Effect of cryopreservation on viability and growth efficiency of stromal-epithelial cells derived from neonatal human thymus

Key Factors for Thymic Function and Development

The thymus is the organ responsible for T cell development and the formation of the adaptive immunity function. Its multicellular environment consists mainly of the different stromal cells and maturing T lymphocytes. Thymus-specific progenitors of epithelial, mesenchymal, and lymphoid cells with stem cell properties represent only minor populations. The thymic stromal structure predominantly determines the function of the thymus. The stromal components, mostly epithelial and mesenchymal cells, form this specialized area. They support the consistent developmental program of functionally distinct conventional T cell subpopulations. These include the MHC restricted single positive CD4+ CD8- and CD4- CD8+ cells, regulatory T lymphocytes (Foxp3+), innate natural killer T cells (iNKT), and γδT cells. Several physiological causes comprising stress and aging and medical treatments such as thymectomy and chemo/radiotherapy can harm the thymus function. The present review summarizes our knowledge of the development and function of the thymus with a focus on thymic epithelial cells as well as other stromal components and the signaling and transcriptional pathways underlying the thymic cell interaction. These critical thymus components are significant for T cell differentiation and restoring the thymic function after damage to reach the therapeutic benefits.

Automated–Mechanical Procedure Compared to Gentle Enzymatic Tissue Dissociation in Cell Function Studies

The first step to obtain a cellular suspension from tissues is the disaggregation procedure. The cell suspension method has to provide a representative sample of the different cellular subpopulations and to maximize the number of viable functional cells. Here, we analyzed specific cell functions in cell suspensions from several rat tissues obtained by two different methods, automated–mechanical and enzymatic disaggregation. Flow cytometric, confocal, and ultrastructural (TEM) analyses were applied to the spleen, testis, liver and other tissues. Samples were treated by an enzymatic trypsin solution or processed by the Medimachine II (MMII). The automated–mechanical and enzymatic disaggregation procedures have shown to work similarly in some tissues, which displayed comparable amounts of apoptotic/necrotic cells. However, cells obtained by the enzyme-free Medimachine II protocols show a better preservation lysosome and mitochondria labeling, whereas the enzymatic gentle dissociation appears to constantly induce a lower amount of intracellular ROS; nevertheless, lightly increased ROS can be recognized as a complimentary signal to promote cell survival. Therefore, MMII represents a simple, fast, and standardized method for tissue processing, which allows to minimize bias arising from the operator’s ability. Our study points out technical issues to be adopted for specific organs and tissues to obtain functional cells.

AIRE deficiency, from preclinical models to human APECED disease

Autoimmune polyendocrinopathy candidiasis ectodermal dystrophy (APECED) is a rare life-threatening autoimmune disease that attacks multiple organs and has its onset in childhood. It is an inherited condition caused by a variety of mutations in the autoimmune regulator (AIRE) gene that encodes a protein whose function has been uncovered by the generation and study of Aire-KO mice. These provided invaluable insights into the link between AIRE expression in medullary thymic epithelial cells (mTECs), and the broad spectrum of self-antigens that these cells express and present to the developing thymocytes. However, these murine models poorly recapitulate all phenotypic aspects of human APECED. Unlike Aire-KO mice, the recently generated Aire-KO rat model presents visual features, organ lymphocytic infiltrations and production of autoantibodies that resemble those observed in APECED patients, making the rat model a main research asset. In addition, ex vivo models of AIRE-dependent self-antigen expression in primary mTECs have been successfully set up. Thymus organoids based on pluripotent stem cell-derived TECs from APECED patients are also emerging, and constitute a promising tool to engineer AIRE-corrected mTECs and restore the generation of regulatory T cells. Eventually, these new models will undoubtedly lead to main advances in the identification and assessment of specific and efficient new therapeutic strategies aiming to restore immunological tolerance in APECED patients.

Optimization of Viable Glioblastoma Cryopreservation for Establishment of Primary Tumor Cell Cultures

Background: Technologies related to the establishment of primary tumor cell cultures from solid tumors, including glioblastoma, are increasingly important to oncology research and practice. However, processing of fresh tumor specimens for establishment of primary cultures on the day of surgical collection is logistically difficult. The feasibility of viable cryopreservation of glioblastoma specimens, allowing for primary culture establishment weeks to months after surgical tumor collection and freezing, was demonstrated by Mullins et al. in 2013, with a success rate of 59% that was not significantly lower than that achieved with fresh tumor tissue. However, research targeting optimization of viable glioblastoma cryopreservation protocols for establishment of primary tumor cultures has been limited. Objectives: The objective of this study was to optimize glioblastoma cryopreservation methods for viable cryobanking and to determine if two-dimensional (2D) or three-dimensional (3D) culture conditions were more supportive of glioblastoma growth after thawing of frozen tumor specimens. Methods: Portions of eight human glioblastoma specimens were cryopreserved by four different protocols differing in the time of enzymatic digestion (before or after cryopreservation), and in the type of cryopreservation media (CryoStor CS10 or 10% dimethyl sulfoxide and 90% fetal calf serum). After 1 month, frozen tissues were thawed, enzymatically digested, if not digested before, and used for initiation of 2D or 3D primary tumor cultures to determine viability. Results: Among the tested cryopreservation and culturing protocols, the most efficient combinations of cryopreservation and culture were those associated with the use of CryoStor CS10 cryopreservation medium, enzymatic digestion before freezing, and 2D culturing after thawing with a successful culture rate of 8 out of 8 cases (100%). Two-dimensional cultures were in general more efficient for the support of tumor cell growth after thawing than 3D cultures. Conclusions: This study supports development of evidence-based viable glioblastoma cryopreservation methods for use in glioblastoma biobanking and research.

Thymus Regeneration and Future Challenges

Thymus regenerative therapy implementation is severely obstructed by the limited number and expansion capacity in vitro of tissue-specific thymic epithelial stem cells (TESC). Current solutions are mostly based on growth factors that can drive differentiation of pluripotent stem cells toward tissue-specific TESC. Target-specific small chemical compounds represent an alternative solution that could induce and support the clonal expansion of TESC and reversibly block their differentiation into mature cells. These compounds could be used both in the composition of culture media designed for TESC expansion in vitro, and in drugs development for thymic regeneration in vivo. It should allow reaching the ultimate objective - autologous thymic tissue regeneration in paediatric patients who had their thymus removed in the course of cardiac surgery.

Stem cell culture conditions and stability: a joint workshop of the PluriMes Consortium and Pluripotent Stem Cell Platform

Human stem cells have the potential to transform medicine. However, hurdles remain to ensure that manufacturing processes produce safe and effective products. A thorough understanding of the biological processes occurring during manufacture is fundamental to assuring these qualities and thus, their acceptability to regulators and clinicians. Leaders in both human pluripotent and somatic stem cells, were brought together with experts in clinical translation, biomanufacturing and regulation, to discuss key issues in assuring appropriate manufacturing conditions for delivery of effective and safe products from these cell types. This report summarizes the key issues discussed and records consensus reached by delegates and emphasizes the need for accurate language and nomenclature in the scientific discourse around stem cells.

Cultured Human Thymic-Derived Cells Display Medullary Thymic Epithelial Cell Phenotype and Functionality

Thymic epithelial cells are one of the main components of the thymic microenvironment required for T-cell development. In this work, we describe an efficient method free of enzymatic and Facs-sorted methods to culture human medullary thymic epithelial cells without affecting the cell phenotypic, physiologic and functional features. Human medulla thymic epithelial cells (mTECs) are obtained by culturing thymic biopsies explants. After 7 days of primo-culture, mTECs keep their ability to express key molecules involved in immune tolerance processes such as autoimmune regulator, tissue-specific antigens, chemokines, and cytokines. In addition, the cells sensor their cultured environment and consequently adjust their gene expression network. Therefore, we describe and provide a human mTEC model that may be used to test the effect of various molecules on thymic epithelial cell homeostasis and physiology. This method should allow the investigations of the specificities and the knowledge of human mTECs in normal or pathological conditions and therefore discontinue the extrapolations done on the murine models.