Switching to external flows: perturbations of developing vasculature within chicken chorioallantoic membrane.

The impact of fluid flow shear stresses, generated by the movement of blood through vasculature, on the organization and maturation of vessels is widely recognized. Nevertheless, it remains uncertain whether external fluid flows outside of the vasculature in the surrounding tissue can similarly play a role in governing these processes. In this research, we introduce an innovative technique called superfusion-induced vascular steering (SIVS).

Surface Coating of Polyurethane Films with Gelatin, Aspirin and Heparin to Increase the Hemocompatibility of Artificial Vascular Grafts.

A hemocompatible substrate can offer a wonderful facility for nitric oxide (NO) production by vascular endothelial cells in reaction to the inflammation following injuries. NO inhibits platelet aggregation this is especially critical in small-diameter vessels. The substrate films were made of polyurethane (PU) in a casting process and after plasma treatments, their surface was chemically decorated with polyethylene glycol (PEG) 2000, gelatin, gelatin-aspirin, gelatin-heparin and gelatin-aspirin-heparin.

Spatiotemporally controlled, aptamers-mediated growth factor release locally manipulates microvasculature formation within engineered tissues.

Spatiotemporally controlled growth factor (GF) delivery is crucial for achieving functional vasculature within engineered tissues. However, conventional GF delivery systems show inability to recapitulate the dynamic and heterogeneous nature of developing tissue's biochemical microenvironment. Herein, an aptamer-based programmable GF delivery platform is described that harnesses dynamic affinity interactions for facilitating spatiotemporal control over vascular endothelial GF (VEGF) bioavailability within gelatin methacryloyl matrices.

Computational modeling of media flow through perfusion-based bioreactors for bone tissue engineering.

Bioreactor system has been used in bone tissue engineering in order to simulate dynamic nature of bone tissue environments. Perfusion bioreactors have been reported as the most efficient types of shear-loading bioreactor. Also, combination of forces, such as rotation plus perfusion, has been reported to enhance cell growth and osteogenic differentiation.

Regenerative Medicine Under the Control of 3D Scaffolds: Current State and Progress of Tissue Scaffolds.

Currently, combining stem cells (SCs) with biomaterial scaffolds provides a promising strategy for the future of biomedicine and regenerative medicine (RG). The cells need similar substrates of the extracellular matrix (ECM) for normal tissue development, which signifies the importance of three dimensional (3D) scaffolds to determine cell fate. Herein, the importance and positive contributions of corresponding 3D scaffolds on cell functions, including cell interactions, cell migrations, and nutrient delivery, are presented.

Bioreactor cultivation condition for engineered bone tissue: Effect of various bioreactor designs on extra cellular matrix synthesis.

Dynamic-based systems are bio-designed in order to mimic the micro-environments of the bone tissue. There is limited direct comparison between perfusion and perfusion-rotation forces in designing a bioreactor. Hence, in current study, we aimed to compare given bioreactors for bone regeneration.

Buccal Fat Pad as a Potential Source of Stem Cells for Bone Regeneration: A Literature Review.

Adipose tissues hold great promise in bone tissue engineering since they are available in large quantities as a waste material. The buccal fat pad (BFP) is a specialized adipose tissue that is easy to harvest and contains a rich blood supply, and its harvesting causes low complications for patients. This review focuses on the characteristics and osteogenic capability of stem cells derived from BFP as a valuable cell source for bone tissue engineering.

The stability evaluation of mesenchymal stem cells differentiation toward endothelial cells by chemical and mechanical stimulation.

Adipose-derived mesenchymal stem cells (ADSCs) are adult multipotent cells able to differentiate into several cell lineages. Vascular endothelial growth factor (VEGF) and the shear stress associated with blood flow are considered as the most important chemical and mechanical cues that play major roles in endothelial differentiation. However, the stability of endothelial-specific gene expression has not been completely addressed yet.

Sustained release of growth hormone and sodium nitrite from biomimetic collagen coating immobilized on silicone tubes improves endothelialization.

Biocompatibility of biomedical devices can be improved by endothelialization of blood-contacting parts mimicking the vascular endothelium's function. Improved endothelialization might be obtained by using biomimetic coatings that allow local sustained release of biologically active molecules, e.g.

Flow Preconditioning of Endothelial Cells on Collagen-Immobilized Silicone Fibers Enhances Cell Retention and Antithrombotic Function.

Stability and antithrombotic functionality of endothelial cells on silicone hollow fibers (SiHFs) are critical in the development of biohybrid artificial lungs. Here we aimed to enhance endothelial cell retention and anti-thrombotic function by low (12 dyn/cm , 24 h) fluid shear stress ("flow") preconditioning of endothelial cells seeded on collagen-immobilized SiHFs. The response of endothelial cells without preconditioning (48 h static culture) and with preconditioning (24 h static culture followed by 24 h flow preconditioning) on hollow fibers to high fluid shear stress (30 dyn/cm , 1 h) was assessed in a parallel-plate flow chamber.

Nanoliposomal Growth Hormone and Sodium Nitrite Release from Silicone Fibers Reduces Thrombus Formation Under Flow.

Biocompatibility of artificial lungs can be improved by endothelialization of hollow fibers. Bioavailability of growth-inducing and anti-thrombotic agents on the hollow fiber-blood interface inhibits thrombosis. We investigated if nanoliposomal growth-inducing growth hormone (nGH) and anti-thrombotic sodium nitrite (nNitrite) incorporation into collagen-coating on silicone hollow fibers improves blood biocompatibility by increasing endothelial cell growth and nitrite bioavailability under flow.

Biomimetic modification of silicone tubes using sodium nitrite-collagen immobilization accelerates endothelialization.

Biomimetic coatings to increase endothelialization of blood-contacting materials in biomedical devices are promising to improve the biocompatibility of these devices. Although a stable extracellular matrix protein coating on a biomaterial's surface is a prerequisite for endothelial cell attachment, it also stimulates platelet adhesion. Therefore, antithrombotic additives, such as nitric oxide donors, to a stable protein coating might lead to successful endothelialization of a material's surface.

Surface modification of silicone tubes by functional carboxyl and amine, but not peroxide groups followed by collagen immobilization improves endothelial cell stability and functionality.

Surface modification by functional groups promotes endothelialization in biohybrid artificial lungs, but whether it affects endothelial cell stability under fluid shear stress, and the release of anti-thrombotic factors, e.g. nitric oxide (NO), is unknown.

Applying shear stress to endothelial cells in a new perfusion chamber: hydrodynamic analysis.

Perfusion bioreactors have been proved to be an impartible part of vascular tissue engineering due to its broad range of applications as a means to distribute nutrients within porous scaffold along with providing appropriate physical and mechanical stimuli. To better understand the mechanical phenomena inside a bioreactor, computational fluid dynamics (CFD) was adopted followed by a validation technique. The fluid dynamics of the media inside the bioreactor was modeled using the Navier-Stokes equation for incompressible fluids while convection through the scaffold was described by Brinkman's extension of Darcy's law for porous media.

Nitric oxide secretion by endothelial cells in response to fluid shear stress, aspirin, and temperature.

Current vascular grafts have a high incidence of failure, especially in the grafts less than 6 mm in diameter, due to thrombus formation. Nitric oxide (NO) is released by endothelium and has some beneficial influences such as an antithrombotic effect. We hypothesized that applying different shear stress regiments and low temperature or aspirin would result in an increase in the amount of NO release from human umbilical vein endothelial cells (HUVECs) and decrease in platelet aggregation in the same manner as expected in vivo.

Engineering parameters in bioreactor's design: a critical aspect in tissue engineering.

Bioreactors are important inevitable part of any tissue engineering (TE) strategy as they aid the construction of three-dimensional functional tissues. Since the ultimate aim of a bioreactor is to create a biological product, the engineering parameters, for example, internal and external mass transfer, fluid velocity, shear stress, electrical current distribution, and so forth, are worth to be thoroughly investigated. The effects of such engineering parameters on biological cultures have been addressed in only a few preceding studies.