Choice of the Right Model Primary Cells or Cell Line

Modern histology has advanced greatly in the understanding and culturing of epithelial and EC in the last decade. Primary cells can be isolated from various sites relevant in fungal infections like the skin, the lung, or the brain. Protocols have been described for epithelial cells (Steele & Fidel, Jr. 2002; Grossmann et al., 1998), macrovascular (HUVEC) (Jaffe et al., 1973; Marin et al., 2001), and microvascular EC (Bowman et al., 1983; Hewett & Murray, 1993; Lamszus et al., 1999; Richard et al., 1998; Vinters et al., 1987). However, several disadvantages are associated with the use of primary cells. Their sources are often not readily available and isolation is time consuming and generally gives low yields. Primary EC, for example, display a loss of viability and a change in typical EC marker expression during the course of their in vitro propagation. The source of the cells (i.e. the donor) and thereby the genetic background from the isolates might also result in differential marker expression (Stins et al., 1997).

The alternative are cell lines, either directly derived from tumours or immortalized primary cells. Methods described for immortalization include forced expression of telomerase (OKF6/TERT2 epithelial cells, (Dickson et al., 2000), fusion of primary EC with carcinoma cells (EA.hy 926, Edgell et al., 1983) or transfection with SV40-T (HPMEC-ST1.6R, Krump-Konvalinkova et al., 2001). While cell lines can reflect the behaviour of primary cells in some aspects (L'Azou et al., 2005), not all cell typical phenotypes have been found to be expressed by them in vitro. A comparative study of endothelial characteristics of primary EC and several cell lines revealed important differences in constitutive expression of vWF and PECAM-1 as well as in the induction of ICAM-1, VCAM-1 and E-selectin, and IL-6, IL-8 and MCP-1 upon activation by different stimuli (Unger et al., 2002).

Generally, the transfer of results obtained with cells cultured in vitro to the conditions found in vivo is hindered by limitations in the modelling of the natural cellular environment. This is especially true for endothelial cell models, since, as stated by Aird (2003), an important feature of the endothelium is that its properties vary between different sites of the vasculature and from one moment in time to the next. EC show a high degree of plasticity and this flexibility is closely linked to the extracellular environment and the available in vitro systems for EC generally may fail to fully capture the spatial and temporal dynamics of the endothelium (Aird, 2005). This point is stressed by a recent study where the microenvironmen-tal modulation of EC was investigated at a molecular level. In a multidimensional protein identification assay with samples from rat lung EC and cultured rat lung EC, 41% of proteins expressed in vivo were not detected in vitro (Durr et al., 2004).

Three-dimensional models aim to reconstitute the cellular environment closely to the situation found in vivo. These models are useful to analyse tissue infections and allow the study of adherence, penetration, and cellular damage in detail. However, they do not yet reproduce perfectly the structure and composition of the respective human tissues. Problems may also arise with the reproducibility of experiments. When commercial models that include primary cells are used, inter-assay variation can be avoided by choosing a supplier who offers batches of tissues that come from a single donor (Netzlaff et al., 2005; Dongari-Bagtzoglou and Kashleva, 2006). Another strategy followed by different authors to validate their particular system is to compare distinct in vitro models or to compare it with an in vivo model of infection (Cheng et al., 2005; Rouabhia et al., 2005; Sanchez et al., 2004).

Cure Your Yeast Infection For Good

Cure Your Yeast Infection For Good

The term vaginitis is one that is applied to any inflammation or infection of the vagina, and there are many different conditions that are categorized together under this ‘broad’ heading, including bacterial vaginosis, trichomoniasis and non-infectious vaginitis.

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