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Regenerative medicine of endocrine glands is one of the newest fields in biomedical research, and promises to become a primary strategy to treat a number of endocrine disorders. Using computational bioengineering we have recently suggested that the three-dimensional (3D) geometry of the thyroid, stromal / vascular matrix may act as an epigenetic guidance for growth and differentiation of developing thyrocytes (1-3). To test this hypothesis, we have bioengineered ex situ (i.e. on the laboratory bench) a bioartificial rat thyroid lobe using its decellularized stromal/vascular matrix as a natural 3D scaffold, to be eventually recellularized with thyroid stem/precursor cells. Sprague-Dawley male rats (125-225 g) were used as thyroid donors, and lobe matrixes were prepared using a N2 freezing/Trypsin-EDTA / Triton-deoxycholate processing. Test matrixes were made electrondense, and analyzed by microTC (Skyscan 1172) to define their architecture. Primary thyroid cells were isolated after 72 h in primary monolayer culture, whereas presence of ABCG2-positive stem/precursor elements was determined using Western blotting. Following trypsinization, 250 - 450 x 103 cells were harvested and dropped onto the empty follicular cavities of the inner matrix of single lobe halves for homing . Cultures were kept in static conditions up to 14 days. The recellularized matrixes were either fixed in aldheydes and analyzed with light, transmission, and scanning electron microscopy, or denaturated and processed for ABCG2 immunoblotting (polyclonal rabbit anti-human 1:2000, Cell Signalling). Culture supernatants were collected every 48 h for assessment of FT3 and FT4 by immuno-chemiluminescence (Beckman-Coulter). Complete decellularization and maintenance of the 3D native architecture of the lobe matrix were achieved. Thyroid-derived cells including thyrocytes, epithelial- mesenchymal elements, and stem/precursors were found to migrate inside matrix septa, self-assemble like follicule, and recellularize the decellularized native follicular spaces. Thyroid hormone secretion occurred for at least 7 days. These results show that the 3D matrix of the rat thyroid may guide both differentiated and stem-like elements to self-assemble into functional follicular units, up to the lobar recellularization. This raises the possibility that a bioartificial, immuno-tolerant thyroid gland be bioengineered ex situ using autologous stem cells, and eventually transplanted.

We describe an innovative methodology combining Additive Layer Manufacturing (ALM) and indirect replication to reconstruct reticular-like, three-dimensional (3D) structures mimicking the vascular network of soft tissue and endocrine organs. Using a fractal-like algorithm capable of modelling the intraparenchymal vascular distribution of these viscera, single intraglandular branches of the human thyroid arteries were prototyped with synthetic resin, based on the algorithmic standard to layer (STL) output and ALM techniques. Satisfactory dimensional accuracy was obtained for these models, which were used as masters to evaluate protocols for their indirect replication, through both single and double procedures. Additional studies were conducted using casts of the human kidney arteries, obtained by injection / corrosion of the isolated organ. Satisfactory 3D reproduction of the external morphology of the kidney vessels was achieved. We conclude that our approach has the potential to develop up to the reconstruction with biomaterials of an entire, intraparenchymal vascular tree of soft tissue and endocrine organs.

The long-accepted thermoelectric model for electro-discharge machining is being brought into question. Several experimental facts prompt the proposal of a new theory based on the effect of gap pollution on the ignition of discharges. The first experimental proof comes from the recently reported observation of debris chains and clusters. In this view, each step of the process depends on the previous ones through a deterministic relation, even if the overall evolution is unpredictable. The paper establishes mathematical grounds for the abovementioned intuitions by setting up and solving a recursive equation for the machining energy employed at each discharge event. By means of numerical and algebraic tools, the above equation is studied and shows a chaotic evolution similar to that of the logistic map. Results reconcile the apparent paradox between deterministic nature and stochastic localization of the discharges and introduce a description of the chaotic dynamics of electro-discharge processes.