Showing papers on "Transdifferentiation published in 1989"
TL;DR: The basic concept of stem cells, the reported findings of limbal stem cells for corneal epithelium, and their therapeutic applications are reviewed to gain a more complete understanding and increase proficiency in treating these diseases.
Abstract: Cumulative reported evidence indicates that some fraction of limbal basal epithelial cells are the stem cells for corneal epithelial cell proliferation and differentiation. Limbal epithelium is therefore crucial in maintaining the cell mass of corneal epithelium under normal conditions and plays an important role in corneal epithelial wound healing. Deficiency or absence of limbal stem cells explains well the pathogenesis of several ocular surface disorders characterised by defective conjunctival transdifferentiation or conjunctivalisation of cornea. This paper reviews and updates the basic concept of stem cells, the reported findings of limbal stem cells for corneal epithelium, and their therapeutic applications. Through this review, one hopes to gain a more complete understanding and increase proficiency in treating these diseases.
628 citations
Journal Article•
TL;DR: The presence of and phenotypic interconversion (transdifferentiation) between two morphologically and biochemically distinct cell types is suggestive of a multipotent embryonal precursor cell of the neural crest.
Abstract: Previous studies of the human neuroblastoma cell line SK-N-SH had demonstrated the presence of and phenotypic interconversion (transdifferentiation) between two morphologically and biochemically distinct cell types: N (neuroblastic) cells with properties of noradrenergic neurons and S (substrate-adherent) cells with properties of melanocytes. Current studies have sought to test the generality of these findings among other cultured human neuroblastoma cell lines and to define further the S-cell phenotype and that of a newly identified, morphologically intermediate, I-type cell. Morphologically homogeneous populations (clonal sublines or subpopulations) of N, S, and I cells were isolated from five additional neuroblastoma cell lines and analyzed biochemically for neuronal, glial, and melanocytic marker enzyme activities and norepinephrine uptake. Immunoblot techniques were used to detect intermediate filament proteins (neurofilament protein, vimentin, glial fibrillary acidic protein) and fibronectin. All N-type cells exhibited neuronal marker enzyme activities, specific uptake of norepinephrine, and presence of one or more neurofilament proteins. S-type cells generally lacked neuronal characteristics but contained, instead, tyrosinase activity (a melanocytic marker enzyme), vimentin, and fibronectin. This combination of attributes is suggestive of a multipotent embryonal precursor cell of the neural crest. I-type cells differentially expressed both S- and N-cell properties and could represent either a stem cell or an intermediate in the transdifferentiation process. Studies of the biological significance of human neuroblastoma cell transdifferentiation and the molecular mechanisms underlying this process may be of relevance to the biological and clinical behavior of this tumor in the patient.
493 citations
TL;DR: This model explains the 'transdifferentiation' of mature cells seen in this system as simply a delayed realization of transitions that normally occur between these stages during development.
38 citations
TL;DR: It is suggested that the SCG10 HSS may represent a molecular marker of the lineage and phenotypic plasticity of chromaffin cells, and can in principle form in any cell type expressing the gene.
30 citations
01 Jan 1989
TL;DR: The well-known plasticity of plant tissues, especially in vitro, is the rule, rather than the exception, and as a topic of transdifferentiation is beyond the scope of this chapter.
Abstract: Transdifferentiation may be generally defined as the change of one recognizable cell type to another different cell type. The term was first used by Selman and Kafatos (1974) to denote the change of the cuticular cells of the moth larval silk gland to those producing HCO3 during metamorphosis/development and has since been used in many different contexts. So as not to produce a welter of semantics to replace the term already in use, I shall instead categorize the phenomenon of transdifferentiation by levels: primary, secondary, and tertiary transdifferentiation. Primary (or true) transdifferentiation would include the cell-type conversion or cell metaplasia that is so well documented to occur in some amphibian eye tissues in vitro and in amphibian (newt) eye tissues in situ (Fig. 1). This level is characterized by verifiably postmitotic cells, terminally differentiated and producing a specific cell product, transforming into a completely different cell type with differing cell product(s). Secondary transdifferentiation is marked by the conversion of those cells or tissues not definitely demonstrable as terminally differentiated, i.e., from an embryonic or possible stem-cell source. Also included is the concept of transdetermination (Hadorn, 1965), in which certain groups of cells in Drosophila occasionally become determined or committed to a developmental fate different from that expected. Tertiary transdifferentiation would encompass other purported/ reported changes of tissue types, e.g., that of muscle to cartilage (Namenwirth, 1974), and of striated to smooth muscle in Anthomedusa as reported by Schmid and Alder (1984) and Weber et al (1987). The well-known plasticity of plant tissues, especially in vitro, is the rule, rather than the exception, and as a topic of transdifferentiation is beyond the scope of this chapter.
12 citations
TL;DR: It is suggested that fibroblast-like cells result from the in vitro transdifferentiation of a limited number of in vivo committed macrophages, which is 2- and 12-fold higher in acutely and chronically infected mice.
Abstract: We developed a method for avoiding contamination by fibroblasts when cultures of peritoneal cells are initiated. Macrophages were identified by immunogold detection [light microscope, transmission (TEM) and scanning (SEM) electron microscopes] of membrane antigens (Mac-1+, Thy-1,2−), non-specific esterase activity and ultrastructural features (TEM). As compared with controls, the yield of peritoneal macrophages was 2- and 12-fold higher, respectively, in acutely and chronically infected mice. In all, 30 “chronic”, 18 “acute” and 18 control cultures were followed up. At a given cell-density seeding, the decline of control, “acute” and “chronic” cultures starts at about day 10, 15, and 27, respectively. In “chronic” cultures only, fibroblast-like cells appear from day 6 onwards; their number increases with time. Cells showing characters intermediary between macrophages and fibroblasts were observed. We suggest that fibroblast-like cells result from the in vitro transdifferentiation of a limited number of in vivo committed macrophages.
9 citations
Journal Article•
TL;DR: Results clearly shown that lens transdifferentiation proceeds via neutral cell state in which both pigment and lens specific genes are repressed, and an elevated expression of the c-myc gene was observed during dedifferentiation process.
Abstract: Pigmented epithelial cells of chicken and human dedifferentiate in the medium containing phenylthiourea and testicular hyaluronidase, and then trans-differentiate into lens cells in vitro. To understand the molecular mechanisms of transdifferentiation, gene expression during lens transdifferentiation was analyzed. As the first step, pigment cell and lens specific genes were isolated and expression of these gene was analyzed by Northern blotting . These results clearly shown that lens transdifferentiation proceeds via neutral cell state in which both pigment and lens specific genes are repressed. Oncogene expression was also analyzed. An elevated expression of the c-myc gene was observed during dedifferentiation process. It is expected that elevated expression of c-myc gene might prevent the cells from entering the G0 phase and thus lead to dedifferentiated state.
5 citations
01 Jan 1989
TL;DR: The adult amphibian eye is a very convenient model for studying the events involved in the process that has been called transdifferentiation, which involves regeneration of the lens and/or retina in the adult newt or certain other amphibia.
Abstract: The adult amphibian eye is a very convenient model for studying the events involved in the process that has been called transdifferentiation. In this system, which involves regeneration of the lens and/or retina in the adult newt or certain other amphibia, fully differentiated cells of adult somatic tissue are released from the control of the differentiated state and are channeled into a new pathway of cell type differentiation.
1 citations
01 Jan 1989
TL;DR: All three factors promote transdifferentiation to the neuronal phenotype but histamine acts with a much shorter latency than bFGF and αMSH, and only histamine produces any modification of pENK gene expression at the times examined.
Abstract: The effects of histamine, basic fibroblast growth factor (bFGF) and a melanocyte stimulating hormone (αMSH) on neurite outgrowth, proenkephalin A (pENK) and tyrosine hydroxylase (TH) gene expression have been studied in primary cultures of chromaffin cells from the adult bovine adrenal medulla. All three factors promote transdifferentiation to the neuronal phenotype (assessed by neurite outgrowth) but histamine acts with a much shorter latency than bFGF and αMSH. Moreover, only histamine produces any modification of pENK gene expression at the times examined (8,24,48 and 72h). Possible intracellular signalling mechanisms linked to transdifferentiation in bovine chromaffin cells are discussed.