Biology subjects

Ramkhelawon, B.

Publications and source records attributed to Ramkhelawon, B..

4 recordsLinked to original sources

bioRxiv2024

Resolving the design principles that control postnatal vascular growth and scaling

After birth, tissues grow continuously until reaching adult size, with each organ exhibiting unique cellular dynamics, growth patterns, and (stem or non-stem) cell sources. Using a suite of experimental and computational multiscale approaches, we found that aortic expansion is guided by specific biological principles and scales with the vertebral column rather than animal body weight. Expansion proceeds via two distinct waves of arterial cell proliferation along blood flow that are spatially stochastic, yet temporally coordinated. Each wave exhibits unique cell cycle kinetics and properties, with the first wave exhibiting cell cycle durations as fast as 6 hours. Single-cell RNA sequencing showed changes in fatty acid metabolism concomitant with an increase in cell size. Mathematical modeling and experiments indicated endothelial cell extrusion is essential for homeostatic aortic growth and balancing excess proliferation. In a genetic model of achondroplasia, the aorta achieves proper scaling through enhanced cell extrusion while maintaining normal proliferation dynamics. Collectively, these results provide a blueprint of the principles that orchestrate aortic growth which depends entirely on differentiated cell proliferation rather than resident stem cells.

developmental biology↗

bioRxiv2024

Integrated forward and reverse degradomics uncovers the proteolytic landscape of aortic aneurysms and the roles of MMP9 and mast cell chymase

BackgroundDysregulated proteolysis is implicated in thoracic (TAA) and abdominal aortic aneurysm (AAA) pathogenesis, but the proteolytic landscapes (degradomes) of aneurysmal and normal aorta, and contributions of individual proteases remain undefined. Here, a proteome-wide approach was used to uncover TAA and AAA degradomes, compare them quantitatively and define the specific role in aortic remodeling of two proteases consistently identified in the aneurysms, mast cell chymase (CMA1) and matrix metalloprotease 9 (MMP9). MethodsThe mass spectrometry-based N-terminomics strategy Terminal Amine Isotopic Labeling of Substrates (TAILS) was applied to Marfan syndrome TAAs (n=5), AAAs (n=16) and corresponding non-diseased aorta (TAs, n=4, and AAs, n=8) as a forward degradomics application, i.e., to define substrate and protease degradomes, and 8-plex iTRAQ-TAILS was used for quantitative comparison. Cleavage sites of CMA1 and MMP9 were sought by reverse degradomics, i.e., digestion of aortic proteins with these proteases, followed by 6-plex iTRAQ-TAILS. CMA1 and MMP9 proteolysis of biglycan was investigated using Amino-Terminal Oriented Mass spectrometry of Substrates (ATOMS). ResultsWe experimentally annotated 16,923 proteolytically derived peptides (substrate degradome) and 90 proteases (protease degradome) in the aorta. Quantitative substrate degradome comparisons identified specific differentially modulated pathways and networks in TAA and AAA. Reverse degradomics elucidated > 300 CMA1 and MMP9 substrate cleavage sites, of which, many, including orthogonally validated biglycan cleavage, occurred in the disease degradomes. ConclusionsUnbiased, proteome-wide forward degradomics of the aortic wall from TAA, AAA and non-diseased tissue generated the first systems biology view of vascular wall breakdown and public resource for the hitherto occult proteolytic landscape, demonstrating widespread extracellular matrix remodeling. The findings provide insights on aortic aneurysm pathways and potential disease biomarkers. Mapping of specific contributions of CMA1 and MMP9 on the aortic forward substrate degradome using reverse degradomics provides a strategy for defining the activities of all proteases involved in aortic disease.

biochemistry↗

bioRxiv2024

Chronic Pod-Mod E-Cigarette Aerosol Exposure Induces Aortic Dysfunction in Hypercholesterolemic Mice: Role of Oxidative Stress and Inflammation

ObjectiveElectronic (e-)cigarettes are the most used tobacco product amongst youth, and adult smokers favor e-cigarettes over approved cessations aids. Despite the lower perceived harm of vaping compared to smoking, inhalation of e-cigarette aerosol elicits cardiovascular responses that may lead to permanent injury when repeated over time. We thus aimed to infer the long-term outcomes of vaping on the function and structure of the aorta and shed light on the underlying cellular and molecular mechanisms. Approach and ResultsWe exposed female hypercholesterolemic mice to either pod-mod e-cigarette aerosol or room air daily for 24 weeks. Chronic inhalation of e-cigarette aerosol triggered accumulation of inflam-matory signals systemically and within aortic tissues, as well as T lymphocyte accrual in the aortic wall. Reduced eNOS expression and enhanced ROS production following eNOS uncoupling and NADPH oxi-dase activation curbed nitric oxide availability in the aorta of mice exposed to e-cigarette aerosol, impairing the endothelium-dependent vasodilatation that regulates blood flow distribution. Inhalation of e-cigarette aerosol thickened and stiffened aortic tissues via collagen deposition and remodeling, hindering the storage of elastic energy and limiting the cyclic distensibility that enables the aorta to function as a pressure reservoir. These effects combined contributed to raising systolic and pulse pressure above control levels. ConclusionsChronic inhalation of aerosol from pod-mod e-cigarettes promotes oxidative stress, inflammation, and fibrosis within aortic tissues, significantly impairing passive and vasoactive aortic functions. This evidence provides new insights on the biological processes that increase the risk for adverse cardio-vascular events as a result of pod-mod e-cigarette vaping.

bioengineering↗

bioRxiv2022

Mapping the unicellular transcriptome of the ascending thoracic aorta to changes in mechanosensing and mechanoadaptation during aging

Aortic stiffening is an inevitable manifestation of chronological aging, yet the mechano-molecular programs that orchestrate region- and layer-specific adaptations along the length and through the wall of the aorta are incompletely defined. Here, we show that the decline in passive cyclic distensibility is more pronounced in the ascending thoracic (ATA) compared to distal segments of the aorta and that tissues in both the medial and adventitial compartments of the ATA stiffen during aging. Single-cell RNA sequencing of aged ATA tissues reveals altered cellular senescence, remodeling, and inflammatory responses accompanied by enrichment of T-lymphocytes and rarefaction of vascular smooth muscle cells, compared to young samples. T-lymphocytes accumulate in the adventitia and likely promote fibrosis, while activation of mechanosensitive piezo-1 enhances medial vasoconstriction. These results portray the immuno-mechanical aging of the ATA as a process that culminates in a stiffer conduit permissive to the accrual of multi-gerogenic signals priming to disease development.

bioengineering↗