Paraxial mesoderm as a direct gateway to lymphatic endothelial cells
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Direct specification of lymphatic endothelium from mesenchymal progenitors
During embryogenesis, endothelial cells (ECs) are generally described to arise from a common pool of progenitors termed angioblasts, which diversify through iterative steps of differentiation to form functionally distinct subtypes of ECs. A key example is the formation of lymphatic ECs (LECs), which are thought to arise largely through transdifferentiation from venous endothelium. Opposing this model, here we show that the initial expansion of mammalian LECs is primarily driven by the in situ differentiation of mesenchymal progenitors and does not require transition through an intermediate venous state. Single-cell genomics and lineage-tracing experiments revealed a population of paraxial mesoderm-derived Etv2+Prox1+ progenitors that directly give rise to LECs. Morphometric analyses of early LEC proliferation and migration, and mutants that disrupt lymphatic development supported these findings. Collectively, this work establishes a cellular blueprint for LEC specification and indicates that discrete pools of mesenchymal progenitors can give rise to specialized subtypes of ECs.
A multiresolution approach with method-informed statistical analysis for quantifying lymphatic pumping dynamics
Despite significant strides in lymphatic system imaging, the timely diagnosis of lymphatic disorders remains elusive. This is driven by the absence of standardized, non-invasive, reliable, quantitative methods for real-time functional analysis of lymphatic contractility with adequate spatial and temporal resolution. Here, we address this unmet need by integrating near-infrared fluorescence lymphangiography imaging with an innovative analytical workflow that combines data acquisition, signal processing, and statistical analysis to integrate traditional peak-and-valley analysis with advanced wavelet time-frequency analyses. Variance component analysis was used to evaluate the drivers of variance attributable to each experimental variable for each lymphangiography measurement type. Generalizability studies were used to assess the reliability of measured parameters and how reliability improves as the number of repeat measurements per subject increases. This allowed us to determine the minimum number of repeat measurements needed per subject for acceptable measurement reliability. This approach not only offers detailed insights into lymphatic pumping behaviors across species, sex and age, but also significantly boosts the reliability of these measurements by incorporating multiple regions of interest and evaluating the lymphatic system under various gravitational loads. For example, the reliability of the peak-and-valley analysis of human lymphatic vessels was increased 3-fold using the described approach. By addressing the critical need for improved imaging and quantification methods, our study offers a new standard approach for the imaging and analysis of lymphatic function that can improve our understanding, diagnosis, and treatment of lymphatic diseases. The results highlight the importance of comprehensive data acquisition strategies to fully capture the dynamic behavior of the lymphatic system.
Mechanical signatures in cancer metastasis
The cancer metastatic cascade includes a series of mechanical barrier-crossing events, involving the physical movement of cancer cells from their primary location to a distant organ. This review describes the physical changes that influence tumour proliferation, progression, and metastasis. We identify potential mechanical signatures at every step of the metastatic cascade and discuss some latest mechanobiology-based therapeutic interventions to highlight the importance of interdisciplinary approaches in cancer diagnosis and treatment.
Endothelial senescence induced by PAI-1 promotes endometrial fibrosis
Intrauterine adhesions (IUAs), also known as Asherman’s syndrome (AS), represent a significant cause of uterine infertility for which effective treatment remains elusive. The endometrium’s ability to regenerate cyclically depends heavily on the growth and regression of its blood vessels. However, trauma to the endometrial basal layer can disrupt the subepithelial capillary plexus, impeding regeneration. This damage results in the replacement of native cells with fibroblasts and myofibroblasts, ultimately leading to fibrosis. Endothelial cells (ECs) play a pivotal role in the vascular system, extending beyond their traditional barrier function. Through single-cell sequencing and experimental validation, we discovered that ECs undergo senescence in IUA patients, impairing angiogenesis and fostering stromal cell fibrosis. Further analysis revealed significant interactions between ECs and PAI-1+ stromal cells. PAI-1, derived from stromal cells, promotes EC senescence via the urokinase-type plasminogen activator receptor (uPAR). Notably, prior to fibrosis onset, TGF-β upregulates PAI-1 expression in stromal cells in a SMAD dependent manner. In an IUA mouse model, inhibiting PAI-1 mitigated EC senescence and endometrial fibrosis. Our findings underscore the crucial role of EC senescence in IUA pathogenesis, contributing to vascular reduction and fibrosis. Targeting PAI-1 represents a promising therapeutic strategy to suppress EC senescence and alleviate endometrial fibrosis, offering new insights into the treatment of IUAs.
Emerging insights in senescence: pathways from preclinical models to therapeutic innovations
Senescence is a crucial hallmark of ageing and a significant contributor to the pathology of age-related disorders. As committee members of the young International Cell Senescence Association (yICSA), we aim to synthesise recent advancements in the identification, characterisation, and therapeutic targeting of senescence for clinical translation. We explore novel molecular techniques that have enhanced our understanding of senescent cell heterogeneity and their roles in tissue regeneration and pathology. Additionally, we delve into in vivo models of senescence, both non-mammalian and mammalian, to highlight tools available for advancing the contextual understanding of in vivo senescence. Furthermore, we discuss innovative diagnostic tools and senotherapeutic approaches, emphasising their potential for clinical application. Future directions of senescence research are explored, underscoring the need for precise, context-specific senescence classification and the integration of advanced technologies such as machine learning, long-read sequencing, and multifunctional senoprobes and senolytics. The dual role of senescence in promoting tissue homoeostasis and contributing to chronic diseases highlights the complexity of targeting these cells for improved clinical outcomes.
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