Cell, animal fibroblast

Compounds tested in a more physiological 3-D environment show increased predictability of in vivo responses and help to span the gap between 2-D tissue culture and animal models. There is also evidence that 3-D cultures can identify active compounds that would fail to show their potential in 2-D (56, 57). The complexity of 3-D cultures can be increased by the addition of one or more cell types (fibroblasts, endothelial cells) and/or culture with different media, substrates, or oxygenation conditions. However, a disadvantage is that there is still a lack of simple, standardized, and reliable 3-D protocols that allow their incorporation into the pre-clinical high-throughput validation and drug evaluation process, although there have been several advances in this area in recent years (30, 58-61). 

Fig. 1. The accuracy of e-beam lithography is illustrated in the scanning electron micrograph (top). The size of the features formed in the silicon oxide is 0.5 pm and the typical animal cell (a fibroblast) has a diameter of 20 pm. This kind of cell adheres actively to surfaces, forming thin filopodia which here have all attached to the micro-hillocks. Semiconductor technology is capable of manufacturing micro-electrodes, sensors, pores and electronic networks with sizes smaller than that of the cell. The lower illustration summarises the main detection and measuring methods currently in use...

There remain many issues that are poorly understood. For example, what determines the level of NGF synthesis in various peripheral tissues and why do Schwann cells and fibroblasts associated with nerve axons increase mRNA concentrations within peripheral nerve, but not apparently within effector tissues, in response to axon degeneration Is the regulation of NGF synthesis in the mature animal the same as that controlling synthesis in development Progress in NGF research has been plagued by the limitations of techniques necessary for quantification and localization of the low concentrations present in normal tissues. Many of the most important questions begging for... 

Because none of the animal models described previously fully recapitulate the pathogenesis/pathology of IPF, attempts are ongoing to humanize a model for IPF. Administration of human IPF fibroblasts, but not fibroblasts from normal human lungs into immunodeficient mice, results in focal alveolar remodeling (Pierce et al., 2007 Trujillo et al., 2010). The cells also tend to activate murine epithelial cells and fibroblasts with resultant remodeling. Use of this model provides a unique opportunity to evaluate the potential for therapeutic intervention. 

Phosphorothioates generally protect normal tissues more than tumors. Tumor protection reported in some animal studies can pardy be explained by physiological effects of the particular dmgs, which are specific to rodents (4). WR-2721 does not appear to protect human and most animal tumors, apparentiy because of the low availabiUty of the dmg to tumor cells (4). Many tumors appear to have a reduced capillary density (44), which may mean that these tumors have altered levels of alkaline phosphatase, the enzyme that converts WR-2721 to WR-1065. A reduced abiUty of thiols to protect the hypoxic cells characteristic of many tumors may also contribute to their selectivity for normal tissues. The observation that WR-1065 protects cultured normal human fibroblasts, but not fibrosarcoma tumor cells, suggests that additional factors may contribute to the selectivity of radioprotection by WR-2721 m vivo (18). 

Vitamins and lipids are often required for animal cells to grow in serum-free medium. Phosphoethanolamine and ethanolamine are key additives that facilitate the growth of the mammary tumor cell line 64024 (Kano-Sueoka and Errick, 1981). In addition, ethanolamine promotes the growth of human lymphocytes and mouse hybridoma cells. Short-term cultures of human diploid lung and foreskin fibroblasts grow in medium that includes among its supplements soybean lecithin, cholesterol, sphingomyelin, and vitamin E. 

IFN-a, -P and -y are all known to induce the enzyme in various animal cells. However, in human epithelial cells the kinase is induced only by type I interferons, whereas none of the interferons seem capable of inducing synthesis of the enzyme in human fibroblasts. The purified kinase is highly selective for initiation factor eIF-2, which it phosphorylates at a specific serine residue. 

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