Table 2.

Future treatment approaches for congenital athymia (in comparison with standard treatment).

Approach	Standard thymus transplantation with cryopreserved thymus tissue	Engineered thymus using a natural scaffold seeded with expanded TEC progenitors	Engineered thymus using a natural scaffold seeded with gene-corrected iTEPCs
ADVANTAGES	-Improved treatment logistics -Potential for partial tissue type matching with possibly reduced autoimmunity	-Generation of large amounts of human thymus tissue -Potential for partial tissue type matching with possibly reduced autoimmunity	-Autologous procedure -Expected reduced autoimmunity
CURRENT STATUS	Pre-clinical Mouse model (147) Frozen & thawed human thymus tissue supporting murine T-cell development upon transplantation into nude mice	Pre-clinical Mouse model (35) Seeding of natural decellularized ECM with human thymic stromal cell progenitors by whole-organ perfusion; supporting human T-cell development upon transplantation into humanized NSG mice	Pre-clinical Mouse model (149) Small RTOCs containing (control) human iTEPCs mixed with mouse embryonic fibroblasts; supporting limited murine T-cell development upon transplantation into nude mice