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 5

Irx1+/– mice show delayed keratinocyte differentiation in the RE at 3 dpi.

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Irx1+/– mice show delayed keratinocyte differentiation in the RE at 3 d...
(A) Schematics showing the structure of stratified epithelium in the gingiva. Keratinocytes originating from the basal layer differentiate and move vertically to become mature keratinocytes to form spinous layer and granular layer. The stratum corneum layer consists of dead keratinocytes, indicating a successful differentiation process. (B and C) Representative H&E staining images showing the regenerative front (RF) during reepithelization in Irx1+/+ and Irx1+/– mice at 3 dpi. Scale bar: 100 μm. (B) The regenerated epithelium of Irx1+/+ at 3 dpi. Arrows indicate the fully formed stratum corneum. (C) The regenerated epithelium of Irx1+/– at 3 dpi. Arrowheads indicate the nucleus-containing cells in the superficial layer of the regenerated epithelium. The regenerative front is ~600 μm to the first molar. The stratum corneum is absent at this stage in Irx1+/–. (D–G) Representative IF staining images of Loricrin and E-cadherin in control and injured gingival tissue of Irx1+/+ and Irx1+/– mice at 3 dpi. Blue staining represents nuclei. E-cadherin (red) marks the epithelial layer. (D) Loricrin expression was examined in the Irx1+/+ control gingiva. Loricrin marks the spinous and granular keratinocytes. (E) Loricrin expression was examined in the regenerated epithelium in Irx1+/+ at 3 dpi. (F) Loricrin expression was examined in the Irx1+/– control gingiva. Loricrin marks the spinous and granular keratinocytes. (G) Loricrin expression was examined in the regenerated epithelium in Irx1+/– at 3 dpi. Arrowheads indicate Loricrin expression in the distal region of the regenerated epithelium. The regenerative front is ~600 μm to the first molar. Image area covers the region of injury. Black or white dashed lines demarcate the gingival epithelium and mesenchyme. Scale bar: 100 μm. RF, regenerative front; T, tooth.