Gene Modification and Three-Dimensional Scaffolds as Novel Tools to Allow the Use of Postnatal Thymic Epithelial Cells for Thymus Regeneration Approaches
Authors
Ileana Bortolomai, Monica Sandri, Elena Draghici, Elena Fontana, Elisabetta Campodoni, Genni Enza Marcovecchio, Francesca Ferrua, Laura Perani, Antonello Spinelli, Tamara Canu, Marco Catucci, Tiziano Di Tomaso, Lucia Sergi Sergi, Antonio Esposito, Angelo Lombardo, Luigi Naldini, Anna Tampieri, Georg A. Hollander, Anna Villa, Marita Bosticardo
Institution
IRCCS San Raffaele Scientific Institute, Milan
Country
Italy
Year
2019
Journal
Stem Cells Translational Medicine
Abstract
Defective functionality of thymic epithelial cells (TECs), due to genetic mutations or injuring causes, results in altered T-cell development, leading to immunodeficiency or autoimmunity. These defects cannot be corrected by hematopoietic stem cell transplantation (HSCT), and thymus transplantation has not yet been demonstrated to be fully curative. Here, we provide proof of principle of a novel approach toward thymic regeneration, involving the generation of thymic organoids obtained by seeding gene-modified postnatal murine TECs into three-dimensional (3D) collagen type I scaffolds mimicking the thymic ultrastructure. To this end, freshly isolated TECs were transduced with a lentiviral vector system, allowing for doxycycline-induced Oct4 expression. Transient Oct4 expression promoted TECs expansion without drastically changing the cell lineage identity of adult TECs, which retain the expression of important molecules for thymus functionality such as Foxn1, Dll4, Dll1, and AIRE. Oct4-expressing TECs (iOCT4 TEC) were able to grow into 3D collagen type I scaffolds both in vitro and in vivo, demonstrating that the collagen structure reproduced a 3D environment similar to the thymic extracellular matrix, perfectly recognized by TECs. In vivo results showed that thymic organoids transplanted subcutaneously in athymic nude mice were vascularized but failed to support thymopoiesis because of their limited in vivo persistence. These findings provide evidence that gene modification, in combination with the usage of 3D biomimetic scaffolds, may represent a novel approach allowing the use of postnatal TECs for thymic regeneration. Stem Cells Translational Medicine 2019;8:1107-1122.