Engineering Cell Fate in Salivary Gland Development - Abstract Regenerative medicine has become increasingly important in the aging U.S. society. Development of effective regenerative therapy requires an understanding of normal cell type-specific fate determination processes— precise mechanisms involving signals that come from interactions with neighboring cells. Currently, no reliable salivary regenerative therapies exist due to a lack of such knowledge. Three major types of mammalian salivary gland—sublingual, submandibular (SMG), and parotid (PG)—differ in their physiology, acinar cell types, and disease susceptibility (1). Recent evidence suggests distinct processes for the two types of salivary acini: mucous and serous (2). While these indicate inherent differences, salivary cell type-specific differentiation processes have not been reported. Furthermore, while PG is most susceptible to conditions related to dry mouth, virtually nothing is known about PG development due to difficulties with organ isolation and culture. Thus, there is a critical need to identify cell fate determination processes specific to salivary cell populations that comprise functional organs. In the absence of such knowledge, a mechanistic framework necessary for the subsequent identification of therapeutic targets will likely remain difficult. Important knowledge gaps include when and how cells commit to their fates, and whether their lineages are plastic during development. The SMG around embryonic day (E) 13 shows epithelial morphological plasticity in response to the adjacent mesenchyme (3), which raises a question of whether transcriptional and lineage plasticity underlies this morphological transformation. Notably, my preliminary findings indeed show transcriptional changes indicative of a shift in cell fate—findings I have obtained after successfully establishing explant culture conditions to evaluate morphogenesis of SMG, PG, and recombined tissues ex vivo. The studies proposed here were developed to elucidate salivary differentiation processes with the ultimate goal of developing regenerative therapies targeted toward salivary gland disorders. Based on my preliminary results and findings from other groups (3-7), my central hypothesis is that the salivary mesenchyme guides epithelial cell fate and eventually organ specificity through interactions between epithelial and mesenchymal tissues. The proposed program will define the regulation of the epithelium by the mesenchyme. Further, it will provide the first comprehensive molecular characterization of cellular differentiation processes using single cell RNA-seq of heterotypic epithelial-mesenchymal recombinants. As a clinician scientist, my goal is to conduct research on the specific roles of epithelial-mesenchymal interactions in lineage specificity and translate this knowledge into regenerative/therapeutic interventions. My career development plan has been tailored toward this goal with solid mentorship and training opportunities. In conjunction with institutional support, I am confident that studies/activities outlined in my application will help build upon my existing skillset and facilitate my transition into an independent investigator.
