Generation of Parathyroid Cells from Human Adipose Derived Stem Cells
Ashley Leberfinger, MD, Srinivas Koduru, PhD, Dino Ravnic, DO, MPH.
Penn State Health Milton S Hershey Medical Center, Hershey, PA, USA.
BACKGROUND: Acquired hypoparathyroidism is most commonly caused by surgical removal or iatrogenic injury. Permanent hypoparathyroidism occurs in up to 5% of patients undergoing total thyroidectomy or neck dissection, which can result in profound hypocalcemia. If injury is noted intraoperatively, the parathyroid gland can be minced and implanted subcutaneously to recover function. Frequently, the manifestations of hypoparathyroidism are only discovered postoperatively when symptoms of calcium and phosphorus dysregulation are noted. Medical management is required to prevent tetany, bone loss, and possibly death. Adipose derived stem cells (ADSCs) are multipotent mesenchymal stem cells which may offer an autologous treatment for this chronic condition. We hypothesize that ADSCs can be converted into functional parathyroid cells in vitro, which could be utilized for delayed subcutaneous implantation and correction of hypoparathyroidism.
METHODS: Adipose tissue was obtained from patients undergoing lipectomy (n = 10). Tissue was digested and the stromal vascular fraction obtained. ADSCs were isolated using magnetic activated cell sorting against CD90 and subsequently underwent in vitro directed differentiation over a 26-day period. Differentiated cells were stained for both Calcium Sensing Receptors (CaSR) and Parathyroid Hormone/related protein-Receptors (PTH/PTHrp-R) being verified by microscopy and flow cytometry. The physiologic response of differentiated parathyroid cells to extracellular calcium was assessed via enzyme-linked immunosorbent assay (ELISA) of secreted PTH.
RESULTS: ADSCs were reliably differentiated into parathyroid cells in all patients as verified by both immunofluorescence and flow cytometry against CaSR and PTH/PTHrp-R. Furthermore, differentiated parathyroid cells exhibited a dose and time dependent release of parathyroid hormone following calcium stimulation. PTH secretion was inversely related to extracellular calcium levels.
CONCLUSIONS: A century ago, Lahey was the first to perform human parathyroid autotransplantation following a partial thyroidectomy. Failure to acutely recognize an iatrogenic injury makes autotransplantation impossible. We have consistently converted adipose derived stem cells into a parathyroid cell phenotype. Our cells demonstrate appropriate responsiveness to extracellular calcium by the controlled release of parathyroid hormone. They may therefore represent a reliable autologous solution to hypoparathyroidism diagnosed in a delayed setting.
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