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There is a great deal of demand for the construction of transplantable liver grafts. Over the last decade, decellularization techniques have been developed to construct whole liver tissue grafts as potential biomaterials. However, the lack of intact vascular networks, especially sinusoids, in recellularized liver scaffolds leads to hemorrhage and thrombosis after transplantation, which is a major obstacle to the development of transplantable liver grafts. In the present study, we hypothesized that both mechanical (e.g., fluid shear stress) and chemical factors (e.g., fibronectin coating) can enhance the formation of hierarchical vascular networks including sinusoid-scale microvessels. We demonstrated that perfusion culture promoted formation of sinusoid-scale microvessels in recellularized liver scaffolds, which was not observed in static culture. In particular, perfusion culture at 4.7 ml/min promoted the formation of sinusoid-scale microvessels compared to perfusion culture at 2.4 and 9.4 ml/min. In addition, well-aligned endothelium was observed in perfusion culture, suggesting that endothelial cells sensed the flow-induced shear stress. Moreover, fibronectin coating of decellularized liver scaffolds enhanced the formation of sinusoid-scale microvessels in perfusion culture at 4.7 ml/min. This study represents a critical step in the development of functional recellularized liver scaffolds, which can be used not only for transplantation but also for drug screening and disease-modeling studies. Decellularized liver scaffolds are promising biomaterials that allow production of large-scale tissue-engineered liver grafts. However, it is difficult to maintain recellularized liver grafts after transplantation due to hemorrhage and thrombosis. To overcome this obstacle, construction of an intact vascular network including sinusoid-scale microvessels is essential. In the present study, we succeeded in constructing sinusoid-scale microvessels in decellularized liver scaffolds via a combination of perfusion culture and surface coating. We further confirmed that endothelial cells in decellularized liver scaffolds responded to flow-derived mechanical stress by aligning actin filaments. Our strategy to construct sinusoid-scale microvessels is critical for the development of intact vascular networks, and addresses the limitations of recellularized liver scaffolds after transplantation. [ABSTRACT FROM AUTHOR]

For a high production rate of microalgae, a high-cell-density culture is an effective strategy for reducing the light intensity per dry weight in the culture to avoid photoinhibition under high light conditions. However, under high cell density microalgae are exposed to nutrient-deficient conditions, resulting in a reduced biomass production rate. To enhance the production rate of high-value bioactives such as fucoxanthin and eicosatetraenoic acid (EPA) by the diatom Chaetoceros gracilis , a perfusion culture was operated at harvesting rates of 10–40 % under light intensities of 300–2000 μmol m−2 s−1. At a harvesting rate of 20 % under a high light intensity of 2000 μmol m−2 s−1, the dry weight increased, and the areal productivity reached 15.6 ± 1.3 g-dry weight (dw) m−2 d−1, which is comparable to the maximum value previously reported in diatoms. The high biomass production, even at a low harvesting rate of 20 %, could result from sufficient nutrient supply by perfusion culture. At a harvesting rate of 20 %, the EPA areal productivity achieved 183 mg-dw m−2 d−1 even under 2000 μmol m−2 s−1 due to the increase in the dry weight using the perfusion culture. However, the fucoxanthin content decreased under 2000 μmol m−2 s−1. A strong relationship was observed between the specific light intensity per dry weight and fucoxanthin content in C. gracilis. This relationship indicates that the fucoxanthin content does not increase unless the specific light intensity per dry weight is adjusted below 20 μmol g-dw−1 s−1. Thus, perfusion culture proved to be useful to control the biomass-specific light intensity for the effective production of EPA and fucoxanthin in C. gracilis under high light conditions expected for outdoor culture. 8Marine diatom Chaetoceros gracilis was cultivated in perfusion culture. • Areal production rate reached 15.6 ± 1.3 g-dw m−2 d−1 under 2000 μmol m−2 s−1. • EPA production rate achieved 183 mg m−2 d−1 even under 2000 μmol m−2 s−1. • There was a correlation between specific light intensity and fucoxanthin content. • Fucoxanthin increased only when specific light is adjusted below 20 μmol g-dw−1 s−1. [ABSTRACT FROM AUTHOR]

In this study, we present a novel approach of expanding Adipose derived hMSCs (human Mesenchymal Stem Cells) seeded on 3D printed Poly-Styrene (PS) scaffolds within a perfusion based cell expansion bioreactor. 3D printed PS scaffolds inoculated with adipose derived hMSCs were cultured statically for 9 days in 2D for assuring the viability and proliferation expansion of hMSCs on PS scaffolds. Thereafter, a batch of pre-seeded scaffolds were dynamically cultured inside a perfusion based bioreactor system for 8 days to assess the expansion of hMSCs on the PS scaffolds. As compared to static 3D culture (control), the 3D perfusion based system resulted in comparable fold-expansion and viability. Osteogenic and Adipogenic differentiation potential of the harvested cells were evaluated to assess if the stem cells retained their stem cell properties at the end of the expansion step. [ABSTRACT FROM AUTHOR]

Cell-based assays are widely used in the various stages of drug discovery. Advances in microfluidic systems over the past two decades have enabled them to become a powerful tool for cell-based assays to achieve both reliability and high throughput. The interface between the micro-world and macro-world is important in industrial assay processes. Therefore, microfluidic cell-based assays using pressure-driven liquid handling are an ideal platform for integrated assays. The aim of this article is to review recent advancements in microfluidic cell-based assays focusing on a pressure-driven perfusion culture device. Here, we review the development of microfluidic cell-based assay devices and discuss the techniques involved in designing a microfluidic network, device fabrication, liquid and cell manipulation, and detection schemes for pressure-driven perfusion culture devices. Finally, we describe recent progress in semiautomatic and reliable pressure-driven microfluidic cell-based assays. [ABSTRACT FROM PUBLISHER]

Abstract: In an effort to engineer capillary-like networks in vitro, different cultivation methods were compared. Five small-diameter tube-like constructs (‘vessel equivalents’) were fabricated from porcine gelatin scaffolds and seeded with human adipose tissue stromal cells and umbilical vein endothelial cells. After initial growth, the vessel equivalents were divided. One segment was exposed to pulsatile perfusion and the other was kept in rotating culture. Specimens harvested at the start of the experiments and after 16 days of rotation or perfusion were compared histomorphometrically with respect to capillary-like network formation in the vessel wall. Most capillary-like structures were found in the luminal portion of perfused vessel equivalents. Maturation of these capillary-like structures ascertained by recruitment of α-actin-positive cells also reached the highest degree in the luminal portion of perfused specimens. Perfused specimens showed significantly less apoptosis. Pulsatile perfusion promotes the development and maturation of a capillary-like network in this in-vitro approach. [Copyright &y& Elsevier]