Periodic Reporting for period 4 - AngioMature (Mechanisms of vascular maturation and quiescence during development, homeostasis and aging)
Periodo di rendicontazione: 2023-02-01 al 2024-10-31
The goal of the ‘Angiomature’ project was to identify, validate, and implement novel mechanisms of vascular maturation and organotypic endothelial cell (EC) differentiation that are active during development, maintenance of vascular stability in adults, and undergo changes in aging. This vision was based on the notion that the maintenance of a mature, quiescent, and organotypically-differentiated layer of ECs lining the inside of all blood vessels is vital for human health and that perturbation of vascular quiescence is associated with numerous critical and life-threatening human diseases making it in essence the single most important cause of human mortality, giving the project important societal relevance.
The Angiomature project was structured to pursue three interrelated research lines (RL). RL1 was aimed at performing bulk and single cell analyses of the transcriptional and epigenetic program(s) of vascular maturation and organotypic differentiation during adolescence and aging. RL2 focused on the analysis of the functional consequences of program(s) and candidate molecules in cellular systems as well as in differentiating EC of adolescent mice and differentiated EC of adult mice and their adaptation to challenge. The most ambitious and logistically most challenging RL3 studies focused on changes of maturation and differentiation program(s) and vascular responses during aging. All three RLs have yielded important and groundbreaking discoveries. In RL1, we could in preclinical mouse models deconvolute on the systems level EC transcriptional programs (i) during development and adolescence, (ii) in the pre-metastatic and metastatic niches of the lung, (iii) spatially resolved in the homeostatic and challenged liver, and (iv) in the lungs during systemic aging. These experimental approaches yielded comprehensive systems maps that were in the liver expanded by proteomics and phosphoproteomics analyses to enable comprehensive datamining for novel organotypically and challenge-specifically expressed EC molecules to feed the pipeline for functional validation and proof-of-concept exploitation, which were pursued in RL2. RL2 led to important discoveries of organotypic angiocrine EC functions, notably, we (i) were able to show that the spatial zonation of the murine placental vasculature is specified by epigenetic mechanisms, (ii) focused on the liver to identify and validate on the basis of complex spatiotemporal transcriptomic, proteomic and phosphoproteomic systems maps a functional crosstalk between Wnt signaling and Angiopoietin/Tie signaling, (iii) elucidated the molecular machinery in endothelial cells that translate biomechanical sensing mechanisms into spatial angiocrine signaling cues that control metabolic liver zonation and liver regeneration, (iv) deconvoluted the interactions of metastasizing tumor cells and endothelial cells on the systems single cell level to identify critical mechanisms through which endothelial cell control fate decisions of metastasizing tumor cells in the metastatic vascular niche, (v) identified a subpopulation of LPL-expressing intratumoral endothelial cells that govern T-cell-mediated regression of low immunogenic tumors by serving as non-canonically antigen presenting cells, (vi) identified epigenetic enhancer modifications that determine the transition of angiogenic to the quiescent endothelial state, and (vii) showed that the Apelin-Apelin receptor system acts as a critical regulator of vascular aging being downregulated during aging in mouse and man controlling the susceptibility towards metastatic colonization
The project has yielded groundbreaking molecular and mechanistic insight pushing the boundaries of existing knowledge and foundationally paving the way for novel research avenues. Related to developmental embryonic and postnatal adolescence vascular maturation mechanisms, we determined up to single cell resolution the transcriptional, epigenetic, and proteomic programs of vascular maturation and organotypic differentiation associated with the acquisition of vascular quiescence (in the placenta as well as in different organs). Related to adult maintenance mechanisms, we studied the functional consequences of different homeostatic and pathophysiologically relevant challenges (among others, biomechanical challenge, immunological challenge, immune challenge, primary and metastatic tumor challenge). Related to changes of vascular maturation and differentiation during aging, we performed groundbreaking mechanistic analyses into the process of vascular aging and identified tumor microenvironmental molecular pathways critically affecting the susceptibility of a primary tumor to age-dependently metastasize to a different organ. Collectively, the project has made major contributions towards advancing the field of vascular research from the simple study of vascular activation programs towards an appreciation of the complexity of the life cycle of a vasculature from developmental angiogenesis over adult quiescence and maintenance mechanisms towards molecular changes during aging that affect organismic aging and the course of age-related diseases. Collectively, the project has fulfilled its ambitious goals. Most of the results have been exploited by making them publicly available in the form of publications in highly ranked scientific journals. Some of discoveries have at the conclusion of the project not yet been communicated. They are in different stages of the review and revision process and will only become publicly available in the course of the next 12 to 24 months.