Project description:The vitamin D receptor (VDR) regulates cell proliferation and differentiation including epidermal keratinocytes by modulating transcription of its target genes. We are investigating the role of VDR in epidermal stem cells and their progenies in the regeneration process of epidermis and hair in the skin. VDR null mice are utilized in which VDR is specifically deleted in keratin 14 (K14) expressing keratinocytes by Cre-lox strategy. The impact of VDR deletion was evaluated by comparison of VDR null mice with no cre littermate control mice. The VDR was abundantly expressed in potential epidermal stem cells including basal cells in interfollicular epidermis (IFE), and in CD34 expressing bulge keratinocytes in hair follicles. Gene expression profiles and subsequent pathway analysis of stem cell enriched keratinocyte populations revealed that the VDR deletion significantly suppressed β-catenin signaling as well as VDR signaling. The role of VDR in epidermal stem cells was studied during hair follicle cycling and wound healing processes. The epidermal stem cells were not appropriately stimulated by hair depilation, and did not reinitiate anagen in the hair follicles resulting in a failure of hair regrowth. In addition, the stem cells were not fully activated after full thickness wounds were generated in VDR null skin under a low calcium diet to suppress compensation pathways. Cell proliferation was not fully induced in potential stem cells located in both IFE and hair follicles near the wounding edges, and re-epithelialization rate was delayed in VDR null skin. Gene expression profiling of the wounded skin (3 days after injury) indicated that β-catenin signaling was not fully induced in VDR null skin comparable to that observed in β-catenin null mice. The β-catenin target genes including Axin2 and cell cycle regulators involved in epidermal stem cell function were not induced in the edges of the wound of VDR null skin. These results demonstrated that VDR plays an essential role in hair cycling and wound healing processes through regulation of β-catenin signaling in epidermal stem cells and their progenies. n=3 CON and KO (each sample contain RNA isolated from wounded skins excised from 3 mice)

Project description:Dendritic epidermal T cells (DETC) reside in murine skin and participate in homeostasis and wound repair. Upon wounding, DETC become activated through the recognition of an unidentified ligand expressed by keratinocytes proximal to sites of injury. Such DETC activation is mediated through a monoclonal T cell receptor (TCR). Using a soluble form of this monoclonal TCR, we have shown that keratinocytes upregulate DETC TCR ligands in wounded tissue within 2 hours following wounding. Down-modulation of the ligand is seen 3 hours following wounding, and no expression is evident in non-wounded skin. In vitro studies on cell lines which express this unknown ligand indicate that antigen recognition by the DETC TCR is dependent upon N-linked glycosylation of the ligand. Given the glycosylation sensitivity of the ligand and the restricted expression following wounding, we are interested in pursuing microarray analysis to identify genes that are modulated in keratinocytes in response to wounding. Keratinocytes represent 90% of the cells in the epidermis (DETC and Langerhan’s cells make up the remaining 10%). As such, we propose to isolate RNA from whole epidermis under either wounded or resting conditions. In addition to comparing RNA from wounded and non-wounded epidermis, we would like to compare RNA from tissue that has been wounded for different times. Initially, we would like to analyze 4 sampes (non-wounded epidermis, and epidermal cells isolated 30 minutes, 2 hours, and 4 hours following wounding). These time points would correlate to a period prior to cell surface expression of ligand (30 minutes), during cell surface expression (2 hours), and following down regulation of cell surface expression (4 hours). In addition to providing possible identification of the unknown DETC TCR ligand, such analysis would provide novel information about early responses by keratinocytes in response to physical wounding in vivo. We propose to isolate RNA from whole epidermis under either wounded or resting conditions. In addition to comparing RNA from wounded and non-wounded epidermis, we would like to compare RNA from tissues that has been wounded for different times.

Project description:The vitamin D receptor (VDR) regulates cell proliferation and differentiation including epidermal keratinocytes by modulating transcription of its target genes. We are investigating the role of VDR in epidermal stem cells and their progenies in the regeneration process of epidermis and hair in the skin. VDR null mice are utilized in which VDR is specifically deleted in keratin 14 (K14) expressing keratinocytes by Cre-lox strategy. The impact of VDR deletion was evaluated by comparison of VDR null mice with no cre littermate control mice. The VDR was abundantly expressed in potential epidermal stem cells including basal cells in interfollicular epidermis (IFE), and in CD34 expressing bulge keratinocytes in hair follicles. Gene expression profiles and subsequent pathway analysis of stem cell enriched keratinocyte populations revealed that the VDR deletion significantly suppressed β-catenin signaling as well as VDR signaling. The role of VDR in epidermal stem cells was studied during hair follicle cycling and wound healing processes. The epidermal stem cells were not appropriately stimulated by hair depilation, and did not reinitiate anagen in the hair follicles resulting in a failure of hair regrowth. In addition, the stem cells were not fully activated after full thickness wounds were generated in VDR null skin under a low calcium diet to suppress compensation pathways. Cell proliferation was not fully induced in potential stem cells located in both IFE and hair follicles near the wounding edges, and re-epithelialization rate was delayed in VDR null skin. Gene expression profiling of the wounded skin (3 days after injury) indicated that β-catenin signaling was not fully induced in VDR null skin comparable to that observed in β-catenin null mice. The β-catenin target genes including Axin2 and cell cycle regulators involved in epidermal stem cell function were not induced in the edges of the wound of VDR null skin. These results demonstrated that VDR plays an essential role in hair cycling and wound healing processes through regulation of β-catenin signaling in epidermal stem cells and their progenies. n=3 CON and KO (each sample contain RNA isolated from wounded or nonwounded skins excised from 3 mice)

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Dedifferentiation of Gata6+ epidermal cells

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