Marc van de Wetering

Mammalian epidermis consists of three self-renewing compartments: the hair follicle, the sebaceous gland, and the interfollicular epidermis. We generated knock-in alleles of murine Lgr6, a close relative of the Lgr5 stem cell gene. Lgr6 was expressed in the earliest embryonic hair placodes. In adult hair follicles, Lgr6+ cells resided in a previously uncharacterized region directly above the follicle bulge. They expressed none of the known bulge stem cell markers. Prenatal Lgr6+ cells established the hair follicle, sebaceous gland, and interfollicular epidermis. Postnatally, Lgr6+ cells generated sebaceous gland and interfollicular epidermis, whereas contribution to hair lineages gradually diminished with age. Adult Lgr6+ cells executed long-term wound repair, including the formation of new hair follicles. We conclude that Lgr6 marks the most primitive epidermal stem cell.

The tongue is essential for swallowing, taste perception, and mechanosensation. The anterior and posterior parts of the tongue have region-specific developmental origins and are maintained by adult epithelial stem/progenitor cells. In vitro models that can be used to investigate anterior tongue biology have been lacking. Here, a protocol is developed to generate a long-term expanding organoid model from the adult mouse dorsal anterior tongue. Anterior tongue organoids consist of Lgr6+ cells, Sox2+ stem/progenitor cells, and Hoxc13+ filiform papillae progenitor cells. Furthermore, anterior tongue organoids share region-specific transcriptomic profiles, gene regulatory networks, and signaling pathways with anterior tongue tissue. Anterior tongue organoids can be differentiated into various epithelial cell types, including Merkel-like cells, keratinocytes, and taste bud cells. Gene regulatory network analysis reveals transcriptional programs associated with Krt8+ cell and Krt23+/Sbsn+ keratinocyte differentiation in the organoids. Together, this study provides an in vitro model of mouse dorsal tongue epithelium.

Abstract Background Pediatric-type diffuse high-grade gliomas (pHGGs) are a leading cause of pediatric cancer-related mortality. Although immunotherapy offers a promising treatment avenue, clinical responses in pHGG patients remain limited. A detailed understanding of the tumor immune microenvironment (TIME) is essential for advancing immunotherapeutic strategies. Methods We performed single-cell spatial analysis integrating cyclical immunofluorescence imaging and spatial molecular imaging to interrogate the proteomic and transcriptomic landscape of pHGGs. A tissue microarray comprising 32 diagnostic patient-derived pHGG samples was utilized to map the spatial distribution of immune and tumor cells. Results Our analyses reveal that the pHGG TIME is predominantly composed of myeloid cells, including brain-­resident microglia and monocyte-derived macrophages, with only few T cells. A significant subset of these myeloid cells expresses mesenchymal (MES)-like genes and is positive for SPP1 and GPNMB. Spatial mapping further demonstrated that SPP1+/GPNMB+ myeloid cells localize in close proximity to MES-like tumor cells, and negatively correlate with the location and presence of CD8+ T cells. These cells also express genes related to immunosuppression and epithelial-to-mesenchymal transition, indicating their potential role in establishing an immunosuppressive niche. Conclusions Our findings reveal a distinct immune landscape in pHGGs characterized by SPP1+/GPNMB+ myeloid cells which may contribute to the exclusion of CD8+ T cells. This spatially resolved insight identifies these myeloid cells as promising therapeutic targets and provides a rationale for developing novel immunotherapeutic strategies to improve outcomes in pediatric high-grade gliomas.