Nanoscale Patterning of Extracellular Matrix Alters Endothelial Function under Shear Stress

Abstract

The role of nanotopographical extracellular matrix (ECM) cues on vascular endothelial cell (EC) organization and function is not well-understood, despite the composition of nano- to micro-scale fibrillar ECMs within blood vessels. Instead, the predominant modulator of EC organization and function is traditionally thought to be hemodynamic shear stress, in which uniform shear stress induces parallel-alignment of ECs with anti-inflammatory function, whereas disturbed flow induce pro-inflammatory cells in disorganized configuration. Since shear stress acts on ECs by applying a mechanical force concomitant with inducing spatial patterning of the cells, we sought to decouple the effects of shear stress using parallel-aligned nanofibrillar collagen films that induce parallel EC alignment prior to stimulation with disturbed flow resulting from spatial wall shear stress gradients. Using real time live-cell imaging, we tracked the alignment, migration trajectories, proliferation, and anti-inflammatory behavior of ECs when they were cultured on parallel-aligned or randomly oriented nanofibrillar films. Intriguingly, ECs cultured on aligned nanofibrillar films remained well-aligned and migrated predominantly along the direction of aligned nanofibrils, despite exposure to shear stress orthogonal to the direction of the aligned nanofibrils. Furthermore, in stark contrast to ECs cultured on randomly oriented films, ECs on aligned nanofibrillar films exposed to disturbed flow had significantly reduced inflammation and proliferation, while maintaining intact intercellular junctions. This work reveals fundamental insights into the importance of nanoscale ECM interactions in the maintenance of endothelial function. Importantly, it provides new insight into how ECs respond to opposing cues derived from nanotopography and mechanical shear force, and has strong implications in the design of polymeric conduits and bioengineered tissues.

Aligned nanofibrillar collagen scaffolds – Guiding lymphangiogenesis for treatment of acquired lymphedema

“…In particular, the scaffold has been extensively tested and optimized in the murine hind limb model as a mean to induce directional angiogenesis and arteriogenesis [2, 3]. The aligned nanofibrillar scaffold preserves endothelial cell phenotype even in ischemic conditions and provides the substrate for endothelial cell alignment and migration along the collagen fibrils [3, 38, 39]. The current results suggest that BioBridge scaffolds may provide a potent stimulus to lymphatic regeneration.…”

Endothelial Cell Mechanotransduction in the Dynamic Vascular Environment

“…CD31 junctional thickness and continuity were similarly enhanced by topographical alignment (Figure 3). [74] Given the influence of cell shape in directing endothelial growth, death, morphogenesis, and function, spatial patterning warrants further study. The limited present understanding of topographical cues has already seen direct translation to tissue engineering applications, which will be covered in a later section.…”

“…Aligned scaffolds promote CD31 junctional thickness (D), cytoskeletal organization and elongation along the direction of anisotropy (E), as shown by merged images (F). Adapted with permission from [74] . Copyright 2016 American Chemical Society.…”

Gradient fluid shear stress regulates migration of osteoclast precursors

“…For example, flow stimulation with different chemical concentration gradients showed obvious effect on the migration of nerve cells, endothelial cells, or cancer cells by using microfluidic devices [5,6]. Another study showed that when FSS was exerted on endothelial cells cultured on nanofiber membranes, the cells tended to migrate along the well-aligned nanofiber direction to maintain the integrity of intercellular connections [7]. In some cases, however, cells may display unexpected behavior under flow stimulation.…”