Characterization of Transgenic NSG-SGM3 Mouse Model of Precision Radiation-Induced Chronic Hyposalivation

Abstract

Regenerative medicine holds promise to cure radiation-induced salivary hypofunction, a chronic side effect in patients with head and neck cancers, therefore reliable preclinical models for salivary regenerative outcome will promote progress towards therapies. In this study, our objective was to develop a cone beam computed tomography-guided precision ionizing radiation-induced preclinical model of chronic hyposalivation using immunodeficient NSG-SGM3 mice. Using a Schirmer's test based sialagogue-stimulated saliva flow kinetic measurement method, we demonstrated significant differences in hyposalivation specific to age, sex, precision-radiation dose over a chronic (6 months) timeline. NSG-SMG3 mice tolerated doses from 2.5 Gy up to 7.5 Gy. Interestingly, 5–7.5 Gy had similar effects on stimulated-saliva flow (∼50% reduction in young female at 6 months after precision irradiation over sham-treated controls), however, >5 Gy led to chronic alopecia. Different groups demonstrated characteristic saliva fluctuations early on, but after 5 months all groups nearly stabilized stimulated-saliva flow with low-inter-mouse variation within each group. Further characterization revealed precision-radiation-induced glandular shrinkage, hypocellularization, gland-specific loss of functional acinar and glandular cells in all major salivary glands replicating features of human salivary hypofunction. This model will aid investigation of human cell-based salivary regenerative therapies.

CSF1R-dependent macrophages in the salivary gland are essential for epithelial regeneration after radiation-induced injury

“…Studies in mice have shown that after irradiation injury, the salivary gland tissue goes through an initial regenerative phase, which ultimately fails in the long term ( 58 – 60 ), mirroring what occurs in humans after radiotherapy ( 41 , 61 , 62 ). We therefore extended our studies to examine the roles of macrophages in the initial regenerative phase by determining the effects of macrophage depletion up to the point at which many indices of damage and inflammation have subsided and repair is under way (day 28) ( 39 , 60 , 63 , 64 ). To this end, we administered DTx every other day from day 17 to day 27, undertook saliva measurements at day 27, and analyzed the SMG at day 28.…”

The Mayo Clinic Salivary Tissue-Organoid Biobanking: A Resource for Salivary Regeneration Research

“…Organoids were then stained as previously described 6 with primary and secondary antibodies described in Supplementary Table S3 . Nuclei were counterstained with DAPI Fluoromount-G® (Southern Biotech, Birmingham, AL, USA).…”

“…Conditions like diabetes, viral infections (mumps, HIV, hepatitis), aging, trauma, surgery-related nerve damage, dehydration, and salivary gland tumors can also contribute to a decline in salivary function, leading to dry mouth. Despite decades of research in salivary gland function using animal models 6 , a curative treatment for salivary dysfunction remains elusive 7 .…”