Human embryonic stem cells with biological and epigenetic characteristics similar to those of mouse ESCs

Human and mouse embryonic stem cells (ESCs) are derived from blastocyst-stage embryos but have very different biological properties, and molecular analyses suggest that the pluripotent state of human ESCs isolated so far corresponds to that of mouse-derived epiblast stem cells (EpiSCs). Here we rewire the identity of conventional human ESCs into a more immature state that extensively shares defining features with pluripotent mouse ESCs. This was achieved by ectopic induction of Oct4, Klf4, and Klf2 factors combined with LIF and inhibitors of glycogen synthase kinase 3β (GSK3β) and mitogen-activated protein kinase (ERK1/2) pathway. Forskolin, a protein kinase A pathway agonist which can induce Klf4 and Klf2 expression, transiently substitutes for the requirement for ectopic transgene expression. In contrast to conventional human ESCs, these epigenetically converted cells have growth properties, an X-chromosome activation state (XaXa), a gene expression profile, and a signaling pathway dependence that are highly similar to those of mouse ESCs. Finally, the same growth conditions allow the derivation of human induced pluripotent stem (iPS) cells with similar properties as mouse iPS cells. The generation of validated “naïve” human ESCs will allow the molecular dissection of a previously undefined pluripotent state in humans and may open up new opportunities for patient-specific, disease-relevant research.     

Cellular therapies for lung disease: a distant horizon

Lung diseases constitute a major global burden of health and are characterized by inflammation and chronic fibrosis resulting in a loss of gas exchange units. To date there has been no effective treatment to reverse these chronic inflammatory changes and tissue remodelling. Recently, stem cells have been shown to successfully treat animal models of lung disease. In addition, certain cells have demonstrated a capacity to differentiate into lung cells. Based on these preliminary data, there are clinical trials underway to examine the potential for cellular therapies in lung disease. Recently, there have been a variety of cell examined for both their immunomodulatory effects on the lung as well as their potential for differentiation into lung cells. These range from lung progenitor cells, circulating cells, mesenchymal stem cells (MSCs), induced pluripotent stem cells (iPS), placental stem cells and embryonic stem cells (ESCs). Several cell types demonstrate immunomodulatory effects including circulating cells, MSCs and placental stem cells. In addition, iPS, placental cells and ESCs have shown some capacity for differentiation. Despite these major steps forward cellular therapy for lung diseases still faces challenges. Issues that need to be resolved include bioethical issues, the safety of cell transplantation, ideal routes of delivery, the timing and the specific indications that would make cellular therapy effective.     

Regenerative medicine for insulin deficiency: creation of pancreatic islets and bioartificial pancreas

Recent advances in pancreas organogenesis have greatly improved the understanding of cell lineage from inner cell mass to fully differentiated ??-cells. Based upon such knowledge, insulin-producing cells similar to ??-cells to a certain extent have been generated from various cell sources including embryonic stem cells (ESCs) and induced pluripotent stem (iPS) cells, although fully differentiated cells comparable to ??-cells are not yet available. The bioartificial pancreas is a therapeutic approach to enable allo- and xenotransplantation of islets without immune suppression. Among several types of bioartificial pancreases (BAPs), micro-encapsulated porcine islets are already in use in clinical trials and may, perhaps, replace islet transplantation in the near future. Some types of bioartificial pancreas such as macro-encapsulation are also useful for keeping transplanted cells enclosed in case retrieval is necessary. Therefore, early clinical applications of artificially generated ??-like cells, especially those from ESCs or iPS cells, will be considered in combination with retrievable BAPs.     

Induced pluripotent stem cells offer new approach to therapy in thalassemia and sickle cell anemia and option in prenatal diagnosis in genetic diseases

The innovation of reprogramming somatic cells to induced pluripotent stem cells provides a possible new approach to treat β-thalassemia and other genetic diseases such as sickle cell anemia. Induced pluripotent stem (iPS) cells can be made from these patients'' somatic cells and the mutation in the β-globin gene corrected by gene targeting, and the cells differentiated into hematopoietic cells to be returned to the patient. In this study, we reprogrammed the skin fibroblasts of a patient with homozygous β⁰ thalassemia into iPS cells, and showed that the iPS cells could be differentiated into hematopoietic cells that synthesized hemoglobin. Prenatal diagnosis and selective abortion have been effective in decreasing the number of β-thalassemia births in some countries that have instituted carrier screening and genetic counseling. To make use of the cells from the amniotic fluid or chorionic villus sampling that are used for prenatal diagnosis, we also showed that these cells could be reprogrammed into iPS cells. This raises the possibility of providing a new option following prenatal diagnosis of a fetus affected by a severe illness. Currently, the parents would choose either to terminate the pregnancy or continue it and take care of the sick child after birth. The cells for prenatal diagnosis can be converted into iPS cells for treatment in the perinatal periods. Early treatment has the advantage of requiring much fewer cells than adult treatment, and can also prevent organ damage in those diseases in which damage can begin in utero or at an early age.     

缺血性心脏病干细胞治疗的争论热点与最新进展

文章讨论了细胞修复治疗在缺血性心脏病中的应用。介绍了不同类型细胞的心脏修复效应。重点介绍了胚胎干细胞(ESCs)及诱导型多能干细胞(iPS)临床应用障碍,而ESC及iPS源心脏前体细胞,心肌源性干细胞等修复心肌的最新进展。尤其重点描述了来自于人胚外或胚胎中胚层的脐带华通胶源间充质干细胞的细胞生物学特性,如：兼有胚胎干细胞及间充质干细胞标志特征,无伦理道德问题,多向分化而无致肿瘤性,多代增殖保持干性特征,独特的免疫调节功能等,使之WJ MSCs将成为心脏再生医学中最具希望的种子细胞。     

干细胞技术治疗糖尿病的研究进展与应用前景

干细胞技术可以为糖尿病的细胞替代治疗提供足量胰岛细胞.胚胎干(embryonic stem,ES)细胞、诱导性多潜能干(induced pluripotentstem,iPS)细胞及成体干细胞可以在体外或体内分化为胰岛素分泌细胞,并可降低糖尿病动物模型的血糖.在小规模的临床试验中,自体骨髓干细胞移植治疗糖尿病已经初步显...     

An introduction to induced pluripotent stem cells

Recent landmark studies show that it is now possible to convert somatic cells, such as skin fibroblasts and B lymphocytes, into pluripotent stem cells that closely resemble embryonic stem cells. These induced pluripotent stem (iPS) cells can be generated without using human embryos or oocytes, thus bypassing some of the ethical issues that have limited the use of human embryonic stems (hES) cells. Additionally, they can be derived from the patient to be treated, thereby overcoming problems of immunological rejection associated with the use of allogeneic hES cell derived progenitors. Whilst these patient‐specific iPS cells have great clinical potential, their immediate utility is likely to be in drug screening and for understanding the disease process. This review discusses the promise of iPS cells as well as the challenges to their use in the clinic.     

Patterning definitive hematopoietic stem cells from embryonic stem cells

Derived from the inner cell mass of blastocysts, embryonic stem cells (ESCs) retain the pluripotent features of early embryonic epiblast cells. In vitro, ESCs undergo spontaneous differentiation into a multitude of tissues, and thus are a powerful tool for the study of early developmental processes and a promising resource for cell-based therapies. We have pursued the derivation of functional, multipotent and engraftable hematopoietic stem cells (HSCs) from ESCs in order to investigate the genetic pathways specifying blood formation, as well as to lay the foundation for hematopoietic cell replacement therapies based on engineered ESCs. Theoretically, the generation of HSCs from patient-specific ESCs derived by nuclear transfer could provide for autologous hematopoietic therapies for the treatment of malignant and genetic bone marrow disorders. Although significant progress has been made in achieving hematopoietic differentiation from both murine and human ESCs, we have only a primitive understanding of the underlying mechanisms that specify hematopoietic cell fate, and a very limited capacity to direct the differentiation of the definitive HSC that would be suitable for clinical engraftment studies. Here we will review the progress to date and the significant problems that remain, and outline a strategy to achieve the directed differentiation of HSCs under conditions that might be appropriate for clinical scale-up and disease applications.     

Current issues and innovations in stem cell based therapy

It is well established that stem cells can differentiate into cell types of the organ in which these are transplanted.However,the process is very slow due to lack of understanding of signals important for their survival and differentiation,most optimal stem cells and their plasticity.Limitations and advantages of various cell subtypes will be described. The rate of stem cells mobilization and their survival in the ischemic environment are major obstacles in engraftment and differentiation of stem cells for meaningful repair of the infarcted myocardium. Manipulation of stem cells with ischemic preconditioning,combined gene and cell therapy together with simultaneous activation of diverse signaling pathways for massive stem cell mobilization & regeneration has significant impact on the repair process by stem cells.These and other difficulties encountered in efficient use of various stem cells have resulted in invention of induced pluripotent stem cells which could revolutionize the stem cell based therapy and their applications for understanding of human disease and drug screening in the near future. Reprogramming of adult cells into iPS cells without the use of viral vectors is a major challenge towards getting iPS cells without viral integration into cells.To meet this challenge we have repro-grammed skeletal myoblasts into iPS cells with high efficiency using epigenetic modifiers.Transplantation of iPS cells derived pure cardiac progenitors into infarcted myocardium led to extensive repopulation of scar area with fully developed myocytes without tumor formation and resulting in marked improvement in cardiac function.Reprogramming with pure chemical means will make therapeutic use of these cells more safer.Targeting the induced pluripotent stem cells towards cardiac progenitors and their application towards transplantation is a major step forward in enhancing the myocardial repair capacity by these cells.     

Hematopoietic stem/progenitor cells, generation of induced pluripotent stem cells, and isolation of endothelial progenitors from 21- to 23.5-year cryopreserved cord blood

Cryopreservation of hematopoietic stem cells (HSCs) and hematopoietic progenitor cells (HPCs) is crucial for cord blood (CB) banking and transplantation. We evaluated recovery of functional HPC cryopreserved as mononuclear or unseparated cells for up to 23.5 years compared with prefreeze values of the same CB units. Highly efficient recovery (80%-100%) was apparent for granulocyte-macrophage and multipotential hematopoietic progenitors, although some collections had reproducible low recovery. Proliferative potential, response to multiple cytokines, and replating of HPC colonies was extensive. CD34(+) cells isolated from CB cryopreserved for up to 21 years had long-term (≥ 6 month) engrafting capability in primary and secondary immunodeficient mice reflecting recovery of long-term repopulating, self-renewing HSCs. We recovered functionally responsive CD4(+) and CD8(+) T lymphocytes, generated induced pluripotent stem (iPS) cells with differentiation representing all 3 germ cell lineages in vitro and in vivo, and detected high proliferative endothelial colony forming cells, results of relevance to CB biology and banking.     

Induced Pluripotent Stem Cells and Their Potential for Basic and Clinical Sciences

Induced pluripotent stem (iPS) cells, are a type of pluripotent stem cell derived from adult somatic cells. They have been reprogrammed through inducing genes and factors to be pluripotent. iPS cells are similar to embryonic stem (ES) cells in many aspects. This review summarizes the recent progresses in iPS cell reprogramming and iPS cell based therapy, and describe patient specific iPS cells as a disease model at length in the light of the literature. This review also analyzes and discusses the problems and considerations of iPS cell therapy in the clinical perspective for the treatment of disease.     

Heme oxygenase-1 deficiency leads to disrupted response to acute stress in stem cells and progenitors

An effective response to extreme hematopoietic stress requires an extreme elevation in hematopoiesis and preservation of hematopoietic stem cells (HSCs). These diametrically opposed processes are likely to be regulated by genes that mediate cellular adaptation to physiologic stress. Herein, we show that heme oxygenase-1 (HO-1), the inducible isozyme of heme degradation, is a key regulator of these processes. Mice lacking one allele of HO-1 (HO-1(+/-)) showed accelerated hematopoietic recovery from myelotoxic injury, and HO-1(+/-) HSCs repopulated lethally irradiated recipients with more rapid kinetics. However, HO-1(+/-) HSCs were ineffective in radioprotection and serial repopulation of myeloablated recipients. Perturbations in key stem cell regulators were observed in HO-1(+/-) HSCs and hematopoietic progenitors (HPCs), which may explain the disrupted response of HO-1(+/-) HPCs and HPCs to acute stress. Control of stem cell stress response by HO-1 presents opportunities for metabolic manipulation of stem cell-based therapies.     

Preparation of pancreatic β-cells from human iPS cells with small molecules

Human induced pluripotent stem (iPS) cells obtained from patients are expected to be a useful source for cell transplantation therapy, because many patients (including those with type 1 diabetes and severe type 2 diabetes) are on waiting lists for transplantation for a long time due to the shortage of donors. At present, many concerns related to clinical application of human iPS cells have been raised, but rapid development of methods for the establishment, culture, and standardization of iPS cells will lead autologous cell therapy to be realistic sooner or later. However, establishment of a method for preparing some of desired cell types is still challenging. Regarding pancreatic β-cells, there have been many reports about differentiation of these cells from human embryonic stem (ES)/iPS cells, but a protocol for clinical application has still not been established. Since there is clear proof that cell transplantation therapy is effective for diabetes based on the results of clinical islet transplantation, pancreatic β-cells prepared from human iPS cells are considered likely to be effective for reducing the burden on patients. In this article, the current status of procedures for preparing pancreatic β-cells from human ES/iPS cells, including effective use of small molecules, is summarized, and some of the problems that still need to be overcome are discussed.