Abstract
The maintenance and propagation of complex mixtures of cells in vitro in the form of native organs or engineered organoids has contributed to understanding mechanisms of cell and organ development and function which can be translated into therapeutic benefits. For example, allogeneic cultured postnatal human thymus tissue has been shown to support production of naïve recipient T cells when transplanted into patients with complete DiGeorge anomaly and other genetic defects that result in congenital lack of a thymus. Patients receiving such transplants typically exhibit reversal of their immunodeficiency and normalization of their peripheral blood T cell receptor V-beta repertoire, with long-term survival. This study was designed to assess the histopathologic changes that occur in postnatal human thymus slices when cultured according to protocols used for transplanted tissues. Results showed that as thymic organ cultures progressed from days 0 through 21, slices developed increasing amounts of necrosis, increasing condensation of thymic epithelium, and decreasing numbers of residual T cells. The architecture of the thymic epithelial network remained generally well-preserved throughout the 21 days of culture, with focal expression of cytokeratin 14, a putative biomarker of thymic epithelial cells with long-term organ-repopulating potential. All organ slices derived from the same donor thymus closely resembled one another, with minor differences in size, shape, and relative content of cortex versus medulla. Similarly, slices derived from different donors showed similar histopathologic characteristics when examined at the same culture time point. Taken together, these results demonstrate that diagnostic criteria based on structural features of the tissue identifiable via hematoxylin and eosin staining and cytokeratin immunohistochemistry can be used to evaluate the quality of slices transplanted into patients with congenital athymia.
Highlights
Patients with complete DiGeorge anomaly and other forms of congenital athymia have severe immunodeficiency due to their lack of a thymus and the resulting absence of T-cell production
The donor thymus used for the research portion of this study was sliced and cultured in a Good Manufacturing Process (GMP)-compliant cell manufacturing laboratory using donor qualification and culture procedures identical to those used for thymus samples intended for transplantation [2,3,5,14,15]
Fixed slices were submitted to a Clinical Laboratory Improvement Act (CLIA)-certified, College of American Pathologists (CAP)-accredited clinical laboratory, where formalinfixed paraffin embedded blocks, hematoxylin and eosin (H&E)-stained sections, and an immunohistochemical panel were prepared using procedures identical to those used to assess lots intended for transplantation
Summary
Patients with complete DiGeorge anomaly and other forms of congenital athymia have severe immunodeficiency due to their lack of a thymus and the resulting absence of T-cell production. The purpose of culture is to partially deplete T cells from the thymic epithelial network This depletion provides space for colonization of the depleted thymus slices by recipient T cell precursors and minimizes the potential for graft-versus-host disease mediated by donor T cells. This study describes the histopathologic changes that occur during the culture of thymus slices Understanding these changes can potentially lead to the validation of enhanced histopathologic criteria for prospective assessment of the quality of cultured thymus slices prior to transplantation, based on characteristics of tissues that have successfully generated immune reconstitution in prior recipients [12]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
