The Choline and Serum Protein Requirements of Mouse Fibroblast Cells (Strain LS) in Culture

Chemiluminometric immuno-analysis of innate immune response against repetitive bacterial stimulations for the same mammalian cells

For monitoring of human cellular response to repetitive bacterial stimulations (e.g., Pseudomonas aeruginosa in a lysate form), we devised a chemiluminescent immuno-analytical system for toll-like receptor 1 (TLR1) as marker present on cell surfaces (e.g., A549). Upon stimulation, TLR1 recognizes pathogen-associated molecular patterns of the infectious agent and are then up-regulated via activation of the nuclear factor-κB (NF-κB) pathway. In this study, the receptor density was quantified by employing an antibody specific to the target receptor and by producing a chemiluminometric signal from an enzyme labeled to the binder. The activated status was then switched back to normal down-regulated stage, by changing the culture medium to one containing animal serum. The major factors affecting activation were the stimulation dose of the bacterial lysate, stimulation timing during starvation, and up- and down-regulation time intervals. Reiterative TLR regulation switching up to three times was not affected by either antibody remained after immunoassay or enzyme substrate (e.g., hydrogen peroxide) in solution. This immuno-analysis for TLRs could be unique to acquire accumulated response of the human cells to repeated stimulations and, therefore, can eventually apply to persistency testing of the cellular regulation in screening of anti-inflammatory substances.

Continuous growth and phosphatidylcholine synthesis of rat hepatoma cells in choline-deprived chemically defined medium

A choline non-required cell line was established from a rat hepatoma cell line. The line designated R-Y121B X cho was able to grow in choline-deprived medium without serum and lipid. Choline is necessary for the biosynthesis of phosphatidylcholine, which is a main component of cell membranes. Phosphatidylcholine can be synthesized by the methylation of phosphatidylethanolamine in liver cells. Phospholipid composition and incorporation of radiolabeled serine into phosphatidylserine or phosphatidylethanolamine were quite similar in R-Y121B X cho and its parental cells. However R-Y121B X cho cells had higher phosphatidylcholine synthesis activity from radiolabeled methionine than parental cells. These results indicate that choline requirement of mammalian cells depends on the activity of phosphatidylethanolamine methyltransferase.

Epithelial-stromal interactions: specific stimulation of corneal epithelial cell growth in vitro by a factor(s) from cultured stromal fibroblasts

By using a recently modified method of isolating and culturing rabbit corneal cells, this study investigated the presence of a diffusible substance(s) in stromal fibroblast conditioned medium that stimulated the growth of cultured corneal epithelial cells. The growth stimulation involved initiation of DNA synthesis (assayed by [3H]-thymidine incorporation) and enhanced cell proliferation (quantified by cell counting). Among the three corneal cell types, only fibroblasts (rabbit and human) released the stimulatory substance, which acted only on epithelial cells. The effect of this stromal fibroblast factor (SFF) was observed after an exposure period of less than 16 hr and persisted as long as it was present. Its action was concentration-dependent and was not a result of improvement in the survival of epithelial cells during culture. Both sparse and confluent epithelial cultures were susceptible to SFF. The release of SFF was correlated with the number of fibroblasts in the culture and appeared to be sensitive to the growth condition of the cells. Both the release and action of SFF did not depend on the presence of serum in the culture medium. The factor was heat resistant and insensitive to proteolytic enzymes. From ultrafiltration studies, the size of SFF was estimated to be in the approximate range of 50-1000 daltons. By direct comparison of the stimulatory effect with other previously studied growth promoting agents, it was concluded that SFF was not epidermal growth factor, fibroblast growth factor, putrescine, cyclic AMP, hydrocortisone or acetate. The implication of SFF in the regulation of epithelial growth by endogenous, intercellular mechanisms is discussed.

Bone cells: a serum-free medium supports proliferation in primary culture

Bone-cells isolated from embryonic rat calvaria increase in number two-to threefold when cultured at high, but not at low, population densities in a serum-free medium that contains albumin. Cultured cells respond to parathyroid hormone and exhibit a marked rise in alkaline phosphatase activity during proliferation, which suggests the progressive differentiation or preferential growth of osteoblast-like cells.