Differentiation in vitro: effects of Sephadex fractions of chick embryo extract

3D Cell Culture of Human Salivary Glands Using Nature-Inspired Functional Biomaterials: The Egg Yolk Plasma and Egg White

The egg yolk plasma (EYP)-a translucent fraction of the egg yolk (EY) obtained by centrifugation-was tested as a developmentally encouraging, cost-effective, biomaterial for salivary gland (SG) tissue engineering. To find optimal incubating conditions for both the human NS-SV-AC SG acinar cell line and SG fibroblasts, cells were stained with Live/Dead®. The cellular contents of 96-well plates were analyzed by high content screening image analysis. Characteristically, the EYP biomaterial had lipid and protein content resembling the EY. On its own, the EYP was non-conducive to cell survival. EYP's pH of 6 mainly contributed to cell death. This was demonstrated by titrating EYP's pH with different concentrations of either commercial cell culture media, NaOH, or egg white (EW). These additives improved SG mesenchymal and epithelial cell survival. The best combinations were EYP diluted with (1) 70% commercial medium, (2) 0.02 M NaOH, or (3) 50% EW. Importantly, commercial medium-free growth was obtained with EYP + NaOH or EYP + EW. Furthermore, 3D cultures were obtained as a result of EW's gelatinous properties. Here, the isolation, characterization, and optimization of three EYP-based biomaterial combinations are shown; two were free of commercial medium or supplements and supported both SG cells' survival.

Turnover and down-regulation of GABA(A) receptor alpha1, beta2S, and gamma1 subunit mRNAs by neurons in culture

Benzodiazepines (BZDs), barbiturates, ethanol, and general anesthetics potentiate the action of gamma-aminobutyric acid (GABA) at the type A GABA receptor (GABA(A)R) and have profound effects on mood, arousal, and susceptibility to seizures. GABA(A)R number and subunit mRNA levels change in animal models of epilepsy and anxiety and following exposure to GABA(A)R agonists and positive modulators, but the mechanism of receptor down-regulation remains unknown. Persistent exposure (48 h) of brain neurons in primary culture to GABA results in a 30% decrease in the levels of mRNA encoding the alpha1, beta2S, and gamma1 GABA(A)R subunit isoforms, which form a receptor enhanced by nonselective BZDs. Down-regulation of alpha1 mRNA (t1/2 = 8 h) precedes down-regulation of receptor number (t1/2 = 25 h), suggesting that GABA-induced GABA(A)R down-regulation is a consequence of decreased mRNA levels. The apparent half-life of the alpha1 mRNA in the presence of alpha-amanitin (9 h) is consistent with the time course of alpha1 mRNA down-regulation. Moreover, the stability of the alpha1, beta2S, and gamma1 subunit mRNAs is not altered by chronic GABA exposure. The results demonstrate that GABA(A)R subunit mRNA down-regulation is not a consequence of accelerated mRNA degradation and argue that GABA-induced GABA(A)R down-regulation is due to inhibition of transcription.

Mitogenic activity of fetal bovine serum, fish fry extract, insulin-like growth factor-I, and fibroblast growth factor on brown bullhead catfish cells--BB line

Bioassays were performed to assess the effects of different levels of growth medium supplementation with fetal bovine serum (FBS), fish fry extract (FE), combinations of FBS and FE, and addition of insulin-like growth factor I (IGF-I) and fibroblast growth factor (FGF) on the proliferation of brown bullhead catfish cells (BB line). Treatments (n = 4) were: 2.5, 5, 10, and 15.0% FBS or FE and 5/2.5, 5/5, 10/2.5, and 10/5 of a FBS/FE combination as supplement to the growth medium, or the addition of 0.1, 1, 2.5, 10, 25, and 75 ng/ml of either IGF-I or FGF to the growth media. Initial cell density was 1.1 x 10(6) cells per well on uncoated 24-well plates. Incubation temperature was 29.5 +/- 0.7 degrees C. Six hours after plating, initial culture medium was removed, plates rinsed with Dulbecco's phosphate buffered saline, treatment media added, and cells allowed to proliferate for 24 hours. Another bioassay was performed with rat myoblast omega cells (RMo) using the same levels of growth medium supplemented with FBS, FE and FBS/FE. Base growth medium was Dulbecco's MEM. The initial cell density was 7.2 x 10(6) cells per well, and the bioassay was carried out at 36.0 +/- 0.5 degrees C, on a 95% air, 5% CO2 incubator. Increasing levels of FBS had a positive effect (P < 0.05) on the proliferation of both BB and RMo cells. Increasing levels of FE had a negative effect (P < 0.05) on the proliferation of BB cells and totally inhibited the proliferation of RMo cells at any level of supplementation. Higher levels of FE on the FBS/FE combinations presented a negative effect on the proliferation of both BB and RMo cells (P < 0.05). Insulin-like growth factor I had a positive quadratic effect (P < 0.05) on the proliferation of BB cells. Apparently, mammalian growth factors slightly stimulated mitogenic activity in fish cells, while FE contained factors which inhibited the mitogenic activity of RMo and BB cell lines.

Regulation of expression of the chondrocytic phenotype in a skeletal cell line (CFK2) in vitro

We have examined in vitro the spontaneous and regulated expression of phenotypic characteristics associated with differentiated chondrocytes in an established skeletal cell line (CFK2) derived from fetal rat calvariae. Extended culture of CFK2 cells resulted in the appearance of glycosaminoglycans and type II collagen in the cell layer in association with the formation of focal nodes of cells. In addition, induction of mRNA-encoding link protein, cartilage-specific proteoglycan core protein, and thrombospondin was observed in the differentiated population (dCFK2 cells). The expression of these mRNAs was present for at least two passages after subculturing the dCFK2 cells. The dCFK2 cells also demonstrated enhanced parathyroid hormone (PTH)-stimulated adenylate cyclase activity. Proliferation of CFK2 cells was stimulated by the peptide regulatory factors EGF and PTH and inhibited by the steroidal agents dexamethasone and retinoic acid. EGF and retinoic acid inhibited the formation of cell foci and glycosaminoglycan deposition and the expression of mRNA-encoding link protein. In contrast, PTH and dexamethasone enhanced the formation of focal cellular nodes and augmented matrix deposition and link protein mRNA expression. These studies therefore show that the CFK2 cell line can serve as a nontransformed model of rat chondrocytic cells in which both induction and regulation of the expression of cartilaginous matrix components can be observed. This line thereby provides a unique renewable source of chondrocytic precursor cells and an excellent in vitro model for evaluating temporal and environmental control of chondrocyte differentiation and cartilage matrix production.

Regulation of lens cell growth and polarity by an embryo-specific growth factor and by inhibitors of lens cell proliferation and differentiation

We used a double-label method, which monitors the rate at which cells enter S-phase of the cell cycle, to identify factors that control the growth of chicken embryo lens epithelial cells in vivo. With this assay, we identified a mitogen for lens epithelial cells in the anterior segment of the embryonic eye. When the anterior chamber was opened briefly, by tearing the cornea or displacing the lens, the growth-promoting activity was lost. None of the purified growth factors tested replaced this growth activity, including EGF, bFGF, PDGF, IGF-1, IGF-2, TGF beta and mixtures of these factors. However, chicken embryo serum or plasma did cause chicken embryo lens epithelial cells to progress through the cell cycle. The activity in serum was destroyed by heat and protease treatment. It was most active in serum from 10-day embryos, decreased with subsequent development and was undetectable from 2 days after hatching through adulthood. When embryo serum or plasma was mixed with vitreous humor or IGF-1, agents that induce lens fiber cell formation, cell elongation was prevented. In contrast to the mitogenic activity in serum, this inhibitor of differentiation was insensitive to trypsin treatment. We also identified an activity in vitreous humor that inhibited the growth-promoting agent in embryo serum. Plasma proteins readily enter the anterior chamber of the eye of chicken embryos.(ABSTRACT TRUNCATED AT 250 WORDS)

Frontiers in mammalian cell culture

For the past 60 years, fundamental discoveries in eukaryotic biology using mammalian cell cultures have been significant but modest relative to the enormous potential. Combined with advances in technologies of cell and molecular biology, mammalian cell culture technology is becoming a major, if not essential tool, for fundamental discovery in eukaryotic biology. Reconstruction of the milieu for cells has progressed from simple salt solutions supporting brief survival of tissues outside the body to synthesis of the complete set of structurally defined nutrients, hormones and elements of the extracellular matrix needed to reconstruct complex tissues from cells. The isolation of specific cell types in completely defined environments reveals the true complexity of the mammalian cell and its environment as a dynamic interactive physiological unit. Cell cultures provide the tool for detection and dissection of the mechanism of action of cellular regulators and the genes that determine individual aspects of cell behavior. The technology underpins advances in virology, somatic cell genetics, endocrinology, carcinogenesis, toxicology, pharmacology, hematopoiesis and immunology, and is becoming a major tool in developmental biology, complex tissue physiology and production of unique mammalian cell-derived biologicals in industry.

Agonist effects on the intracellular cyclic AMP concentration of retinal pigment epithelial cells in culture

Accumulation of cyclic AMP in intact cultured pigment epithelial cells was rapidly enhanced by several agonists. These included vasoactive intestinal peptide (100-fold), glucagon (fivefold), thyroid-stimulating hormone (threefold), prostaglandin E1 (24-fold), L-isoproterenol (27-fold), and histamine (fourfold). The rapidity and magnitude of these effects suggest that these agonists may regulate important retinal pigment epithelial cell functions.

Chick retinal pigment epithelium. A new culture system for studying H2-histamine receptors

Histamine elevates the intracellular cyclic AMP levels in cultured embryonic chick retinal pigment epithelium. The half-maximal activity is 6 X 10(-6) M. The effect of histamine is mediated by H2 receptors, i.e., inhibited by the H2 antagonist cimetidine and not affected by the H1 antagonists diphenhydramine and pyrilamine. The inhibition constant (KI) of cimetidine is 1.3 X 10(-8) M. Thus, the present system offers the opportunity of studying the nature of coupling between histamine receptors and adenylate cyclase under controlled conditions in a homogeneous cell type.

Analysis of cartilage differentiation from skeletal muscle grown on bone matrix. III. Environmental regulation of glycosaminoglycan and proteoglycan synthesis

The ability of numerous nutritional and topographic factors to influence differentiation of embryonic mesenchyme has given rise to several theories which attempt to explain the development of muscle and cartilage from these similar-appearing cells. Some theories are challenged by the observation that a substratum of demineralized bone is capable of supporting the transformation of skeletal muscle into cartilage in vitro and that the potential to form cartilage still resides within cloned myoblasts and fibroblasts of skeletal muscle. In the present study, culture media CMRL-1066, minimal essential medium (MEM), and F-12 provide varied nutritional environments and are tested for their ability to support the morphological and biochemical transformation of skeletal muscle into cartilage. Morphologically, CMRL-1066 reproducibly supports hyaline cartilage formation, whereas MEM does so in only one out of three explants onto demineralized bone, and F-12 is incapable of supporting formation of a hyaline matrix. Biochemically, each medium is sufficient to elicit synthesis of cartilage-like patterns of sulfated glycosaminoglycans and proteoglycan monomer. Synthesis of hyaluronic acid (HA) initially increases in explants grown in CMRL-1066, but decreases prior to chondrogenesis. MEM elicits a similar increase in HA synthesis, but the subsequent decrease is not as rapid. In F-12, synthesis remains depressed throughout the experiment. The data show that increases in HA synthesis occur concurrent with the appearance of fibroblast-like cells, which normally precede chondroblasts. Decreases in HA synthesis correlate well with the onset of chondrogenesis. Explants grown in CMRL-1066 reproducibly from cartilage and synthesize the greatest amounts of proteoglycan aggregate. Those grown in MEM form cartilage infrequently, synthesize reduced amounts of proteoglycan aggregate-like material, and contain greater amounts of HA, of low molecular weight. The data demonstrate that chondrogenesis can be subtly regulated by environmental factors, and such factors regulate both the morphological and biochemical expression of the phenotype through HA synthesis.

Modulation of melanosome ultrastructure in cultured embryonic pigment cells

Melanosomes synthesized by embryonic chick retinal pigment cells in vitro are of a different size and shape than those made in ovo and in vivo. Ultrastructurally, the melanosomes made by cultured cells are small, spherical, contain an irregular internal matrix, and appear similar to the pheomelanosomes found in red hair and feathers. This modulation in melanosome ultrastructure in cultured retinal pigment cells does not appear to be caused by an irreversible change in differentiated capability but to a response of cells to the culture environment. Cells grown in embryo extract-free and serum-free defined media were found to synthesize melanosomes of normal size and shape in vitro, although at a much reduced number. The predominant melanosome type found was still the smaller, spherical variety. It appears that some still unknown factors in the culture environment have produced a shift to a different type of melanogenesis.

Selective emergence of differentiated chondrocytes during serum-free culture of cells derived from fetal rat calvaria

Cells dispersed from the chondrocranial portions of fetal rat calvaria proliferated and performed specialized functions during primary culture in a chemically defined medium. Mature cultures were typified by multilayered clusters of redifferentiating cartilage cells. Flattened cells that lacked distinguishing features occupied areas between the clusters. Alkaline phosphate-enriched, ultrastructurally typical chondrocytes within the clusters were encased in a dense extracellular matrix that stained prominently for chondroitin sulfate proteoglycans. This matrix contained fibrils measuring 19 nm in diameter, which were associated with proteoglycan granules that preferentially bound ruthenium red. A progressive increase in the number of cells indicated the proliferation of certain elements in the primary culture. The cells in primary culture were biochemically as well as morphologically heterogeneous since they were found to synthesize type I and type II collagens. Homogeneous populations of redifferentiated chondrocytes were recovered as floating cells and were shown to express the chondrocyte phenotype in secondary culture. Subcultured cells synthesized type II collagen and its precursors almost exclusively and incorporated 35SO4 into proteoglycan monomer and aggregates to a greater degree than the cells in primary culture. The pattern of proteoglycan monomer and aggregate labeling resembled that of intact cartilage segments and bovine articular chondrocytes. Skin fibroblasts harvested from the same rat fetuses failed to proliferate when maintained under identical conditions. Hence, exogenous hormones, growth factors, and protein are not required for chondrocyte growth and maturation.

Isolation and culture techniques of foetal calf chondrocytes

Large quantities of differentiated mammalian chondrocytes from normal hyaline cartilage were isolated after digestion of foetal bovine tracheas with collagenase. Incubation of the newly isolated cells for 1 day in the presence of dextran sulphate inhibited formation of cell aggregates during subsequent subculture in the absence of dextran sulphate. After incubation with dextran sulphate, the cells were plated in Ham's F12 medium with or without foetal calf serum on hydrophilic or hydrophobic Petri dishes. Chondrocytes cultured on hydrophilic substrates in the presence of serum attached to the substrate and showed cytoplasmic spreading. The cells did not attach to hydrophobic substrates in the presence of serum, but remained in suspension as single cells. In the absence of serum the chondrocytes attached to either substrate, but did not show any cytoplasmic spreading. By using labelling with [35S]sulphate and [3H]-thymidine it was shown that glycosaminoglycan synthesis did not require the presence of serum, whereas DNA synthesis required serum factors. Extracellular glycosaminoglycans were recovered in two pools: the medium pool and the pericellular pool, the latter being isolated by proteolytic digestion. The kinetics of these pools differed, depending on the presence or absence of serum and the type of substrate used. The turnover of the pericellular pool was studied in a pulse-chase experiment. At the end of the chase (72 h), only 60% of the material in the pericellular pool had been metabolized.

Growth of adult human cells in culture at clonal densities

The effect of varying medium concentrations of fetal calf serum (FCS), horse serum (HS) and chicken embryo extract (EE) on the growth capacity of adult human cells cultured at clonal densities was investigated. The best growth was consistently obtained with medium containing 20 parts FCS and 2 parts heat-treated commercial EE. The growth potential of human muscle cells was not related to the age of the patient from which the biopsy was taken, but was dependent on the microenvironment of the culture and the cell density.

Effect of 5-bromo-2'-deoxyuridine on growth and differentiation of cultured embryonic retinal pigment cells

Chicken embryo retinal pigment cells cultured for 2 weeks in 1 or 10 microns BrdU accumulate only 25% of the amount of melanin found in controls. Growth is inhibited by 10 microns BrdU but not by 1 micron BrdU. Cells cultured with BrdU had decreased tyrosinase activity and lost the typical epithelial appearance of controls. Equimolar concentrations of deoxythymidine did not prevent the inhibition of melanogenesis due to BrdU but did prevent the growth inhibition of the higher concentration of BrdU (10 microns). Tenfold higher concentrations of deoxythymidine prevented inhibition of epithelial differentiation and melanogenesis. Ultrastructurally, BrdU produced an absence of melanosomes and disruption of the lamellar array of rough endoplasmic reticulum. The perinuclear arrangement of microfilaments became irregular. The cell surface was radically affected as membranes were no longer ruffled and cell junctions disappeared. Melanogenesis is a complex form of differentiated function, involving synthesis of tyrosinase and control of its activity, macromolecular synthesis of the melanosome, and the subsequent synthesis of melanin within the melanosome. BrdU appears to inhibit melanogenesis through a coordinated and simultaneous interference with these processes, suggesting that there may be a "program" of gene activity for melanogenesis that is regulated as a unit.

A quantitative assessment of the effect of medium composition on mouse myogenesis in vitro

The effect of variations in medium horse serum (HS) and chick embryo extract on the extent of myogenesis in primary mouse muscle cultures was investigated. Seeding efficiency at 24 h in culture did not vary with medium composition, but total cell number at 8 days was diminished at low embryo extract concentrations. Five media from the range of 16 tested, supported significantly greater myogenesis. Within this group of 5, there was no difference in ability to support myogenesis. The effect of medium composition on myogenesis is discussed.

Ultrastructural observations on differentiating human preadipocytes cultured in vitro

A cell type, preadipocytes, isolated from the stroma of adult human adipose tissue appears capable of differentiating, in culture, into a cell with morphological features similar to that observed in terminally differentiated human adipocytes cultured under similar conditions. During this process of differentiation, preadipocytes develop extensive rough endoplasmic reticulum with prominent cisternae, the chromatin of most nuclei becomes decondensed and lipid bodies accumulate to levels observed in cultured adipocytes. Fibroblasts derived from non-adipose tissue do not undergo the same morphological changes when cultured under similar conditions.

The synthesis of cartilage collagen by rabbit and human chondrocytes in primary cell culture

This report describes a method for preparing primary cell cultures of differentiated rabbit sternal and human vertebral cartilage cells. These cell cultures were shown to synthesize primarily alpha1 chains, which is taken to mean that at least 82% of the collagen produced is cartilage specific collagen (type II).

An effect of accumulated matrix on sulfation among cells in a cartilage colony: an autoradiographic study

In this report an autoradiographic approach is used to compare synthetic activities of cells within differentiated cartilage colonies. While amino acid incorporation is umiform throughout the colony, H-3-uridine is incorporated more actively by cells having little matrix, cells which are typically in the peripheral regions of a colony. On the other hand S-35-O4 is incorporated most actively by cells in the colony centers. This difference in sulfation appears to occur independently of the mitotic state of the cells, since it is apparent in both growing and near-stationary cultures. Instead, there is a correlation between the accumulation of extracellular matrix and more active levels of sulfation. In support of the idea that matrix creates a microenvironment more favorable to chondrogenesis is the observation that a brief treatment with hyaluronidase, which removes about 60% of the S-35-O4 from prelabeled cultures, depresses isolation of labeled glycosaminoglycans. The possible role of extracellular matrices in altering the expression of differentiated functions by creating a more favorable microenvironment is considered.

Influence of external potassium on the synthesis and deposition of matrix components by chondrocytes in vitro

The effect of a high external potassium concentration on the synthesis and deposition of matrix components by chondrocytes in cell culture was determined. There is a twofold increase in the amount of chondroitin 4- and 6-sulfate accumulated by chondrocytes grown in medium containing a high potassium concentration. There is also a comparable increase in the production of other sulfated glycosaminoglycans (GAG) including heparan sulfate and uncharacterized glycoprotein components. The twofold greater accumulation of GAG in the high potassium medium is primarily the result of a decrease in their rate of degradation. In spite of this increased accumulation of GAG, the cells in high potassium fail to elaborate appreciable quantities of visible matrix, although they do retain the typical chondrocytic polygonal morphology. Although most of the products are secreted into the culture medium in the high potassium environment, the cell layer retains the same amount of glycosaminoglycan as the control cultures. The inability of chondrocytes grown in high potassium to elaborate the typical hyaline cartilage matrix is not a consequence of an impairment in collagen synthesis, since there is no difference in the total amount of collagen synthesized by high potassium or control cultures. There is, however, a slight increase in the proportion of collagen that is secreted into the medium by chondrocytes in high potassium. Synthesis of the predominant cartilage matrix molecules is not sufficient in itself to ensure that these molecules will be assembled into a hyaline matrix.