Maintenance of expression of differentiated function of kidney cells following transformation by SV40 early region DNA

Generation and Characterization of Eptesicus fuscus (Big brown bat) kidney cell lines immortalized using the Myotis polyomavirus large T-antigen

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Eptesicus fuscus kidney cells immortalized using Myotis polyomavirus T-antigen.

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E. fuscus interferon competent kidney cell line supports the growth of vesicular stomatitis virus, porcine epidemic diarrhea virus, herpes simplex virus and Middle-East respiratory syndrome coronavirus.

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All cell lines exhibit a marker for fibroblasts (vimentin), some also exhibit an epithelial marker (cytokeratin).

It is speculated that bats are important reservoir hosts for numerous viruses, with 27 viral families reportedly detected in bats. Majority of these viruses have not been isolated and there is little information regarding their biology in bats. Establishing a well-characterized bat cell line supporting the replication of bat-borne viruses would facilitate the analysis of virus-host interactions in an in vitro model. Currently, few bat cell lines have been developed and only Tb1-Lu, derived from Tadarida brasiliensis is commercially available. Here we describe a method to establish and immortalize big brown bat (Eptesicus fuscus) kidney (Efk3) cells using the Myotis polyomavirus T-antigen. Subclones of this cell line expressed both epithelial and fibroblast markers to varying extents. Cell clones expressed interferon beta in response to poly(I:C) stimulation and supported the replication of four different viruses, namely, vesicular stomatitis virus (VSV), porcine epidemic diarrhea coronavirus (PED-CoV), Middle-East respiratory syndrome coronavirus (MERS-CoV) and herpes simplex virus (HSV). To our knowledge, this is the first bat cell line from a northern latitude insectivorous bat developed using a novel technology. The cell line has the potential to be used for isolation of bat viruses and for studying virus-bat interactions in culture.

Establishment, immortalisation and characterisation of pteropid bat cell lines

Background

Bats are the suspected natural reservoir hosts for a number of new and emerging zoonotic viruses including Nipah virus, Hendra virus, severe acute respiratory syndrome coronavirus and Ebola virus. Since the discovery of SARS-like coronaviruses in Chinese horseshoe bats, attempts to isolate a SL-CoV from bats have failed and attempts to isolate other bat-borne viruses in various mammalian cell lines have been similarly unsuccessful. New stable bat cell lines are needed to help with these investigations and as tools to assist in the study of bat immunology and virus-host interactions.

Methodology/Findings

Black flying foxes (Pteropus alecto) were captured from the wild and transported live to the laboratory for primary cell culture preparation using a variety of different methods and culture media. Primary cells were successfully cultured from 20 different organs. Cell immortalisation can occur spontaneously, however we used a retroviral system to immortalise cells via the transfer and stable production of the Simian virus 40 Large T antigen and the human telomerase reverse transcriptase protein. Initial infection experiments with both cloned and uncloned cell lines using Hendra and Nipah viruses demonstrated varying degrees of infection efficiency between the different cell lines, although it was possible to infect cells in all tissue types.

Conclusions/Significance

The approaches developed and optimised in this study should be applicable to bats of other species. We are in the process of generating further cell lines from a number of different bat species using the methodology established in this study.

Characterization of a long-term rat mTAL cell line

A medullary thick ascending limb (mTAL) cell line, termed raTAL, has been established from freshly isolated rat mTAL tubules and cultured continuously for up to 75 passages; it retains characteristics of mTAL cells even after retrieval from storage in liquid nitrogen for several months. The cells express Tamm-Horsfall glycoprotein (THP), a TAL-specific marker, grow to confluence, exhibit a polygonal morphology characteristic of epithelial cells, and form “domes.” Detection of THP, Na+-K+-2Cl−cotransporter (NKCC2), Na+-K+-ATPase, and renal outer medullary K+channel (ROMK) was achieved using indirect immunofluorescence and confocal microscopy. Western blot analysis of NKCC2 expression using two different antibodies revealed a band of ∼160 kDa, and RT-PCR analysis demonstrated the presence of NKCC2 isoforms A and F, which was confirmed by DNA sequencing; transport of Cl−into raTAL cells was inhibited by furosemide. Ouabain- and bumetanide-sensitive oxygen consumption, an index of ion transport activity in the mTAL, was observed in raTAL cells, and the number of domes present was reduced significantly when cells were incubated in the presence of ouabain or bumetanide. The specific activity of Na+-K+-ATPase activity was determined in raTAL cells (0.67 ± 0.18 nmol Pi·μg protein−1·min−1), primary cultures of mTAL cells (0.39 ± 0.08 nmol Pi·μg protein−1·min−1), and freshly isolated mTAL tubules (1.10 ± 0.29 nmol Pi·μg protein−1·min−1), and ∼30–50% of total cellular ATPase activity was inhibited by ouabain, in accord with other mTAL preparations. This cell line will be used in studies that address biochemical, molecular, and physiological mechanisms in the mTAL.

Mutant Tamm-Horsfall Glycoprotein Accumulation in Endoplasmic Reticulum Induces Apoptosis Reversed by Colchicine and Sodium 4-Phenylbutyrate

As a consequence of uromodulin gene mutations, individuals develop precocious hyperuricemia, gout, and progressive renal failure. In vitro studies suggest that pathologic accumulation of uromodulin/Tamm-Horsfall glycoprotein (THP) occurs in the endoplasmic reticulum (ER), but the pathophysiology of renal damage is unclear. It was hypothesized that programmed cell death triggered by accumulation of misfolded THP in the ER causes progressive renal disease. Stably transfected human embryonic kidney 293 cells and immortalized thick ascending limb of Henle's loop cells with wild-type and mutated uromodulin cDNA were evaluated to test this hypothesis. Immunocytochemistry, ELISA, and deglycosylation studies indicated that accumulation of mutant THP occurred in the ER. FACS analyses showed a significant increase in early apoptosis signal in human embryonic kidney 293 and thick ascending limb of Henle's loop cells that were transfected with mutant uromodulin constructs. Colchicine and sodium 4-phenylbutyrate treatment increased secretion of THP from the ER to the cell membrane and into the culture media and significantly improved cell viability. These findings indicate that intracellular accumulation of THP facilitates apoptosis and that this may provide the pathologic mechanism responsible for the progressive renal damage associated with uromodulin gene mutations. Colchicine and sodium 4-phenylbutyrate reverse these processes and could potentially be beneficial in ameliorating the progressive renal damage in uromodulin-associated kidney diseases.

Sensitivity of primary cells immortalised by oncogene transfection for the detection and isolation of foot-and-mouth disease and swine vesicular disease viruses

Primary cells derived from calf thyroid (CTY), calf kidney (CK) and piglet kidney (PK) were immortalised by oncogene transfection and their susceptibility to infection by foot-and-mouth disease (FMD) virus and swine vesicular disease (SVD) virus examined. Eighty-five immortalised cell lines (47 CTY, 20 CK and 18 PK) proved stable upon repeated cell culture passage and many supported the growth of FMD virus and several of the PK cell lines supported SVD virus. However, none of the immortalised lines exhibited either the degree of sensitivity or the specificity for all virus serotypes and strains as shown by primary CTY and IB-RS-2 cell cultures which are routinely employed for vesicular virus diagnosis.

Polarized function of thick ascending limbs of Henle cells in osmoregulation

BACKGROUND

Organic osmolytes are necessary for osmoregulation in mammalian kidney. Since renal epithelial cells in many cases possess specific mechanisms both for uptake and osmotically regulated release, we investigated their localization in polarized cells.

METHODS

An immortalized epithelial cell line derived from the thick ascending limb of Henle's loop (TALH) was used to examine the transport characteristics of the apical and basolateral plasma membranes for osmotic regulation of organic osmolytes. Cells were cultured on filters in a two-compartment chamber.

RESULTS

In culture under hypertonic conditions the TALH cells accumulated in the following balance: sorbitoverline> betaine = myo-inositoverline> glycerophosphoryl choline (GPC). When extracellular osmolarity was decreased, then sorbitol was released on the apical side, whereas betaine and myo-inositol efflux occurred on the basolateral side. GPC release showed no preference of either side. Taurine did not seem to be necessary for osmoregulation under these conditions. Osmotically regulated myo-inositol and betaine uptake was located on the apical side, and choline uptake took place on both sides equally.

CONCLUSION

These results show that in renal epithelial cells, both osmotically induced release and the uptake of organic osmolytes are divided between the apical and the basolateral sides. This might be important for volume regulation.

Extracellular ATP increases [CA(2+)](i) in distal tubule cells. I. Evidence for a P2Y2 purinoceptor

Experiments were performed to characterize the P2 purinoceptor subtype responsible for cytoplasmic calcium mobilization in cells from the initial part of rabbit distal convoluted tubule (DCT). Free calcium concentration was measured in a DCT cell line (DC1) with the probe fura 2. Both ATP and UTP increased cytosolic Ca(2+) concentration ([Ca(2+)](i); EC(50) 3 and 6 microM, respectively). The order of potency for nucleotide analogs was ATP = UTP > adenosine 5'-O-[thiotriphosphate] >> ADP > UDP, which is consistent with the pharmacology of the P2Y2 receptor subtype. The increased [Ca(2+)](i) responses to ATP and UTP were strongly inhibited by suramin. Pretreatment of cells with pertussis toxin (PTX) attenuated the action of both nucleotides. Inhibition of phospholipase C with U-73122 totally blocked the [Ca(2+)](i) response to ATP. Thus ATP- and UTP-stimulated [Ca(2+)](i) mobilization in DC1 cells appears to be mediated via the activation of P2Y2 purinoceptors coupled to a G protein mechanism that is partially sensitive to PTX. Calcium flux measurements showed that lanthanum- and nifedipine-sensitive calcium channels are involved in the [Ca(2+)](i) response to ATP.

Immortalized kidney epithelial cells as tools for hormonally regulated ion transport studies

The development of transgenic mice carrying the simian virus-40 large T antigen gene or the temperature-sensitive simian virus-40 large T antigen gene, either alone or placed under the control of the 5'-regulatory regions of tissue-specific or ubiquitous genes, has permitted the production of differentiated, polarized kidney epithelial cells. This review covers the immortalized cell lines issued from the various parts of the renal tubule and, in particular, the recently established collecting duct cell lines that have been used as ex-vivo cell models to analyze the regulation of ion transport processes by hormones.

Osmotic regulation of the Na+/myo-inositol cotransporter and postinduction normalization

BACKGROUND

In renal cells, hyperosmolarity has been shown to induce the accumulation of myo-inositol, via the Na+/myo-inositol cotransporter (SMIT). Previously we showed that SMIT mRNA in the kidney is localized in the medullary thick ascending limb of Henle (TALH). Here we used renal cells derived from the rabbit outer medullary TALH to examine the regulation of myo-inositol transport by hyperosmolarity. In addition, using both cultured renal and endothelial cells, we examined the normalization of SMIT activity and mRNA levels following induction by hyperosmolarity.

METHODS

TALH cells were exposed to isotonic or hyperosmotic medium, and then SMIT mRNA levels and myo-inositol accumulation were determined. To examine postinduction normalization, cultured endothelial and renal cells were first exposed to hyperosmotic medium and then to isotonic medium containing actinomycin D or cycloheximide. Afterwards, SMIT mRNA levels and myo-inositol accumulation were determined.

RESULTS

Hyperosmolarity increased SMIT mRNA levels and myo-inositol accumulation in TALH cells. The hyperosmolarity-induced increase in myo-inositol uptake by TALH cells was characterized by an increase in the Vmax for the high-affinity myo-inositol transport system, with no change in the Km. This increase was blocked by actinomycin D or cycloheximide. Examination of postinduction normalization showed that returning hyperosmotic-treated cells to isotonic medium caused a rapid reversion of SMIT mRNA levels, followed by a return of myo-inositol accumulation to basal values. However, the addition of cycloheximide or actinomycin D partially to totally prevented the reversal in SMIT mRNA levels and activity.

CONCLUSIONS

These results suggest that RNA and protein synthesis is required for the hyperosmotic induction of SMIT mRNA levels and myo-inositol accumulation by TALH cells. Furthermore, normalization of SMIT mRNA levels and myo-inositol accumulation following hyperosmotic induction requires RNA transcription and protein synthesis.

Characteristics of urea transport of cells derived from rabbit thick ascending limb of Henle's loop

BACKGROUND

The thick ascending limb of Henle's loop (TALH) is thought to be involved in the regulation of the renal urea gradient.

METHODS

We have characterized the uptake of urea (oil density centrifugation and 2-compartment-culture) and volume regulation (impedance measurement) in highly differentiated cells derived from rabbit outer medulla.

RESULTS

TALH cells exposed to 600 mOsm/liter (300 mM urea) shrunk to 72 +/- 5% of the isoosmotic volume. Due to a regulatory volume increase (RVI), the cell volume was almost completely regained at 92 +/- 6% after five minutes. The uptake of 14C-urea in the presence of urea concentrations up to 600 mM did not show any saturation. In the presence of phloretin the urea uptake decreased to 69 +/- 14%. The transport was sodium and chloride independent. Changing the membrane potential caused an increase of regulatory volume increase and urea uptake. Hyperosmolarity induced by sucrose (300 mM) and NaCl (150 mM) caused a decrease of urea uptake to 70 +/- 14% and 53 +/- 11%, respectively. The permeability coefficient (P) in a two compartment culture was P = 1.7 . 10(-6) +/- 0.39.10(-6) cm/second, suggesting a relatively low permeability.

CONCLUSION

Due to the low permeability, it seems impossible to achieve a physiologically significant participation of the TALH in the urea circulation within the nephron. However, the results of this study provides significant hints about the existence of a specific urea transport mechanism that enables the cell to adapt rapidly to different osmolarities.

Involvement of macromolecule synthesis, endonuclease activation and c-fos expression in cisplatin-induced apoptosis of mouse proximal tubule cells

We have previously demonstrated that cisplatin-induced nephrotoxicity is associated with the induction of apoptosis using mouse renal cells derived from the terminal proximal tubule (S3) which is the major target site of cisplatin-induced injury. The purpose of this study was to elucidate the intracellular mechanisms leading to the cisplatin-induced apoptosis of S3 cells. Actinomycin D (an inhibitor of RNA synthesis), cycloheximide (an inhibitor of protein synthesis) and aurintricarboxylic acid (an endonuclease inhibitor) reduced the extent of DNA fragmentation, a biochemical parameter of apoptosis, in cisplatin-treated S3 cells. Furthermore, cisplatin-induced apoptosis of S3 cells was accompanied by an increase in the level of c-fos mRNA expression, which is inhibited by pretreatment of the cells with actinomycin D, but not with cycloheximide or aurintricarboxylic acid. In contrast, outer medullary collecting duct cells treated with cisplatin exhibited morphological changes characteristic of apoptosis and an increase in the level of c-fos mRNA expression, but no increase in the extent of DNA fragmentation. In conclusion, the synthesis of macromolecules such as RNA and protein, endonuclease activation and c-fos expression appear to be involved in the intracellular pathways leading to the induction of apoptosis in cisplatin-treated S3 cells. In addition, the response to cisplatin may be different in different cells.

Detection of human viruses using primary cells immortalised by oncogene transfection, in comparison with primary cells and established cell lines

No single established cell line was found capable of substituting for primary baboon kidney (PBK) or primary rhesus macacque kidney (PRK) cells for detection of human viruses. Although a panel of cell lines could detect influenza, parainfluenza, and enteroviruses, which are among the most important viruses encountered in routine diagnostic laboratories, the sensitivity of this panel was not as high as that of PBK or PRK cells. However, in a promising complementary approach, PBK and PRK cells have been immortalised successfully by oncogene transfection, and some of the resulting cell lines have retained susceptibility to human viruses, and may be suitable for routine diagnostic use.

Characteristics of a rat cortical collecting duct cell line that maintains high transepithelial resistance

This study describes the establishment of a rat kidney cortical collecting duct (CCD) clonal cell line (RCCD1 cells) that maintains high transepithelial resistance and specific hormonal sensitivities. Immortalized cells were obtained by infection of primary cultured CCD cells with the wild-type simian virus 40. Grown on Petri dishes, RCCD1 cells are organized as monolayers of cuboid cells separated by tight junctions and form domes. Grown on permeable filters, confluent RCCD1 cells exhibit high transepithelial resistance (Rt: 2390 +/- 140 omega. cm2), transepithelial potential difference (PD) of -10.5 +/- 1.2 mV lumen negative, an associated short-circuit current (Isc) of 4.3 +/- 0.5 microA/cm2, and generated significant Na+, K+, H+ and HCO3- gradients, reflecting Na+ and H+ reabsorption and K+ and HCO3- secretion. RCCD1 cells exhibit features of both principal (PC) and intercalated (IC) cells. Consistent with PC phenotype, about 50% of the cells were positively stained by a PC-specific agglutinin. In situ hybridization studies revealed the presence of alpha, beta and gamma subunit mRNAs of the amiloride-sensitive epithelial Na+ channel and alpha 1 and beta 1 subunits of Na(+)-K(+)-ATPase. Moreover, Na(+)-K(+)-ATPase was immunolocalized at the basolateral side of the cells. Arginine vasopressin (AVP) induced a significant increase in both cellular cAMP content and Isc. Amiloride decreased in a dose-dependent manner Isc from untreated and AVP-treated RCCD1 cells. In addition, a barium-sensitive K+ conductance was evidenced in the apical side of the cells. Consistent with IC phenotype, isoproterenol (ISO) provoked a large increase in cellular cAMP and stimulated Isc. The effect of ISO on Isc was blocked by 5 x 10(-3) M DPC, a chloride channel blocker. Finally, AVP plus ISO had additive effect on Isc. Taken together, these results provide evidence that the RCCD1 cell line has maintained many of the original properties of rat CCD from which they were derived.

Osmotic regulation of the betaine metabolism in immortalized renal cells

Betaine plays an important role in the osmoregulation of various renal cells. In the kidney betaine synthesis seems to be highest in the cortex, whereas osmotically regulated accumulation seems to play a crucial role in the inner medulla. Therefore, the influence of betaine synthesis on the long-term osmotic regulation of betaine content was investigated in epithelial SV40 transfected cell culture, derived from the outer medullary thick ascending limb of the loop of Henle (TALH) of rabbit kidney. Under hyperosmotic conditions the betaine content of TALH was significantly increased from 218 +/- 35 mumol/g protein (300 mOsm/liter; control) to 334 +/- 27 mumol/g (600 mOsm/liter; P < 0.0005). In addition the intracellular accumulation of 14C-betaine from 14C-choline was significantly elevated from 4.3 +/- 1.0 mumol/g protein x hr) to 8.2 +/- 1.0 mumol/g protein x hr; P < 0.001) under hyperosmotic conditions. Synthesis of betaine was also influenced by the extracellular betaine content. In a betaine free medium the synthesis of betaine was increased by 7% (300 mOsm/liter; NS) or 40% (600 mOsm/liter; P < 0.0001) when compared to betaine containing medium. The alteration of betaine synthesis is presumably caused by osmotic regulation of the betaine aldehyde dehydrogenase. Activity of this enzyme was significantly higher under hyperosmotic conditions compared to isoosmotic control conditions (Vmax 4.1 +/- 0.8 U/g protein; 600 mOsm/liter) versus 1.4 +/- 0.1 U/g (300 mOsm/liter; P < 0.0001), while the affinity to betaine aldehyde remained unaltered. These results demonstrate that during long-term adaptation, betaine synthesis in TALH cells of the outer medulla of rabbit kidney can be regulated by extracellular osmolarity.

Temperature sensitive simian virus 40 large T antigen immortalization of murine odontoblast cell cultures: establishment of clonal odontoblast cell line

During tooth formation instructive epithelial-mesenchymal interactions result in the cytodifferentiation of ectomesenchymal cells into odontoblasts which produce the dentin extracellular matrix (DECM). The purpose of our study was to establish a stable murine odontoblast cell line by immortalization of odontoblasts using retrovirus transfection. In order to accomplish this goal, we utilized a previously characterized odontoblast monolayer cell culture system supportive of odontoblast cytodifferentiation from dental papilla mesenchyme (DPM), expression and secretion of a DECM and dentin biomineralization. First mandibular molars from E-18 Swiss Webster mice were dissected, the DPM isolated, and pulp cells dissociated. Pulp cells (5 x 10(5)/well) were plated as monolayers and grown in alpha-MEM supplemented with 10% FCS, 100 units/ml penicillin and streptomycin, 50 micrograms/ml ascorbic acid. Cultures were maintained for 6 days at 37 degrees C in a humidified atmosphere of 95% air and 5% CO2, with media changes every two days. Immortalization was performed using a recombinant defective retrovirus containing the temperature sensitive SV-40 large T antigen cDNA and the neomycin (G418) resistance gene recovered from CRE packaging cells. Cultures were infected for 24 h with CRE conditioned medium containing 8 micrograms/ml of polybrene, the media was replaced with selective media containing 300 micrograms/ml of G418, and the cultures incubated at 33 degrees C for one month with media changes every 3-5 days. Neomycin resistant cells were cloned by serial dilution to single cells in 96-well culture plates and grown in selection medium at 33 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Pathophysiology of middle ear epithelium: a new role for prostaglandin E2

INTRODUCTION

Otitis media with effusion is a disease of the middle ear epithelium resulting from a decreased sol layer as well as increased mucus secretion and plasma-derived protein transudation, which causes mucus plugging. Because the epithelium keeps the middle ear cavities fluid-free and air-filled, we investigated its fluid transport capacities, which may be involved in both efficacy of the mucociliary clearance and drying-out of the posterior ear cavities (Yen PT et al: Acta Otolaryngol (Stockh) 113, 1993). We have established the absorptive capacity of middle ear epithelial cells in primary culture (Herman P, et al: Am J Physiol 262, 1992). However, the paucity of cells obtained by enzymatic digestion led us to develop a new model for further investigation of middle ear epithelial cell.

METHODS

We established a middle ear cell line (MESV) using simian virus 40 (SV40) infection of middle ear epithelial cells from the Mongolian gerbil.

RESULTS

Investigation of the transport processes using the short-circuit current technique showed that MESV cells retain most characteristics of the original middle ear epithelial cells. Transepithelial sodium transport from the apical to the basal side was responsible for the transepithelial lumen-negative potential difference.

CONCLUSION

The presence of high concentrations of prostaglandin E2 in the middle ear effusions has been documented. This work investigates the effect of prostaglandin E2 on the rate of transepithelial ion transport of MESV cells. Prostaglandin E2 increased the rate of electrogenic sodium transport by means of increase in the intracellular cyclic adenosine monophosphate (cAMP) content. Such a modulation of sodium transport in the course of otitis media could be responsible for the reduced periciliary sol layer that impairs the mucociliary clearance.

Functional properties of proximal tubule cell lines derived from transgenic mice harboring L-pyruvate kinase-SV40 (T) antigen hybrid gene

This study describes the functional characterization of two cell lines derived from the proximal convoluted (PKSV-PCT cells) and proximal straight (PKSV-PR) tubules microdissected out from kidneys of transgenic mice harboring the simian virus 40 (SV40) large T and small t antigens placed under the control of the rat L-type pyruvate kinase (L-PK) 5′ regulatory sequence. Both cell lines exhibited cellular cyclic AMP stimulated by parathormone (PTH) and calcitonin (CT) and a sodium-dependent glucose transporter. Uptake of the fluid-phase marker [3H]inulin showed that both cell lines grown on filters exhibited biphasic apical and basolateral endocytic rates. Results from Northern blot analysis indicate that the expression of the T antigen gene (Tag) is dependent on the concentration of D-glucose in the medium and show that the L-PK construct has maintained its capacity for up- or down-regulation by carbohydrates. Replacement of D-glucose by neoglucogenic substrates (lactate, oxaloacetate) blunted the expression of Tag transcripts and induced arrest of cell growth. Compared to cell grown in D-glucose-enriched medium, the hormonal sensitivities to PTH and CT and the sodium-dependent glucose uptake were unchanged whereas quiescent cells exhibited increased hydrolase content. Thus the proximal function has been preserved in these cultured cells derived from tissue-specific targeted oncogenesis in transgenic mice. As the expression of Tag transcripts is controlled by D-glucose, the structural and physiological characteristics of these cell lines can be studied in either quiescent or active growth conditions.

Middle ear cell line that maintains vectorial electrolyte transport

The middle ear epithelium plays a major role in keeping the temporal bone cavities fluid-free and air-filled, which is a mandatory condition to allow optimum transmission of the sound vibrations from the tympanic membrane to the inner ear. Previous works have recently established the absorptive function of the middle ear epithelium, using primary cultures derived from Mongolian gerbil (Meriones unguiculatus). Because of the paucity of cells as obtained by enzymatic digestion, we developed a middle ear cell line (MESV) using wild-type SV40 infection of primary culture of Mongolian gerbil's middle ear epithelial cells. Transformation was attested by nuclear expression of SV40 large T antigen, prolonged in vitro passages (presently beyond 50 passages), and tumor-inducing ability when subcutaneously injected in athymic mice. Transport properties were evaluated after the fifteenth passage. MESV cells retained most cardinal properties of the original middle ear epithelial cells: cell polarization was evidenced by the presence of mature junctional complexes that separate the cell membrane in two distinct domains, with apical microvilli at the luminal side, and by vectorial sodium transport responsible for the transepithelial lumen-negative potential difference (-9.3 +/- 0.14 mV in culture conditions (n = 9), -2.1 +/- 0.25 mV after overnight growth factors and serum deprivation). Short-circuit current was, like in primary cultures, mainly related to a sodium transport occurring through amiloride-sensitive apical sodium channels, since apical addition of amiloride (10(-5) M) reduced ISC from 7.0 +/- 1.4 to 0.6 +/- 0.1 microA/cm2 (P < 0.01, n = 6). Cellular cAMP content was increased by isoproterenol and prostaglandin E2 from 40.5 +/- 5.6 to 258.5 +/- 17.3 and 55.6 +/- 6.2 pmol/mg protein per 5 min, respectively (P < 0.05, n = 10). Isoproterenol and prostaglandin E2 increased ISC with very similar maximal effects: isoproterenol (10(-4) M) increased ISC from 5.73 +/- 0.31 to 12.77 +/- 0.39 microA/cm2, while prostaglandin E2 increased ISC from 5.47 +/- 0.21 to 12.87 +/- 0.42 (n = 3). Since amiloride (10(-5) M) abolished this stimulation, this may be related to an increase of the electrogenic sodium transepithelial transport. The MESV cell line could provide an interesting tool as a model of middle ear epithelial cells for the study of pathophysiological modulations of ion transport.

Mineralocorticoid receptors in SV40-transformed tubule cell lines derived from rabbit kidney

The presence of mineralocorticoid (MR) and glucocorticoid (GR) receptors was investigated in two renal tubular cell lines, derived from primary cultures of isolated rabbit kidney cortical cells infected with the wild-type SV40 virus, which exhibit thick ascending limb (RC.SV2) and collecting tubule (RC.SV3) phenotypes (Vandewalle et al. J. Cell. Physiol. 141, 1989, 203-221). MR and GR were quantified, in cell monolayers and cell cytosolic fractions, with [3H]aldosterone, [3H]dexamethasone and [3H]RU486, an antiglucocorticoid with no affinity for MR. Cytosolic receptors from RC.SV2 and RC.SV3 cells labeled with [3H]aldosterone, [3H]dexamethasone or [3H]RU486 sedimented at approximately 8 S in a 15-40% glycerol gradient. All steroids displaced bound [3H]dexamethasone to the same extent, suggesting that dexamethasone bound to both MR and GR: under the conditions of assay, [3H]aldosterone binds exclusively to MR, and [3H]RU486 to GR. In both RC.SV2 and RC.SV3 cells, [3H]aldosterone bound to one class of high affinity sites (Kd 0.14-0.8 nM; Nmax 8 to 22 fmol/mg protein). In both cell lines, the number of high affinity binding sites for [3H]dexamethasone ranged from 9 to 18 fmol/mg protein with an affinity of 0.5-1.3 nM. Compared to renal cortex, the most striking observation was a marked decrease in [3H]dexamethasone binding in primary cultures and SV40-transformed cells. These results indicate that MR and GR are expressed in two established mammalian kidney tubular cell lines providing new models of cultured renal cells for studies on the physiological effects of corticosteroid hormones.

Regulation by calcitonin of Na(+)-K(+)-Cl- cotransport in a rabbit thick ascending limb cell line

The hormonal regulation of a Na(+)-K(+)-Cl- cotransport was investigated in a renal tubule cell line (RC.SV2 cells) transformed by the simian virus 40. This cell line has the main characteristics of cells from the thick ascending limb of Henle, including the presence of Tamm-Horsfall protein and stimulation of adenosine 3',5'-cyclic monophosphate (cAMP) production by calcitonin (CT). Kinetic studies with 22Na+, 36Cl-, and 86Rb+ indicated the existence of a Na(+)-K(+)-Cl- cotransport with a stoichiometry of 1Na+:1K+: 2Cl-. All compounds stimulating cAMP production enhanced the ouabain-resistant bumetanide-sensitive (Or-Bs) Rb+ influx mediated by Na(+)-K(+)-Cl- cotransport. CT (100 ng/ml) increased the Or-Bs influx twofold by enhancing maximum velocity without changing the apparent Michaelis constant. The K(+)-channel blocker barium blunted the CT-stimulated Or-Bs influx by 64-74%, whereas the Cl(-)-channel blocker 5-nitro-2-(3-phenylpropylamino)benzoate reduced the CT-stimulated influx by 28-40%. These results suggest that CT stimulates the Na(+)-K(+)-Cl- cotransport by a cAMP-dependent mechanism and that K+ recycling through K+ membrane channels is an important modulator of cotransporter-mediated ion fluxes.

Ammonium chloride-induced acidification in renal TALH SVE.1 cells monitored by 31P-NMR

The aim of this study was to investigate the effect of NH4+ on the intracellular pH in TALH SVE.1 cells derived from the medullary thick ascending limb of Henle's loop (TALH) of rabbit kidney. These cells are specialized to perform NH4+ transport in vivo. Intracellular pH was monitored by 31P-NMR. The steady state intracellular pH (pHi) under standard conditions was 7.24 +/- 0.04 (n = 46). Exposure to NH4Cl resulted in an initial intracellular acidification of the TALH SVE.1 cells, followed by a recovery to the initial steady-state pHi value. The NH4(+)-induced acidification followed saturation kinetics up to 20 mM NH4Cl (delta pHmax = 0.2 pHunits). Half-maximal acidification was observed at 0.6 mmol/l. The intracellular acidification due to NH4Cl exposure was completely inhibited by 0.1 mM of the diuretic bumetanide, an inhibitor of the Na+/K+/2Cl- cotransporter. The effect of bumetanide was dose-dependent and a Ki value of 8.10(-7) M was calculated. NH4+ influx via K+ channels or the (Na+ + K+)ATPase could not be detected. pHi recovery to the initial value was caused mainly by amiloride-sensitive Na+/H+ exchange and to a lesser extent by an amiloride-insensitive system, which was not studied in detail. In the presence of bumetanide, pulses of high concentrations of NH4Cl induced small intracellular alkalinizations. From these experiments, an intrinsic buffer capacity (beta i) in TALH SVE.1 cells of 26 +/- 3 mM x pH-1 (pHi = 7.65) was determined. It could also be shown that the TALH SVE.1 cells exhibit maximal 'functional buffer capability' between pHout 6.9 and 7.3. Within these limits the cells can maintain their intracellular pH at a constant level, even though the extracellular pH changes. These data strongly suggest that the Na+/K+/2Cl- cotransporter is the main site of NH4+ entry into rabbit thick ascending limb cells in culture. A high intracellular buffer capacity and potent acid extrusion mechanism cooperate in counteracting the intracellular acidification caused by NH4+ influx into the cell.

Activation of the simian virus 40 (SV40) genome abrogates sensitivity to AVP in a rabbit collecting tubule cell line by repressing membrane expression of AVP receptors

To analyze the role of SV40 genome in the phenotypic alterations previously observed in SV40-transformed cell lines, we infected rabbit renal cortical cells with a temperature-sensitive SV40 mutant strain (tsA58) and compared the cell phenotypes at temperatures permissive (33 degrees C) and restrictive (39.5 degrees C) for SV40 genome expression. At both temperatures, the resulting cell line (RC.SVtsA58) expresses cytokeratin and uvomorulin, but epithelial differentiation is more elaborate at 39.5 degrees C as shown by the formation of a well-organized cuboidal monolayer with numerous tight junctions and desmosomes. Functional characteristics are also markedly influenced by the culture temperature: cells grown at 33 degrees C respond only to isoproterenol (ISO, 10(-6) M) by a sevenfold increase in cAMP cell content above basal values; in contrast, when transferred to 39.5 degrees C, they exhibit increased sensitivity to ISO (ISO/basal: 19.1) and a dramatic response to 10(-7) M dDarginine vasopressin (dDAVP/basal: 18.2, apparent Ka: 5 X 10(-9) M) which peaks 48 h after the temperature shift. The latter is associated with membrane expression of V2-type AVP receptors (approximately 50 fmol/10(6) cells) which are undetectable when SV40 genome is activated (33 degrees C). Clonal analysis, additivity studies, and desensitization experiments argue for the presence of a single cell type responsive to both AVP and ISO. The characteristics of the RC. SVtsA58 cell line at 39.5 degrees C (effector-stimulated cAMP profile, lack of expression of brush-border hydrolases and Tamm-Horsfall protein) suggest that it originates from the cortical collecting tubule, and probably from principal cells.

An NMR spectroscopic characterization of a new epithelial cell line, TALH-SVE, with properties of the renal medullary thick ascending limb of Henle's loop

NMR spectroscopy has been used to characterize a new renal cell line, TALH-SVE.1, which is derived from the medullary thick ascending limb of Henle's loop. From the 31P-NMR spectrum of a suspension of TALH-SVE cells using the chemical shift of the intracellular inorganic phosphate a value of 7.24 +/- 0.04 for the steady-state intracellular pH (pHi) was determined at pHo = 7.40. In addition, the 31P-NMR spectrum indicated rather high levels of UDPG, a finding confirmed by 1H-NMR spectra of perchloric acid extracts. The 1H-NMR data also demonstrate the presence of 'organic osmolytes' such as inositol, sorbitol, choline and glycerophosphoryl choline (GPC). 13C-NMR spectra of perchloric acid extracts of TALH-SVE cells incubated with [2-13C]- and [3-13 C]alanine were used to determine the relative influx in the Krebs cycle via pyruvate carboxylase (PCB) versus the influx via pyruvate dehydrogenase (PDH). The ratio was 0.41, while about 52% of all acetyl-CoA entering the Krebs cycle was unlabeled. 13C-NMR experiments also indicated that TALH-SVE cells lack gluconeogenic activity. The NMR study presented indicates that TALH-SVE cells possess metabolic pathways similar to those of the parental cells.

Altered growth regulation of rat kidney proximal tubule epithelial cells transformed in vitro by SV40 viral DNA: fibroblast growth factors (heparin-binding growth factors) are potent inducers of anchorage-independent growth

The majority of renal cancers are thought to arise from the proximal tubule epithelium, but little is known about their etiology. In this investigation, we have established an in vitro model to study the transformation of these target cells using rat kidney proximal tubule epithelial cells (RPTE) transformed in defined medium with SV40-viral DNA. Selection by passaging cells onto plastic surfaces yielded a population of cells (SV-RPTE) that expressed keratin and vimentin along with SV40 large-T antigen. The cells were morphologically transformed and lost their differentiated character as determined by several RPTE markers. SV-RPTE cells grew in soft agar in serum-supplemented medium containing insulin, epidermal growth factor, and cholera toxin, but were unable to grow when serum and growth factors were not combined. Acidic and basic fibroblast growth factors (aFGF and bFGF) were unique since they were the only single factor that induced anchorage-independent growth in the presence of serum alone. Transforming growth factor-beta 1 (TGF-beta 1) was a potent inhibitor of anchorage-independent growth, but the inhibition was partially overcome by a combination of growth factors. The growth factor responses of SV-RPTE in monolayer cultures differed from those in soft agar; the cells were more sensitive to growth stimulation by insulin and insulin-like growth factor, neither of which stimulated anchorage-independent growth. SV-RPTE cells in monolayer cultures had also lost the sensitivity to growth inhibition by TGF-beta 1 characteristic of normal RPTE. The RPTE transformation model described here will be very useful for investigating the molecular basis and etiology of renal cancers. Furthermore, the data suggest that maintenance of the transformed phenotype by aFGF and bFGF and loss of negative growth regulation by TGF-beta 1 could play a role in renal carcinogenesis.

Development of new cell lines for animal cell biotechnology

Mammalian cell culture has been an important technique in laboratory-scale experimentation for many decades. Developments in large-scale culture have been due to the need to grow large numbers of cells to support the growth of viruses for vaccine production, and more recently, for growing hybridoma cells as a source of monoclonal antibody. Increasingly, however, pharmaceutical products such as hormones, enzymes, growth factors, and clotting factors are being produced from cell lines which have been manipulated by recombinant DNA techniques. It is clear, therefore, that the high cost of growing mammalian cells on a large scale does not necessarily prohibit their use for biotechnology, and indeed there is considerable evidence to suggest that animal cell biotechnology will continue to be a major growth area in the future.

Maintenance of proximal and distal cell functions in SV40-transformed tubular cell lines derived from rabbit kidney cortex

This paper reports the preparation and describes the properties of three renal tubular cell lines derived using SV40 infection of primary cultures of rabbit kidney cortical cells, enriched in proximal cells. RC.SV1 was initially derived from cultures grown in the presence of fetal calf serum exhibiting a low degree of proximal differentiation. The cells were subsequently adapted to grow in serum-free hormonally defined medium and display basic properties of proximal tubule cells including well-developed apical microvilli, strong expression of brush-border hydrolases, Na+-coupled glucose uptake, and increased cyclic AMP production when exposed to PTH. The other two cell lines were derived from cultures in serum-free hormonally defined medium and propagated in the same medium. They are characterized by some common properties including rare and short microvilli, low expression of apical hydrolases, and low or undetectable Na+-dependent glucose uptake, but differ by their abilities to respond by an increase in cAMP to various hormonal stimuli. RC.SV2 cells are sensitive to calcitonin and to a lesser extent to isoproterenol and PTH, suggesting that they may originate from the thick ascending limb of Henle's loop and the bright portion of the distal tubule. RC.SV3 responds essentially to isoproterenol and arginine vasopressin, suggesting a more distal origin (late distal and initial collecting tubule). Emergence of distal cell lines from cultures exhibiting proximal characteristics may be related to distal cell overgrowth as suggested by analysis of growth kinetics and increased Na+/H+ exchanger activity in RC.SV2 compared with RC.SV1.

A Na-K-Cl cotransporter in isolated rat papillary collecting duct cells

Lactate production and ion fluxes were measured in isolated rat papillary collecting duct cells (PCD) to gain further insight into the transport properties of the papillary collecting duct. Lactate production was found to be inhibited by bumetanide in a dose-dependent manner, a maximum inhibition of 22% was obtained at 10(-4) M bumetanide and an apparent Ki of 10(-8) M was determined. Bumetanide inhibition of lactate production was dependent on the presence of sodium and chloride. Chloride removal inhibited lactate production also by 20%. Bumetanide (10(-4) M) inhibited by 35% sodium uptake into PCD cells exposed to 10 mM ouabain and chloride uptake into ion depleted PCD cells by 40%. In addition, this bumetanide-sensitive chloride uptake was dependent on the presence of sodium and potassium in the incubation medium. Furthermore, 86Rb uptake into these cells was significantly reduced in the presence of 10(-4) M bumetanide. These data provide evidence for the operation of a Na-K-Cl cotransport system in rat papillary collecting duct cells. This transport system might be involved in active chloride transport in the papillary collecting duct and/or volume regulation of the PCD cells.

Rabbit urinary tamm-horsfall glycoprotein. Chemical composition and tentative carbohydrate structure

The urinary Tamm-Horsfall protein (THP) is the major glycoprotein secreted by the mammalian kidney. We recently isolated and immortalized thick ascending limb of Henle cells from rabbit kidney, which produce Tamm-Horsfall protein in cell culture in vitro. In order to further study the yet undefined functional role and biosynthetic pathways of this protein, we first re-examined the chemical composition and the carbohydrate structure of rabbit urinary Tamm-Horsfall protein. Using precipitation with 0.58 mol/l NaCl a protein was isolated from rabbit urine which showed extensive microheterogeneity and had an average molecular mass of 95 kDa. Deglycosylation of the protein led to a loss of microheterogeneity and yielded a molecular mass of 58-60 kDa. Amino-acid analysis of the native and deglycosylated protein revealed a lower cysteine (20 mol/mol THP) and a higher histidine (20 mol/mol THP) content than described previously. Chemical analysis of the carbohydrates showed a high glucosamine (50 mol/mol THP), galactose (43 mol/mol THP), and mannose (24 mol/mol THP) content. The amount of sialic acid was 15 mol/mol THP. Using lectins to identify the structure of the carbohydrate chains it was shown that rabbit Tamm-Horsfall protein possesses complex-type oligosaccharide chains with terminal sialic acid, beta-galactose, and probably alpha-fucose and chains of the mucin type. These results indicate that some of the cysteine residues in the polypeptide chain of THP can be replaced by histidine, suggesting a role of some cysteins in metal binding rather than intramolecular stabilization.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of human tracheal epithelial cells transformed by an origin-defective simian virus 40

To facilitate understanding of the mechanisms underlying pulmonary diseases, including lung cancer and cystic fibrosis, we have transformed and characterized cultures of human tracheal epithelial cells. Cells were transfected by calcium phosphate precipitation with a plasmid containing a replication-defective simian virus 40 (SV40) genome. Colonies of cells with enhanced growth potential were isolated and analyzed for transformation- and epithelial-specific characteristics. Precrisis cells were observed to express the SV40 large tumor antigen, produce cytokeratins, have microvilli, and form tight junctions. After crisis, cells continued to express the SV40 large tumor antigen as well as epithelial-specific cytokeratins and to display the apical membrane microvilli. Apical membrane Cl channels were opened in postcrisis cells exposed to 50 microM forskolin. These channels showed electrical properties similar to those observed in primary cultures. The postcrisis cells have been in culture for greater than 250 generations and are potentially "immortal." In addition to providing a useful in vitro model for the study of ion transport by human airway epithelial cells, the cells can be used to examine stages of neoplastic progression.

Human bronchial epithelial cells with integrated SV40 virus T antigen genes retain the ability to undergo squamous differentiation

Human bronchial epithelial cells transformed by either DNA virus infection (SV40 or Adenovirus 12-SV40 hybrid virus) or transfection with the SV40 large T antigen gene were studied for their ability to undergo squamous differentiation when exposed to 12-O-tetradecanoylphorbol-13 acetate (TPA), transforming growth factor-beta 1 (TGF-beta 1), or fetal bovine serum (FBS), agents that induce the squamous differentiation of normal human bronchial epithelial cells. Squamous differentiation occurred in all ten T-antigen-positive cell cultures when they were exposed to either FBS or TGF-beta 1, but none differentiated when exposed to TPA. From one cell line, designated BEAS-2B, two subclones were isolated, one of which was induced to undergo squamous differentiation by FBS, and a second that failed to undergo squamous differentiation and was mitogenically stimulated when exposed to serum. These phenotypically different subclones provide a new in vitro cellular system for delineating the mechanism(s) of human bronchial epithelial cell squamous differentiation in response to FBS or TGF-beta 1.

Differentiation in vitro of primary cultures and transfected cell lines of epithelial cells derived from the thick ascending limb of Henle's loop

The use of primary cell cultures derived from defined locations of the kidney has enabled the study of certain kidney cell type-specific characteristics under defined environmental conditions. The use of primary cell cultures, however, has a number of inherent disadvantages, many of which may be overcome by the use of differentiated cell lines of defined origin. In this paper I describe in detail an approach to: (a) the isolation and culture of primary cultures derived from the thick ascending limb of Henle's loop (TALH), and (b) the production of differentiated cell lines by the transfection of these primary cell cultures with early region SV40 virus genes. The characteristics of these cultures and other TALH-derived cell lines are described.