The topography of microstructured surfaces differently affects fibrillin deposition by blood and lymphatic endothelial cells in culture

The Effects of Biomimetic Surface Topography on Vascular Cells: Implications for Vascular Conduits

Cardiovascular diseases (CVDs) are the leading cause of mortality worldwide and represent a pressing clinical need. Vascular occlusions are the predominant cause of CVD and necessitate surgical interventions such as bypass graft surgery to replace the damaged or obstructed blood vessel with a synthetic conduit. Synthetic small-diameter vascular grafts (sSDVGs) are desired to bypass blood vessels with an inner diameter <6 mm yet have limited use due to unacceptable patency rates. The incorporation of biophysical cues such as topography onto the sSDVG biointerface can be used to mimic the cellular microenvironment and improve outcomes. In this review, the utility of surface topography in sSDVG design is discussed. First, the primary challenges that sSDVGs face and the rationale for utilizing biomimetic topography are introduced. The current literature surrounding the effects of topographical cues on vascular cell behavior in vitro is reviewed, providing insight into which features are optimal for application in sSDVGs. The results of studies that have utilized topographically-enhanced sSDVGs in vivo are evaluated. Current challenges and barriers to clinical translation are discussed. Based on the wealth of evidence detailed here, substrate topography offers enormous potential to improve the outcome of sSDVGs and provide therapeutic solutions for CVDs.

Dynamic interplay between breast cancer cells and normal endothelium mediates the expression of matrix macromolecules, proteasome activity and functional properties of endothelial cells

BACKGROUND

Breast cancer-endothelium interactions provide regulatory signals facilitating tumor progression. The endothelial cells have so far been mainly viewed in the context of tumor perfusion and relatively little is known regarding the effects of such paracrine interactions on the expression of extracellular matrix (ECM), proteasome activity and properties of endothelial cells.

METHODS

To address the effects of breast cancer cell (BCC) lines MDA-MB-231 and MCF-7 on the endothelial cells, two cell culture models were utilized; one involves endothelial cell culture in the presence of BCCs-derived conditioned media (CM) and the other co-culture of both cell populations in a Transwell system. Real-time PCR was utilized to evaluate gene expression, an immunofluorescence assay for proteasome activity, and functional assays (migration, adhesion and invasion) and immunofluorescence microscopy for cell integrity and properties.

RESULTS

BCC-CM decreases the cell migration of HUVEC. Adhesion and invasion of BCCs are favored by HUVEC and HUVEC-CM. HA levels and the expression of CD44 and HA synthase-2 by HUVEC are substantially upregulated in both cell culture approaches. Adhesion molecules, ICAM-1 and VCAM-1, are also highly upregulated, whereas MT1-MMP and MMP-2 expressions are significantly downregulated in both culture systems. Notably, the expression and activity of the proteasome β5 subunit are increased, especially by the action of MDA-MB-231-CM on HUVEC.

CONCLUSIONS AND GENERAL SIGNIFICANCE

BCCs significantly alter the expression of matrix macromolecules, proteasome activity and functional properties of endothelial cells. Deep understanding of such paracrine interactions will help to design novel drugs targeting breast cancer at the ECM level. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.

Impact of electrospun conduit fiber diameter and enclosing pouch pore size on vascular constructs grown within rat peritoneal cavities

The generation of vascular grafts by recruiting autologous cells within the peritoneal cavity has shown promise. However, the microenvironment affects cell differentiation and elastic matrix production. Therefore, this study determined the impact of systematic changes in the average fiber diameter of electrospun poly(ɛ-caprolactone) conduits, and the pore size of pouches used to enclose the conduits, on recruited cells. After 2 weeks in the peritoneal cavity, fibrous capsules formed containing macrophages, α-smooth muscle actin (α-SMA)(+) and SM22α(+) myofibroblastic or smooth muscle like-cells, and what appeared to be mesothelial cells on the outer surfaces. These cells infiltrated and deposited matrix (e.g., collagen, hyaluoronan, and limited elastin) within conduit walls. Constructs enclosed within the largest pore pouches exhibited significantly better tissue generation responses (e.g., better cell infiltration, elongation, and matrix deposition). Additionally, the healing response was impacted by the conduit average fiber diameter, and consequently, the effective pore diameter, with the largest diameter fibers promoting the most positive healing response (e.g., greater total cellularity, extracellular matrix deposition, and α-SMA(+) cells). Six weeks post-intra-aortal grafting, constructs were occluded, but significant remodeling also occurred in the arterial microenvironment. Overall, these results demonstrate the importance of microenvironmental cues on recruited peritoneal cells and the necessity of developing strategies to further improve elastic matrix synthesis.

Rapid fabrication of complex 3D extracellular microenvironments by dynamic optical projection stereolithography

The topographic features of the extracelluar matrix (ECM) lay the foundation for cellular behavior. A novel biofabrication method using a digital-mirror device (DMD), called dynamic optical projection stereolithography (DOPsL) is demonstrated. This robust and versatile platform can generate complex biomimetic scaffolds within seconds. Such 3D scaffolds have promising potentials for studying cell interactions with microenvironments in vitro and in vivo.

Tissue engineering and regenerative strategies to replicate biocomplexity of vascular elastic matrix assembly

Cardiovascular tissues exhibit architecturally complex extracellular matrices, of which the elastic matrix forms a major component. The elastic matrix critically maintains native structural configurations of vascular tissues, determines their ability to recoil after stretch, and regulates cell signaling pathways involved in morphogenesis, injury response, and inflammation via biomechanical transduction. The ability to tissue engineer vascular replacements that incorporate elastic matrix superstructures unique to cardiac and vascular tissues is thus important to maintaining vascular homeostasis. However, the vascular elastic matrix is particularly difficult to tissue engineer due to the inherently poor ability of adult vascular cells to synthesize elastin precursors and organize them into mature structures in a manner that replicates the biocomplexity of elastic matrix assembly during development. This review discusses current tissue engineering materials (e.g., growth factors and scaffolds) and methods (e.g., dynamic stretch and contact guidance) used to promote cellular synthesis and assembly of elastic matrix superstructures, and the limitations of these approaches when applied to smooth muscle cells, the primary elastin-generating cell type in vascular tissues. The potential application of these methods for in situ regeneration of disrupted elastic matrix at sites of proteolytic vascular disease (e.g., abdominal aortic aneurysms) is also discussed. Finally, the review describes the potential utility of alternative cell types to elastic tissue engineering and regenerative matrix repair. Future progress in the field is contingent on developing a thorough understanding of developmental elastogenesis and then mimicking the spatiotemporal changes in the cellular microenvironment that occur during that phase. This will enable us to tissue engineer clinically applicable elastic vascular tissue replacements and to develop elastogenic therapies to restore homeostasis in de-elasticized vessels.

Spatial arrangement of polycaprolactone/collagen nanofiber scaffolds regulates the wound healing related behaviors of human adipose stromal cells

A sufficient cell source and minimal invasiveness in obtaining human adipose stromal cells (hASCs) hold great promise for their utilization in wound repair. However, little is known about how cell-residing microenvironments regulate the cellular response. In this study we explored the effects of polycaprolactone (PCL)/collagen nanofibers with distinct spatial arrangements (aligned and random) on phenotypic expression of hASCs in vitro. Elongated cell morphology, higher proliferation, and faster migration rate were observed for hASCs cultured on the aligned nanofibers, showing that hASCs could detect the nanofiber spatial arrangement and then distinctively respond. This study on the expression of extracellular matrix (ECM) related genes in hASCs revealed higher synthesis capacity for critical ECM molecules including tropoelastin, collagen I, and matrix metalloproteinase (MMP)-1 on the aligned nanofibers. Integrins α(5), β(1), β(3), β(6,) and transforming growth factor (TGF)-β(1) were differentially regulated by PCL/collagen nanofiber arrangements. Our results indicate that fiber orientation-induced phenotypic change of hASCs may be regulated by integrins and TGF-β signaling synergistically. These findings demonstrate the potential application of hASCs and aligned PCL/collagen nanofibers for accelerated wound repair.

Biomaterial guides for lymphatic endothelial cell alignment and migration

Axillary dissection during breast cancer surgery produces extensive lymphatic vessel damage that often leads to lifelong secondary lymphedema of the arm. We have developed a biodegradable material conduit for lymphatic vessel reconstruction where fibers electrospun along the conduit lumen promote endothelial cell alignment and migration in vitro. The diameter and density of the electrospun fibers were optimized for cell migration and direction on two-dimensional substrates by seeding human lymphatic endothelial cells (LECs) onto aligned fibers of varying diameters and densities, randomly oriented fibers, and film substrates with no fibers. We found that LECs became aligned in the fiber direction, with cells seeded on the randomly oriented fibers becoming oriented in random directions, whereas cells seeded on the highly aligned fibers became highly aligned. Cell migration was dependent upon fiber alignment and density, with optimal migration found on 1300 nm diameter aligned fibers of low density. Blood endothelial cells seeded on the fibers exhibited similar behavior as the LECs. Fiber alignment was preserved upon rolling the two-dimensional substrate into the tubular geometry of a lymphatic vessel. The data suggest that aligned electrospun fibers may promote endothelial migration across the conduit in a manner that is independent of lymphatic growth factors.

Functional surfaces for high-resolution analysis of cancer cell interactions on exogenous hyaluronic acid

Hyaluronic acid, a nonsulfated, linear glycosaminoglycan, is ubiquitously distributed in the extracellular matrix and is known to facilitate tumor progression by enhancing invasion, growth, and angiogenesis. Native HA has been attached to substrates to create patterned surfaces resistant to cell adhesion, and has been utilized in a variety of cell adhesion studies using either non covalently bound layers patterned by soft lithography or related methods. We use a new approach to study cell interactions with HA-presenting regions, by covalently linking HA adjacent to PEG-ylated regions, which resist cell adhesion. Colon and breast cancer cells seeded on the patterned HA surfaces adhere preferentially on HA-presenting regions and proliferate there. Furthermore, we demonstrate that cell adhesion is inhibited with the blocking of HA receptor, CD44, and that cellular adhesive processes, through protrusions spreading onto the HA surface, enhance spreading and movement outside the HA-presenting regions. Overall, this approach allows high-resolution analysis of cancer cell attachment, growth, and migration on exogenous native HA.

Vascular regeneration: engineering the stem cell microenvironment

Vascular diseases are a major threat to human health nowadays. While current treatments can cure some vascular diseases, their beneficial effects are only temporary; vascular regeneration holds the promise of permanent, effective treatments for many vascular diseases. Stem cells and endothelial progenitor cells can differentiate into vascular lineages and therefore have the potential to repair vascular systems. However, engineering appropriate microenvironments that will allow cell maturation and delivery remains the major challenge to the successful implementation of this treatment. This review introduces the cells that are being studied for vascular differentiation and regeneration; we then consider recent approaches to engineering microenvironments, including proper signaling cues and biodegradable scaffolds that will guide the development of these cells into vessels suitable for cell-based vascular therapy.