Abstract 7446: Transcriptomic and histological analysis of radiation-induced damage in the murine submandibular gland
Authors: Paz Cristina , Glassey Annemarie , Frick Abigail , Melzer Lauryn , Robinson Jasmine M. , Baus Rebecca M. , Kimple Randall J. 
Published: March 2024

Abstract
Many head and neck cancer patients develop radiation-induced xerostomia (RIX). There are few clinical solutions for this condition and there is a critical need for novel therapeutics for this condition. To better understand the molecular alterations induced by radiation to the salivary glands, we used transcriptional profiling to assess acute and long-term alterations. Based on evidence that immunologic changes are induced by radiation, we used immune-depletion experiments to investigate the role of B-cells and macrophages in RIX. The submandibular gland (SMG) of male-C57/BL6-mice was irradiated (15Gy) mice were followed for 90 days. Saliva was collected throughout the time-course. SMGs were collected 3-, 7-, 60-, and 90-days following radiation. Tissues were analyzed by Nanostring Digital-Spatial-Profiling (DSP) utilizing the murine whole-transcriptome panel. Regions of interest corresponding to acini, ducts, and granular convoluted tubules (GCTs) were delineated and gene expression was assessed. Immunohistochemical staining was performed on SMG’s for fibrosis (masons trichrome), α-amylase, F4/80, Lgr5, Sox2, and MIST1 to evaluate glandular structure, salivary proteins, immune-microenvironment and pro-acinar salivary-stem-cell presence. Specific immune populations were depleted using anti-CD20 and clodronate-liposome prior to radiation and salivary function and histology was assessed at 3-, 7-, and 60-days following radiation. Radiation resulted in a significant decrease in salivary production (p-value = 0.03) in immune competent models. Transcriptional pathway analysis identified early alterations in signal-transduction and innate immune-response. Late timepoints identified alterations in B-cell activity and Wnt signaling pathways. Histological evaluation of the tissues showed increased disorganization of the gland, with decreases in size and distribution of the acinar compartments (mean area stained: No RT=25.81% vs 90d RT=19.98%, p-value=0.005). Acutely, there was an increase in expression of MIST1 and macrophages (mean area stained: No RT=14.8% vs 7d RT=18.76%, p-value=0.0004) within the SMG that resolved by the 60- and 90-day time-points. Results of immune depletion studies will be presented.Results implicate alterations in macrophages and B-cells in radiation-induced damage. These data along with the data from our immune-depletion experiments will provide valuable mechanistic insight guiding modulation of cell-therapies for treatment of RIX which can be further tested in preclinical models.
Citation Format: Cristina Paz, Annemarie Glassey, Abigail Frick, Lauryn Melzer, Jasmine M. Robinson, Rebecca M. Baus, Randall J. Kimple. Transcriptomic and histological analysis of radiation-induced damage in the murine submandibular gland [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7446.