Defined Serum Free Medium Research Articles

Modulations of the epithelial phenotype and functional activity of cultured bovine tracheal gland cells: dependence on the culture medium and passage number

Bovine tracheal gland (BTG) cells in culture show an epithelial-fibroblastoid transition after several passages. To investigate these BTG cell phenotype changes, we studied the effects of both the culture medium and passage number on the expression of epithelial cytoskeletal proteins and glandular serous cell markers. We also analyzed the intracellular cAMP level in the basal state and after adrenergic stimulation. Three culture media were used: 1) serum-free defined medium (SFDM); 2) medium supplemented with 2% Ultroser G; and 3) medium supplemented with 10% fetal calf serum (FCS). Using immunofluorescence microscopy, we showed that, in the first 4 passages whatever the culture conditions, BTG cells expressed immunoreactivities to cytokeratin filaments and desmoplakins I and II, whereas vimentin filaments were not detected. After four passages, BTG cells cultured in 10% FCS or 2% Ultroser G became progressively fibroblastoid and showed immunoreactivities to both vimentin and cytokeratin intermediate filaments. No immunoreactivity to vimentin filaments was observed on BTG cells cultured in a SFDM. Using biochemical analysis, we showed that basal levels of cAMP in cultured BTG cells and lysozyme secretion by these cells vary according to the culture medium and passage number. It was higher in BTG cells cultured in a SFDM compared to that recovered from cells cultured in medium supplemented with Ultroser G or FCS. Whatever the culture medium, BTG cells responded to stimulation by isoproterenol. However, the results of stimulation in a SFDM were higher than in Ultroser G or FCS supplemented medium. We conclude that the BTG epithelial cell organization and the regulation of biosynthesis of secretory proteins by these cells in culture depend on both the culture medium and passage number.(ABSTRACT TRUNCATED AT 250 WORDS)

PDGF‐stimulated fibroblast proliferation is enhanced synergistically by receptor‐recognized α2‐Macroglobulin

alpha-Macroglobulins derived from plasma or secreted by macrophages are platelet-derived growth factor (PDGF) binding proteins that compete with cell-surface receptors on fibroblasts for PDGF binding. alpha 2-Macroglobulin (alpha 2M) derived from bovine plasma was tested for its ability to modulate the PDGF-induced proliferation of primary passage rat lung fibroblasts (RLFs) and a human skin fibroblast cell line (CRL 1508). Fibroblasts were grown in 10% fetal bovine serum (FBS) for 24 hr, then washed with serum-free medium before adding serum-free defined medium (SFDM) containing insulin and transferrin. To this medium were added varying concentrations of human plasma-derived AB-PDGF and alpha 2 M, alone or in combination. Receptor-recognized alpha 2M was prepared by treatment with methylamine. Both native alpha 2M and the alpha 2M-methylamine (alpha 2M-MA) were tested for growth promoting activity in the absence or presence of PDGF. After 3 days, a concentration-dependent growth curve of fibroblast proliferation was demonstrated for PDGF alone, with near maximal stimulation reached at 15-20 ng/ml PDGF. alpha 2M and alpha 2M-MA alone had no effect on cell proliferation. However, alpha 2M-MA concentrations above 32 micrograms/ml synergistically enhanced PDGF-stimulated proliferation greater than 100% in the presence of 15 ng/ml PDGF. Native alpha 2M enhanced PDGF-stimulated growth 80-100% above PDGF controls only at low concentrations (32-64 micrograms/ml alpha 2M). High concentrations of native alpha 2M (128-256 micrograms/ml) either had no effect on growth or were inhibitory to PDGF-stimulated growth, depending on the cell type tested. Rat lung fibroblasts were shown to secrete a factor(s) that inhibited the trypsin-binding capacity of native alpha 2M. We further demonstrated that early passage RLFs possess specific cell-surface receptors for [125I]-PDGF and [125I]-alpha 2M-MA, and preincubation of RLFs with alpha 2M-MA increased the specific binding of [125I]-PDGF to the cell surface of these fibroblasts. Considered together, these data support the view that receptor-recognized alpha 2M synergistically enhances the proliferative capacity of PDGF. We postulate that receptor-recognized alpha Ms enhance PDGF-stimulated growth by increasing the local concentration of PDGF at the cell surface, where the PDGF could be released in close proximity to its own receptors.

Decreased Prolactin Secretion by Explant Cultures of Fibroids from Women Treated with a Gonadotropin-Releasing Hormone Agonist*

Endometrium, myometrium and uterine leiomyomata (fibroids) all secrete PRL. Although the regulation of endometrial PRL secretion has been extensively studied, little is known about myometrial and fibroid PRL. This study investigated the effects of the GnRH agonist (GnRH-a) leuprolide acetate depot, administered in vivo, on fibroid and myometrial PRL secretion by explant cultures. Tissue was obtained from 17 patients enrolled in a prospective, randomized, double-blind, placebo-controlled clinical trial. Explant cultures of fibroid and myometrium were established in defined serum free media and harvested media assayed for PRL and total protein. Fibroid PRL secretion was substantially greater than myometrial PRL secretion. Fibroid PRL secretion increased with time whereas myometrial PRL secretion did not. Fibroid, but not myometrial, PRL secretion in GnRH-a treated patients was significantly lower when compared to controls. Fibroid protein secretion was not affected by GnRH-a administration in vivo. Progesterone supplementation in vitro inhibited fibroid PRL secretion; estrogen and GnRH-a in vitro had a minimal effect. Western blot analysis showed a small proportion of PRL secreted by fibroids to be glycosylated. These results demonstrate: 1) PRL secretion is greater from fibroids than myometrium; 2) fibroid PRL secretion in vitro is specifically reduced after 24 h after in vivo treatment with GnRH-a; 3) estrogen or progesterone in vitro does not reverse the suppression by in vivo administration of GnRH-a; and 4) GnRH-a in vitro has no effect on fibroid PRL secretion.

Characterization of sodium currents in mammalian sensory neurons cultured in serum-free defined medium with and without nerve growth factor

The influence of nerve growth factor (NGF) on Na currents of rat dorsal root ganglia (DRG) was studied in neurons obtained from newborns and cultured for 2-30 hr in serum-free defined medium (SFM). Cell survival for the period studied was 78-87% both with and without NGF. Na currents were detected in all cells cultured for 6-9 hr. They were also detected after 2 hr in culture in 21.5% of the cells cultured without NGF (-NGF cells), and in 91.5% of the cells cultured with NGF (+NGF cells). Current density of the -NGF cells was 2.3 and 2 pA/microns 2 after growth for 2 and 6-9 hr, respectively, compared to 3.0 and 3.9 pA/microns 2 for the +NGF cells. The +NGF cells were separated into fast (F), Intermediate (I) and slow (S) cells, based on the Na current they expressed, while -NGF cells were all of the I type. F, I and S currents differed in their voltage-dependent inactivation (Vh50 = -79, -28 and -20 mV), kinetics of inactivation (tau h = 0.55, 1.3 and 7.75 msec), and TTX sensitivity (Ki = 60, 550 and 1100 nM). All currents were depressed by [Ca]0 with a KdCa of 22, 17 and 8 mM for F, I and S currents, respectively. Current density of F and S currents was 5.5 and 5 pA/micron 2 for the I current. The concentration-dependent curve of I current vs. TTX indicated that I current has two sites: one with F-like and another with S-like Ki for TTX. Hybridization of F and S currents yielded I-like currents. Thus, the major effect of NGF on Na currents in SFM is the acceleration of Na current acquisition and diversity, reflected in an increase of either the S or F type in a cell.

Phenolic and tyrosyl ring iodothyronine deiodination by the caco-2 human colon carcinoma cell line

Thyroid hormone metabolism was studied in the human Caco-2 colon carcinoma cell line, which at confluence exhibits several functions of differentiated enterocytes. Cells were harvested two to 17 days after reaching confluence. Intact cells and homogenates were tested for deiodination of [ 125I]-labeled substrates. Small amounts of thyroxine (T 4) were converted by homogenates to 3,3′,5′-triiodothyronine (rT 3), 3,3′-diiodothyronine (3,3′-T 2), and I −, with no detectable production of 3,5,3′-triiodothyronine (T 3) by homogenates or cells. rT 3 was converted to 3,3′-T 2 and I − with an apparent Michaelis constant (K m) for rT 3 of 24 nmol/L; 6-n-propyl-2-thiouracil (PTU) had a 50% inhibitory concentration of 30 nmol/L and abolished rT 3 5′-deiodination at 1 mmol/L in the presence of 20 mmol/L dithiothreitol (DTT). T 3 was deiodinated to 3,3′-T 2 and 3′-monoiodothyronine (3′-T 1) with an apparent Michaelis constant (K m) for T 3 of 5.7 nmol/L; this reaction was not inhibited by 1 mmol/L PTU. Phenolic and tyrosyl ring deiodinating activities were maximal four and six days, respectively, after the cells reached confluence. Homogenates of cells grown in standard medium containing fetal calf serum had fivefold higher rT 3 5′-deiodinating activity than cells grown in a serum-free defined culture medium, reflecting a fivefold difference in the apparent V max with no difference in the apparent K m for rT 3. There was no difference in T 3 5-deiodination rates in homogenates of Caco-2 cells grown in the two media until 12 days postconfluence, when cells grown in standard medium had higher activity. These findings indicate that Caco-2 cells have two deiodinating pathways. rT 3 5′-deiodination more closely resembles the low K m process described in rat kidney microsomes than classic type I deiodination in either rat or human tissues. T 3 5-deiodination occurs via the type III pathway, which is regulated by changes in cell growth and differentiation as in several other cell types.

Immunohistochemical localization of myelin basic protein and 2',3'-cyclic nucleotide 3'-phosphohydrolase in flattened membrane expansions produced by cultured oligodendrocytes

Oligodendrocytes, the cells responsible for myelin sheath formation in the central nervous system, were isolated from primary dissociated mixed glial cultures prepared from newborn mouse forebrain, and further cultured in a serum-free defined culture medium. Single and double indirect immunofluorescence using antibodies against the myelin glycolipids, galactocerebroside and sulfatide, and the myelin proteins, myelin basic protein and 2',3'-cyclic nucleotide 3'-phosphohydrolase, was used to investigate the composition of the flat membrane extensions produced by some oligodendrocytes in culture. Galactocerebroside and sulfatide were both expressed on the external surface of the plasma membrane of oligodendrocyte cell bodies and processes and also the membrane expansions. Neither myelin basic protein nor 2',3'-cyclic nucleotide 3'-phosphohydrolase were expressed on the external surface of oligodendrocytes. Myelin basic protein could be localized to the cell body and the membrane expansions but not the major and fine processes. The localization of these myelin components suggests that the expansions have characteristics of the mature myelin membrane. 2',3'-Cyclic nucleotide 3'-phosphohydrolase was found to be localized in the cell body, and in total contrast to myelin basic protein, in the major processes and the fine interconnecting processes, but not the membrane expansions. In some of the cells 2',3'-cyclic nucleotide 3'-phosphohydrolase was present at the outer extremities of the flat membrane sheets, giving the appearance of an extending growth region. Our results thus clearly show that 2',3'-cyclic nucleotide 3'-phosphohydrolase is localized within oligodendrocytes in discrete regions of plasma membranes and suggest that this protein has a possible role in the early stages of myelin formation.

Hydrogen peroxide induces squamous metaplasia In a hamster tracheal organ explant culture model

Reactive oxygen species have been shown in several systems to have a role in tumor promotion and carcinogenesis, although the exact mechanisms are yet to be elucidated. To investigate this further, the effect of hydrogen peroxide was studied in a hamster tracheal organ explant epithelial model. Hydrogen peroxide was added exogenously to tracheal explants maintained in defined serum free media at concentrations of 50, 100, 500 or 1000 microM daily for 1 h for a period of two weeks. The explants were then examined using scanning electron microscopy for evidence of morphologic alteration and for the development of squamous metaplasia. Control tracheal explants maintained in serum free media exhibited normal morphology (except for some decrease in the number of ciliated cells) and developed minimal squamous metaplasia after four weeks in culture. At concentrations of 500 and 1000 microM, hydrogen peroxide was toxic to the epithelium, resulting in complete necrosis of the epithelium within seven days. At concentrations of 50 and 100 microM, hydrogen peroxide treatment resulted within three weeks in the development of a significant degree of squamous metaplasia (covering 52 and 48.7%, respectively, of the surface epithelium). This effect could be negated by the exogenous addition of catalase. This model should be useful in the study of the early cellular events following oxidant injury that contribute to the development of squamous metaplasia.

Dexamethasone treatment increases neuropeptide Y levels in rat hypothalamic neurones

Immunoreactive glucocorticoid receptors (GR) have previously been demonstrated in neuropeptide Y (NPY) neurones of the rat hypothalamus. To determine whether NPY synthesis is influenced by glucocorticoids, the effect of dexamethasone (DEX) on the levels of immunoreactive NPY in rat hypothalamic neurones was investigated in vivo and in vitro. Daily injections of DEX (0.1 mg/day) for 5 days increased the NPY content of the mediobasal hypothalamus in female rats by 117% (p less than 0.002). Primary cultures of hypothalamic neurones were also sensitive to the effect of glucocorticoids. Intracellular NPY levels were significantly increased (p less than 0.001) compared to control values by 151%, 222% and 268% when cultures were maintained in a defined serum free medium containing DEX 10(-9), 10(-8) and 10(-7) M respectively.

Evidence that stimulation of growth hormone release by epinephrine and vasoactive intestinal peptide is based on cell-to-cell communication in the pituitary.

Epinephrine (Epi) evoked a strong concentration-dependent (1-1000 nM) rise of GH release from perifused rat anterior pituitary cells cultured as aggregates in a serum-free defined culture medium. Dexamethasone (Dex), added to the culture medium, enhanced the secretory response to Epi. Aggregates of pituitary cells separated by gradient sedimentation at unit gravity widely differed in responsiveness to Epi, provided Dex was added to the culture medium. The poorest response was seen in aggregates composed of a population highly enriched in large somatotrophs from adult male rats even when cultured in the presence of 80 nM Dex. However, when these large somatotrophs were coaggregated with various somatotroph-poor cell populations, all of which were enriched in lactotrophs, the GH response to Epi increased by a factor of 3-4. The latter populations also enhanced GH secretion stimulated by vasoactive intestinal peptide (1-10 nM). In contrast, the GH response to rat GH-releasing factor (GRF, 0.01-0.1 nM) was not significantly potentiated in the coaggregates. The facilitation of the GH response to Epi was not seen when Dex was omitted from the culture medium. All of the lactotroph-enriched populations enhancing the response to Epi also contained corticotrophs, but none were highly enriched in the latter cell type. The magnitude of the Epi effect on GH release was not affected when the large somatotrophs were coaggregated with enriched populations of gonadotrophs, thyrotrophs, or folliculostellate cells. However, coaggregation with GH3 tumor cells provoked some stimulation. The present data suggest that GH release stimulated by Epi is modulated by facilitatory interactions of somatotrophs with other cells, the latter being most likely lactotrophs, although participation of corticotrophs in this interactions cannot be unequivocally excluded. Facilitatory interactions also modulate GH secretion in response to vasoactive intestinal peptide, but the GH response to GRF weakly, if at all.

Role of cell membrane composition in receptor-mediated internalization of vesicular stomatitis virus in human HEp-2 cells.

The role of essential fatty acids in membrane functions related to receptor-mediated endocytosis of vesicular stomatitis virus (VSV) was investigated using a human laryngeal carcinoma cell line (HEp-2) grown in chemically defined serum-free medium (DM) to deplete their essential fatty acid contents. VSV replicated much less effectively in HEp-2 cells grown in DM as compared to serum containing complete medium (CM). Observed reduction in the rate of virus multiplication was, at least in part, due to reduced virus penetration which was monitored using VSV labeled with nitroxyl free radicals as electron spin probe. Surface proteins of VSV were labeled with maleimide spin-label, and succinimide spin-label. Ni2+ was used as a broadening agent to identify the spin-label signals from viruses inside the cell. HEp-2 cells and mouse leukemia cell line L1210 treated with 5-dimethylaminonaphthalene-1-sulfonyl (dansyl) cadaverine, an agent previously shown to inhibit the uptake of VSV in vitro, was used as a positive control in some experiments. VSV penetrated less effectively in both DM-grown cells and in CM-grown cells in the presence of dansylcadaverine. Similar results were obtained by monitoring the uptake of 125I-labeled VSV. When HEp-2 cells grown for several generations in DM were incubated with 10% fetal calf serum for 16 h, the cells supported virus replication to a similar extent as the cells grown in CM. In contrast, addition of arachidonic acid restored VSV growth only partially. Continued growth of HEp-2 cells in DM resulted in a shift in fatty acyl chain composition of phospholipids. The results indicate a finite role for essential fatty acids in receptor-mediated internalization of virus particles.

Chemically defined requirements for the survival of cultured 8-day chick embryo ciliary ganglion neurons

We have previously demonstrated that both peripheral and central neurons from embryonic chick and newborn mouse can be maintained in a serum-free defined culture medium containing the appropriate neuronotrophic agent and the N1 supplement consisting of insulin, transferrin, putrescine, progesterone and selenite. In the present studies we have examined the short-term survival requirements of 8-day embryonic chick ciliary ganglion (CG) neurons. By comparing CG neuronal survival in our standard culture medium, Eagle's Basal Medium (EBM), with several other commercially available basal media, we have established that CG neurons also have specific requirements for pyruvate, serine and iron (Fe 3+), in addition to their trophic factor (Ciliary Neuronotrophic Factor, CNTF) and the N1 supplement. The data suggest the existence of 3 subsets of CG neurons differing in their essential needs, namely: (1) those supported by glucose in the absence of pyruvate, (2) those requiring exogenous pyruvate but not serine or Fe 3+, and (3) those which need pyruvate, serine and Fe 3+. The minimal effective concentration of pyruvate could be decreased by a factor of 50 in the concurrent presence of serine and Fe 3+. Serine was also a limiting element in the survival of some of these CG neurons. The Fe 3+ concentration required by the same neurons was considerably diminished with the availabilitty of transferrin, perhaps reflecting an increased Fe 3+ transmembrane transport efficiency. Insulin was found to be the only N1 ingredient required for the survival of CG neurons. Insulin was a constant requirement for all 3 subsets of CG neurons, even when cultured in the total absence of glucose (but presence of pyruvate).

Development of a serum-free defined culture medium for lymphoblast transformation tests of mouse spleen and thymus cells.

By analysis of thymidine uptake during the first 4 h of incubation and by examining the responsiveness of unfractionated mouse spleen cells upon mitogenic or allogeneic stimulation, some serum factors of major importance for in vitro cultivation of lymphocytes have been examined. Albumin and l-alanine are essential for the maximal preservation of the in vivo-initiated lymphocyte activity during the first hours of incubation in vitro. Transferrin plays a major role in the lymphocyte proliferation, induced by mitogens in vitro, and, finally, zinc and selenium exert a clear enhancing effect on the response to an allogeneic stimulation. The AATSZ medium (RPMI 1640 enriched with l-alanine, albumin, transferrin, zinc chloride, and sodium selenite) enables a proliferation of the same magnitude as or higher than FCS medium. The kinetics are the same, and the cell viability is comparable, but standardization is much simpler with AATSZ. This is primarily because FCS binds some mitogens and contains inhibitors. Consequently, the standardization of such a culture system is dependent on variations from serum batch to serum batch. On the other hand, the current composition of the AATSZ medium promotes the sticking capacity of T lymphocytes and does not support growth of all lymphoid cell lines. Consequently, this defined medium, although not yet suitable as optimal medium for all lymphocyte functions, can advantageously be used for short-term studies of most murine lymphocyte functional and cooperation studies in vitro.

Spinal cord neuronotrophic factors (SCNTFs): I. Bioassay of Schwannoma and other conditioned media

We present a procedure for the dissociation and growth in serum-free defined culture medium of 4-day chick embryo lumbar spinal cord (LC4) neurons. LC4 neurons will not survive for even 24 h without the addition of trophic supplements (putative spinal cord neuronotrophic factors, SCNTFs). Serum-free medium conditioned over chick embryo heart and skeletal muscle, mouse Schwann and rat RN22 Schwannoma cell cultures were found to contain SCNTF activity which could be quantitated using a convenient neuronal survival bioassay. RN22 conditioned medium also contains polyornithine-binding neurite promoting factors (PNPFs) which can be physically separated from SCNTF. When SCNTF and PNPF were presented to LC4 neurons individually or in combination (i) SCNTF, but not PNPF, supported neuronal survival whereas (ii) PNPF, but not SCNTF, induced neurite production. When LC4 neurons were grown in SCNTF alone, nearly all of them exhibited a flattened, circular, ‘fried-egg’ morphology. The subsequent addition of PNPF caused these cells to extend long neurites with characteristic terminal growth-cone-like structures.