Multilineage potential of adult human mesenchymal stem cells

Human mesenchymal stem cells are thought to be multipotent cells, which are present in adult marrow, that can replicate as undifferentiated cells and that have the potential to differentiate to lineages of mesenchymal tissues, including bone, cartilage, fat, tendon, muscle, and marrow stroma. Cells that have the characteristics of human mesenchymal stem cells were isolated from marrow aspirates of volunteer donors. These cells displayed a stable phenotype and remained as a monolayer in vitro. These adult stem cells could be induced to differentiate exclusively into the adipocytic, chondrocytic, or osteocytic lineages. Individual stem cells were identified that, when expanded to colonies, retained their multilineage potential.     

Gene targeting in stem cells from individuals with osteogenesis imperfecta

Adult stem cells offer the potential to treat many diseases through a combination of ex vivo genetic manipulation and autologous transplantation. Mesenchymal stem cells (MSCs, also referred to as marrow stromal cells) are adult stem cells that can be isolated as proliferating, adherent cells from bones. MSCs can differentiate into multiple cell types present in several tissues, including bone, fat, cartilage, and muscle, making them ideal candidates for a variety of cell-based therapies. Here, we have used adeno-associated virus vectors to disrupt dominant-negative mutant COL1A1 collagen genes in MSCs from individuals with the brittle bone disorder osteogenesis imperfecta, demonstrating successful gene targeting in adult human stem cells.     

Kinetic differences in unresponsiveness of thymus and bone marrow cells

Both thymus and bone marrow cells of adult mice can be made specifically unresponsive to human gamma globulin, but each cell population displays a distinct kinetic pattern for both the induction and spontaneous loss of the unresponsive state. These kinetics appear to be much slower in the bone marrow cells than in the thymus cells. In addition, the dose of deaggregated human gamma globulin needed to induce unresponsiveness in bone marrow cells is much greater than that needed to induce unresponsiveness in thymus cells. Apparently, unresponsiveness in only one cell type is sufficient for the tolerant state to be exhibited by the intact animal.     

Lin28b reprograms adult bone marrow hematopoietic progenitors to mediate fetal-like lymphopoiesis

The immune system develops in waves during ontogeny; it is initially populated by cells generated from fetal hematopoietic stem cells (HSCs) and later by cells derived from adult HSCs. Remarkably, the genetic programs that control these two distinct stem cell fates remain poorly understood. We report that Lin28b is specifically expressed in mouse and human fetal liver and thymus, but not in adult bone marrow or thymus. We demonstrate that ectopic expression of Lin28 reprograms hematopoietic stem/progenitor cells (HSPCs) from adult bone marrow, which endows them with the ability to mediate multilineage reconstitution that resembles fetal lymphopoiesis, including increased development of B-1a, marginal zone B, gamma/delta (γδ) T cells, and natural killer T (NKT) cells.     

Ontogeny and peripheralization of thymic lymphocytes

Reciprocal transplantation of undifferentiated thymic primordia between diploid and triploid chromosomally marked frog embryos has revealed that thymic lymphocytes are ontogenically derived from elements of the thymic primordium rather than from blood-borne stem cells that migrated into the developing organ. Virtually all the lymphocytes in the spleen, kidneys, and bone marrow of adult frogs are descendants of these original thymic stem lymphocytes.     

Cell biology. Stem cells: new excitement, persistent questions

On pages 1775 and 1779, independent research teams describe experiments in which bone marrow cells became neuronlike cells in the brain, providing new evidence for the versatility of adult stem cells. But ample uncertainties must be resolved before such results can be translated into therapeutics. The most important next step, say several stem cell researchers, is to identify the molecular processes that underlie the impressive feats of stem cells, as many of the purported breakthroughs are simply observations.     

微核试验检测5-氟尿嘧啶对小鼠外周血及骨髓细胞的影响

目的探讨抗肿瘤药物5-氟尿嘧啶(5-Fu)对小鼠外周血及骨髓细胞的影响。方法 80只小鼠随机分为8组,其中4组用于小鼠外周血细胞实验,另4组用于骨髓细胞微核实验;分别为对照组、1/30给药组、1/10给药组和1/3给药组,对照组注射生理盐水0.5mL,其余各组2次腹腔注射不同剂量5-Fu,微核试验观察小鼠外周血和骨髓细胞中微核形成。结果第1次给药后,各组外周血和骨髓细胞中微核率均高于对照组(P<0.01)。第2次给药较第1次给药的微核率明显升高,差异亦有统计学意义(P<0.05)。结论 5-Fu能引起小鼠外周血及骨髓细胞染色体损伤。     

Prospects for human gene therapy

Procedures have now been developed for inserting functional genes into the bone marrow of mice. The most effective delivery system at present uses retroviral-based vectors to transfer a gene into murine bone marrow cells in culture. The genetically altered bone marrow is then implanted into recipient animals. These somatic cell gene therapy techniques are becoming increasingly efficient. Their future application in humans should result in at least partial correction of a number of genetic disorders. However, the safety of the procedures must still be established by further animal studies before human clinical trials would be ethical.     

Gene expression in mice after high efficiency retroviral-mediated gene transfer

A retroviral expression vector (N2) containing the selectable gene, neoR, has been used to determine the optimal conditions for infecting murine hematopoietic progenitor cells at high efficiency. After infected bone marrow cells were introduced into lethally irradiated mice, the presence, stability, and expression of the vector DNA sequences were analyzed either in individual spleen foci 10 days later or in the blood, bone marrow, and spleens of mice 4 months later. When bone marrow cells were cultured in medium containing virus with titers of more than 10(6) colony-forming units per milliliter in the presence of purified murine interleukin-3, more than 85 percent of the resulting foci contained vector DNA. This proviral vector DNA was intact. Efficient expression of the neoR gene was demonstrated in most of the DNA-positive foci examined. The spleens of reconstituted animals (over a long term) contained intact "vector DNA" and the blood and bone marrow expressed the neoR gene in some animals. Thus, a retroviral vector can be used to introduce intact exogenous DNA sequences into hematopoietic stem cells with high efficiency and with substantial expression.     

The application of bone marrow transplantation to the treatment of genetic diseases

Genetic diseases can be treated by transplantation of either normal allogeneic bone marrow or, potentially, autologous bone marrow into which the normal gene has been inserted in vitro (gene therapy). Histocompatible allogeneic bone marrow transplantation is used for the treatment of genetic diseases whose clinical expression is restricted to lymphoid or hematopoietic cells. The therapeutic role of bone marrow transplantation in the treatment of generalized genetic diseases, especially those affecting the central nervous system, is under investigation. The response of a generalized genetic disease to allogeneic bone marrow transplantation may be predicted by experiments in vitro. Gene therapy can be used only when the gene responsible for the disease has been characterized. Success of gene therapy for a specific genetic disease may be predicted by its clinical response to allogeneic bone marrow transplantation.     

Bone marrow stromal cells generate muscle cells and repair muscle degeneration

Bone marrow stromal cells (MSCs) have great potential as therapeutic agents. We report a method for inducing skeletal muscle lineage cells from human and rat general adherent MSCs with an efficiency of 89%. Induced cells differentiated into muscle fibers upon transplantation into degenerated muscles of rats and mdx-nude mice. The induced population contained Pax7-positive cells that contributed to subsequent regeneration of muscle upon repetitive damage without additional transplantation of cells. These MSCs represent a more ready supply of myogenic cells than do the rare myogenic stem cells normally found in muscle and bone marrow.     

A model of human acute lymphoblastic leukemia in immune-deficient SCID mice

A human acute lymphoblastic leukemia (ALL) cell line that was transplanted into immune-deficient SCID mice proliferated in the hematopoietic tissues, invaded various organs, and led to the death of the mice. The distribution of leukemic cells in SCID mice was similar to the course of the disease in children. A-1 cells marked with a retrovirus vector showed clonal evolution after the transplant. SCID mice that were injected with bone marrow from three patients with non-T ALL had leukemic cells in their bone marrow and spleen. This in vivo model of human leukemia is an approach to understanding leukemic growth and progression and is a novel system for testing new treatment strategies.     

Seminal vesicle formation and specific male protein secretion by female cells in allophenic mice

The relation of cellular sex genotype to phenotype was examined in seminal vesicles of adult allophenic mice with cellular sex chromosome mosaicism. Each animal originated from conjoined blastomeres of an embryo of female (XX) and one of male (XY) constitution, from different inbred strains. Cells of both sexes were detected in bone marrow and certain other somatic tissues; cellular sex of seminal vesicles was deduced from strain-associated electrophoretic variants of proteins coded for at autosomal loci. Seminal vesicles composed partly or entirely of female cells were found in male and pseudohermaphrodite individuals. In a pseudohermaphrodite, both allelic variants of the tissue-specific normal male seminal vesicle protein (Svp-locus) were present, signifying that female as well as male cells were synthesizing the protein. Male-determining factors on the Y chromosome are thus not required in cells that differentiate into functional seminal vesicles.     

Stem cells and their niches

A constellation of intrinsic and extrinsic cellular mechanisms regulates the balance of self-renewal and differentiation in all stem cells. Stem cells, their progeny, and elements of their microenvironment make up an anatomical structure that coordinates normal homeostatic production of functional mature cells. Here we discuss the stem cell niche concept, highlight recent progress, and identify important unanswered questions. We focus on three mammalian stem cell systems where large numbers of mature cells must be continuously produced throughout adult life: intestinal epithelium, epidermal structures, and bone marrow.     

Influence of SHIP on the NK repertoire and allogeneic bone marrow transplantation

Natural killer cell (NK) receptors for major histocompatibility complex (MHC) class I influence engraftment and graft-versus-tumor effects after allogeneic bone marrow transplantation. We find that SH2-containing inositol phosphatase (SHIP) influences the repertoire of NK receptors. In adult SHIP-/- mice, the NK compartment is dominated by cells that express two inhibitory receptors capable of binding either self or allogeneic MHC ligands. This promiscuous repertoire has significant functional consequences, because SHIP-/- mice fail to reject fully mismatched allogeneic marrow grafts and show enhanced survival after such transplants. Thus, SHIP plays an important role in two processes that limit the success of allogeneic marrow transplantation: graft rejection and graft-versus-host disease.     

Bone marrow transplantation

The goals in bone marrow transplantation are its application to the treatment of diseases arising in the blood-forming tissues of man. Techniques for procuring and grafting marrow are of the needle-and-syringe type and are based on the normal physiological processes in which stem cells circulate through blood and other fluids of the mammalian organism. Destruction of bone marrow by irradiation, chemicals, or unknown agencies provides the immediate experimental system for demonstrating the therapeutic value of marrow transplants. Genetic diseases characterized by abnormal marrow function are also modifiable by grafts of blood-forming tissues. Studies with identical twins are critical experiments for showing the clinical value of grafts, even though the transplanted cells cannot be identified by the usual marker techniques. Among the best results seen with marrow grafting is the presumed cure of certain rare hereditary immune-deficiency disorders of children. A major problem in bone marrow transplantation-one that delays its wider clinical application-is the immune reaction from cells growing out of the foreign transplant which attack the host (the graft-versus-host reaction). Attempts to use a graft-versus-host response to eliminate tumor cells is a part of the marrow research program. The history of the processes that led to some of the achieved goals in marrow grafting shows the usual multicentric origin of an idea. Certain individuals play critical roles in developing the idea. Finally, a body of knowledge is accumulated that opens up or limits prospects for the future. In bone marrow transplantati on, future achievements will depend in part on the progress that is made in the areas of cell separation, bone marrow banking, and tissue culture.     

Retroviral vector-mediated gene transfer into human hematopoietic progenitor cells

The transfer of the human gene for hypoxanthine phosphoribosyltransferase (HPRT) into human bone marrow cells was accomplished by use of a retroviral vector. The cells were infected in vitro with a replication-incompetent murine retroviral vector that carried and expressed a mutant HPRT complementary DNA. The infected cells were superinfected with a helper virus and maintained in long-term culture. The production of progeny HPRT virus by the bone marrow cells was demonstrated with a colony formation assay on cultured HPRT-deficient, ouabain-resistant murine fibroblasts. Hematopoietic progenitor cells able to form colonies of granulocytes or macrophages (or both) in semisolid medium in the presence of colony stimulating factor were present in the nonadherent cell population. Colony forming units cloned in agar and subsequently cultured in liquid medium produced progeny HPRT virus, indicating infection of this class of hematopoietic progenitor cell.     

喹乙醇对鸡骨髓细胞染色体畸变和微核率的影响

为了评价喹乙醇对家禽的致突变性,试验将鸡分为试验组(150 mg.kg-1.diet喹乙醇)、阴性对照组(灭菌生理盐水)、阳性对照组(环磷酰胺),连续染毒15 d,间隔5 d采样一次,检测骨髓细胞染色体畸变率和微核率。结果表明,试验组骨髓细胞染色体畸变率和微核率与阴性对照组比较差异显著(P0.01),且呈时间-效应关系。表明喹乙醇是鸡骨髓细胞突变的诱变剂。