Craniofacial Developmental Dynamics

National Institute Of Dental & Craniofacial Research

Investigators

Linked publications & trials

Abstract

This project is focused primarily on determining mechanisms of morphogenesis, differentiation, and maintenance of salivary glands and other organs. We are addressing the following major questions: 1. How do embryonic glands and other organs generate their characteristic architectures during development? 2. What are the contributions of local regulation of organ-specific gene expression, cell adhesion, extracellular matrix, integrins, signal transduction, and local cell migration to organ development? Branching morphogenesis of developing organs requires coordinated but still relatively incompletely understood changes in gene expression, epithelial cell-cell adhesion, cell-matrix adhesion, and cell motility. We have been applying New Approach Methodologies (NAMs) to investigate this complex question by using ex vivo 3D organ culture methods. We used a tissue recombination approach to evaluate whether switching analogous tissues of two organs would alter their cell fates. Specifically, we switched the epithelium and mesenchyme of parotid versus submandibular salivary glands to determine whether either the mesenchyme or the epithelium of one gland would alter the gene expression and cell type of the other gland as determined by single-cell RNA sequencing and immunofluorescence imaging analyses on recombined tissues. The results documented intriguing a series of alterations or partial inductions of gene expression patterns that define gland-specific acinar and myoepithelial cells in recombined salivary epithelia. We concluded that the cell fate of some epithelial cells is plastic and alterable by mesenchymal-epithelial signaling, whereas other epithelial cells are already committed to a specific fate. We also documented a parallel alteration in gene expression patterns of salivary gland mesenchyme cells after exposure to foreign epithelia. Our findings indicate a substantial level of plasticity of gene expression in embryonic salivary glands that can result in altered cell fate after exposure to a homologous tissue (mesenchyme or epithelium) from a different salivary gland, i.e., submandibular vs. parotid gland. In a collaboration, we contributed to characterizing dental pulp stem cells compared to periodontal ligament stem cells. Our laboratory is continuing the various types of studies described above by applying related approaches to investigating features of other oral tissues (gingiva and mucosa) compared to skin. These studies are beginning to elucidate the complex mechanisms that underlie the cell and tissue dynamics involved in craniofacial organ development and maintenance. Understanding these underlying morphogenetic mechanisms during embryonic development should promote more effective tissue engineering for restoration of damaged organ function. In all our research projects, our Section emphasizes rigorous and responsible conduct of research to conduct investigations that are reproducible and transparent, e.g., by describing in detail our specific methods, reagents, and the instrument settings we use, to be able to ensure that our work can be replicated. We perform at least 3 independent biological repeats (vs. technical repeats) for each experiment we report, as well as using orthogonal approaches with skepticism to test any important conclusion. A key component of rigorous and reproducible research, we feel, is the continuous conscientious use of electronic lab notebooks that provide forensic tracking and backups (we use the Federal version of LabArchives), as well as retaining two backups of all primary data, of which one copy is retained at NIH after a lab member leaves. We evaluate and communicate error and uncertainty by using quantification, unbiased data analysis approaches, and appropriate statistical tests. In our publications, we discuss reservations, caveats, and limitations of our work and the assumptions on which it is based. We aim to construct experimental tests to obtain yes/no and/or quantitative answers in order to rigorously test our hypotheses. We welcome negative results as opening new avenues of exploration into areas that had not been predicted. We avoid conflicts of interest in our research, as well as in our reviewing for journals and grant funding agencies, and we take care to submit our research to journals with unbiased peer review, as well as avoiding “predatory” journals. We encourage collaboration and interdisciplinary research, which enriches and broadens our approaches. This approach includes sharing our underlying primary data as much as practical, e.g., by deposition in public repositories after publication of our research. Public availability of the raw data underlying research allows others to evaluate and replicate our findings. We also continue to emphasize the training and mentoring of the next generation of biomedical researchers.