scRNAseq of healthy and irradiated mouse parotid glands highlights crosstalk between immune and secretory cells during chronic injury

Abstract

Translational frameworks to understand the chronic loss of salivary dysfunction that follows after clinical irradiation, and the development of regenerative therapies remain an unmet clinical need. Understanding the transcriptional landscape long after irradiation treatment that results in chronic salivary hypofunction will help identify injury mechanisms and develop regenerative therapies to address this need. Advances in single cell (sc)RNAseq have made it possible to identify previously uncharacterized cell types within tissues and to uncover gene regulatory networks that mediate cell-cell communication and drive specific cell states. scRNAseq studies have been performed for virtually all major tissues including salivary glands; however, there are currently no scRNAseq studies the long-term chronic effects of irradiation on salivary glands. Here, we present scRNAseq from control and irradiated murine parotid glands collected 10 months post-irradiation. We identify a previously uncharacterized population of epithelial cells in the gland defined by expression of Etv1, which may be an acinar cell precursor. These Etv1+ cells also express Ntrk2 and Erbb3 and thus may respond to myoepithelial cell-derived growth factor ligands. Furthermore, our data suggests that CD8+ T-cells and secretory cells are the most transcriptionally affected during chronic injury with radiation, suggesting active immune involvement during chronic injury post-irradiation. Thus, our study provides a resource to understand the transcriptional landscape in a chronic post-irradiation microenvironment and identifies cell-specific pathways that may be targeted to repair chronic damage.

Parotid glands have a dysregulated immune response following radiation therapy

“…Interestingly, a study utilizing single cell RNA sequencing (scRNAseq) found that fractionated IR resulted in a significant increase in DPT cells at 10 months following treatment, and further, reported that DPT cells had the highest number of radiation-induced differentially expressed genes (73). This paper also reported substantial immune-epithelial cell interactions, specifically increased signaling from acinar to DPT and CD8+ T cells.…”

The First Transcriptomic Atlas of the Adult Lacrimal Gland Reveals Epithelial Complexity and Identifies Novel Progenitor Cells in Mice

“…In addition, this Tfrc hi cluster expressed higher levels of Nktr, which is also found in the kidney and colon epithelium (Human Protein Atlas, www.proteinatlas.org), of the extracellular component Fgg (fibrinogen), of the transporter for long-chain fatty acids Slc27a2, and of the long noncoding RNA (lncR-NAs) Gm26917 that promotes the survival of satellite cells [64]. Recently, a putative acinar precursor characterized by high expression of Etv1, Neat1, and Gm26917 was identified in irradiated parotid glands [65]. Together with a relatively low RNA content (Figure S6A), the Tfrc hi cluster might correspond to cells with minimal secretory function, which could suggest incomplete differentiation or a functionally quiescent state.…”