Generation of functional thymic organoids from human pluripotent stem cells.

The thymus is critical for the establishment of a functional and self-tolerant adaptive immune system but involutes with age, resulting in reduced naive T cell output. Generation of a functional human thymus from human pluripotent stem cells (hPSCs) is an attractive regenerative strategy. Direct differentiation of thymic epithelial progenitors (TEPs) from hPSCs has been demonstrated in vitro, but functional thymic epithelial cells (TECs) only form months after transplantation of TEPs in vivo. We show the generation of TECs in vitro in isogenic stem cell-derived thymic organoids (sTOs) consisting of TEPs, hematopoietic progenitor cells, and mesenchymal cells, differentiated from the same hPSC line. sTOs support T cell development, express key markers of negative selection, including the autoimmune regulator (AIRE) protein, and facilitate regulatory T cell development. sTOs provide the basis for functional patient-specific thymic organoid models, allowing for the study of human thymus function, T cell development, and transplant immunity.

Generation of functional human thymic cells from induced pluripotent stem cells.

BACKGROUND: The thymus is a glandular organ that is essential for the formation of the adaptive immune system by educating developing T cells. The thymus is most active during childhood and involutes around the time of adolescence, resulting in a severe reduction or absence of naive T-cell output. The ability to generate a patient-derived human thymus would provide an attractive research platform and enable the development of novel cell therapies. OBJECTIVES: This study sought to systematically evaluate signaling pathways to develop a refined direct differentiation protocol that generates patient-derived thymic epithelial progenitor cells from multiple induced pluripotent stem cells (iPSCs) that can further differentiate into functional patient-derived thymic epithelial cells on transplantation into athymic nude mice. METHODS: Directed differentiation of iPSC generated TEPs that were transplanted into nude mice. Between 14 and 19 weeks posttransplantation, grafts were removed and analyzed by flow cytometry, quantitative PCR, bulk RNA sequencing, and single-cell RNA sequencing for markers of thymic-cell and T-cell development. RESULTS: A direct differentiation protocol that allows the generation of patient-derived thymic epithelial progenitor cells from multiple iPSC lines is described. On transplantation into athymic nude mice, patient-derived thymic epithelial progenitor cells further differentiate into functional patient-derived thymic epithelial cells that can facilitate the development of T cells. Single-cell RNA sequencing analysis of iPSC-derived grafts shows characteristic thymic subpopulations and patient-derived thymic epithelial cell populations that are indistinguishable from TECs present in primary neonatal thymus tissue. CONCLUSIONS: These findings provide important insights and resources for researchers focusing on human thymus biology.

Estrogen Mitigates the Negative Effects of Arsenic Contamination in an In Vitro Wound Model.

Arsenic, a naturally occurring environmental contaminant, is harmful to humans at elevated concentrations. Increased levels of arsenic in the environment occur as a result of human activities and from natural geologically sourced leaching into ground and surface water. These sources pose an exposure risk above the USEPA standard to individuals whose food and water sources become contaminated. Arsenic exposure negatively impacts organ function and increases the risk for developing pathologies, including cancer. Some of the effects of arsenic on cancer translate to normal cell function in wound healing. To evaluate whether arsenic influences wound healing, an in vitro scratch assay was employed to study the effects of arsenic on cellular migration, which is a key component in the normal wound-healing process. In this study, skin cells were exposed to environmentally relevant concentrations of arsenic, and wound closure was evaluated. Results indicated that arsenic significantly decreased the rate of cellular migration in the scratch assay when compared with controls. In addition, estradiol, which has been shown to positively influence cellular and tissue processes involved in wound healing, reversed the slowing effects of arsenic on wound closure. These results suggest that arsenic contamination may inhibit, and estrogen may provide a therapeutic benefit for individuals with arsenic-contaminated wounds.

Epigenetics of breast cancer: Modifying role of environmental and bioactive food compounds.

SCOPE: Reduced expression of tumor suppressor genes (TSG) increases the susceptibility to breast cancer. However, only a small percentage of breast tumors is related to family history and mutational inactivation of TSG. Epigenetics refers to non-mutational events that alter gene expression. Endocrine disruptors found in foods and drinking water may disrupt epigenetically hormonal regulation and increase breast cancer risk. This review centers on the working hypothesis that agonists of the aromatic hydrocarbon receptor (AHR), bisphenol A (BPA), and arsenic compounds, induce in TSG epigenetic signatures that mirror those often seen in sporadic breast tumors. Conversely, it is hypothesized that bioactive food components that target epigenetic mechanisms protect against sporadic breast cancer induced by these disruptors. METHODS AND RESULTS: This review highlights (i) overlaps between epigenetic signatures placed in TSG by AHR-ligands, BPA, and arsenic with epigenetic alterations associated with sporadic breast tumorigenesis; and (ii) potential opportunities for the prevention of sporadic breast cancer with food components that target the epigenetic machinery. CONCLUSIONS: Characterizing the overlap between epigenetic signatures elicited in TSG by endocrine disruptors with those observed in sporadic breast tumors may afford new strategies for breast cancer prevention with specific bioactive food components or diet.