Isolation of pluripotent embryonic stem cells from reprogrammed adult mouse somatic cell nuclei

Pluripotent human stem cells isolated from early embryos represent a potentially unlimited source of many different cell types for cell-based gene and tissue therapies [1-3]. Nevertheless, if the full potential of cell lines derived from donor embryos is to be realised, the problem of donor-recipient tissue matching needs to be overcome. One approach, which avoids the problem of transplant rejection, would be to establish stem cell lines from the patient's own cells through therapeutic cloning [3,4]. Recent studies have shown that it is possible to transfer the nucleus from an adult somatic cell to an unfertilised oocyte that is devoid of maternal chromosomes, and achieve embryonic development under the control of the transferred nucleus [5-7]. Stem cells isolated from such a cloned embryo would be genetically identical to the patient and pose no risk of immune rejection. Here, we report the isolation of pluripotent murine stem cells from reprogrammed adult somatic cell nuclei. Embryos were generated by direct injection of mechanically isolated cumulus cell nuclei into mature oocytes. Embryonic stem (ES) cells isolated from cumulus-cell-derived blastocysts displayed the characteristic morphology and marker expression of conventional ES cells and underwent extensive differentiation into all three embryonic germ layers (endoderm, mesoderm and ectoderm) in tumours and in chimaeric foetuses and pups. The ES cells were also shown to differentiate readily into neurons and muscle in culture. This study shows that pluripotent stem cells can be derived from nuclei of terminally differentiated adult somatic cells and offers a model system for the development of therapies that rely on autologous, human pluripotent stem cells.     

成体干细胞的可塑性:横向分化还是细胞融合?

近年来研究显示成体干细胞(adult stem cells)具有可塑性(plasticity),不仅可以生成它们所在组织的成熟细胞,而且在特定环境下能分化成其他组织类型细胞,这种跨系或跨胚层分化现象称为横向分化或转分化(transdifferentiation)。横向分化已为成体干细胞的研究和临床应用包括组织器官损伤的修复提供了新的思路和应用前景。然而,最近的一些研究进展又引出不同的解释,即成体干细胞的可塑性是由于细胞融合(cellfusion)的结果。在此,就成体干细胞的可塑性、横向分化、细胞融合等方面研究作一综述。     

Rejuvenating regeneration: Metformin activates endogenous adult stem cells

Comment on: Wang J, et al. Cell Stem Cell 2012; 11:23-35.     

Developmental mechanisms and adult stem cells for therapeutic lung regeneration

Chronic degenerative lung diseases are essentially untreatable pathological conditions. By contrast, the healthy lung has numerous mechanisms that allow for rapid repair and restoration of function following minor acute injuries. We discuss the normal endogenous processes of lung development, homeostatic maintenance and repair and consider the research strategies required for the development of methods for human therapeutic lung regeneration.     

The satellite cell in male and female, developing and adult mouse muscle: distinct stem cells for growth and regeneration

Satellite cells are myogenic cells found between the basal lamina and the sarcolemma of the muscle fibre. Satellite cells are the source of new myofibres; as such, satellite cell transplantation holds promise as a treatment for muscular dystrophies. We have investigated age and sex differences between mouse satellite cells in vitro and assessed the importance of these factors as mediators of donor cell engraftment in an in vivo model of satellite cell transplantation. We found that satellite cell numbers are increased in growing compared to adult and in male compared to female adult mice. We saw no difference in the expression of the myogenic regulatory factors between male and female mice, but distinct profiles were observed according to developmental stage. We show that, in contrast to adult mice, the majority of satellite cells from two week old mice are proliferating to facilitate myofibre growth; however a small proportion of these cells are quiescent and not contributing to this growth programme. Despite observed changes in satellite cell populations, there is no difference in engraftment efficiency either between satellite cells derived from adult or pre-weaned donor mice, male or female donor cells, or between male and female host muscle environments. We suggest there exist two distinct satellite cell populations: one for muscle growth and maintenance and one for muscle regeneration.     

Melanocyte regeneration reveals mechanisms of adult stem cell regulation

Utilization of adult stem cells in regenerative therapies may require a thorough understanding of the mechanisms that establish, recruit and renew the stem cell, promote the differentiation of its daughters, or how the stem cell is repressed by its target tissue. Regeneration of melanocytes in the regenerating zebrafish caudal fin, or following larval melanocyte-specific ablation, or recruitment of new melanocytes during pigment pattern metamorphosis each provides evidence for melanocyte stem cells (MSCs) that support the melanocyte pigment pattern. We discuss the mechanisms of MSC regulation provided from analysis of normal or mutant regeneration in each of these systems, including the implications drawn from evidence that regeneration does not simply recapitulate ontogenetic development. These results suggest that analysis of melanocyte regeneration in zebrafish will provide a fine scale dissection of mechanisms establishing or regulating adult stem cells.     

Recent advances in bone regeneration using adult stem cells

Bone is a highly vascularized tissue reliant on the close spatial and temporal association between bloodvessels and bone cells. Therefore, cells that participate in vasculogenesis and osteogenesis play a pivotal role in bone formation during prenatal and postnatal periods. Nevertheless, spontaneous healing of bone fracture is occasionally impaired due to insufficient blood and cellular supply to the site of injury. In these cases, bone regeneration process is interrupted, which might result in delayed union or even nonunion of the fracture. Nonunion fracture is difficult to treat and have a high financial impact. In the last decade, numerous technological advancements in bone tissue engineering and cell-therapy opened new horizon in the field of bone regeneration. This review starts with presentation of the biological processes involved in bone development, bone remodeling, fracture healing process and the microenvironment at bone healing sites. Then, we discuss the rationale for using adult stem cells and listed the characteristics of the available cells for bone regeneration. The mechanism of action and epigenetic regulations for osteogenic differentiation are also described. Finally, we review the literature for translational and clinical trials that investigated the use of adult stem cells(mesenchymal stem cells, endothelial progenitor cells and CD34+ blood progenitors) for bone regeneration.     

Immunomodulatory effects of fetal and adult mesenchymal stem cells

Mesenchymal stem cells (MSC) derived from adult BM or fetal liver form several mesenchymal tissues after appropriate stimulation. Reports indicate that MSC have unique immunologic properties, making them ideal for cellular therapy. MSC are not immunogenic, they do not stimulate alloreactivity, and they escape lysis by cytotoxic T-cells and natural killer (NK)-cells. Thus, MSC may be transplantable between HLA-mismatched individuals without the need for host immunosuppression. Furthermore, adult MSC appear to be immunosuppressive as they reduce alloreactivity and the formation of cytotoxic lymphocytes in vitro. In vivo, adult MSC prolong the time to rejection of mis-matched skin grafts in baboons. The immunosuppressive properties of first trimester fetal MSC are less pronounced, but inducible with IFNgamma. These findings imply a potential role for MSC, not only in the repair of damaged tissues, but also in the manipulation of immune responses.     

Insights into kidney stem cell development and regeneration using zebrafish

Kidney disease is an escalating global health problem,for which the formulation of therapeutic approaches using stem cells has received increasing research attention.The complexity of kidney anatomy and function,which includes the diversity of renal cell types,poses formidable challenges in the identification of methods to generate replacement structures.Recent work using the zebrafish has revealed their high capacity to regenerate the integral working units of the kidney,known as nephrons,following acute injury.Here,we discuss these findings and explore the ways that zebrafish can be further utilized to gain a deeper molecular appreciation of renal stem cell biology,which may uncover important clues for regenerative medicine.     

Fetal and adult liver stem cells for liver regeneration and tissue engineering

For the development of innovative cell-based liver directed therapies, e.g. liver tissue engineering, the use of stem cells might be very attractive to overcome the limitation of donor liver tissue. Liver specific differentiation of embryonic, fetal or adult stem cells is currently under investigation. Different types of fetal liver (stem) cells during development were identified, and their advantageous growth potential and bipotential differentiation capacity were shown. However, ethical and legal issues have to be addressed before using fetal cells. Use of adult stem cells is clinically established, e.g. transplantation of hematopoietic stem cells. Other bone marrow derived liver stem cells might be mesenchymal stem cells (MSC). However, the transdifferentiation potential is still in question due to the observation of cellular fusion in several in vivo experiments. In vitro experiments revealed a crucial role of the environment (e.g. growth factors and extracellular matrix) for specific differentiation of stem cells. Co-cultured liver cells also seemed to be important for hepatic gene expression of MSC. For successful liver cell transplantation, a novel approach of tissue engineering by orthotopic transplantation of gel-immobilized cells could be promising, providing optimal environment for the injected cells. Moreover, an orthotopic tissue engineering approach using bipotential stem cells could lead to a repopulation of the recipients liver with healthy liver and biliary cells, thus providing both hepatic functions and biliary excretion. Future studies have to investigate, which stem cell and environmental conditions would be most suitable for the use of stem cells for liver regeneration or tissue engineering approaches.     

Positional identity of adult stem cells in salamander limb regeneration

Limb regeneration in larval and adult salamanders proceeds from a mound of mesenchymal stem cells called the limb blastema. The blastema gives rise just to those structures distal to its level of origin, and this property of positional identity is reset to more proximal values by treatment with retinoic acid. We have identified a cell surface protein, called Prod1/CD59, which appears to be a determinant of proximodistal identity. Prod1 is expressed in an exponential gradient in an adult limb as determined by detection of both mRNA and immunoreactive protein. Prod1 protein is up-regulated after treatment of distal blastemas with RA and this is particularly marked in cells of the dermis. These cells have previously been implicated in pattern formation during limb regeneration.     

Muscle-derived stem cells: potential for muscle regeneration

Duchenne muscular dystrophy (DMD) is a devastating X-linked muscle disease characterized by progressive muscle weakness caused by the lack of dystrophin expression at the sarcolemma of muscle fibers. Although various approaches to delivering dystrophin in dystrophic muscle have been investigated extensively (e.g., cell and gene therapy), there is still no treatment that alleviates the muscle weakness in this common inherited muscle disease. The transplantation of myoblasts can enable transient delivery of dystrophin and improve the strength of injected dystrophic muscle, but this approach has various limitations, including immune rejection, poor cellular survival rates, and the limited spread of the injected cells. The isolation of muscle cells that can overcome these limitations would enhance the success of myoblast transplantation significantly. The efficiency of cell transplantation might be improved through the use of stem cells, which display unique features, including (1) self-renewal with production of progeny, (2) appearance early in development and persistence throughout life, and (3) long-term proliferation and multipotency. For these reasons, the development of muscle stem cells for use in transplantation or gene transfer (ex vivo approach) as treatment for patients with muscle disorders has become more attractive in the past few years. In this paper, we review the current knowledge regarding the isolation and characterization of stem cells isolated from skeletal muscle by highlighting their biological features and their relationship to satellite cells as well as other populations of stem cells derived from other tissues. We also describe the remarkable ability of stem cells to regenerate skeletal muscle and their potential use to alleviate the muscle weakness associated with DMD.     

In vitro regeneration of kidney from pluripotent stem cells

Although renal transplantation has proved a successful treatment for the patients with end-stage renal failure, the therapy is hampered by the problem of serious shortage of donor organs. Regenerative medicine using stem cells, including cell transplantation therapy, needs to be developed to solve the problem. We previously identified the multipotent progenitor cells in the embryonic mouse kidney that can give rise to several kinds of epithelial cells found in adult kidney, such as glomerular podocytes and renal tubular epithelia. Establishing the method to generate the progenitors from human pluripotent stem cells that have the capacity to indefinitely proliferate in vitro is required for the development of kidney regeneration strategy. We review the current status of the research on the differentiation of pluripotent stem cells into renal lineages and describe cues to promote this research field.     

胚胎和成体神经干细胞分化机制的研究

神经干细胞的分化调控一直是发育神经生物学的重要研究课题。综述了调节胚胎和成体神经干细胞分化的细胞内在因素和外部环境因素,初步探讨了胚胎和成体神经干细胞分化机制的差异。