Tissue-engineered Thyroid Gland By Microencapsulation And Stem Cell Technology

Background and purposeHypothyroidism is a common condition of hormone deficiency,and oral administration of thyroid hormones is currently the only available treatment option.However,there are some disadvantages with this treatment modality including compliance challenges to patients.Therefore a physiologically-based alternative therapy for hypothyroidism with little or no side effects is needed.Our study focused on the tissue-engineered thyroid gland.Methodswe developed a method for microencapsulating porcine thyroid cells as a thyroid hormone replacement approach.The hybrid wall structure of the microcapsules permits thyroid hormone release while preventing immunoglobulin antibodies from entry.This strategy could potentially enable implantation of the microcapsule organoids containing allogeneic or xenogeneic thyroid cells to secret hormones over time without the need for immunosuppression of recipients.Porcine thyroid cells were isolated and encapsulated in alginate-poly-L-ornithine-alginate(APA)microcapsules using a three-dimensional microfluidic device.The viability,proliferation,hormonal secretion,and permeability of encapsulated porcine thyroid cells were evaluated in vitro.We performed the thyroid differentiation from murine induced pluripotent stem(iPS)cells under both hypoxic and normoxic conditions by using a modified method.We mimicked physiological hypoxic environments and compared differentiation efficiency in morphology,function,gene and protein expression to normoxic cells.ResultThe porcine thyroid cells formed three-dimensional follicular spheres in the microcapsules with decent cell viability and proliferation.Thyroxine release from the encapsulated cells was higher than from unencapsulated cells(p<0.05),and was maintained during the entire duration of experiment(>28 days).The microcapsules were impermeable to IgG but not smaller molecules such as thyroid hormones.The thyroid cells could be successfully differentiated from murine iPS cells.Hypoxia promoted adhesion and outgrowth of embryoid bodies(EBs)derived from murine iPS cells.Expression of endodermal markers(Foxa2 and Gata 4)and thyroid transcription factors(Pax8 and Nkx2.1)was increased by hypoxia at both gene and protein levels during early-mid differentiation stages(p<0.05).And so were the thyroid specific markers NIS and TSHR in the end of the experiment(p<0.05).Thus,thyroid differentiation from iPS cells is enhanced under hypoxia and this may involve hypoxia inducible factors(HIFs).ConclusionOur study suggests that the microencapsulated thyroid cell organoids and the thyroid cells differentiated from murine iPS cells may have the potential to be used for cell therapy to treat thyroid deficiency.