Adherent cell

The cells which form a monolayer on the dish or ask need to be released from the substratum into suspension in order to be 

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The influence of mechanical forces on cell viability is of great importance when growing the cells in agitated systems. By far the greatest amount of work reported in the literature has been done on suspension cells but adherent cells also experience shear forces not only in bioreactors also in vivo. Therefore, most research has be done on endothelial cells but studies exists done on non-endothelial cells. The influence of shear forces on cell growth, morphology and productivity will be discussed as well as possibilities of making the cells more resistant. 

Keywords. Adherent cells. Chemical stress. Shear stress. Growth inhibition. Stress protection... 

Concerning adherent cells there are few studies in the literature. Some of them deal with the influence of stirrer speed on microcarrier cultures. Most studies using defined forces are from medical research. These studies, as well as those with production cells, use different types of exposure systems based on the parallel plate theory. They investigate the influence of stress on cell morphology and viability which is most important for arteriosclerosis research. 

Two different concepts are described in the literature for investigating the influence of shear stress on adherent cells Microcarrier cultures in stirred reactors and defined stress levels in flow chambers. 

Tablet. Summary of the main literature on the influence of shear forces on adherent cells ...

The overall conclusion is that there is already some data available on the influence of stress on adherent cells but there is still important data missing to understand the behavior of adherent cells in bioreactors. 

In this volume not all stress types are treated. Various aspects have been reviewed recently by various authors e.g. The effects of oxygen on recombinant protein expression by Konz et al. [2]. The Mechanisms by which bacterial cells respond to pH was considered in a Symposium in 1999 [3] and solvent effects were reviewed by de Bont in the article Solvent-tolerant bacteria in biocatalysis [4]. Therefore, these aspects are not considered in this volume. Influence of fluid dynamical stresses on micro-organism, animal and plant cells are in center of interest in this volume. In chapter 2, H.-J. Henzler discusses the quantitative evaluation of fluid dynamical stresses in various type of reactors with different methods based on investigations performed on laboratory an pilot plant scales. S. S. Yim and A. Shamlou give a general review on the effects of fluid dynamical and mechanical stresses on micro-organisms and bio-polymers in chapter 3. G. Ketzmer describes the effects of shear stress on adherent cells in chapter 4. Finally, in chapter 5, P. Kieran considers the influence of stress on plant cells. 

Cells in vivo exist either attached to a surface or free in suspension. Adherent cell lines originate from cells of solid tissue. Breast carcinoma cell lines (such as MCF7, T47D, and SK-BR-3) are adherent cultures, and these cells are grown on the surface of plastic flasks that have been treated to facilitate adhesion (see Fig. 6.2). Suspension culture cell lines originate from cells that exist in suspension, such as those cells present in the blood and the lymphatic system (see Fig. 6.3). 

When a cell suspension is applied to a surface, the events that occur can be conceptually classified into three stages (1) a cell approaches the surface, (2) the cell attaches to the surface, and (3) the cell adheres, and thus, spreads out on the surface. Most studies of cell adhesion on artificial materials measure the number of adherent cells, the cell morphology, and changes in protein expression. To gain more detailed insight into the biophysical mechanism of cell adhesion requires... 

TIRFM was used for time-lapse observations of initial cell adhesion to SAMs with different surface functionalities (Fig. 2). After 10 min of plating a suspension of human umbilical vein endothelial cells (HUVECs), a few bright spots were observed on SAMs with COOH and NH2 functionalities this indicated cell adherence. The number of bright spots increased and the spot areas enlarged with incubation time, indicating that HUVECs adhered and spread well on COOH-SAM and NH2-SAM surfaces. Quantitative analysis of the number of adherent cells and cell adhesion areas... 

Fig. 3 Relationship between water contact angles on mixed SAMs and the number of adherent cells. HUVECs (open circles) and HeLa cells (filled circles) were allowed to adhere for 1 h. The averages ( SEM) of five experiments are shown [21]...

Fig. 4 The effect of proteins on cell adhesion, (a) Kretschmann configuration for SPR. (b) Reflectance (R) as a function of incident angle (9), before (black) and after (red) the adsorption of substances, (c) Left. Time course of SPR angle shift during exposure to culture medium supplemented with 2% FBS (solid line) and the fraction of adherent cells determined by TIRFM (circles) on NH2-SAM. The dashed line is a manual fit to the symbols, included simply as a guide [42]. Right The concentrations of serum proteins in FBS...

Figure 4c shows one example of the time course of an SPR angle shift during exposure of a NH2-SAM to culture medium supplemented with 2% fetal bovine serum (FBS). It also includes the time course of the fraction of adherent cells on the same surface determined by TIRFM observation (Fig. 2). The SPR angle shift rapidly increased, and then leveled off within a few minutes. Cells adhered much more slowly than proteins. Those results indicated that serum proteins in a medium rapidly adsorbed to the surface then, cells interacted with the adsorbed protein layer, as shown schematically in Fig. 5.

Eichel-Streiber C, Warfolomeow I, Knautz D, Sauerborn M, Hadding U Morphological changes in adherent cells induced by Clostridium difficile toxins. Biochem Soc Trans 1991 19 1154-1160. 

Adhesion molecules are indispensable components of nervous tissue. They adhere cell membranes to each other with varying degrees of strength and translate adhesion into cellular responses via signal-transduction pathways (see, for example, [45]). The major classes of adhesion molecules, the integrins, IgCAMs and cadherins, act cooperatively [46] and in concert to coordinate brain development and maturation and, in adulthood, to maintain the normal tissue architecture. 

Near, R., et. al., Regulation of preB cell apoptosis by aryl hydrocarbon/transcription factor-expressing stromal/adherent cells, Proc. Soc. Exp. Biol. Med., 221, 242, 1999. 

Ullrich, S. E., Mechanism involved in the systemic suppression of antigen-presenting cell function by UV irradiation Keratinocyte-derived IL-10 modulates antigen-presenting cell function of splenic adherent cells, J. Immunol. 152, 3410-3416, 1994. 

The principal difference between adsorbed and solid substrates is that the latter are adsorbed to molecules of their own kind. With respect to their bioavailability, multilayer-sorbed molecules should behave like a solid substrate. A calculation shows that the direct uptake of truly adsorbed molecules is probably neither advantageous to bacteria nor can it be shown experimentally. Cells of the dibenzofuran-degrading Sphingomonas sp. HH19k consume at maximum 100 000 molecules per second [14], Assuming that an adhered cell touches a sorbent with 1% of its cell surface at a time, as was proposed by van Loosdrecht et al. [60], it would contact about 100000 sorbed molecules at a time, representing substrate for only one second. This does not contradict the possibility of direct uptake of truly adsorbed molecules, but it illustrates that such an uptake-mechanism would be relatively unimportant. 

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