Endocrine bioengineering: reconstruction of a bioartificial thyroid lobe using its natural, three-dimensional (3D) stromal / vascular matrix as a scaffold

To test the feasibility of reconstructing ex situ an entire bioartificial thyroid gland suitable for transplantation we have bioengineered a rat thyroid lobe using its decellularized stromal / vascular matrix, eventually 3D recellularized with thyroid stem / precursor cells. Sprague-Dawley male rats (220–240 g) were used as thyroid donors, and lobe matrixes obtained by freezing / detergent / enzyme processing. Test matrixes were made electrondense and analyzed by microtomography (microTC). Primary thyroid cells and ABCG2-positive, thyroid stem/precursor elements were expanded and isolated either in primary monolayer or 3D matrigel cultures for 72 h, using low-glucose DMEM and high vs low serum media. Following trypsinization, 250–450.000 cells were harvested to coat the empty follicular and vascular cavities of the inner matrix surface, and grown up to 21 days in static conditions. The colonized matrixes were either fixed in aldheydes for processing by light (LM), transmission (TEM) and scanning electron (SEM) microscopy or denaturated to get total proteins, and run for ABCG2 westen blotting. Culture supernatants were collected every 48 h, and free thyroid hormone levels assessed with chemiluminescent immunoassays. Complete decellularization and maintenance of the 3D native architecture of the thyroid SVS were achieved. Thyroid-derived cell, including differentiated thyrocytes, elements showing epithelial-mesenchymal transitions, and stem/precursor cells were found both to heterotopically migrate inside matrix septa and to orthotopically aggregate, link and give rise to intracytoplasmic cavities, up to recellularize the decellularized follicular spaces. Thyroid hormone secretion occurred for at least 7 days. These results show that the natural 3D matrix of the rat thyroid acts as a scaffold to bioengineer ex situ a functional thyroid lobe with progenitor-like elements (Fig.), suggesting that a biocompatible construct can be realized for eventual transplantation replacement.