Chondrocyte seeded scaffolds were cultured in an ultrasound (US) assisted bioreactor,

Chondrocyte seeded scaffolds were cultured in an ultrasound (US) assisted bioreactor, which supplied the cells with acoustic energy around resonance frequencies (~5. CS and CSB scaffolds, but COL2A1/COL1A1 ratios were significantly lower compared to BM scaffolds. Expression of SOX9 was also elevated under US and paralleled the ratio of COL2A1/COL1A1. As an original IL17RA contribution, a simplified mathematical model based on Biot theory was developed to understand the propagation of the incident US wave through the scaffolds and the model analysis was connected to cellular responses. Scaffold architecture influenced the distribution of US field; with the US field being the least attenuated in BM scaffolds, thus coupling more mechanical energy into cells, leading to increased cellular activity. 1. INTRODUCTION The field of tissue engineering promises to yield substitutes that could potentially overcome the limited availability of native explants [1C3]. For example, tissue designed neo-cartilage with appropriate biomechanical properties holds promise both for graft applications and as a model system for controlled studies of chondrogenesis [4, 5]. Research in the engineering aspects of cartilage-tissue equivalents typically involves the fabrication of scaffold, design and evaluation of appropriate bioreactors and controlling stem-cell fate to enable an alternate source of cells [6, 7]. Currently, all aspects of the tissue engineering process are undergoing intensive research, starting with the choice of cell source, cell selection, in vitro cell growth, scaffold design, cell seeding and bioreactor cultivation and conditioning [8C11]. Typically, many of these aspects are inter-related. For example, while bioreactors are mainly designed to alleviate mass-transfer limitations, they also provide mechanical conditioning to the developing tissue and impact cell colonization depending upon the scaffold microstructure [12C16]. The long-term research objective is to achieve uniform cell distribution and cell differentiation throughout the scaffold volume so that a strong tissue, both biochemically and biomechanically, may be generated. To obtain uniform cell colonization and cellular in-growth into the thickness of the scaffold over the duration of culture, scaffold designs offering highly interconnected and accessible pore networks are often fabricated. Most of the scaffolds used in current tissue engineering applications possess pore diameters ranging from 50C500 m, with a total porosity of 48C95% [17]. Other features indicative of successful cell infiltration include pore interconnectivity/tortuosity and scaffold buy Loxistatin Acid permeability. We note that reduced pore connectivity may indicate closed pores, thus limiting the route for colonization with duration of culture. Factors that impact cell colonization other than the structural features of scaffold are: (1) the cell seeding method employed which controls the initial spatial distribution of cells and (2) mechanical conditioning of the cell-scaffold construct during culture [11, 18, 19]. In static surface seeding method; where the cells are first evenly layered on top of the scaffold and cultured, variable results were obtained and many studies reporting non-uniform cellular distributions [20]. To better exploit the theory of convective transport of cells in scaffold seeding, perfusion of cell suspensions through porous polymeric foams in flow bioreactor or under orbital shaking and centrifugation was investigated [18, 21C23]. buy Loxistatin Acid Variable results have been achieved with dynamic seeding; orbital shaking has been noted to yield highest buy Loxistatin Acid spatial distribution of cells in the construct at 7 days in culture [21]. In general, static or dynamic cell seeding methods used in conjunction with perfusion bioreactors yielded a uniform initial cell distribution. Conditioning of cell-seeded constructs during culture offers several important advantages compared to static culture systems, such as enhanced mass transfer of O2 and nutrients by convective fluid flow, the ability to provide mechanical forces influencing tissue development and better control over culture conditions [24]. The flow of medium through the scaffold porosity benefits cell differentiation by enhancing nutrient transport to the scaffold interior and by providing mechanical stimulation to cells in the form of fluid shear [25, 26]. Our previous work has shown that the stimulation buy Loxistatin Acid of in vitro chondrocyte cultures by low intensity continuous US can modulate the signal-transduction pathways leading to chondrocyte-specific gene regulation or RNA translation of a protein product, or both [27, 28]. Thus, to capitalize around the positive bioeffects of low intensity continuous US and apply them to.