Abstract: SA-PO0277
mTORC1 Hyperactivation Drives Hyperparathyroidism and Cyst Formation
Session Information
- Bone and Mineral Metabolism: Basic Research
November 08, 2025 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Bone and Mineral Metabolism
- 501 Bone and Mineral Metabolism: Basic
Authors
- Hassan, Alia, Hadassah Hebrew University Medical Center, Nephrology, Jerusalem, Israel
- Brook, Efrat, Hadassah Hebrew University Medical Center, Nephrology, Jerusalem, Israel
- Ben-Dov, Iddo Z., Hadassah Hebrew University Medical Center, 4Laboratory of Medical Transcriptomics, Jerusalem, Israel
- Naveh-Many, Tally, Hadassah Hebrew University Medical Center, Nephrology, Jerusalem, Israel
Background
Secondary hyperparathyroidism (SHP) is a common complication of chronic kidney disease (CKD) that increases morbidity and mortality. The signaling pathways driving SHP remain undefined. mTOR regulates cell growth and metabolism, acting through two complexes: mTORC1 and mTORC2. The tuberous sclerosis complex (TSC), encoded by Tsc1 and Tsc2, negatively regulates mTORC1. Loss of TSC function leads to constitutive mTORC1 activation and abnormal cell proliferation. TSC syndrome is a multisystem disorder associated with renal cysts and progressive CKD. Parathyroid involvement in TSC remains unexplored, with only isolated reports of adenomas or hyperparathyroidism. Building on our prior findings of enhanced mTORC1 activity in parathyroids of CKD-induced SHP models, we now show that parathyroid-specific deletion of Tsc1 promotes mTORC1-driven hyperparathyroidism and parathyroid cyst formation.
Methods
Parathyroid specific Tsc1 knockout (PT-Tsc1-/-) and control mice were generated, both expressing a tdTomato reporter for gland visualization. Female PT-Tsc1−/− mice received weekly IP injections of the mTOR inhibitors rapamycin or everolimus (2 mg/kg), starting at 1 month of age for 4 weeks. Serum PTH, calcium and phosphate were measured. Parathyroid tissue sections were analyzed by IF staining.
Results
PT-Tsc1−/− mice exhibited parathyroid mTORC1 hyperactivation, elevated serum PTH and calcium, gland enlargement, and early-onset cysts that increased in size and number with age. Female mice had higher cyst burden than males. IF staining revealed strong PTH expression within parathyroid cells and cystic fluid, suggesting cysts contribute to PTH elevation. Treatment of female PT-Tsc1−/− mice with rapamycin or everolimus reduced phospho-S6 levels, confirming mTORC1 inhibition. Importantly, treated PT-Tsc1-/- mice had smaller, more compact glands with fewer and smaller or absent cysts and normalized serum PTH levels.
Conclusion
Parathyroid-specific mTORC1 activation via Tsc1 deletion induces cystogenesis and dysregulated PTH secretion. Pharmacologic mTORC1 inhibition reduces cysts burden and PTH levels, highlighting its role in parathyroid cyst formation and hormone secretion. mTORC1 may be a therapeutic target for cystic parathyroid disease in SHP and TSC patients.