PRODUCTION AND CHARACTERIZATION OF MULTIPLE-LAYERED POPULATIONS OF ANIMAL CELLS

Dense populations containing 129 x 10⁶ Jensen sarcoma, 134 x 10⁶ DON Chinese hamster, 28.9 x 10⁶ WI-38 human diploid, 61.8 x 10⁶ HEp-2 human carcinoma, and 67.4 x 10⁶ WISH human amnion cells were produced from dilute inocula, 0.85 to 5.33 x 10⁶, in 7 to 8 days in a perfusion system using replicate T-60 flasks. Perfusion rates as high as 560 ml medium/day/T-60 were required to maintain pH (to ca ±0.1 unit) and adequate nutrient supplies. The cell densities encountered are described by the term "monolayer equivalents" (M.E.), defined as number of cells per culture divided by number of cells in a monolayer. The M.E.'s for T-60 cultures containing unusually dense populations of 40 x 10⁶ WI-38 and 250 x 10⁶ DON cells (9-day perfusion) were 5 and 17, respectively, and numbers of cells in illustrations of stained cross-sections of membranes from these cultures were in excellent agreement. Threshold M.E.'s exist below which proliferation is the chief cellular activity and above which one or more cell functions may predominate even though proliferation persists. Cellular nutrition and metabolism may change with changes in M.E., as illustrated in different patterns of glutamic acid, proline, and glycine utilization or production in dense vs. dilute WI-38 cell populations. The results indicated that the role of contact inhibition phenomena in arresting cellular proliferation was diminished in perfusion system environments.     

Changes in membrane transport function in G0 and G1 cells

Confluent quiescent monolayers of aneuploid and euploid cells in culture can be stimulated to proliferate by appropriate nutritional changes. In confluent monolayers of WI-38 human diploid fibroblasts the uptake of cycloleucine is increased three hours after these cells are stimulated to proliferate by a change of medium plus 10% serum. No changes in the uptake of cycloleucine are observed in logarithmically-growing WI-38 cells exposed to fresh medium plus 10% serum, or in WI-38 confluent monolayers in which the conditioned medium has been replaced by fresh medium with 0.3% serum (a change that does not cause stimulation of cellular proliferation in WI-38 cells). In 3T6 cells in the stationary phase stimulated to proliferate by nutritional changes, there is a prompt increase in the uptake of cycloleucine, within one hour after stimulation of cell proliferation. Similar results were obtained with stationary 2RA cells which are SV-40 transformed WI-38 fibroblasts. In addition, chromatin template activity which is known to increase in the early stages after stimulation of confluent WI-38 cells, was unchanged in confluent 3T6 or 2RA cells stimulated to proliferate. These results show that at least two of the very early biochemical events occurring in response to stimulation of cell proliferation are different in WI-38 diploid cells and in aneuploid 2RA or 3T6 cells. It is proposed that WI-38 cells in the stationary phase are arrested in the G₀ phase of the cell cycle, while 2RA and 3T6 cells are arrested in the G₁ phase.     

Cultivation and Survival Studies of Neisseria gonorrhoeae in a Human Diploid Cell Strain

Neisseria gonorrhoeae was cultivated in a human diploid cell strain (WI-38). Eighty percent of the cultures contained viable gonococci for at least 4 m at 36°C, as evidenced by subculture to brain heart infusion broth. Monthly subcultures of bacteria could be made to fresh WI-38 cultures for at least 11 monthly passages with a 69% survival rate. The identity of gonococci was confirmed by morphology, gram staining, oxidase testing and fermentation reactions. Viability in brain heart infusion broth, minimum essential medium (Eagle), and WI-38 spent fluid was of much shorter duration. The organisms grown in WI-38 cultures appeared to orient largely in the vicinity of the WI-38 cells as well as within the cytoplasm of the cells.     

Inhibition by collagen chains of lysyl hydroxylase of chick embryo and of WI-38 human lung fibroblasts.

Lysyl hydroxylase from chick embryos was strongly inhibited by heat-denatured collagens from various vertebrate sources, and by separated a chains and β components of rat tail tendon collagen. The kinetics exhibited with this enzyme when heat-denatured calf or rabbit skin collagens was used showed a mixed type of inhibition. On the other hand, a preparation of homologous heat-denatured 4,5-³H-L-lysine-labeled collagen, in itself an extremely poor substrate for the hydroxylase, showed non-competitive inhibition with a K_i of about 8–9 μM. Finally, the lysyl hydroxylase preparations from WI-38 fetal human lung fibroblasts and from transformed WI-38 cells (WI-38 VA 13) were also inhibited by heat-denatured collagens or, where tested, by separated collagen chains.     

INTERMITTENT DNA SYNTHESIS AND PERIODIC EXPRESSION OF ENZYME ACTIVITY IN THE CELL CYCLE OF WI-38

Synchronous cultures of WI-38 were obtained using an automated system for detachment and partitioning of mitotic cells which operates without the use of inhibitors, altered medium, or lowered temperatures. The generation time in synchronous WI-38 is 19.5 h and the duration of S phase when determined from the percentage of labeled metaphase cells or nuclei is 12 h. DNA replication in WI-38 occurs in three temporally distinct and rapid bursts separated by intervals of greatly reduced synthesis within what is nominally described as the DNA synthetic (S) period. Lactate dehydrogenase (LDH) displayed maxima in G₁ between 2 and 4 h and again at 10 and 16 h. Peaks in LDH activity were coordinated with DNA replication in a fashion similar to that reported for diploid Chinese hamster cells. Oscillations in LDH activity are more pronounced in normal diploid fibroblasts than in established and neoplastic lines.     

The growth of WI-38 cells in a serum-free,growth factor-free,medium with elevated calcium concentrations

Summary The growth of WI-38 cells in serum-free growth medium with and without hormone supplementation in the presence of elevated Ca²⁺ concentrations was investigated. At 5 mM CaCl₂, WI-38 cells seeded at low density without serum or hormone supplementation showed up to a 12-fold increased in cell number at saturation density over that obtained at day 1. Saturation densities were comparable when either 5 mM CaCl₂ or epidermal growth factor (1 mM CaCl₂) was used in the presence of insulin, dexamethasone and transferrin. Combining suboptimal doses of epidermal growth factor and CaCl₂ resulted in an additive effect on saturation density. Thus, nornal human diploid cells are capable of substantial growth in serum-free, hormone-free growth medium. In contrast, confluent cultures refed with the same medium are not responsive to elevated Ca²⁺ concentrations. In fact, elevated Ca²⁺ concentrations inhibited the proliferative response of confluent cultures to epidermal growth factor, but enhanced their response to the combined treatment of insulin, transferrin and dexamethasone. This work was supported by the United States Public Health Society grants T-32, CA09171 and AG-00378. Editor's Statement This paper rigorously dissects the interplay among external Ca²⁺ concentration, cell density and specific growth factors on fibroblast growth in defined medium. Wallace L. McKeehan     

epsilon-(gamma-Glutamyl)lysine isopeptide bonds in normal and virus transformed human fibroblasts.

Normal human lung cells (WI-38) possessed 20–40 times more ε-(γ-glutamyl)lysine isopeptide bonds than Simian virus transformed counterparts, WI-38 VA13A and WI-38 VA13-2RA. Normal cells arrested in an essentially nonmitotic state had more isopeptide bonds than proliferating cells. Isopeptide content paralleled the transglutaminase activity of these cells. The results suggest that isopeptide crosslinks contribute to a cellular architecture conducive to a nonproliferating state.     

beta-Adrenergic receptors and cyclic AMP responses to epinephrine in cultured human fibroblasts at various population densities

The beta-adrenergic receptors of the intact human lung diploid fibroblast line Wl-38 and an SV-40 transformed clone of Wl-38, Wl-38-VA-13-2RA (VA13), were estimated in experiments utilizing the beta-adrenergic ligand, 125l-hydroxybenzylpindolol (125IHYP). When specific 125IHYP binding was measured in cells grown to relatively low population densities (0.15x10(6)cells/35mm dish), both Wl-38 and VA13 cells had approximately 40,000 beta-adrenergic receptors per cell. Wl-38 cells, when cultured to a high population density (0.5x10(6) cells/35/mm dish) had clearly diminished numbers of beta-adrenergic receptors and greatly decreased cAMP responses to epinephrine stimulation. On the other hand, in VA13 cells, neither the receptor number nor the beta-adrenergic response was affected by cell population density. In Wl-38 cells, the diminished cAMP response to epinephrine paralleled the decrease in number of beta-adrenergic receptors. Prostaglandin E1 (PGE1) stimulation of cAMP levels was unaffected by cell population density in either Wl-38 or VA13 cells. Thus, increased cell population density, perhaps related to density dependent inhibition of growth, caused a specific diminution in 125IHYP binding concomitant with decreased cAMP responses to epinephrine.     

Adenosine 3',5'-monophosphate-dependent protein kinase(s) in diploid and SV40 transformed human fibroblasts.

Cyclic AMP-dependent protein kinases (EC 2.7.1.37; ATP:protein phosphotransferase) in the human diploid fibroblast WI-38 and an SV40-transformant WI-38-VA13-2RA (VA13) have been compared on the basis of their concentrations in cells, isoenzyme composition and susceptibility to hormonal activation. In high population density cultures, total soluble cyclic AMP-dependent kinase activities measured with histone were essentially the same in WI-38 and VA13. Two soluble protein kinase forms separated by chromatography on DEAE-cellulose were present in both cell lines. The concentration of cyclic AMP required for half-maximal activation of both enzyme forms was 10-30 nM. Overall kinase stimulation was greater for the Peak I enzymes. Kinase activation induced in the presence of 0.5 M KCl was more rapid and complete for the Peak I enzymes. Under conditions which elevated the concentration of cyclic AMP in WI-38 and VA13 cells the activities of the soluble histone kinases were increased. Incubation of the cells with either of 5.7 micronM prostaglandin E1 or 1 micronM isopropylnorepinephrine induced complete activation of the cyclic AMP-dependent histone kinases within 5 min and maintained the effect for 20 min. When intracellular cyclic AMP levels were raised by prostaglandin E1, activation of glycogen phosphorylase (assayed-AMP) suggested that this enzyme cascade involving cyclic AMP-dependent protein kinase(s) was intact and responsive in both cell lines.     

The culture of rat myeloma and rat hybridoma cells in a protein-free medium

Y0 is a rat x rat hybridoma cell line, which does not secrete immunoglobulin, produced using a fusion partner derived from the Y3 (Y3,Ag.1.2.3) rat myoloma cell line. Y0 and Y3 have both been widely used as fusion partners in the production of rat x rat hybridomas. Y0 has also been used in recombinant gene technology. Y0 cells grown in shake flask culture, using RPMI 1640 medium with 4mM l-glutamine and 5% foetal bovine serum, reached a maximal cell density of 1.5×10⁶ cells ml^–1 with 86% viability. Y0 cells which has been adapted to grow in ABC protein-free medium reached a maximal density, in shake flask culture, of 8.75×10⁵ cells ml^–1 with 79% viability. An improved protein-free medium, designated W38 medium, was developed. In shake flask culture, W38 medium supported Y0 cell growth to a density of 2.02×10⁶ cells ml^–1 with 96% viability. Two Y3 hybridomas, YID 13.9.4 cells and SAM 618 cells were adapted to growth in W38 medium. For both hybridomas, cell growth and product yield in shake flask culture using W38 medium was superior to that obtained with serum-containing RPMI 1640 medium.Abbreviations F12 Hams F12 medium - DMEM Dulbeccos medium - RPMI RPMI 1640 medium - FBS foetal bovine serum     

Dissimilar cyclic nucleotide phosphodiesterase activities in subcellular fractions from normal and SV40-transformed WI-38 fibroblasts.

Broken cell preparations of WI-38 and SV40-transformed WI-38 (VA13) fibroblasts were used to compare the cyclic nucleotide phosphodiesterase activities of the two cell strains. The bulk of the cAMP or cGMP phosphodiesterase activity of WI-38 and VA13 homogenates was found in the 100,000 x g fibroblast supernatant fractions. WI-38 and VA13 soluble phosphodiesterase activities showed anomalous kinetic behavior with either cAMP or cGMP as the substrate. At low substrate concentrations, e.g., 0.1 muM, WI-38 supernatant fractions hydrolyzed cGMP much more rapidly than cAMP. At high substrate concentrations, e.g., 100muM, the same enzyme preparations degraded cAMP more than twice as fast as cGMP. In contrast, VA13 soluble phosphodiesterase activity catalyzed the hydrolysis of a wide range of cAMP and cGMP concentrations at similar rates. Phosphodiesterase activity in WI-38 supernatant fractions was generally more sensitive than that of the comparable VA13 enzyme activity to inhibition by MIX and papaverine. The cAMP phosphodiesterase activity of both WI-38 and VA13 supernatant preparations was decreased by cGMP in a concentration-dependent manner. cAMP was an effective inhibitor of cGMP hydrolysis by VA13 soluble phosphodiesterase activity. Yet, the cGMP phosphodiesterase activity of WI-38 supernatant fractions was only slightly reduced in the presence of cAMP. DEAE-cellulose chromatography of WI-38 and VA13 supernatant preparations revealed two major peaks of phosphodiesterase activity for each cell type. WI-38 peak I showed much greater activity with 1muM cGMP than with 1muM cAMP and appeared to be composed of two different phosphodiesterase activities. WI-38 peak Ia included phosphodiesterase activity which could be stimulated by boiled, dialyzed fibroblast homogenates while WI-38 peak Ib coincided with column fractions which contained most of the cyclic GMP hydrolytic activity. VA13 peak I phosphodiesterase activity was eluted from DEAE cellulose columns at the same ionic strength as WI-38 peak Ia and hydrolyzed these two substrates at nearly identical rates. This enzyme activity was also increased in the presence of boiled, dialyzed fibroblast preparations. Peak II phosphodiesterase activities from both WI-38 and VA13 fibroblasts were relatively specific for cAMP as the substrate. Phosphodiesterase activity with the properties of WI-38 peak Ib was not isolated from VA13 supernatant fractions. These results suggested that the dissimilar patterns of cAMP accumulation in WI-38 and VA13 cultures may be at least partially related to different phosphodiesterase activities in the normal and the transformed fibroblasts.     

Changes in enzymic activity during cultivation of human cells in vitro

The composition of chromatin, its template activity and the activity of certain chromatin-associated enzymes, including DNA polymerase (DP) and soluble RNase, DNase, DP and seryl tRNA synthetase, were examined in early and late passage of WI-38 cells and of WI-38VA13 cells.No significant changes in soluble RNase, DNase, seryl tRNA synthetase or soluble and chromatin-associated DP were found with increasing passage of WI-38 cells. The activity of seryl tRNA synthetase and DP in WI38VA13 cells was, however, significantly higher than WI-38 cells in all passages. A decline in RNA synthesizing activity of chromatin, an increase in the proportion of RNA and histone in chromatin, as well as an increase in the activities of ‘chromatin-associated enzymes’ (RNase, DNase, protease, nucleoside triphosphatase, DPN pyrophosphorylase) were noted in WI-38 cells with increasing passages. Although RNA synthesizing activity of chromatin from WI38VA13 cells was lower than that from WI-38 cells, the former also were much lower in ‘chromatin-associated enzymes’. An increase of chromatin-associated enzymes responsible for RNA, DNA and protein degradation in WI-38 cells in successive passages, and a much lower activity of these enzymes in WI-38VA13 cells (which have an indefinite doubling potential in vitro) suggests that an elevation in the activity of these enzymes, which would seriously interfere with the chromatin function, could result in ‘aging’ of WI-38 cells.     

Direct mitogenic effects of human somatomedin on human embryonic lung fibroblasts

The ability of purified basic somatomedin to reinitiate cell division in nondividing cultures of human embryonic lung fibroblasts (WI-38) maintained in serum-free medium was determined in order to assess the direct mitogenic effect of this substance on mammalian tissue. Resting cultures were prepared by incubation of the cells in serum-free medium for 48–72 hours. Addition of partially purified somatomedin resulted in cellular hypertrophy, DNA synthesis and cell division with a time course similar to that seen when serum was added. Although cells divided in response to physiological concentrations of somatomedin, doses up to 100x in excess of this did not produce as much cell division as 10% fetal calf serum. Addition of fresh medium containing somatomedin to cells previously stimulated by somatomedin failed to induce further cell division. A highly purified somatomedin preparation also stimulated cell division.     

Senescent human diploid cells (WI-38) : Attempted induction of proliferation by infection with SV40 and by fusion with irradiated continuous cell lines

When proliferating WI-38 cells (phase II and early phase III) were infected with the Simian papovavirus SV40, or fused with lethally irradiated cells of the continuous line VA13 (containing the SV40 genome), they underwent morphological changes, showed accelerated proliferation and subsequently ceased proliferation (crisis). Senescent WI-38 cells maintained for weeks after the termination of proliferation (late phase III), however, showed neither accelerated proliferation, nor morphological changes by infection or by fusion. Proliferating WI-38 cells fused with lethally irradiated cells of several continuous cell lines, such as HeLa, did not produce continuously proliferating cell lineages. Genes responsible for the morphological changes do not appear to be responsible for the property of continuous proliferation. The crisis of morphologically changed cells appears to be equivalent to the senescent state (late phase III) of normal human diploid cells.     

Enhanced transglutaminase activity in transformed human lung fibroblast cells after exposure to sodium butyrate

The low level of transglutaminase activity in virus-transformed human embryonic lung fibroblasts (WI-38 VA13A) increased markedly when cells were exposed to sodium butyrate. The effect of sodium butyrate was time- and concentration-dependent and fully reversible. Transformed cells exposed for 5 days to 1 mM sodium butyrate had fewer cells, showed an 8–10-fold higher transglutaminase activity, and stained more abundantly for transglutaminase and pericellular fibronectin than control cells when examined by indirect immunofluorescence. Non-transformed cells (WI-38) showed only a 2–4-fold increase in transglutaminase activity when treated in a similar manner. Studies with metabolic inhibitors revealed the increase in activity was the result of synthesis of new protein. Kinetic studies showed the affinity of putrescine for the enzyme was essentially unchanged but the number of active sites increased 9-fold following exposure to sodium butyrate. Enhanced transglutaminase activity returned to control levels within 7 days after subculture and sodium butyrate removal. These findings suggest that sodium butyrate offers a potential model system to understand better the role of transglutaminase in cells in culture; particularly growth control in transformed cells.     

Effect of cell cycle inhibitor p19ARF on senescence of human diploid cell

To investigate the effect of cell cycle inhibitor p19ARF on replicative senescence of human diploid cell, recombinant p19ARF eukaryotic expression vector was constructed and p19ARF gene was transfected into human diploid fibroblasts (WI-38 cells) by liposome-mediated transfection for overexpression. Then, the effects of p19ARF on replicative senescence of WI-38 cells were observed. The results re- vealed that, compared with control cells, the WI-38 cells in which p19ARF gene was introduced showed significant up-regulation of p53 and p21 expression level, decrease of cell generation by 10 12 generations, decline of cell growth rate with cell cycle being arrested at G1 phase, increase of positive rate of senescent marker SA-β-gal staining, and decrease of mitochondrial membrane potential. The morphology of the transfected fibroblasts presented the characteristics changes similar to senescent cells. These results indicated that high expression of p19ARF may promote the senescent process of human diploid cells.     

Perfusion culture using microcarrier for the production of Varicella-Zoster virus in human embryonic lung cells

Perfusion culture with microcarriers was conducted to produce cell-associated and cell-free Varicella-Zoster virus (VZV) with human embryonic lung cells. After the cells were infected with VZV infected cells, glucose in the medium decreased rapidly, suggesting that VZV propagation was related closely to the use of glucose. While the yield of cell-associated VZV in microcarriers was 9,350 PFU/cm2, almost two-thirds of that in T-80 flask and cell factory, the yield of cell-free VZV in microcarriers was only about 10% of that in T-80 flask and cell factory.     

Development of a live attenuated varicella vaccine.

The Oka strain of varicella virus, isolated in our labolatory, was serially cultivated in guinea-pig embryo cultures (GPEC), and a considerable amount of cell-free virus was obtained from infected cell. GPEC passage virus at the 6th passage level was used in a small scale field trial. Susceptible children of 1 to 10 years old were injected subcutaneously with 100 to 1,000 PFU of virus. No clinical reactions due to the vaccination were observed in any children, and a high rate of antibody response was obtained with viral doses of more than 200 PFU. Attenuated virus obtained by passage in GPEC was propagated in human diploid (WI-38) cells, and it was also effective in inducing an immune response without clinical reactions. The results show that the Oka strain of varicella virus passaged in GPEC and human diploid (WI-38) cells may be used safely and effectively as a live attenuated vaccine.     

Carnitine uptake and fatty acid utilization by diploid cells aging in culture

Uptake of carnitine by cultured human fetal lung flbroblasts (WI-38 and IMR-90) and by smooth muscle cells from calf aorta and from human uterus was found to be temperature dependent and saturable. IMR-90 cells showed an apparent K_m of 6–8 μM and a V of 21–28 pmol/h/10⁶ cells for l-carnitine. Transport was abolished by N-ethylmaleimide and was inhibited variably by octanoyl-d-carnitine, d-carnitine, and carbonyl cyanide p-trifluoromethoxyphenylhydrazone. Although WI-38 and IMR-90 cells accumulate lipids as they age in culture, they take up carnitine as rapidly as do smooth muscle cells of aorta and uterus that do not exhibit such accumulation. Comparison of the rates of carnitine uptake by IMR-90 fibroblasts during the logarithmic phase of growth shows no difference between “young” and “old” cultures. In contrast, when confluent or postconfluent monolayers were compared and uptake expressed as a function of cell number, cells grown from late passages took up carnitine more rapidly than did cells grown from early passages. However, when account was taken of cell size, and carnitine expressed as a function of cell volume, the differences in carnitine uptake between early and late passages were no longer apparent for the confluent or postconfluent monolayers examined. Moreover, late passage fibroblasts took up and oxidized radioactive palmitate at least as rapidly as did cells from early passages. Our results suggest that accumulation of lipid in aging fibroblasts is not due to decreased carnitine uptake or fatty acid oxidation.