Generation and Differentiation of Adult Tissue-Derived Human Thyroid Organoids.

Total thyroidectomy as part of thyroid cancer treatment results in hypothyroidism requiring lifelong daily thyroid hormone replacement. Unbalanced hormone levels result in persistent complaints such as fatigue, constipation, and weight increase. Therefore, we aimed to investigate a patient-derived thyroid organoid model with the potential to regenerate the thyroid gland. Murine and human thyroid-derived cells were cultured as organoids capable of self-renewal and which expressed proliferation and putative stem cell and thyroid characteristics, without a change in the expression of thyroid tumor-related genes. These organoids formed thyroid-tissue-resembling structures in culture. (Xeno-)transplantation of 600,000 dispersed organoid cells underneath the kidney capsule of a hypothyroid mouse model resulted in the generation of hormone-producing thyroid-resembling follicles. This study provides evidence that thyroid-lineage-specific cells can form organoids that are able to self-renew and differentiate into functional thyroid tissue. Subsequent (xeno-)transplantation of these thyroid organoids demonstrates a proof of principle for functional miniature gland formation.

Lack of DNA Damage Response at Low Radiation Doses in Adult Stem Cells Contributes to Organ Dysfunction.

PURPOSE: Radiotherapy for head and neck cancer may result in serious side effects, such as hyposalivation, impairing the patient's quality of life. Modern radiotherapy techniques attempt to reduce the dose to salivary glands, which, however, results in low-dose irradiation of the tissue stem cells. Here we assess the low-dose sensitivity of tissue stem cells and the consequences for tissue function. EXPERIMENTAL DESIGN: Postirradiation rat salivary gland secretory function was determined after pilocarpine induction. Murine and patient-derived salivary gland and thyroid gland organoids were irradiated and clonogenic survival was assessed. The DNA damage response (DDR) was analyzed in organoids and modulated using different radiation modalities, chemical inhibition, and genetic modification. RESULTS: Relative low-dose irradiation to the high-density stem cell region of rat salivary gland disproportionally impaired function. Hyper-radiosensitivity at doses <1 Gy, followed by relative radioresistance at doses ≥1 Gy, was observed in salivary gland and thyroid gland organoid cultures. DDR modulation resulted in diminished, or even abrogated, relative radioresistance. Furthermore, inhibition of the DDR protein ATM impaired DNA repair after 1 Gy, but not 0.25 Gy. Irradiation of patient-derived salivary gland organoid cells showed similar responses, whereas a single 1 Gy dose to salivary gland-derived stem cells resulted in greater survival than clinically relevant fractionated doses of 4 × 0.25 Gy. CONCLUSIONS: We show that murine and human glandular tissue stem cells exhibit a dose threshold in DDR activation, resulting in low-dose hyper-radiosensitivity, with clinical implications in radiotherapy treatment planning. Furthermore, our results from patient-derived organoids highlight the potential of organoids to study normal tissue responses to radiation.