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      Differential Expression of TGF-β Isoforms During Differentiation of HaCaT Human Keratinocyte Cells: Implication for the Separate Role in Epidermal Differentiation

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          The three mammalian isoforms of transforming growth factor-β (TGF-β1, β2, β3) are potent regulators of cell growth, differentiation, and extracellular matrix deposition. To study their role in skin differentiation, we investigated the expression of TGF-β isoforms on cell growth and differentiation induction of the human keratinocyte cell line, HaCaT by elevating the Ca 2+ concentration. An ELISA and RT-PCR assay revealed secreted TGF-β1 protein and TGF-β1 mRNA were increased during calci-um-induced differentiation. In contrast, major differences were seen for TGF-β2 and TGF-β3 mRNA which were decreased during differentiation, but TGF-β2 and TGF-3β protein were not evident on an ELISA. These results suggest different functions for each TGF-β isoforms in epidermal differentiation, such that TGF-β1 is associ-ated with the more differentiated state, and TGF-β2 and TGF-β3 may be associ-ated the more proliferated state.

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          Most cited references 20

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          Separation of human epidermal stem cells from transit amplifying cells on the basis of differences in integrin function and expression.

          The epidermis is believed to contain two types of proliferating cells: stem cells and cells with a lower capacity for self-renewal and higher probability of undergoing terminal differentiation (transit amplifying cells). We report that keratinocytes with characteristics of stem cells can be isolated from cultured human epidermis on the basis of high surface expression of beta 1 integrins and rapid adhesion to extracellular matrix (ECM) proteins. Among keratinocytes there was a log linear relationship between the relative level of beta 1 integrins on the cell surface and proliferative capacity; furthermore, the cells with the highest colony-forming efficiency adhered most rapidly to type IV collagen, fibronectin, or keratinocyte ECM. Proliferating keratinocytes that adhered more slowly had characteristics of transit amplifying cells: after one to five rounds of division, all of their daughters underwent terminal differentiation. Since stem cells can be isolated to greater than 90% purity on the basis of their adhesive properties, it will now be possible to investigate the mechanisms that regulate the fate of their progeny.
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            Immunohistochemical localization of TGF beta 1, TGF beta 2, and TGF beta 3 in the mouse embryo: expression patterns suggest multiple roles during embryonic development

             B. Saxena,  L Gold,  R. Pelton (1991)
            Isoform-specific antibodies to TGF beta 1, TGF beta 2, and TGF beta 3 proteins were generated and have been used to examine the expression of these factors in the developing mouse embryo from 12.5-18.5 d post coitum (d.p.c.). These studies demonstrate the initial characterization of both TGF beta 2 and beta 3 in mammalian embryogenesis and are compared with TGF beta 1. Expression of one or all three TGF beta proteins was observed in many tissues, e.g., cartilage, bone, teeth, muscle, heart, blood vessels, lung, kidney, gut, liver, eye, ear, skin, and nervous tissue. Furthermore, all three TGF beta proteins demonstrated discrete cell-specific patterns of expression at various stages of development and the wide variety of tissues expressing TGF beta proteins represent all three primary embryonic germ layers. For example, specific localization of TGF beta 1 was observed in the lens fibers of the eye (ectoderm), TGF beta 2 in the cortex of the adrenal gland (mesoderm), and TGF beta 3 in the cochlear epithelium of the inner ear (endoderm). Compared to the expression of TGF beta mRNA transcripts in a given embryonic tissue, TGF beta proteins were frequently colocalized within the same cell type as the mRNA, but in some cases were observed to localize to different cells than the mRNA, thereby indicating that a complex pattern of transcription, translation, and secretion for TGF beta s 1-3 exists in the mouse embryo. This also indicates that TGF beta 1, beta 2, and beta 3 act through both paracrine and autocrine mechanisms during mammalian embryogenesis.
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              Expression of murine epidermal differentiation markers is tightly regulated by restricted extracellular calcium concentrations in vitro

              Epidermal differentiation is characterized by a series of coordinated morphological and biochemical changes which result in a highly specialized, highly organized, stratified squamous epithelium. Among the specific markers expressed in differentiating epidermis are (a) two early spinous cell proteins, keratins 1 and 10 (K1 and K10); and (b) two later granular cell proteins, filaggrin and a cornified envelope precursor (CE). In vitro, epidermal basal cells are selectively cultured in 0.05 mM Ca2+ medium, and terminal differentiation is induced when the Ca2+ concentration is increased to 1 mM. However, only a small fraction of the cells express the markers K1, K10, CE, or filaggrin in the higher Ca2+ medium. To explore the factors required for marker expression, cultured epidermal cells were exposed to intermediate Ca2+ concentrations and extracts were analyzed using specific antibody and nucleic acid probes for the four markers of interest. These studies revealed that marker expression was enhanced at a restricted concentration of Ca2+ in the medium of 0.10-0.16 mM. At this Ca2+ concentration, both protein and mRNA levels for each marker were substantially increased, whereas at higher or lower Ca2+ concentrations they were diminished or undetected. The percentage of cells expressing each marker was increased two- to threefold in the permissive Ca2+ medium as determined by immunofluorescence analysis. This optimal level of Ca2+ was required both to initiate and sustain marker expression. At the permissive Ca2+ concentration, expression of the markers was sequential and similar to the order of appearance in vivo. K1 was expressed within 8-12 h and K10 was expressed in the ensuing 12-24-h period. CE and filaggrin were expressed in the subsequent 24 h. Inhibition of K1 expression by cycloheximide suggested that an inducible protein was involved. Other investigators have determined that a shallow Ca2+ gradient exists in epidermis, where the basal cells and spinous cells are in a Ca2+ environment substantially below serum Ca2+ levels. These in vitro results suggest that the Ca2+ environment is a fundamental regulator of expression of epidermal differentiation markers and provide an explanation for the existence of the Ca2+ gradient in vivo.

                Author and article information

                J Korean Med Sci
                Journal of Korean Medical Science
                The Korean Academy of Medical Sciences
                December 2004
                31 December 2004
                : 19
                : 6
                : 853-858
                Department of Dermatology, College of Medicine, Kyung Hee University, Seoul, Korea.
                [* ]East-West Medical Research Institute, College of Medicine, Kyung Hee University, Seoul, Korea.
                Author notes
                Address for correspondence: Nack-In Kim, M.D. Department of Dermatology, College of Medicine, Kyung Hee University, 1 Hoeki-dong, Dongdaemun-gu, Seoul 130-702, Korea. Tel: +82.2-958-8511, Fax: +82.2-969-6538, nikim@ 123456khmc.or.kr
                Copyright © 2004 The Korean Academy of Medical Sciences

                This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

                Original Article


                keratinocytes, transforming growth factor beta, cell differentiation, calcium


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