Mitomycin C treated cells as feeders

Feeder cells treated with ethanol can be used to maintain self-renewal and pluripotency of human pluripotent stem cells

Feeder cells play an important role in the culture of human pluripotent stem cells (hPSCs) in vitro. Previously, we used methanol as a fixative to prepare feeder cells for the cultivation of pluripotent stem cells (PSCs), and this method could maintain the self-renewal and pluripotency of PSCs. However, methanol is toxic, and so here we examined whether ethanol could be used to prepare feeder cells as a fixative for hPSC culturing. Primed, naïve, and extended human embryonic stem cells and induced pluripotent stem cells can maintain self-renewal and undifferentiated potential on feeder cells treated with ethanol for an extended period. RNA sequencing analysis showed that the expression of collagen-related genes in hPSCs cultured on feeder cells treated with ethanol was significantly lower as compared with hPSCs cultured on feeder cells treated with mitomycin C. Therefore, we speculate that the signaling pathway mediated by collagen-related genes may, at least in part, contribute to the maintenance of self-renewal and pluripotency of PSCs induced by feeder cells treated with chemicals.

Isolation, culture and characterisation of somatic cells derived from semen and milk of endangered sheep and eland antelope

Semen and milk are potential sources of somatic cells for genome banks. In the present study, we cultured and characterised cells from: (1) cooled sheep milk; (2) fresh, cooled and frozen–thawed semen from Gulf Coast native (GCN) sheep (Ovis aries); and (3) fresh eland (Taurotragus oryx) semen. Cells attached to the culture surface from fresh (29%), cooled (43%) and slow-frozen (1°C/min; 14%) ram semen, whereas no attachment occurred in the fast-frozen (10°C/min) group. Proliferation occurred in fresh (50%) and cooled (100%) groups, but no cells proliferated after passage 1 (P1). Eland semen yielded cell lines (100%) that were cryopreserved at P1. In samples from GCN and cross-bred milk, cell attachment (83% and 95%, respectively) and proliferation (60% and 37%, respectively) were observed. Immunocytochemical detection of cytokeratin indicated an epithelial origin of semen-derived cells, whereas milk yielded either fibroblasts, epithelial or a mixture of cell types. Deoxyribonucleic acid microsatellite analysis using cattle-derived markers confirmed that eland cells were from the semen donor. Eland epithelial cells were transferred into eland oocytes and 12 (71%), six (35%) and two (12%) embryos cleaved and developed to morulae or blastocyst stages, respectively. In conclusion, we have developed a technique for obtaining somatic cells from semen. We have also demonstrated that semen-derived cells can serve as karyoplast donors for nuclear transfer.

Comparison of HepG2 feeder cells generated by exposure to gamma-rays, X-rays, UV-C light or mitomycin C for ability to activate 7,12-dimethylbenz[a]anthracene in a cell-mediated Chinese hamster V79/HGPRT mutation assay

The cell-mediated Chinese hamster V79/HGPRT mutagenicity assay is an established in vitro testing method. Although gamma-irradiated human HepG2 hepatoma cells have been used recently for chemical activation, an alternative is now needed due to scheduled retirement of the available gamma-source. X-irradiation, 254 nm UV-C light and mitomycin C were examined as possible HepG2 mitotic inhibitors, and treated cells compared for activation of 7, 12-dimethylbenz[a]anthracene (DMBA). In colony-forming assays, V79 and HepG2 cells differed in sensitivity to DMBA, with V79 survival declining sharply between 1-2.5 microM (LD50=1.75 microM) while HepG2 survival decreased gradually, beginning at 0.01 microM DMBA (LD50=0.045 microM). When HepG2 feeder cells generated by each method were included in V79/HGPRT mutation assays, activation of 1 microM DMBA was found to vary according to the mitotic inhibitor used, with mutation frequencies decreasing in the order 4000 rads gamma-rays>25 microg/ml mitomycin C>4000 rads X-rays>25 J/m2 UV-C light. Only assays containing gamma-irradiated HepG2 cells generated an increase (2-3-fold) in mutation frequency when DMBA exposure was extended from 24 to 48 h. The effect of HepG2 preincubation with either Aroclor 1254 or DMBA on feeder cell activation of DMBA was also assessed using concentrations of Aroclor 1254 (10 microg/ml) or DMBA (1.0 microM) which were found to produce optimum induction of ethoxyresorufin-O-deethylase (EROD) activity (3.1-fold and 2-fold increases, respectively). Compared to results obtained with uninduced HepG2 cells, assays incorporating HepG2 cells activated by either Aroclor 1254 or DMBA produced slightly increased V79/HGPRT mutation frequencies after 24 h of exposure to mutagen; however, a 48 h incubation with mutagen in the presence of HepG2 preincubated with either Aroclor 1254 or DMBA resulted in higher mutation frequencies regardless of the mitotic inhibitor treatment. EROD activity was also induced 1.4-fold following exposure of HepG2 cells to mitomycin C alone. Although gamma-irradiation remains the treatment of choice for producing metabolically active HepG2 feeder cells, comparison of the alternatives tested suggests that mitomycin C would be a convenient and suitable replacement.

The E1B 19-kilodalton protein is not essential for transformation of rodent cells in vitro by adenovirus type 5

The newly constructed adenovirus type 5 mutant in1 carries a single AT base pair insertion immediately after nucleotide position 1715 in the E1B gene sequence which destroys the proximal AUG normally present in E1B messages and prevents production of intact E1B 19-kDa protein in infected cells. We have used in1, variants of in1 containing mutant alleles of viral genes known to enhance transformation frequency, and adenovirus type 5 mutant dl337 (S. Pilder, J. Logan, and T. Shenk, J. Virol. 52:664-671, 1984), in which the sequence between nucleotides 1770 and 1916 within the 19-kDa reading frame is deleted, to test the generally accepted hypothesis that this E1B protein is essential for the transformation of rodent cells and maintenance of the transformed phenotype. We find that these mutants transform rat embryo cells, rat kidney and mouse kidney primary cells, and cells of the 3Y1 rat line with decreased frequencies only when virus is added to these various cells at high input multiplicities of infection. In contrast, when lower doses of virus are used, the mutants transform with wild-type frequencies. Cells infected with higher doses of mutant virus show increased levels of DNA degradation and cell killing compared with those of cells infected with the same levels of wild-type virus, and these effects most likely contribute to the decreased transformation frequencies observed. On the basis of these results and the results of phenotypic analyses of numerous transformants, we propose that the E1B 19-kDa protein is not required for induction and/or maintenance of transformed-cell characteristics in rodent cells infected with adenovirus type 5.

Serial cultivation of epithelial cells from human and macaque salivary glands

To study the regulation of human salivary-type gene expression we developed cell culture systems to support the growth and serial cultivation of salivary gland epithelial and fibroblastic cell types. We have established 22 independent salivary gland epithelial cell strains from parotid or submandibular glands of human or macaque origin. Nineteen strains were derived from normal tissues and three from human parotid gland tumors. Both the normal and the tumor-derived salivary gland epithelial cells could be serially cultivated with the aid of a 3T3 fibroblast feeder layer in a mixture of Ham's F12 and Dulbecco's modified Eagle's media supplemented with fetal bovine serum, calcium, cholera toxin, hydrocortisone, insulin, and epidermal growth factor. Salivary gland epithelial cells cultured under these conditions conditioned to express the genes for at least two acinar-cell-specific markers at early passages. Amylase enzyme activity was detected in conditioned media from cultured rhesus parotid epithelial cells as late as Passage 5. Proline-rich-protein-specific RNAs were detected in primary cultures of both rhesus and human parotid epithelial cells. Neither amylase enzyme activity nor PRP-specific RNAs were detected in fibroblasts isolated from the same tissues. In addition, salivary gland epithelial cells cultured under our conditions retain the capacity to undergo dramatic morphologic changes in response to different substrata. The cultured salivary gland epithelial cells we have established will be important tools for the study of salivary gland differentiation and the tissue-specific regulation of salivary-type gene expression.

Dimethyl sulfoxide enhances lipid synthesis and secretion by long-term cultures of adult rat hepatocytes

Dimethyl sulfoxide (DMSO) was tested for its effects on lipid metabolism of long-term cultures of adult rat hepatocytes. The addition of 1% DMSO to 3T3-hepatocyte cultures was not toxic to cells and in fact treated cultures maintained better their characteristic morphology for up to 14 days of exposure. DMSO treatment increased 2-3 fold the de novo synthesis of total lipids from[14C]acetate. The analysis by thin layer chromatography of cellular and secreted lipids revealed that DMSO increased the levels of cellular triglycerides, phospholipides and free and sterified cholesterol at 7 days of exposure while at 14 days there was also a 2-3-fold increase in medium secreted lipids. Additionally, DMSO increased the activity of glycerol-phosphate dehydrogenase, a marker enzyme of glycerolipid synthesis, by greater than 50% at either 7 or 14 days of exposure. These results show that 1% DMSO not only is not detrimental to cultured hepatocytes but also enhances lipid synthesis and secretion, both hepatic-differentiated functions.

Effects of probucol on lipid metabolism and secretion in long-term cultures of adult rat hepatocytes

To study the effects of probucol on hepatic lipid metabolism, we used adult rat hepatocytes cultured on a feeder layer of 3T3 cells lethally treated with mitomycin C. These cultures synthesize and secrete for at least 2 weeks various lipids from [14C]acetate and [14C]oleate precursors. Treatment with 20 micrograms/ml of probucol for 7 and 14 days decreased the secretion of various radiolabeled lipid species to the culture medium and produced an intracytoplasmic accumulation of triacylglycerol droplets. The lipids whose secretion was most decreased were free and esterified cholesterol (50-70% reduction). Secretion of triacylglycerols and phospholipids was also reduced but to a lower extent. Intracytoplasmic triacylglycerols accumulated and the activity of glycerol phosphate dehydrogenase, a marker enzyme of glycerolipid synthesis, also increased (35-56%). The total incorporation of both radioactive precursors into free and esterified cholesterol and phospholipids was reduced 20-60%. Our data show that 2-week treatment of 3T3-hepatocyte cultures with pharmacological concentrations of probucol reduces significantly lipid secretion and suggest that at least part of the in vivo hypolipidemic effect of probucol could be attributed to a decrease in the secretion of lipids (i.e., lipoproteins) by hepatocytes.

Light microscopic, cytochemical and ultrastructural studies of a rat odontogenic epithelial cell line

An odontogenic epithelial cell line, ROE-2B, was established by propagating disaggregated immature, unmineralized maxillary third molar tooth germs from 11-day old Sprague-Dawley rats on a feeder layer of Mitomycin-C treated NIH 3T3 embryonic mouse fibroblasts. The cell line has been maintained for more than 6 months and through 7 passages. Light microscopic examination of cells revealed colonies with epithelial morphology. Electron microscopic examination confirmed the epithelial nature by the demonstration of tonofilaments, desmosomes and basal lamina. Cells were also shown to have secretory vacuoles, an abundance of granular endoplasmic reticulum, free ribosomes, Golgi complex and mitochondria. Surface activity in the form of pseudopodia-like projections and micropinocytosis were noted. Epithelial cells forming keratin were demonstrated by a positive histochemical reaction with Rhodanile Blue. Immunohistochemical studies showed a positive reaction for CAM 5.2 indicating that the ROE-2B cells express the cytokeratins of simple or glandular epithelia. The ROE-2B cell line will be useful for studies on in vitro biological behaviour of odontogenic epithelial cells, and may allow the establishment of in vitro models of odontogenic tumours.

Synthesis and secretion of apolipoprotein E by cultured human keratinocytes

Non-polar lipids are synthesized by keratinocytes in the epidermis and transported to the extracellular space where they contribute to formation of a permeability barrier. Transport of non-polar lipids in other organs and tissues usually occurs with the lipid complexed to an apolipoprotein. In this study we set out to learn if apolipoprotein E is produced by human epidermal keratinocytes in culture. Analysis of total cellular RNA from cultured keratinocytes showed the presence of human apolipoprotein E mRNA at concentrations ranging from 2.5 to 35 molecules/cell. The cells secrete a protein identified as apo E on the basis of molecular weight, isoform pattern, and immunoreactivity. Enzyme linked immunosorbent assay of media from keratinocyte cultures indicated that apolipoprotein E is secreted at a rate of 0.92 ng/h/10(6) cells.

Growth potential of the cells of permanent lines (HeLa, BHK/21, NRK)

A variety of culture parameters was tested to determine optimum growth conditions for the permanent cell lines HeLa, BHK/21 and NRK. Although the lines grew as well at clonal density as in mass culture, clonal analysis of cells transferred on coverslip fragments showed that only 71%-85% were able to produce permanent sublines. Kinetic analysis of the growth of individual clones showed that they varied widely in growth rate, despite continuous low density propagation designed to select out slowly growing cells. In addition, cytopathology was frequently evident in all lines studied, either when cultured at clonal density or under "ideal" conditions at moderate density. The results indicate that defective cells are continuously produced and that they exist in stable proportion in equilibrium cultures. These findings are at variance with claims that some permanent lines (i.e., HeLa) plate with 100% efficiency. Results are discussed in terms of the methodology used to determine plating efficiency, and also in terms of stochastic theories of cell kinetics, which predict the occurrence of cell death in permanent lines and explain the interconversion of permanent and limited cell lines observed in other systems.

Study of intestinal cell differentiation with monoclonal antibodies to intestinal cell surface components

Monoclonal antibodies that react with antigens of the plasma membrane of rat intestinal villus and crypt cells have been prepared by fusion of mouse myeloma (NSI) cells with spleen cells of mice immunized with various intestinal cellular fractions, including the luminal membrane of adult villus and crypt cells, and of newborn rat intestinal cells. The antigenic targets of most antibodies have been identified. They include major protein components of the brush border (luminal) membrane of adult villus cells (sucrase-isomaltase, maltase, lactase, aminopeptidase N, alkaline phosphatase) and newly identified protein antigens specific for intestinal epithelial cells. Of 25 independently derived monoclonal antibodies prepared, 18 reacted exclusively with the brush border membrane of the villus cells, confirming its unique protein composition. Antibodies specifically staining the crypt cells, the newly differentiated epithelial cells present in the lower half of the villi, the top villus cells, and both villus and crypt cells were also obtained and characterized. These antibodies have been used to study the expression of cell- and tissue-specific functions during differentiation and development of the intestinal epithelium. Contrary to results obtained with polyclonal antisera, no inactive forms of the brush border enzymes have been detected in the crypt cells. The identification of cell surface components expressed at different levels of the villi, and in both undifferentiated and differentiated intestinal cells, suggests that cell differentiation in the intestinal epithelium is a continuous and gradual process involving both transcriptional and translational regulation of different sets of genes.

Crypt cell development in newborn rat small intestine

Three monoclonal antibodies were prepared against luminal membranes from small intestinal cells of 3-d-old rats (YBB 1/27, YBB 3/10) and crypt cell membranes from adult rats (CC 4/80). The antibodies were shown to define specific stages of development of the intestinal crypt cells. The YBB 1/27 antigen was first detected at the luminal membrane of the epithelial cells in fetal intestine at day 20 of gestation; it was confined to the crypt cells and lower villus cells between 1 and 20-22 d after birth, and could not be detected in any region of the intestine in older animals. The YBB 3/10 antigen, identified as a set of high Mr proteins, was localized over the entire surface membrane of fetal intestinal cells and of crypt and villus cells after birth; after weaning (20-22 d after birth) it gradually disappeared from the villus cells and became confined to the region of the crypts. The CC 4/80 antigen, identified as a protein (or a set of related proteins) of molecular mass 28-34 kD, was shown to appear in the crypt cells 10-14 d after birth. Its distribution changed after weaning, when it disappeared from the crypts, and was localized in the absorptive lower villus cells. This change in pattern could, in part, be prematurely elicited by cortisone injection in younger animals. These results have demonstrated the presence of specific surface membrane components on the intestinal crypt cells, and suggested that fetal antigens may be retained in these cells after birth.

Monoclonal antibodies to sucrase/isomaltase: probes for the study of postnatal development and biogenesis of the intestinal microvillus membrane

Two monoclonal antibodies, designated BB 3/34/12 and BB 5/8/40/90, have been produced to rat intestinal sucrase/isomaltase (SI) by the hybridoma technique using microvillus membranes as antigen. The BB 3/34/12 antibody was shown to be specific for the sucrase subunit. These antibodies provided new information regarding the biosynthesis and postnatal development of SI. In rat intestinal fetal transplants, SI was found exclusively in the form of an enzymatically active high molecular weight precursor, confirming our previous observations concerning the role of luminal proteases for the processing of SI in the microvillus membrane. The SI precursor, purified by affinity chromatography using the BB 3/34/12 antibody, had both sucrase and isomaltase activities, suggesting that a single precursor protein generates both sucrase and isomaltase subunits by proteolytic cleavage. The initial appearance of SI during normal postnatal development in the rat intestine was found to be confined to the cells present at the base of the villi. The same localization was observed after precocious induction of SI by cortisone acetate. In both cases, no immunofluorescence was observed in the crypts, suggesting that only the differentiated enterocyte is capable of synthesizing this enzyme. Even at the earliest times of appearance, newly synthesized SI was found almost completely split into its subunits, suggesting that the protease(s) responsible for the processing of the precursor in the microvillus membrane develop(s) in parallel with SI or earlier.

Control of cell proliferation in human glioma by glucocorticoids

Survival and proliferation of cell cultures from human anaplastic astrocytomas were shown to be enhanced by glucocorticoids with an optimal concentration of approximately 2.5 x 10(-5)M (10 micrograms/ml). The stimulation of proliferation was only observed in a clonal growth assay and was reversed as the size of individual colonies reached approximately 50 cells. Above this size, and in regular monolayer cultures, glucocorticoids were found to inhibit cell proliferation as measured by direct cell counting and incorporation of [3H] thymidine. Cultures grown to maximum cell densities in non-limiting medium conditions reached a lower terminal cell density, and had a reduced labelling index with [3H] thymidine in the presence of glucocorticoids. Although there was little difference between the actions of beta-methasone, dexamethasone and ethyl prednisolone, methyl prednisolone was found to be more effective, both in terms of stimulation of clonal growth and inhibition of growth at high cell densities. There was no evidence of cytotoxicity with glucocorticoids up to 5 x 10(-5)M (20 micrograms/ml) and it is suggested that glucocorticoids act via a normal regulatory process, perhaps enhancing cell-cell recognition.

Epithelioid cell cultures from rat small intestine. Characterization by morphologic and immunologic criteria

Rat small intestinal epithelial cell lines have been established in vitro and subcultured serially for periods up to 6 mo. These cells have an epithelioid morphology, grow as monolayers of closely opposed polygonal cells, and during the logarithmic phase of growth have a population doubling time of 19--22 h. Ultrastructural studies revealed the presence of microvilli, tight junctions, an extensive Golgi complex, and the presence of extracellular amorphous material similar in appearance to isolated basement membrane. These cells exhibit a number of features characteristic of normal cells in culture; namely, a normal rat diploid karyotype, strong density inhibition of growth, lack of growth in soft agar, and a low plating efficiency when seeded at low density. They did not produce tumors when injected in syngeneic animals. Immunochemical studies were performed to determine their origin using antisera prepared against rat small intestinal crypt cell plasma membrane, brush border membrane of villus cells and isolated sucrase-isomaltase complex. Antigenic determinants specific for small intestinal epithelial (crypt and villus) cells were demonstrated on the surface of the epithelioid cells, but they lacked immunological determinants specific for differentiated villus cells. An antiserum specifically staining extracellular material surrounding the cells cultured in vitro demonstrated cross-reactivity to basement membrane in rat intestinal frozen sections. It is concluded that the cultured epithelioid cells have features of undifferentiated small intestinal crypt cells.

Use of enzyme-deficient cell lines as feeder layers

Enzyme-deficient cell lines, lacking TK or HPRT and therefore unable to grow in HAT medium, may be used as feeder layers to enhance clonal growth of wild-type cells. Low numbers of wild-type test cells may be plated in HAT medium with 5 X 10(5) HAT-sensitive feeder cells per Petri dish. The feeder cells remain attached and metabolizing for 1 to 2 weeks, but ultimately die and detach, leaving colonies of test cells. This feeder layer technique is very simple and flexible and could have wide applicability.

Effects of dexamethasone and betamethasone on in vitro cultures from human astrocytoma

Cultures of human astrocytoma have been derived by collagenase digestion and are presumed, from their aneuploid karyotypes, to be predominantly neoplastic. Early passage cultures in proliferative phase have been cloned in the presence of dexamethasone and betamethasone, both commonly used in management of patients with brain tumours. These steroids raise both the cloning efficiency and the proliferative capacity of cells within each clone. Inhibition was detected only in very high steroid concentrations (25-50 microng/ml). Since these concentrations are unlikely to be attained in vivo it is concluded that anticipated physiological levels of these steroids enhance cell survival at low densities in culture. The significance of this in vivo is discussed.