3D printed hydrogel scaffold promotes the formation of hormone-active engineered parathyroid tissue

The parathyroid glands are localized at the back of the thyroid glands in the cervical region and are responsible for regulation of the calcium level in the blood, through specialized cells that sense Ca²⁺ and secrete parathyroid hormone (PTH) in response to a decline in its serum level. PTH stimulates the skeleton, kidneys and intestines and controls the level of Ca²⁺ through specialized activities. Iatrogenic removal of the parathyroid gland, as well as damage to its vascular integrity during cauterization are some of the common complications of thyroid surgery. Therefore, regeneration and/or replacement of malfunctioning parathyroid tissue is required. Tissue engineering is an emerging and promising field for patients with organ failure with recent pioneering clinical applications. The success of tissue engineering strategy depends on the use of proper cells, bioactive factors that stimulate the activities of these cells and scaffolds that are produced to recapitulate the tissue structure and support the function of the engineered tissues. 3D printing is a developing strategy for the production of these scaffolds by providing a delicate control over their structure and properties. In this study, human primary parathyroid cells were successfully isolated and their viability and ability to secrete PTH upon stimulation with different levels of Ca²⁺ were shown in vitro. These cells were then seeded onto 3D printed alginate scaffolds and 3D bioprinted within alginate bioink, and cell viability as well as the ability to secrete PTH upon stimulation were also demonstrated. Therefore, functional hormone-active parathyroid tissue substitute was engineered in vitro through 3D printed hydrogels and autologous cells.