Dissertation
Identification and functional analyses of stem cell niches during oral tissue development and regeneration
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Summer 2023
DOI: 10.25820/etd.006962
Abstract
Oral health is the state of the mouth, teeth and orofacial structures that enables people to perform oral functions such as breathing, chewing and speaking. Having good oral health is one of the best indicators of overall health, well-being, and quality of life. Oral health varies over the life course from early life to old age, and can be affected by congenital factors, trauma, or bad oral hygiene, which will further develop into oral diseases. Approximately 3.5 million people are affected by oral diseases, which results in the increasing global burden of oral health conditions. Nowadays, a tool for oral tissue engineering and regenerative therapy has drawn both clinical and scientific attention, which highly involves stem/progenitor cells in the oral cavity. Thus, identification and functional analyses of stem cell niches during oral tissue development and regeneration are essential.
Dental health is one of the main factors that contribute to oral health. Tooth anomalies, is one of the most common congenital defects all around the world that can occur in both deciduous and permanent dentitions. It is defined as abnormalities that alters the size, shape, and numbers of teeth. These dental defects are mainly due to the defective development of the dental germ. Patients suffer from tooth anomalies need rather costly and challenging multidisciplinary treatments. Thus, studying the genetic regulations underpinning the tooth developmental program responsible for the condition is rather crucial. Wolf-Hirschhorn syndrome (WHS) is a developmental disorder attributed to a partial deletion on the short arm of chromosome 4, which has been reported related to tooth anomalies. Wolf-Hirschhorn syndrome candidate 1 (WHSC1) is a H3K36-specific methyltransferase that is deleted in every reported case of WHS. Mutation in this gene exhibited tooth anomalies in patients. In this study, we used mouse as a model, determined that Whsc1 expression was reduced in the mouse incisor and molar tooth germs as tooth development proceeds. We also found Whsc1 and Pitx2, the first transcription factor in tooth development, positively and reciprocally regulated each other through their promoters. MicroRNAs are known to regulate gene expression post-transcriptionally during development. We demonstrated that miR-23a/b and miR-24-1/2, which were known to be highly expressed in the mature tooth germ, directly targeted to Whsc1 and repressed its expression. Additionally, this miR cluster was negatively regulated by Pitx2. The expression of these two miRs and Whsc1 were negatively correlated during mouse mandibular development.
Gingiva, a pink-colored resilient tissue surrounding the teeth, also serves as a major contributor to oral health. It functions as a barrier to protect the deeper dental and periodontal tissues from trauma and infection. This effective protection is largely attributed to the rapid and scarless wound healing of gingival tissue upon injuries. As part of the oral mucosa, gingiva is primed with wound-activated gene signatures to facilitate the festinating wound healing resolution. However, the genetic and molecular mechanism underlying this process is still largely unknown. Our lab previously found Iroquois Homeobox 1 (IRX1/Irx1) expressed in the basal layer of gingival epithelium and cell populations in the mesenchyme in human samples. In the present study, we established a mouse gingival injury model to investigate the role of Irx1 in epithelial basal cells during gingival wound healing. By analyzing the wound healing progression and the basal cell activity during gingival wound healing, we demonstrated that Irx1 haploinsufficiency delays re-epithelialization, as indicated by delayed wound closure, delayed structural changes in regenerated epithelium and altered differentiation of keratinocytes. The transcriptomic analysis revealed a diminished wound-activated signature in the Irx1+/- regenerated epithelium at 3 dpi. In the study, Irx1 was identified as a new gene that is primed at the base of the gingiva, which may facilitate rapid and scarless wound healing through the EGF signaling pathway.
Details
- Title: Subtitle
- Identification and functional analyses of stem cell niches during oral tissue development and regeneration
- Creators
- Dan Su
- Contributors
- Brad A Amendt (Advisor)Huojun Cao (Committee Member)Andrew Russo (Committee Member)Liu Hong (Committee Member)Ling Yang (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Biomedical Science (Cell and Developmental Biology)
- Date degree season
- Summer 2023
- DOI
- 10.25820/etd.006962
- Publisher
- University of Iowa
- Number of pages
- xv, 105 pages
- Copyright
- Copyright 2023 Dan Su
- Language
- English
- Date submitted
- 07/24/2023
- Description illustrations
- illustrations, tables, graphs
- Description bibliographic
- Includes bibliographical references (pages 94-105).
- Public Abstract (ETD)
- Oral health is the state of the mouth, teeth and orofacial structures which allows individuals to perform oral functions such as breathing, chewing and speaking. Oral diseases comprise a series of diseases and conditions that can be congenital or acquired over the life course, affecting an estimated 3.5 million people. When the global burden of oral health conditions is still growing, a tool for oral tissue engineering and regenerative therapy has drawn both clinical and scientific attention, which highly involves stem/progenitor cells in the oral cavity. Thus, identification and functional analyses of stem cell niches during oral tissue development and regeneration are imperative.
In our study, we have found Wolf-Hirschhorn Syndrome Candidate 1 (WHSC1), a causative gene for a craniofacial syndrome, is expressed from early stage of mouse lower incisor development and then restricts to epithelial and mesenchymal stem cell niches in homeostatic tooth germ. In the dental epithelial stem cell niche, WHSC1 functions as transcription co-activator that mediates the considered earliest tooth gene Paired Like Homeodomain 2 (PITX2) in regulating tooth development. In addition, tooth-related microRNAs miR-23-a/b and miR-24-1/2 negatively regulate WHSC1 in the differentiated dental epithelial cell types to restrict its expression. Thus, we define a role of WHSC1 as a stem cell marker that regulates tooth development.
Gingiva recession is an irreversible process of losing gingiva tissue, which further results in tooth mobility or even tooth loss. Approaches relies on the gingival stem cells to regenerate gingiva tissue for treating gingiva recession are crucial to maintain oral health. However, the genetic and molecular mechanism underlying gingival regeneration is still largely unknown. We report that transcription factor Iroquois Homeobox 1 (IRX1) is expressed in the stem cell niches in human and mouse epithelium and mesenchyme under homeostasis and confirm that IRX1 haploinsufficiency impairs re-epithelialization during gingival wound healing, which is supported by delayed wound closure, delayed morphological change of regenerated epithelium, and defected keratinocyte proliferation and differentiation.
- Academic Unit
- Biomedical Science Program; Craniofacial Anomalies Research Center
- Record Identifier
- 9984454187202771
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