Title: Iroquois Homeobox 1 in the Development of Dental Supporting Structures
Miguel Romero Bustillos (Presenter)
University of Iowa
Wenjie Yu, University of Iowa
Steven Eliason, University of Iowa
Huojun Cao, University of Iowa
Gustavo Avila-Ortiz, University of Iowa
Brad Amendt, University of Iowa
Objectives: The objective of this study is to characterize the expression of Iroquois homeobox 1 (Irx1) in dental gingiva of two different species, mouse and human. In addition, to evaluate the role of Irx1 in root and dental supporting structures during development.
Methods: Gingival samples from genetically modified mice with a lacZ reporter replacing the coding sequence of Irx1 and healthy human gingival samples were collected to perform immunostaining against Irx1 and E-Cadherin (E-Cad). In addition, the pattern of expression during root development of Irx1 was studied in mice. The expression of Irx1 and Pituitary homeobox 2 (Pitx2) in cementoblast cell line (OCCM30) was quantified by real-time PCR. Stable Irx1 knockdown by a short hairpin RNA was performed in the OCCM30 cell line and changes in gene expression were analyzed.
Results: Iroquois homeobox 1 protein has been found in a collar disposition in the gingiva around dental tissues in mice and humans. Irx1 positive cells are observed in a cluster disposition embedded in the connective tissue at parallel/apical position to the junctional epithelium. In these cell clusters, the immunofluorescence staining against Irx1 is limited to the cell nucleus. Irx1 positive cells show low expression of E-Cad. Irx1 is expressed in Hertwig s Epithelial root sheath and OCCM30. The mRNA knockdown of Irx1 in OCCM30 regulate genes involved in cementum formation producing a decrease in mineralization in vivo. Irx1 plays a role in mineralization and cell differentiation and the expression is regulated by Pitx2.
Conclusions: A new cell population has been identified in the dental connective tissue attachment. These cells are identified in clusters, show high expression of Irx1 and low expression of E-Cad. These findings are observed in mice and humans. Irx1 seems to play a role in the development of dental supporting tissues.