BRADFORD SCHOLARS

    • Sign in
    View Item 
    •   Bradford Scholars
    • University of Bradford eTheses
    • Theses
    • View Item
    •   Bradford Scholars
    • University of Bradford eTheses
    • Theses
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Browse

    All of Bradford ScholarsCommunitiesAuthorsTitlesSubjectsPublication DateThis CollectionAuthorsTitlesSubjectsPublication Date

    My Account

    Sign in

    HELP

    Bradford Scholars FAQsCopyright Fact SheetPolicies Fact SheetDeposit Terms and ConditionsDigital Preservation Policy

    Statistics

    Most Popular ItemsStatistics by CountryMost Popular Authors

    The roles of vitamin D in cutaneous wound healing: In vitro and ex vivo studies of the effect of 1,25(OH)2D3 and its precursors on human dermal fibroblasts and epidermal keratinocytes in cutaneous wound healing

    • CSV
    • RefMan
    • EndNote
    • BibTex
    • RefWorks
    Thumbnail
    View/Open
    tay, j.q.pdf (4.241Mb)
    Download
    Author
    Tay, Jing Q.
    Supervisor
    Thornton, M. Julie
    Graham, Anne M.
    Keyword
    Vitamin D
    Wound healing
    Cholecalciferol
    Rights
    Creative Commons License
    The University of Bradford theses are licenced under a Creative Commons Licence.
    Institution
    University of Bradford
    Department
    Faculty of Life Sciences
    Awarded
    2018
    
    Metadata
    Show full item record
    Abstract
    In humans, the epidermis is the main site for the synthesis of Vitamin D3 (cholecalciferol) from 7-dehydrocholesterol. Cholecalciferol undergoes further hydroxylation in the liver and kidney to produce the active form of the circulating hormone 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3). In target cells, 1,25(OH)2D3 interacts with the specific intracellular vitamin D receptor (VDR), a member of the nuclear receptor superfamily. However, epidermal keratinocytes, in addition to being target cells, have enzymes required for autocrine production of 1,25(OH)2D3. They can convert cholecalciferol to 1,25(OH)2D3 via 25-hydroxylase (CYP2R1) and 1α-hydroxylase (CYP27B1). Another enzyme, 24-hydroxylase (CYP24A1), regulates local levels by inactivating 1,25(OH)2D3. While recent studies have shown that absence of VDR or 1,25(OH)2D3 impairs formation of granulation tissue during wound healing in mice, little is known about the autocrine and paracrine regulation of biologically active vitamin D3 by human dermal fibroblasts during cutaneous wound healing. Primary cultures of human keratinocytes and fibroblasts expressed VDR and all the cytochrome enzymes necessary for autocrine production of vitamin D. The relative expression of VDR mRNA was higher in dermal fibroblasts than donor-matched keratinocytes. In contrast, epidermal keratinocytes had a higher mRNA expression of vitamin D3 metabolising enzymes. A scratch wound assay confirmed that 1,25(OH)2D3 stimulated keratinocyte migration, but paradoxically inhibited fibroblast migration as early as 4h, yet neither cholecalciferol nor 25-hydroxyvitamin D3 had any effect. VDR knockdown using small interfering RNA (siRNA) abolished the inhibitory effect of 1,25(OH)2D3 on fibroblast migration, demonstrating the requirement for the VDR in this response. Immunofluorescent staining revealed that 1,25(OH)2D3 increased nuclear VDR protein expression, without a corresponding increase in VDR mRNA transcription only in mechanically wounded dermal fibroblasts, indicating activation of the receptors. Incubation with either 1,25(OH)2D3, cholecalciferol or 25(OH)D3 up-regulated CYP24A1 transcription. This response was most pronounced with 1,25(OH)2D3, suggesting a tightly regulated feedback control on 1,25(OH)2D3 bioavailability within the dermis. In addition, cholecalciferol also increased CYP2R1 and CYP27B1 mRNA expression in scratched dermal fibroblasts, providing evidence for autocrine regulation of 1,25(OH)2D3 by dermal fibroblasts. Expression of α-SMA protein was up-regulated in cultured dermal fibroblasts following scratching, which was down-regulated in the presence of 1,25(OH)2D3. These observations suggest that 1,25(OH)2D3 may restrict differentiation of wounded dermal fibroblasts into pro-fibrotic myofibroblasts. 1,25(OH)2D3 also down-regulated MMP-2 secretion and collagen type I to III ratio in scratched dermal fibroblasts. Using a human ex vivo wound healing model, it was demonstrated that 1,25(OH)2D3, but not cholecalciferol, stimulated the rate of wound closure. In summary, this study has confirmed that human dermal fibroblasts express the transcriptional machinery for autocrine production of 1,25(OH)2D3, and a higher VDR expression suggests they are more responsive than keratinocytes. Changes in CYP and VDR expression in the presence of cholecalciferol, 25-hydroxyvitamin D3 or 1,25(OH)2D3 indicate fine-tuning of the bioavailability of vitamin D in the dermis after wounding. Down-regulation of α-SMA, MMP-2 secretion and the collagen type I to III ratio by 1,25(OH)2D3 highlight an important role for 1,25(OH)2D3 in modulating wound healing and the scarring process.
    URI
    http://hdl.handle.net/10454/17350
    Type
    Thesis
    Qualification name
    PhD
    Collections
    Theses

    entitlement

     
    DSpace software (copyright © 2002 - 2023)  DuraSpace
    Quick Guide | Contact Us
    Open Repository is a service operated by 
    Atmire NV
     

    Export search results

    The export option will allow you to export the current search results of the entered query to a file. Different formats are available for download. To export the items, click on the button corresponding with the preferred download format.

    By default, clicking on the export buttons will result in a download of the allowed maximum amount of items.

    To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export. The amount of items that can be exported at once is similarly restricted as the full export.

    After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.