The convergence of haemodynamics, genomics, and endothelial structure in studies of the focal origin of atherosclerosis

Abstract

The completion of the Human Genome Project and ongoing sequencing of mouse, rat and other genomes has led to an explosion of genetics-related technologies that are finding their way into all areas of biological research; the field of biorheology is no exception. Here we outline how two disparate modern molecular techniques, microarray analyses of gene expression and real-time spatial imaging of living cell structures, are being utilized in studies of endothelial mechanotransduction associated with controlled shear stress in vitro and haemodynamics in vivo. We emphasize the value of such techniques as components of an integrated understanding of vascular rheology. In mechanotransduction, a systems approach is recommended that encompasses fluid dynamics, cell biomechanics, live cell imaging, and the biochemical, cell biology and molecular biology methods that now encompass genomics. Microarrays are a useful and powerful tool for such integration by identifying simultaneous changes in the expression of many genes associated with interconnecting mechanoresponsive cellular pathways.

Fig. 1

Regional, local, focal, and subcellular approaches to endothelial mechanotransduction. A decentralized model of biomechanical responses is proposed at the subcellular level in which spatially-constrained physical (structural) and biochemical elements are integrated. Candidate signaling locations include the luminal cell surface (A), the cytoskeleton (B), nuclear membrane (C), intercellular junctional proteins (D), and sites of cell adhesion (E). It is proposed (see text) that genomics-based analyses will provide insights into the structures and pathways linking these elements in the coordination of biomechanical signal transduction.

Fig. 2

A: Three-dimensional distribution of GFP-vimentin (intermediate filaments, IF) in confluent monolayers of living endothelial cells. Deconvolved optical sections at indicated heights above the coverslip (1.5, 3.5 and 5.5 μm, respectively) and a volume projection show that GFP-vimentin is distributed to the endogenous IF network in transiently expressing cells. Scale bar, 10 μm. B: Change in IF motion due to the onset of shear stress (12 dyn/cm²). The positions of IF in fluorescence optical sections were compared at consecutive time points under no-flow conditions (t₂, t₃), and before (t₃) and after (t₄) a step increase in flow. A correlation coefficient, ρ, measured the degree of overlap of images; ρ = 1 for perfect overlap (no movement), and ρ decreases for less overlap (increased IF movement). A significant decrease of ρ demonstrates the marked displacement of IF position associated with the flow step. Condensed from Helmke et al., Circ. Res. 86 (2000), 745–752 with permission.