TGF-β3 increases the severity of radiation-induced oral mucositis and salivary gland fibrosis in a mouse model

Abstract

Purpose: Toxicities from head and neck (H&N) radiotherapy (RT) may affect patient quality of life and can be dose-limiting. Proteins from the transforming growth factor beta (TGF-B) family are key players in the fibrotic response. While TGF-B1 is known to be pro-fibrotic, TGF-B3 has mainly been considered anti-fibrotic. Moreover, TGF-B3 has been shown to act protective against acute toxicities after radio- and chemotherapy. In the present study, we investigated the effect of TGF-B3 treatment during fractionated H&N RT in a mouse model. Materials and methods: 30 C57BL/6J mice were assigned to three treatment groups. The RT + TGF-B3 group received local fractionated H&N RT with 66 Gy over five days, combined with TGF-B3-injections at 24-hour intervals. Animals in the RT reference group received identical RT without TGF-B3 treatment. The non-irradiated control group was sham-irradiated according to the same RT schedule. In the follow-up period, body weight and symptoms of oral mucositis and lip dermatitis were monitored. Saliva was sampled at five time points. The experiment was terminated 105 days after the first RT fraction. Submandibular and sublingual glands were preserved, sectioned, and stained with Massons trichrome to visualize collagen. Results: A subset of mice in the RT + TGF-B3 group displayed increased severity of oral mucositis and increased weight loss, resulting in a significant increase in mortality. Collagen content was significantly increased in the submandibular and sublingual glands for the surviving RT + TGF-β3 mice, compared with non-irradiated controls. In the RT reference group, collagen content was significantly increased in the submandibular gland only. Both RT groups displayed lower saliva production after treatment compared to controls. TGF-B3 treatment did not impact saliva production. Conclusions: When repeatedly administered during fractionated RT at the current dose, TGF-B3 treatment increased acute H&N radiation toxicities and increased mortality. Furthermore, TGF-B3 treatment may increase the severity of radiation-induced salivary gland fibrosis.