone marrow as a source of hematopoietic stem cells for allogeneic transplantation to siblings or to unrelated recipients; women can donate cord blood for unrelated recipients to public banks. However, private banks are now open that offer expectant parents the option to pay a fee for the chance to store cord blood for possible future use by that same child (autologous transplantation).     

脐带血移植的应用进展及脐带血库建设

脐带血(umbilical cord blood)作为公认的造血干细胞重要来源之一,已经被广泛地用于治疗儿童和成人的良恶性血液系统疾病以及中枢神经系统疾病、实体瘤、缺血性下肢血管病和组织再生等。相对于骨髓移植和外周血来源的造血干细胞移植,脐带血移植(UCBT)在细胞收集使用、干细胞增殖能力以及移植物抗宿主反应等方面都具有明显的优势。目前的数据显示,因为HLA配型等原因而无法进行骨髓移植的患者应该尽早进行UCBT。此外,UCBT的增多促进了脐带血库的快速建设。本文针对UCBT和脐带血库的最新进展进行了综述。     

人脐带血来源造血干细胞体外扩增的研究进展

造血干细胞（HSCs）是血液系统中的一类成体干细胞群,具有自我更新和多谱系分化两个基本特征。造血干细胞移植（HSCT）可以治疗退行性疾病和多种血液系统疾病。脐带血来源造血干细胞（CB HSCs）是降低HLA配型要求的突破点,但单份脐带血中HSCs数量不能满足使用要求,为了获得足够数量的CB HSCs,体外扩增是一种可行的方法。近几年,学者们探索了多种体外扩增方法,包括优化细胞生长因子混合物、与基质细胞共培养及加入小分子化合物（SMCs）激动剂等。目前应用细胞因子联合小分子的扩增方法在多个临床试验中获得成功。本文对目前体外扩增CB HSCs的研究进展做一综述。     

Insights into the biology of cord blood stem/progenitor cells

OBJECTIVES: To review information on cord blood banking and transplantation with respect to the author's studies, and in context of this field of investigation. RESULTS: Cord blood transplantation has been successfully used to treat a number of malignant and non-malignant disorders. However, this technique is still associated with limited numbers of cells for transplantation, and with delayed engraftment of neutrophils and platelets. The field of cord blood transplantation will benefit from enhanced and mechanistically based information on haematopoietic stem cell function and potential means to enhance its effectiveness are reviewed. This includes notions concerning possibility of retrieving more cells from the placenta and cord blood, to expand haematopoietic stem cells ex vivo and to increase efficiency of homing and engraftment of these cells. Also discussed are cryopreservation and long-term storage of cord blood haematopoietic and progenitor cells, and new laboratory findings and animal studies for non-haematopoietic uses of cord blood.     

Transplantation of endothelial progenitor cells for therapeutic neovascularization

Endothelial progenitor cells (EPCs), which were first identified in adult peripheral blood mononuclear cells (MNCs), play an important role in postnatal neovascularization. Tissue ischemia augments mobilization of EPCs from bone marrow into the circulation and enhances incorporation of EPCs at sites of neovascularization. Two methods to obtain EPCs from bone marrow, peripheral blood or cord blood MNCs have been evaluated for therapeutic neovascularization: (1) fresh isolation using anti-CD34, anti-KDR or anti-AC133 antibody, and (2) ex vivo expansion of total MNCs. In an immunodeficient mouse model of hindlimb ischemia, systemic transplantation of human ex vivo expanded EPCs improves limb survival through the enhancement of blood flow in the ischemic tissue. A similar strategy also leads to histological and functional preservation of ischemic myocardium of nude rats. Recently, a preclinical study of catheter-based, intramyocardial transplantation ofautologous EPCs in a swine model of chronic myocardial ischemia demonstrated the therapeutic potential of cell-based therapy, with attenuation of myocardial ischemia and improvement in left ventricular function. These favorable outcomes strongly suggest a therapeutic impact of EPC transplantation in clinical settings. Further basic research, with improved understanding of the mechanisms governing homing and incorporation of EPCs, will be still necessary to optimize the methodology of the cell therapy.     

Comparative analysis of the heterogeneity of mononuclear cells present in adult and cord blood by simultaneous examination of multiple phenotypic characteristics

In an attempt to better relate specific membrane characteristics of human adult and cord blood lymphocytes to specific functional activities, the phenotypic differences that exist in these two populations have been examined. Cord blood cells have considerably more spontaneous suppressor cell activity than adult cells. A technique that allows cells to be examined simultaneously for their ability to ingest latex beads, react with specific monoclonal antisera, bind sheep erythrocytes, or react with the Fc portion of IgG was used. As well as assessing fresh populations, phenotypic changes that occur when such cells are held in culture or stimulated with phytohemagglutinin for 3 days were sought. Many differences were found when comparing these mononuclear populations. These included the observations that 12% of adult and 9% of cord blood E-rosette-forming cells ingest latex beads and that 9% of OKT3 reactive cells in both populations did not form E rosettes. In cord blood 58% of T cells that bind OKT8 do not form E rosettes. A similar percentage of cord blood T8-positive cells express a receptor for Fc gamma, such cells being very uncommon in adult blood. Four "monocyte" subpopulations were identified in both samples. One such population (an OKM1- and Fc gamma-positive, nonphagocytic cell) was three times more common in cord blood. In cord blood some OKM1-positive cells also appeared to be simultaneously OKT8 positive. These phenotypic variations forward populations that may be candidates responsible for the functional differences noted in vitro.     

Ethnically mismatched cord blood transplants in African Americans: the Saint Louis Cord Blood Bank experience

BACKGROUND: For ethnic minority patients where a suitably matched BM or peripheral blood donor is frequently unavailable, cord blood offers an opportunity for hematopoietic stem cell transplantation. Focused recruitment of ethnic minorities for cord blood donation has been proposed as the preferred strategy to improve access for minority recipients to cord blood for transplantation. The aim of this study was to evaluate cord blood characteristics for Caucasian and African American donors and the success of ethnically mismatched UC blood transplantation in African American recipients. METHODS: Retrospective data analysis was performed comparing the characteristics of 556 cord blood units from African American and Caucasian donors. The outcomes of 18 African American ethnically mismatched transplant recipients were compared with a paired sample of 18 ethnically matched Caucasian recipients. RESULTS: The fraction of collected units meeting acceptability criteria from African Americans was significantly lower compared with Caucasians (P = <0.0001). Additionally, African Americans had a significantly lower post-processing total nucleated cell count (TNC) compared with Caucasians (P=0.007) but there were no other significant differences in conventionally measured product characteristics. In the transplant analysis, there was no difference in overall survival at 1 year (P=0.85) or time to neutrophil engraftment (P=0.92) between the two patient populations. DISCUSSION: At comparable levels of TNC dose and HLA matching, the use of ethnically mismatched UC blood units as a source for allogeneic unrelated transplant can result in successful transplant outcomes for African American patients.     

Are induced pluripotent stem cells the future of cell‐based regenerative therapies for spinal cord injury?

Despite advances in medical and surgical care, current clinical therapies for spinal cord injury (SCI) are limited. During the last two decades, the search for new therapies has been revolutionized by the discovery of stem cells, inspiring scientists and clinicians to search for stem cell‐based reparative approaches for many disorders, including neurotrauma. Cell‐based therapies using embryonic and adult stem cells in animal models of these disorders have provided positive outcome results. However, the availability of clinically suitable cell sources for human application has been hindered by both technical and ethical issues. The recent discovery of induced pluripotent stem (iPS) cells holds the potential to revolutionize the field of regenerative medicine by offering the option of autologous transplantation, thus eliminating the issue of host rejection. Herein, we will provide the rationale for the use of iPS cells in SCI therapies. In this review, we will evaluate the recent advancements in the field of iPS cells including their capacity for differentiation toward neural lineages that may allow iPS cells transplantation in cell‐based therapy for spinal cord repair. J. Cell. Physiol. 222: 515–521, 2010. © 2009 Wiley‐Liss, Inc.     

Can cord blood cells support the cytokine storm in GvHD?

Cord blood has a high number of proliferating hematopoietic progenitors and is therefore used as an alternative source of hematopoietic cells for allogeneic transplantation. In addition there is a wider availability of cord blood and a lower cost of procurement compared to bone marrow. However one of the most interesting immunological benefits of a cord blood transplant that has been proposed is the low severity of Graft versus Host Disease (GvHD). This review aims to address some of the immunological reasons why this may be the case by assessing the role of cord blood cytokines in the cytokine storm of GvHD.     

Enhancement of proliferation of human umbilical cord blood–derived CD34+ hematopoietic stem cells by a combination of hyper-interleukin-6 and small molecules

Umbilical cord blood (UCB) is an alternative source of allogeneic hematopoietic stem cells (HSCs) for transplantation to treat various hematological disorders. The major limitation to the use of UCB-derived HSCs (UCB–HSCs) in transplantation, however, is the low numbers of HSCs in a unit of cord blood. To overcome this limitation, various cytokines or small molecules have been used to expand UCB-HSCs ex vivo. In this study, we investigated a synergistic effect of the combination of HIL-6, SR1, and UM171 on UCB-HSC culture and found that this combination resulted in the highest number of CD34⁺ cells. These results suggest that the combination of SR1, UM171 and HIL-6 exerts a synergistic effect in the proliferation of HSCs from UCB and thus, SR1, UM171 and HIL-6 is the most suitable combination for obtaining HSCs from UCB for clinical transplantation.     

Isolation and therapeutic potential of human haemopoietic stem cells

The haemopoietic stem cell (HSC) has long been regarded as an archetypal, tissue specific, stem cell, capable of completely regenerating haemopoiesis after myeloablation. It has proved relatively easy to harvest HSC, from bone marrow or peripheral blood. In turn, isolation of these cells has allowed therapeutic stem cell transplantation protocols to be developed, that capitalise on their prodigious self renewal and proliferative capabilities. Ex vivo approaches have been described to isolate, genetically manipulateand expand pluripotent stem cell subsets. These techniques have been crucial to the development of gene therapy, and may allow adults to enjoy the potential advantages of cord blood transplantation. Recently, huge conceptual changes have occurred in stem cell biology. In particular, the dogma that, in adults, stem cells are exclusively tissue restricted has been questioned and there is great excitement surrounding the potential plasticity of these cells, with the profound implications that this has, for developing novel cellular therapies. Mesenchymal stem cells, multipotent adult progenitor cells and embryonic stem cells are potential sources of cells for transplantation purposes. These cells may be directed toproduce HSC, in vitro and in the future may be used for therapeutic, or drug development, purposes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Human cord blood-derived viral pathogens as the potential threats to the hematopoietic stem cell transplantation safety:A mini review

Umbilical cord blood(UCB) is a valuable source of hematopoietic stem cells(HSCs) and potential alternative for bone marrow transplantation for patients who lack human leukocyte antigen(HLA)-matched donors. The main practical advantages of UCB over other HSC sources are the immediate availability, lower incidence of graft-versus-host disease, minimal risk to the donor, and lower requirement for HLA compatibility. However, the use of UCB is limited by delayed engraftment and poor immune reconstitution, leading to a high rate of infection-related mortality. Therefore, severe infectious complications, especially due to viral pathogens remain the leading cause of morbidity and mortality during the post-UCB transplantation(UCBT) period. In this context, careful screening and excluding the viral-contaminated UCB units might be an effective policy to reduce the rate of UCBT-related infection and mortality. Taken together,complete prevention of the transmission of donor-derived viral pathogens in stem cell transplantation is not possible. However, having the knowledge of the transmission route and prevalence of viruses will improve the safety of transplantation. To the best of our knowledge, there are few studies that focused on the risk of virus transmission through the UCB transplant compared to other HSC sources. This review summarizes the general aspects concerning the prevalence, characteristics, and risk factors of viral infections with a focus on the impact of viral pathogens on cord blood transplantation safety.     

The umbilical cord: a rich and ethical stem cell source to advance regenerative medicine

Science and medicine place a lot of hope in the development of stem cell research and regenerative medicine. This review will define the concept of regenerative medicine and focus on an abundant stem cell source - neonatal tissues such as the umbilical cord. Umbilical cord blood has been used clinically for over 20 years as a cell source for haematopoietic stem cell transplantation. Beyond this, cord blood and umbilical cord-derived stem cells have demonstrated potential for pluripotent lineage differentiation (liver, pancreatic, neural tissues and more) in vitro and in vivo. This promising research has opened up a new era for utilization of neonatal stem cells, now used beyond haematology in clinical trials for autoimmune disorders, cerebral palsy or type I diabetes.     

The Clinical Relevance of Pre-Formed Anti-HLA and Anti-MICA Antibodies after Cord Blood Transplantation in Children

Preformed anti-HLA antibodies (AHA) are known to be associated with delayed engraftment and reduced overall survival after adult hematopoietic stem cell transplantation. However, limited data is available in pediatric patients. In this study, we explored the role of AHA on clinical outcomes in 70 pediatric patients who received a single unit of HLA mismatch cord blood for hematologic malignancies, immunodeficiencies or metabolic diseases. The presence of AHA was detected in 44% (31/70) of the patients. Preformed class I AHA was associated with an increased occurrence of grade 1–4 acute graft-versus host disease (p<0.05). The presence of anti- major-histocompatibility-complex class I–related chain A antigens (MICA) antibodies was significantly associated with a reduced platelet recovery after transplantation (p<0.05). AHA of class II with the strength of antibody titer measured as the mean fluorescence intensity above 2000 was associated with reduced event-free survival (p<0.05). A reduction of high titer of AHA and anti-MICA antibodies might have to be considered before cord blood transplantation in pediatric patients for better outcomes.     

Osmotic tolerance limits of red blood cells from umbilical cord blood

Effective methods for long-term preservation of cord red blood cells (RBCs) are needed to ensure a readily available supply of RBCs to treat fetal and neonatal anemia. Cryopreservation is a potential long-term storage strategy for maintaining the quality of cord RBCs for the use in intrauterine and neonatal transfusion. However, during cryopreservation, cells are subjected to damaging osmotic stresses during cryoprotectant addition and removal and freezing and thawing that require knowledge of osmotic tolerance limits in order to optimize the preservation process. The objective of this study was to characterize the osmotic tolerance limits of cord RBCs in conditions relevant to cryopreservation, and compare the results to the osmotic tolerance limits of adult RBCs. Osmotic tolerance limits were determined by exposing RBCs to solutions of different concentrations to induce a range of osmotic volume changes. Three treatment groups of adult and cord RBCs were tested: (1) isotonic saline, (2) 40% w/v glycerol, and (3) frozen–thawed RBCs in 40% w/v glycerol. We show that cord RBCs are more sensitive to shrinkage and swelling than adult RBCs, indicating that osmotic tolerance limits should be considered when adding and removing cryoprotectants. In addition, freezing and thawing resulted in both cord and adult RBCs becoming more sensitive to post-thaw swelling requiring that glycerol removal procedures for both cell types ensure that cell volume excursions are maintained below 1.7 times the isotonic osmotically active volume to attain good post-wash cell recovery. Our results will help inform the development of optimized cryopreservation protocol for cord RBCs.