Characterization of decellularized thymus scaffolds for use in engineering thymus tissue - John Jackson
The thymus is a primary lymphoid organ that is responsible for the maturation of T lymphocytes. During aging, the thymus undergoes a process of involution. This results in a decrease in T cell output from the thymus as well as a change in the distribution of T cells in the periphery. To overcome these problems of aging, we are developing an engineered thymus that may provide a method to increase the number of naive mature T cells and to enhance immune responses to pathogens. The goal of this project is to engineer a thymus by developing decellularization protocols to produce natural scaffolds having the potential to support the production of a functional thymus. Thymi from mouse and pig were treated with 2% Triton-X 100 and 0.1% ammonium hydroxide to remove all cellular components of the organ. The resultant decellularized scaffolds were characterized. The decellularization procedure resulted in the elimination of all cells in both mouse and pig scaffolds. Masson’s trichrome staining of the scaffolds showed a decrease in collagen in the mouse scaffolds compared to the pig scaffolds, suggesting more damage to the mouse scaffold during the decellularization procedure. In addition, staining of the scaffolds using Alcian Blue indicated a reduction in glycosaminoglycans in both the mouse and pig scaffolds after the decellularization procedure. Acid extraction of the decellularized porcine thymus scaffold contained activity that increased the proliferation of thymus epithelial cells. The results indicated that the decellularization procedure eliminated the cells in the thymi but caused damage to the scaffolds. The porcine scaffolds appeared to sustain less damage than the mouse scaffolds and retained activity that increased epithelial cell proliferation. The ability to induce epithelial cell proliferation will be important for epithelial recellularization of the scaffolds to produce an engineered thymus. In summary, the decellularization procedure eliminated the cellular components of the thymus but caused damage to the scaffolds, resulting in decreased collagen and proteoglycan content. However, some of the activity that induced epithelial proliferation remained on the porcine scaffolds. The results show that decellularized thymus scaffolds have the potential to be used as the foundation for tissue engineering of the thymus.