1,720,991 research outputs found
Post-natal skeletal stem cells
No full textPostnatal skeletal stem cells are a subpopulation of the bone marrow stromal cell network. To date, the most straightforward way of assessing the activity of skeletal stem cells within the bone marrow stromal cell (BMSC) population is via analysis of the rapidly adherent, colony-forming unit-fibroblast (CFU-F), and their progeny, BMSCs. Several in vitro methods are employed to determine the differentiation capacity of BMSCs, using osteogenic and adipogenic "cocktails" and staining protocols, and pellet cell culture for chondrogenic differentiation. However, true differentiation potential is best determined by in vivo transplantation in either closed or open systems. By in vivo transplantation, approximately 10% of the clonal strains are able to form bone, stroma, and marrow adipocytes, and are true skeletal stem cells. Furthermore, when derived from patients or animal models with abnormalities in gene expression, they recapitulate the disease phenotype on in vivo transplantation. Although ex vivo expansion of BMSCs inevitably dilutes the skeletal stem cells, when used en masse, they are attractive candidates for reconstruction of segmental bone defects, and as targets for gene therapy
Enumeration of the colony-forming units-fibroblast from mouse and human bone marrow in normal and pathological conditions
No full textBone marrow stromal cell populations, containing a subset of multipotential skeletal stem cells, are increasingly contemplated for use in tissue engineering and stem cell therapy, whereas their involvement in the pathogenetic mechanisms of skeletal disorders is far less recognized. We compared the concentrations of stromal clonogenic cells, colony forming units-fibroblast (CFU-Fs), in norm and pathology. Initially, culture conditions were optimized by demonstrating that fetal bovine serum heat inactivation could significantly repress colony formation. Using non-heat-inactivated fetal bovine serum, the concentration of CFU-Fs (colony-forming efficiency, CFE) ranged from 3.5 +/- 1.0 to 11.5 +/- 4.0 per 1 x 10(5) nucleated cells in five inbred mouse strains. In four transgenic lines with profound bone involvement, CFE was either significantly reduced or increased compared to wild-type littermates. In normal human donors, CFE decreased slightly with age and averaged 52.2 +/- 4.1 for children and 32.3 +/- 3.0 for adults. CFE was significantly altered in patients with several skeletal, metabolic, and hematological disorders: reduced in congenital generalized lipodystrophy, achondroplasia (SADDAN), pseudoachondroplasia, and Paget disease of bone and elevated in alcaptonuria and sickle cell anemia. Our findings indicate that under appropriate culture conditions, CFE values may provide useful insights into bone/bone marrow pathophysiology
Post-Natal Skeletal Stem Cells Methods for Isolation and Analysis of Bone Marrow Stromal Cells (BMSCs) from Post-natal Murine and human marrow
No full textOsteoclastogenesis in fibrous dysplasia of bone: In situ and in vitro analysis of IL-6 expression
No full textFibrous dysplasia of bone (FD) is caused by somatic mutations of the GNAS1 gene, which lead to constitutive activation of adenylyl cyclase and overproduction of cAMP in osteogenic cells. Previous in vitro studies using nonclonal, heterogeneous strains of FD-derived cells suggested that IL-6 might play a critical role in promoting excess osteoclastogenesis in FD. In this study, we investigated IL-6 expression in FD in situ and its relationship to the actual patterns of osteoclastogenesis within the abnormal tissue. We found that osteoclastogenesis is not spatially restricted to bone surfaces in FD but occurs to a large extent ectopicly in the fibrous tissue, where stromal cells diffusely express IL-6 mRNA and exhibit a characteristic cell morphology. We also observed specific expression of IL-6 mRNA in a proportion of osteoclasts, suggesting that an autocrine/paracrine loop may contribute to osteoclastogenesis in vivo in FD, as in some other bone diseases, including Paget's disease. We also generated homogeneous, clonally derived strains of wild-type and GNAS1-mutated stromal cells from the same individual, parent FD lesions. In this way, we could show that mutated stromal cells produce IL-6 at a basal magnitude and rate that are significantly higher than in the cognate wild-type cells. Conversely, wild-type cells respond to db-cAMP with a severalfold increase in magnitude and rate of IL-6 production, whereas mutant strains remain essentially unresponsive. Our data establish a direct link between GNAS1 mutations in stromal cells and IL-6 production but also define the complexity of the role of IL-6 in regulating osteoclastogenesis in FD in vivo. Here, patterns of osteoclastogenesis and bone resorption reflect not only the cell-autonomous effects of GNAS1 mutations in osteogenic cells (including IL-6 production) but also the local and systemic context to which non-osteogenic cells, local proportions of wild-type vs mutated cells, and systemic hormones contribute
Circulating skeletal stem cells.
No full textWe report the isolation of adherent, clonogenic, fibroblast-like cells with osteogenic and adipogenic potential from the blood of four mammalian species. These cells phenotypically resemble but are distinguishable from skeletal stem cells found in bone marrow (stromal stem cells, "mesenchymal stem cells"). The osteogenic potential of the blood-borne cells was proven by an in vivo transplantation assay in which either polyclonal or single colony-derived strains were transplanted into the subcutis of immunocompromised mice, and the donor origin of the fully differentiated bone cells was proven using species-specific probes. This is the first definitive proof of the existence of circulating skeletal stem cells in mammals
Age dependent demise of GNAS-mutated skeletal stem cells and "normalization" of fibrous dysplasia of bone.
No full textWe studied the role of somatic mosaicism in fibrous dysplasia of bone (FD) within the context of skeletal ("mesenchymal") stem cells by assessing the frequency of mutated colony forming unit-fibroblasts (CFU-Fs) from FD lesions, and in some cases, from unaffected sites, in a series of patients. There was a tight inverse correlation between the percentage mutant CFU-F versus age, suggesting demise of mutant stem cells caused by exuberant apoptosis noted in samples from young patients. In older patients, either partially or completely normal bone/marrow histology was observed. On in vivo transplantation, FD ossicles were generated only by cell strains in which mutant CFU-Fs were identified. Strains that lacked mutant CFU-F (but were mutation positive) failed to regenerate an FD ossicle. These data indicate that GNAS mutations are only pathogenic when in clonogenic skeletal stem cells. From these data, we have evolved the novel concept of "normalization" of FD. As a lesion ages, mutant stem cells fail to self-renew, and their progeny are consumed by apoptosis, whereas residual normal stem cells survive, self-renew, and enable formation of a normal structure. This suggests that activating GNAS mutations disrupt a pathway that is required for skeletal stem cell self-renewal
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
- …
