RESUMO
The ductal system of the salivary gland has long been postulated to be resistant to radiation-induced damage, a common side effect incurred by head and neck cancer patients receiving radiotherapy. Yet, whether the ducts are capable of regenerating after genotoxic injury, or whether damage to ductal cells induces lineage plasticity, as has been reported in other organ systems, remains unknown. Here, using the murine salivary gland, we show that two ductal progenitor populations, marked exclusively by KRT14 and KIT, maintain non-overlapping ductal compartments after radiation exposure but do so through distinct cellular mechanisms. KRT14+ progenitor cells are fast-cycling cells that proliferate in response to radiation-induced damage in a sustained manner and divide asymmetrically to produce differentiated cells of the larger granulated ducts. Conversely, KIT+ intercalated duct cells are long-lived progenitors for the intercalated ducts that undergo few cell divisions either during homeostasis or after gamma radiation, thus maintaining ductal architecture with slow rates of cell turnover. Together, these data illustrate the regenerative capacity of the salivary ducts and highlight the heterogeneity in the damage responses used by salivary progenitor cells to maintain tissue architecture.
Assuntos
Lesões por Radiação/terapia , Ductos Salivares/patologia , Ductos Salivares/efeitos da radiação , Transplante de Células-Tronco , Células-Tronco/citologia , Células Acinares/metabolismo , Animais , Animais Recém-Nascidos , Divisão Celular Assimétrica , Linhagem da Célula , Proliferação de Células , Células Epiteliais/metabolismo , Feminino , Humanos , Queratina-14/metabolismo , Masculino , Camundongos Endogâmicos C57BL , Modelos Biológicos , Proteínas Proto-Oncogênicas c-kit/metabolismo , Lesões por Radiação/patologia , Ductos Salivares/metabolismo , Glândula Submandibular/metabolismo , Glândula Submandibular/patologia , Glândula Submandibular/efeitos da radiaçãoRESUMO
Background: Tanning bed users have a significantly increased risk of melanoma, but it remains unclear how indoor tanning drives melanomagenesis. Tanning bed radiation is often thought of as a substitute for natural UV radiation despite differences in the maximum doses, UV content, body sites exposed, and patterns of melanoma that arise. Methods: To better understand the epidemiologic trends and etiology of melanoma associated with tanning bed use, we described the patterns of melanoma in patients with quantifiable tanning bed usage and performed exome sequencing of 182 melanocytes from normal skin of a subset of these patients. Results: Tanning bed users were more likely than non-users to have melanoma on body sites with low cumulative levels of sun damage and were more likely to have multiple melanomas. The melanocytes in normal appearing skin from tanning bed users had higher mutation burdens, a higher proportion of melanocytes with pathogenic mutations, and distinct mutational signatures. These differences were most prominent over body sites that experience comparatively less exposure to natural sunlight. Conclusions: We conclude that tanning bed radiation induces melanoma by increasing the mutation burden of melanocytes and by mutagenizing a broader field of melanocytes than are typically exposed to natural sunlight. The unique signatures of mutations in skin cells of tanning users may be attributable to the distinct spectra of radiation emitted from solariums.
RESUMO
We performed multi-omic profiling of epidermal keratinocytes, precancerous actinic keratoses, and squamous cell carcinomas to understand the molecular transitions during skin carcinogenesis. Single-cell mutational analyses showed that most keratinocytes in normal skin had lower mutation burdens than melanocytes and fibroblasts, however keratinocytes with TP53 or NOTCH1 mutations had substantially higher mutation burdens, suggesting that these mutations prime keratinocytes for transformation by increasing their mutation rate. Mutational profiling and spatial transcriptomics on squamous cell carcinomas adjacent to actinic keratoses revealed TERT promoter and CDKN2A mutations emerging in actinic keratoses, whereas additional mutations inactivating ARID2 and activating the MAPK-pathway delineated the transition to squamous cell carcinomas. Spatial variation in gene expression patterns was common in both tumor and immune cells, with high expression of checkpoint molecules at the invasive front of tumors. In conclusion, this study documents key events during the evolution of cutaneous squamous cell carcinoma.
RESUMO
Acral melanoma is an aggressive type of melanoma with unknown origins. It is the most common type of melanoma in individuals with dark skin and is notoriously challenging to treat. We examine exome sequencing data of 139 tissue samples, spanning different progression stages, from 37 patients. We find that 78.4% of the melanomas display clustered copy number transitions with focal amplifications, recurring predominantly on chromosomes 5, 11, 12, and 22. These complex genomic aberrations are typically shared across all progression stages of individual patients. TERT activating alterations also arise early, whereas MAP-kinase pathway mutations appear later, an inverted order compared to the canonical evolution. The punctuated formation of complex aberrations and early TERT activation suggest a unique mutational mechanism that initiates acral melanoma. The marked intratumoral heterogeneity, especially concerning MAP-kinase pathway mutations, may partly explain the limited success of therapies for this melanoma subtype.
Assuntos
Melanoma , Mutação , Neoplasias Cutâneas , Telomerase , Humanos , Melanoma/genética , Melanoma/patologia , Neoplasias Cutâneas/genética , Neoplasias Cutâneas/patologia , Telomerase/genética , Variações do Número de Cópias de DNA , Evolução Molecular , Masculino , Sequenciamento do Exoma , Feminino , Sistema de Sinalização das MAP Quinases/genéticaRESUMO
Spatial transcriptomic technologies, such as the Visium platform, measure gene expression in different regions of tissues. Here, we describe new software, STmut, to visualize somatic point mutations, allelic imbalance, and copy number alterations in Visium data. STmut is tested on fresh-frozen Visium data, formalin-fixed paraffin-embedded (FFPE) Visium data, and tumors with and without matching DNA sequencing data. Copy number is inferred on all conditions, but the chemistry of the FFPE platform does not permit analyses of single nucleotide variants. Taken together, we propose solutions to add the genetic dimension to spatial transcriptomic data and describe the limitations of different datatypes.
Assuntos
Formaldeído , Neoplasias , Humanos , Transcriptoma , Inclusão em Parafina , Neoplasias/genética , Perfilação da Expressão Gênica , Sequenciamento de Nucleotídeos em Larga EscalaRESUMO
Acinar cells are the principal secretory units of multiple exocrine organs. A single-cell, layered, lumenized acinus forms from a large cohort of epithelial progenitors that must initiate and coordinate three cellular programs of acinar specification, namely, lineage progression, secretion, and polarization. Despite this well-known outcome, the mechanism(s) that regulate these complex programs are unknown. Here, we demonstrate that neuronal-epithelial cross-talk drives acinar specification through neuregulin (NRG1)-ERBB3-mTORC2 signaling. Using single-cell and global RNA sequencing of developing murine salivary glands, we identified NRG1-ERBB3 to precisely overlap with acinar specification during gland development. Genetic deletion of Erbb3 prevented cell lineage progression and the establishment of lumenized, secretory acini. Conversely, NRG1 treatment of isolated epithelia was sufficient to recapitulate the development of secretory acini. Mechanistically, we found that NRG1-ERBB3 regulates each developmental program through an mTORC2 signaling pathway. Thus, we reveal that a neuronal-epithelial (NRG1/ERBB3/mTORC2) mechanism orchestrates the creation of functional acini.
Assuntos
Neurregulinas , Transdução de Sinais , Humanos , Camundongos , Animais , Alvo Mecanístico do Complexo 2 de Rapamicina , Células Acinares , Transporte Biológico , Neuregulina-1 , Receptor ErbB-3RESUMO
Salivary gland acinar cells are severely depleted after radiotherapy for head and neck cancer, leading to loss of saliva and extensive oro-digestive complications. With no regenerative therapies available, organ dysfunction is irreversible. Here, using the adult murine system, we demonstrate that radiation-damaged salivary glands can be functionally regenerated via sustained delivery of the neurogenic muscarinic receptor agonist cevimeline. We show that endogenous gland repair coincides with increased nerve activity and acinar cell division that is limited to the first week after radiation, with extensive acinar cell degeneration, dysfunction, and cholinergic denervation occurring thereafter. However, we found that mimicking cholinergic muscarinic input via sustained local delivery of a cevimeline-alginate hydrogel was sufficient to regenerate innervated acini and retain physiological saliva secretion at nonirradiated levels over the long term (>3 months). Thus, we reveal a previously unknown regenerative approach for restoring epithelial organ structure and function that has extensive implications for human patients.
RESUMO
Salivary gland acinar cells are routinely destroyed during radiation treatment for head and neck cancer that results in a lifetime of hyposalivation and co-morbidities. A potential regenerative strategy for replacing injured tissue is the reactivation of endogenous stem cells by targeted therapeutics. However, the identity of these cells, whether they are capable of regenerating the tissue, and the mechanisms by which they are regulated are unknown. Using in vivo and ex vivo models, in combination with genetic lineage tracing and human tissue, we discover a SOX2+ stem cell population essential to acinar cell maintenance that is capable of replenishing acini after radiation. Furthermore, we show that acinar cell replacement is nerve dependent and that addition of a muscarinic mimetic is sufficient to drive regeneration. Moreover, we show that SOX2 is diminished in irradiated human salivary gland, along with parasympathetic nerves, suggesting that tissue degeneration is due to loss of progenitors and their regulators. Thus, we establish a new paradigm that salivary glands can regenerate after genotoxic shock and do so through a SOX2 nerve-dependent mechanism.
Assuntos
Lesões por Radiação/patologia , Lesões por Radiação/fisiopatologia , Regeneração , Fatores de Transcrição SOXB1/metabolismo , Glândulas Salivares/patologia , Glândulas Salivares/fisiopatologia , Acetilcolina/metabolismo , Células Acinares/metabolismo , Células Acinares/efeitos da radiação , Adulto , Idoso , Animais , Linhagem da Célula/efeitos da radiação , Proliferação de Células/efeitos da radiação , Nervo da Corda do Tímpano/patologia , Nervo da Corda do Tímpano/efeitos da radiação , Feminino , Homeostase , Humanos , Masculino , Camundongos Endogâmicos C57BL , Pessoa de Meia-Idade , Lesões por Radiação/metabolismo , Radiação Ionizante , Receptores Muscarínicos/metabolismo , Glândulas Salivares/efeitos da radiação , Transdução de Sinais , Células-Tronco/metabolismo , Células-Tronco/efeitos da radiaçãoRESUMO
Acinar cells play an essential role in the secretory function of exocrine organs. Despite this requirement, how acinar cells are generated during organogenesis is unclear. Using the acini-ductal network of the developing human and murine salivary gland, we demonstrate an unexpected role for SOX2 and parasympathetic nerves in generating the acinar lineage that has broad implications for epithelial morphogenesis. Despite SOX2 being expressed by progenitors that give rise to both acinar and duct cells, genetic ablation of SOX2 results in a failure to establish acini but not ducts. Furthermore, we show that SOX2 targets acinar-specific genes and is essential for the survival of acinar but not ductal cells. Finally, we illustrate an unexpected and novel role for peripheral nerves in the creation of acini throughout development via regulation of SOX2. Thus, SOX2 is a master regulator of the acinar cell lineage essential to the establishment of a functional organ.
Assuntos
Células Acinares/fisiologia , Diferenciação Celular , Organogênese , Fatores de Transcrição SOXB1/metabolismo , Glândulas Salivares/citologia , Glândulas Salivares/embriologia , Animais , Técnicas de Inativação de Genes , Humanos , CamundongosRESUMO
The lacrimal gland (LG) secretes aqueous tears necessary for maintaining the structure and function of the cornea, a transparent tissue essential for vision. In the human a single LG resides in the orbit above the lateral end of each eye delivering tears to the ocular surface through 3 - 5 ducts. The mouse has three pairs of major ocular glands, the most studied of which is the exorbital lacrimal gland (LG) located anterior and ventral to the ear. Similar to other glandular organs, the LG develops through the process of epithelial branching morphogenesis in which a single epithelial bud within a condensed mesenchyme undergoes multiple rounds of bud and duct formation to form an intricate interconnected network of secretory acini and ducts. This elaborate process has been well documented in many other epithelial organs such as the pancreas and salivary gland. However, the LG has been much less explored and the mechanisms controlling morphogenesis are poorly understood. We suspect that this under-representation as a model system is a consequence of the difficulties associated with finding, dissecting and culturing the LG. Thus, here we describe dissection techniques for harvesting embryonic and post-natal LG and methods for ex vivo culture of the tissue.
Assuntos
Aparelho Lacrimal/citologia , Aparelho Lacrimal/cirurgia , Técnicas de Cultura de Tecidos/métodos , Animais , Dissecação/métodos , Feminino , Aparelho Lacrimal/crescimento & desenvolvimento , Aparelho Lacrimal/metabolismo , Camundongos , Camundongos Transgênicos , Gravidez , Transdução de SinaisRESUMO
A fundamental question in development is how cells assemble to form a tubular network during organ formation. In glandular organs, tubulogenesis is a multistep process requiring coordinated proliferation, polarization and reorganization of epithelial cells to form a lumen, and lumen expansion. Although it is clear that epithelial cells possess an intrinsic ability to organize into polarized structures, the mechanisms coordinating morphogenetic processes during tubulogenesis are poorly understood. Here, we demonstrate that parasympathetic nerves regulate tubulogenesis in the developing salivary gland. We show that vasoactive intestinal peptide (VIP) secreted by the innervating ganglia promotes ductal growth, leads to the formation of a contiguous lumen, and facilitates lumen expansion through a cyclic AMP/protein kinase A (cAMP/PKA)-dependent pathway. Furthermore, we provide evidence that lumen expansion is independent of apoptosis and involves the cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP-regulated Cl(-) channel. Thus, parasympathetic innervation coordinates multiple steps in tubulogenesis during organogenesis.