Irx1 mechanisms for oral epithelial basal stem cell plasticity during reepithelialization after injury
Dan Su, … , Steven Eliason, Brad A. Amendt
Dan Su, … , Steven Eliason, Brad A. Amendt
Published January 9, 2025
Citation Information: JCI Insight. 2025;10(1):e179815. https://doi.org/10.1172/jci.insight.179815.
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Research Article Cell biology Stem cells

Irx1 mechanisms for oral epithelial basal stem cell plasticity during reepithelialization after injury

Abstract

The oral mucosa undergoes daily insults, and stem cells in the epithelial basal cell layer regenerate gingiva tissue to maintain oral health. The Iroquois Homeobox 1 (IRX1) protein is expressed in the stem cell niches in human/mouse oral epithelium and mesenchyme under homeostasis. We found that Irx1+/– heterozygous (Het) mice have delayed wound closure, delayed morphological changes of regenerated epithelium, and defective keratinocyte proliferation and differentiation during wound healing. RNA-Seq analyses between WT and Irx1+/– mice at 3 days postinjury (dpi) found impaired epithelial migration and decreased keratinocyte-related genes upon injury. IRX1-expressing cells are found in the gingival epithelial basal cell layer, a stem cell niche for gingival maintenance. IRX1-expressing cells are also found in cell niches in the underlying stroma. IRX1 activates SOX9 in the transient amplifying layer to increase cell proliferation, and EGF signaling is activated to induce cell migration. Krt14CreERT lineage tracing experiments reveal defects in the stratification of the Irx1+/– HET mouse oral epithelium. IRX1 is primed at the base of the gingiva in the basal cell layer of the oral epithelium, facilitating rapid and scarless wound healing through activating SOX9 and the EGF signaling pathway.

Authors

Dan Su, Tadkamol Krongbaramee, Samuel Swearson, Yan Sweat, Mason Sweat, Fan Shao, Steven Eliason, Brad A. Amendt

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Figure 11

IRX1 regulates SOX9 expression.

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IRX1 regulates SOX9 expression. (A) Representative IF staining image sho...
(A) Representative IF staining image showing the SOX9 expression in the homeostatic gingiva of Irx1+/+ mice. (B) Representative IF staining image showing the SOX9 expression in the homeostatic gingiva of Irx1+/– mice. (C) Irx1 plasmid or a control empty vector were overexpressed along with the WT Sox9 promoter fused to luciferase reporter or with a promoter containing a mutated canonical Irx1 binding site. n = 4. (D) A schematic of the Sox9 promoter, highlighting the IRX1 binding site and the negative control regions that were amplified by the given primer sets in the ChIP assay. (E) Gel-electrophoresis of PCR amplified products from the input and ChIP reactions using primers flanking the IRX1 binding site and the negative control region. The specific band amplified is labeled with an asterisk. (F) qPCR demonstrating an enrichment using primers flanking the IRX1 binding site when the specific antibody was used compared with the nonspecific control. n = 3. (G) There is no difference in the samples pulled down with IgG and the specific IRX1 antibody when the primer set flanking a control region lacking an IRX1 binding site is used. n = 3.