Cross-linked collagen surface for cell culture that is stable, uniform, and optically superior to conventional surfaces

Peritoneal Mesothelial Cell Culture and Biology

The peritoneal mesothelium is composed of an extensive monolayer of mesothelial cells that lines the body's serous cavity and internal organs and was previously thought to act principally as a protective nonadhesive lubricating surface to facilitate intracoelomic movement. With the introduction of peritoneal dialysis over three decades ago, there has been much interest in the cell biology of peritoneal mesothelial cells. Independent studies have highlighted specific properties of the peritoneal mesothelial cell, including antigen presentation, regenerative properties, clearance of fibrin; synthesis of cytokines, growth factors, and matrix proteins; and secretion of lubricants to protect the tissue from abrasion, adhesion, infection, and tumor dissemination. It is now evident that the mesothelium is not merely a passive membrane but, rather, a dynamic membrane that contributes substantially to the structural, functional, and homeostatic properties of the peritoneum. Since peritoneal mesothelial cells in culture possess immunohistochemical markers identical to mesothelial stem cells, the culture of mesothelial cells offers researchers an essential tool to assess their morphologic, structural, and functional properties. This review will discuss current procedures to isolate peritoneal mesothelial cells from human omental specimens, animal sources, and spent dialysate. Furthermore, the functional and morphologic properties of mesothelial cells are discussed, together with the potential use of mesothelial cell culture in research and clinical applications.

Double-stranded RNA induces an antiviral defense status in epidermal keratinocytes through TLR3-, PKR-, and MDA5/RIG-I-mediated differential signaling

Emerging evidence suggests an important role for human epidermal keratinocytes in innate immune mechanisms against bacterial and viral skin infections. The proinflammatory effect of viral infections can be mimicked by double-stranded RNA (dsRNA). Herein, we demonstrate that keratinocytes express all known dsRNA sensing receptors at a constitutive and inducible level, and that they use several downstream signaling pathways leading to a broad pattern of gene expression, not only proinflammatory and immune response genes under the control of NF-kappaB, but also genes under transcriptional control of IRF3. As a consequence, dsRNA, a stimulus for TLR3, protein kinase R (PKR), and the RNA helicases retinoic acid-inducible gene I (RIG-I) and MDA5, induces a status of antiviral defense in keratinocytes. Using inhibitors for the various dsRNA signaling pathways and specific small interfering RNA for TLR3, RIG-I, and MDA5, we demonstrated that in human keratinocytes, TLR3 seems to be necessary for NF-kappaB but not for IRF3 activation, whereas RIG-I and MDA5 are crucial for IRF3 activation. PKR is essential for the dsRNA response in both signaling pathways and thus represents the central antiviral receptor for dsRNA stimulation. Moreover, human keratinocytes up-regulate TLR7, the receptor for single-stranded RNA, in response to stimulation with dsRNA, which renders keratinocytes functionally responsive to the TLR7 agonist gardiquimod, a member of the imidazoquinoline antiviral immune response modifier family. Thus, in addition to building a physical barrier against infectious pathogens, keratinocytes are specially equipped with a full antiviral defense program that enables them to efficiently target viral infections of the skin.

Investigation of the mechanism of enhancement of central nervous system delivery of 2'-beta-fluoro-2',3'-dideoxyinosine via a blood-brain barrier adenosine deaminase-activated prodrug

Enhanced central nervous system (CNS) delivery of certain poorly penetrating 2',3'-dideoxynucleosides has been achieved by designing prodrugs that are substrates for enzymes, such as adenosine deaminase (ADA), that are present at high activities in brain tissue. In this study, the potential role of adenosine deaminase localized within the endothelial cells of the blood-brain barrier (BBB) in providing enhanced intracellular and CNS delivery of an ADA-activated prodrug is assessed in vitro using cell culture models of the BBB. The kinetics of uptake and bioconversion of 2'-beta-fluoro-2',3'-dideoxyadenosine (F-ddA), a model ADA-activated prodrug of 2'-beta-fluoro-2',3'-dideoxyinosine, were determined in primary cultured bovine brain microvascular endothelial cells. Model-based simulations of CNS availability derived from in vitro estimates of parameters for simple passive diffusion and ADA-catalyzed deamination suggest that ADA that is localized within the BBB plays an important role in the conversion of F-ddA to 2'-beta-fluoro-2',3'-dideoxyinosine during its passage across the BBB. Consistent with in vivo observations, these simulations demonstrate that elevated levels of certain enzymes, such as ADA, in the brain microvascular endothelial cells of the BBB may be exploited in the design of brain-targeted prodrugs or drug-carrier conjugates, which brain tissue selectively converts.

In-vitro nasal drug delivery studies: comparison of derivatised, fibrillar and polymerised collagen matrix-based human nasal primary culture systems for nasal drug delivery studies

The aim of this study was to establish a collagen matrix-based nasal primary culture system for drug delivery studies. Nasal epithelial cells were cultured on derivatised (Cellagen membrane CD-24), polymerised (Vitrogen gel) and fibrillar (Vitrogen film) collagen substrata. Cell morphology was assessed by microscopy. The cells were further characterised by measurement of ciliary beat frequency (CBF), transepithelial resistance (TER), permeation of sodium fluorescein, mitochondrial dehydrogenase (MDH) activity and lactate dehydrogenase (LDH) release upon cell exposure to sodium tauro-24, 25 dihydrofusidate (STDHF). Among the three collagen substrata investigated, the best epithelial differentiated phenotype (monolayer with columnar/cuboidal morphology) occurred in cells grown on Cellagen membrane CD-24 between day 4 and day 11. Cell culture reproducibility was better with Cellagen membrane CD-24 (90%) in comparison with Vitrogen gel (70%) and Vitrogen film (< 10%). TER was higher in cells grown on Vitrogen gel than on Cellagen membrane CD-24 and Vitrogen film. The apparent permeability coefficient (Papp x 10(-7)cm s(-1)) of sodium fluorescein in these conditions was 0.45+/-0.08 (Vitrogen gel) and 1.91+/-0.00 (Cellagen membrane CD-24). Except for LDH release, CBF and cell viability were comparable for all the substrata. Based on MDH activity, LDH release, CBF, TER and permeation studies, Cellagen membrane CD-24- and Vitrogen gel-based cells were concluded to be functionally suitable for in-vitro nasal drug studies. Vitrogen film-based cultures may be limited to metabolism and cilio-toxicity studies.

Modulation of keratinocyte gene expression and differentiation by PPAR-selective ligands and tetradecylthioacetic acid

Peroxisome proliferator-activated receptors (PPARs) are pleiotropic regulators of growth and differentiation of many cell types. We have performed a comprehensive analysis of the expression of PPARs, transcriptional cofactors, and marker genes during differentiation of normal human keratinocytes using a combination of reverse transcriptase polymerase chain reaction, Northern and Western blotting, and immunohistochemistry. PPARdelta was the predominant PPAR subtype in human keratinocytes and highly expressed in basal cells and suprabasal cells. Induction of PPARalpha and PPARgamma expression was linked to differentiation, and accordingly, expression of PPARalpha and PPARgamma was in essence confined to suprabasal cells. Differentiation was not accompanied by significant changes in the expression of the coactivators CREB-binding protein, p300, steroid receptor coactivator 1, or the corepressors nuclear receptor corepressor and silence mediator for retinoid and thyroid hormone receptors. We critically evaluated the effects of selective PPAR ligands and a synthetic fatty acid analog, tetradecylthioacetic acid. Tetradecylthioacetic acid activated all human PPAR subtypes in the ranking order PPARdelta >> PPARalpha > PPARgamma. All selective PPAR ligands marginally induced transglutaminase-1 expression with the PPARdelta-selective ligand L165041 being the most potent. The PPARalpha- and PPARgamma-selective ligands Wy14643 and BRL49653 had negligible effect on involucrin expression, whereas a dose-dependent induction was observed with L165041. Simultaneous addition of L165041 and BRL49653 synergistically induced strong involucrin expression. Additionally, L165041 potently induced CD36 mRNA expression. Administration of tetradecylthioacetic acid resulted in a dramatic decrease in proliferation and a robust upregulation of the expression of involucrin and transglutaminase. Our results indicate that tetradecylthioacetic acid may affect keratinocyte gene expression and differentiation via PPAR-dependent and PPAR-independent pathways, and that the latter play an important role.

Use of cultured cerebral capillary endothelial cells in modeling the central nervous system availability of 2',3'-dideoxyinosine

The biochemical and physiological mechanisms responsible for the limited central nervous system (CNS) uptake of dideoxynucleoside reverse transcriptase inhibitors currently used to treat HIV-1 infection in humans are poorly understood. In vitro models of the blood-brain barrier (BBB) offer an attractive alternative to in vivo or in situ animal studies for understanding the role of the blood-brain barrier in regulating brain tissue concentrations of these agents. In the present study, the kinetics of 2', 3'-dideoxyinosine (ddI) uptake and purine nucleoside phosphorylase (PNP) mediated catabolism in primary cultures of bovine brain microvessel endothelial cells (BBMECs) were determined in order to ascertain the importance of both transport and metabolism governing the CNS availability of this purine dideoxynucleoside. Initial rates of ddI uptake as a function of ddI donor concentration suggest the involvement of both passive diffusion and carrier-mediated processes. These studies confirm earlier in vivo findings that transporters may play a role in regulating the CNS concentration of ddI. Analysis of ddI uptake and metabolite accumulation in BBMECs over longer time intervals (beyond the intial rate region) provide substantial in vitro evidence for an enzymatic BBB for ddI. Simulations of the CNS availability of ddI derived from in vitro estimates of parameters for passive diffusion, carrier-mediation, and metabolism indicate that the fraction of ddI entering the BBB cells which actually reaches the brain parenchyma may be quite low (< 2%) due to metabolism by PNP localized within the BBB, consistent with the low CNS delivery of ddI observed in vivo. Transporters and metabolic enzymes within the BBB may function in coordinated fashion to reduce the CNS concentrations of both rapidly metabolized and poorly metabolized dideoxynucleosides.

In vitro models of the blood-brain barrier to polar permeants: comparison of transmonolayer flux measurements and cell uptake kinetics using cultured cerebral capillary endothelial cells

Given that the cerebral microvasculature within the brain constitutes the rate-limiting barrier to drug entry, primary cultures of cerebral capillary endothelial cells would appear to offer a potentially useful model system for predicting drug delivery to the central nervous system. In the present study, the predictive capabilities of two potential models of the in vivo blood-brain barrier (BBB) to the passive diffusion of polar permeants were assessed. A comparison of the logarithms of the in vitro transmonolayer permeability coefficients (Pmonolayer) for several polar permeants varying in lipophilicity (from this study and literature data) with the well-established relationship between the logarithms of the in vivo BBB permeability coefficients (log PBBB) and permeant lipophilicity as measured by the logarithm of the octanol/water partition coefficient (log PCoctanol/water) demonstrated that in vitro permeation across these monolayers is largely insensitive to polar permeant lipophilicity as a result of the predominance of the paracellular component in the transmonolayer flux. Conversely, kinetic studies of uptake of the same compounds into monolayers yielded transfer rate constants (kp) reflecting membrane permeability coefficients ranging over several orders of magnitude, similar to the variation in permeant lipophilicity. Furthermore, a linear relationship could be demonstrated between the logarithms of kp and in vivo BBB log P (slope = 1.42 +/- 0.35; r = 0. 92). In conclusion, this preliminary investigation suggests that monitoring the kinetics of cell uptake into cerebral capillary endothelial cell monolayers may be superior to transmonolayer flux measurements for predicting the passive diffusion of polar permeants across the BBB in vivo.

A tissue-like culture system using microstructures: influence of extracellular matrix material on cell adhesion and aggregation

Special microenvironmental conditions are required to induce and/or maintain specific qualities of differentiated cells. An important parameter is the three-dimensional tissue architecture that cannot be reproduced in conventional monolayer systems. Advanced tissue culture systems will meet many of these demands, but may reach their limits, especially when gradients of specific substances over distinct tissue layers must be established for long-term culture. These limitations may be overcome by incorporating microstructures into tissue-like culture systems. The microstructured cell support presented consists of a flat array of 625 cubic microcontainers with porous bottoms, in which cells can be supplied with specific media from both sides of the tissue layer. Permanent cell lines and primary rat hepatocytes have been used to test the culture system. In order to define reproducible conditions for tissue formation and for cell adherence to the structure, several ECM (extracellular matrix) components were tested for coating of microstructured substrata. The described tissue culture system offers great flexibility in adapting the cell support to specific needs.

Induction of a cAMP-stimulated chloride secretion in regenerating poorly differentiated airway epithelial cells by adenovirus-mediated CFTR gene transfer

In cystic fibrosis (CF), the airway epithelium is in the process of injury and regeneration. In the context of the CF gene therapy, we previously reported that regenerating poorly differentiated (PD) cells of human airway epithelium represent preferential cell targets for recombinant adenoviral gene vectors. To define whether PD non-CF and CF epithelial cells possess a functional cystic fibrosis transmembrane conductance regulator protein (CFTR) chloride channel, we analyzed the CFTR expression and the regulation of chloride secretion under cyclic (c)AMP stimulation in these regenerating PD epithelial cells of non-CF and CF airway tissue. Moreover, we studied the effects of CFTR gene transfer mediated by a replication-defective adenovirus containing the wild-type CFTR gene (AdCFTR) on CFTR expression and on cAMP-stimulated chloride secretion. Distribution of the CFTR protein was evaluated in regenerating PD airway cells by light fluorescence microscopy and scanning laser confocal microscopy. The cAMP-mediated regulation of cell membrane chloride secretion was investigated using the whole-cell patch clamp and SPQ (6-methoxy-N-[3-sulfopropyl]quinolinium) techniques. Compared with the absence of CFTR expression and cAMP-regulated chloride secretion in nontransduced regenerating PD cells of either non-CF or CF origin, transduction with AdCFTR induces a CFTR expression and a cAMP-regulated stimulation of the cell membrane chloride secretion in the regenerating PD cells. These results suggest that, out of the context of CF, remodeled and poorly differentiated airway epithelium may present abnormalities in ion transport. Moreover, our data suggest that, in the context of CF gene therapy, adenoviral vectors can be efficient in correcting, at least partially, the chloride secretion defect in the remodeled CF airway epithelium.

Okadaic acid reversibly inhibits neurite outgrowth in embryonic dorsal root ganglion neurons

The aim of this study was to assess the effects of low concentrations of okadaic acid (OA) on neurite outgrowth and cellular integrity in cultures of dissociated dorsal root ganglion (DRG) neurons. The complete and fully reversible arrest of neurite outgrowth was achieved at 1 nM OA, thus ruling out the involvement of protein phosphatase 1 in the observed inhibitory effect. OA at 0.5 nM did not completely block neurite outgrowth, although it reduced the rate of growth by about one third. Protein phosphorylation and the integrity of microtubules and neurofilaments in neuron-enriched cultures were unaffected by 1 nM OA. The rate of synthesis of the low-molecular-weight neurofilament subunit (NFL) was also unchanged by OA treatment. Antimitotic agents used to eliminate proliferating cells did not alter the rate of neurite elongation. Since 1 nM OA does not suffice to inhibit neuronal protein phosphatase 2A fully, owing to the high concentration of this enzyme in neurons, we propose that the inhibitor is affecting a neuronal compartment that contains low levels of the phosphatase. This putative compartment is likely to be located in neurites, which were shown to contain levels of protein phosphatase 2A that were two- to threefold lower than in neuronal perikarya.

Aberrant stress-induced phosphorylation of perikaryal neurofilaments

The aberrant phosphorylation of the neurofilament high molecular weight subunit (NFH) in the neuronal perikaryon is a common feature of several neurological diseases. We demonstrated a strong correlation between hyperphosphorylation of the NFH carboxyl-terminal domain and activation of stress-activated protein kinase (SAPK) -gamma in PC12 cells. Agents that activated SAPKgamma in PC12 cells also caused the hyperphosphorylation of perikaryal NFH in cultured dorsal root ganglion neurons. The NFH carboxyl-terminal domain was phosphorylated by SAPKgamma in vitro, and the use of peptide substrates indicated that this event occurred preferentially at KSPXE motifs. We propose that SAPKgamma, perhaps in concert with other SAPKs, is involved in the abnormal phosphorylation of perikaryal NFH. This finding could lead to new insights into the etiology of several neurological diseases.

Fibronectin regulates calvarial osteoblast differentiation

The secretion of fibronectin by differentiating osteoblasts and its accumulation at sites of osteogenesis suggest that fibronectin participates in bone formation. To test this directly, we determined whether fibronectin-cell interactions regulate progressive differentiation of cultured fetal rat calvarial osteoblasts. Spatial distributions of alpha 5 integrin subunit, fibronectin, osteopontin (bone sialoprotein I) and osteocalcin (bone Gla-protein) were similar in fetal rat calvaria and mineralized, bone-like nodules formed by cultured osteoblasts. Addition of anti-fibronectin antibodies to cultures at confluence reduced subsequent formation of nodules to less than 10% of control values, showing that fibronectin is required for normal nodule morphogenesis. Anti-fibronectin antibodies selectively inhibited steady-state expression of mRNA for genes associated with osteoblast differentiation; mRNA levels for alkaline phosphatase and osteocalcin were suppressed, whereas fibronectin, type I collagen and osteopontin were unaffected. To identify functionally relevant domains of fibronectin, we treated cells with soluble fibronectin fragments and peptides. Cell-binding fibronectin fragments (type III repeats 6–10) containing the Arg-Gly-Asp (RGD) sequence blocked both nodule initiation and maturation, whether or not they contained a functional synergy site. In contrast, addition of the RGD-containing peptide GRGDSPK alone did not inhibit nodule initiation, although it did block nodule maturation. Thus, in addition to the RGD sequence, other features of the large cell-binding fragments contribute to the full osteogenic effects of fibronectin. Nodule formation and osteoblast differentiation resumed after anti-fibronectin antibodies or GRGDSPK peptides were omitted from the media, showing that the inhibition was reversible and the treatments were not cytotoxic. Outside the central cell-binding domain, peptides from the IIICS region and antibodies to the N terminus did not inhibit nodule formation. We conclude that osteoblasts interact with the central cell-binding domain of endogenously produced fibronectin during early stages of differentiation, and that these interactions regulate both normal morphogenesis and gene expression.

Primary cultures of rat hepatocytes in hollow fiber chambers

Hepatocyte culture may represent an alternative to the use of animals to study drug detoxification by the liver. An ideal in vitro system should closely mimic the in vivo environment by providing continuous media perfusion and oxygenation, and should facilitate sampling of cells and culture media. To meet these criteria, a hollow fiber bioreactor seeded with isolated rat hepatocytes was developed and tested by measuring the formation of three products of the oxidative metabolism of diazepam and the glucuronidation of phenolsulfonphthalein (PSP). To compare the performance of conventional monolayer culture to that of the bioreactor system, diazepam metabolism was studied for 45 days in both systems. The oxygen dependency of diazepam metabolism was evaluated by perfusing the bioreactor in an oxygen-rich atmosphere (30%). Total diazepam metabolism was twofold higher in the O2-rich perfused hollow fiber cultures than in the cultures perfused under normal conditions, reflecting an increase in temazepam and oxazepam production. Diazepam detoxification activity was significantly enhanced by oxygen (P < or = 0.001) over the life of the perfused cultures. PSP metabolism was similar in all three culture systems. By Day 10, diazepam metabolism in the oxygenated bioreactor system was 44% of the in vivo activity of rat hepatocytes. This activity dropped to 30% by Day 25 of culture. These results justify the use of perfused culture systems for in vitro detoxification studies as an alternative to animal use and emphasize the capacity of a culture device perfused under O2-enriched conditions to maintain long-term P450 activity of rat hepatocytes.

Xenobiotic-modulated expression of hepatic glutathione S-transferase genes in primary rat hepatocyte culture

CYP 2B1/B2 and 1A1 expression in primary rat hepatocytes plated on a substratum of Vitrogen using Chee's Essential Medium has been reported to be responsive to xenobiotic treatment (Jauregui, H.O., Ng, S.F., Gann, K.L. and Waxman, D.J. (1991) Xenobiotica 21, 1091-1106). Class alpha, mu and pi glutathione S-transferase (GST) gene expression in response to xenobiotic treatment using this primary hepatocyte culture system was examined and the results compared with those obtained for P4502B1/B2 and 1A1 expression. Cytosolic GST activity decreased approx. 75% during the first 48 h of culture relative to freshly isolated hepatocytes and subsequently, increased, attaining a level at 96 h that was 134% of the activity at 48 h post-plating. Treatment of the hepatocyte cultures with phenobarbital (2 mM) or 3-methylcholanthene (5 microM) for 24, 48, or 72 h, beginning 24 h after plating, resulted in significant increases in glutathione S-transferase activity relative to control, with maximal increases of 158 and 164% measured at 72 h following phenobarbital or 3-methylcholanthrene treatment, respectively. SDS-PAGE analysis of cytosolic proteins showed a substantial increase in the intensities of protein bands migrating in the region of the GSTs following phenobarbital, beta-naphthoflavone or 3-methylcholanthrene treatment. Immunoblot analysis of cytosolic fractions using affinity-purified class-specific GST IgGs confirmed that alpha, mu and pi-class GST isozymes were elevated approx. 1.5- to 2-fold following phenobarbital, or beta-naphthoflavone treatment; 3-methylcholanthrene was less effective in enhancing GST expression in cultured hepatocytes as compared to phenobarbital or beta-naphthoflavone. Although GST pi was below the limit of detection in freshly-isolated hepatocytes, enhanced expression of this form was observed in untreated hepatocytes cultured for longer than 72 h. Immunoblot analysis of microsomal fractions revealed that cytochrome P-4502B1/2B2 and 1A1 levels were increased significantly in hepatocyte cultures treated with phenobarbital or 3-methylcholanthrene, respectively, relative to the undetectable levels found in untreated controls. Northern blot analysis of poly(A)+ mRNA isolated from cultures that had been treated with phenobarbital or 3-methylcholanthrene showed an approx. 2- and 4-fold increase in the expression of alpha and pi class glutathione S-transferase mRNAs, respectively, as compared to untreated cells. The level of P-4501A1 or 2B1 mRNA was also markedly elevated following 3-methylcholanthrene or phenobarbital treatment, respectively. The results of this study demonor the first time, that expression of alpha, mu and pi-class glutathione S-transferase genes is effectively modulated in primary yet culture system by different classes of xenobiotics.

Tissue culture of epithelial cells from esophageal specialized columnar epithelium (Barrett's esophagus)

A procedure is described for the tissue culture of epithelial cells from Barrett's specialized columnar epithelium. The method employs use of nonenzymatic disaggregation techniques and use of a specialized growth medium, M-19. Successful growth can be achieved in 60-70% of cases. Characteristics of four cultures are presented including PAS, Alcian blue, and cytokeratin staining properties. Ultrastructural studies showed the presence of distended rough endoplasmic reticulum, abundant Golgi apparatus, glycogen granules, and cell-cell junctional complexes. Colony formation in anchorage-independent growth in soft agar was not observed in any culture. The cultured cells were not capable of indefinite growth. Thus, they do not behave as fully transformed cells. Availability of this culture system should be of use to the study of the biology of this metaplastic premalignant lesion.

Xenobiotic induction of P-450 PB-4 (IIB1) and P-450c (IA1) and associated monooxygenase activities in primary cultures of adult rat hepatocytes

1. The long-term maintenance of metabolism of representative drugs and steroid hormone substrates by cytochromes P-450, and their inducibility, was investigated in primary cultures of adult rat hepatocytes. Collagenase-isolated cells were seeded on collagen-coated tissue culture dishes and cultured in Chee's essential media in the presence or absence of phenobarbital (PB, 0.75 mM, 96 h or continuously) and 3-methylcholanthrene (MC, 5 microM, 48 h) for up to 45 days. 2. Hepatic P-450-dependent metabolism of diazepam to its primary oxidized metabolite was inducible by PB both in vivo (monitored in isolated liver microsomes) and in cultured cells (up to 100% and 400% increases in the formation of temazepam and nordiazepam, respectively, after 25 days in culture). Hepatocyte microsomal androstenedione 16 beta-hydroxylase activity was also induced by PB treatment of the hepatocytes (350-650% increase in 20-day-old cells). 3. Western blot analysis revealed that immunoreactive P-450 form PB-4 (IIB1), which catalysed the N-demethylation of diazepam to yield nordiazepam as well as androstenedione 16 beta-hydroxylation when assayed in a purified enzyme system, was substantially elevated following PB treatment of the cultured cells. Similarly, MC induced 7-ethoxycoumarin O-deethylase activity (up to 2000% increase from 5 to 45 days) as well as immunoreactive P-450c (IA1) in the hepatocyte cultures. 4. These studies demonstrate that cytochrome P-450 activities can be maintained, and also induced, after extended periods of time in hepatocytes cultured using a simple collagen mixture as substrate and a commercially available tissue culture media. This culture system should provide an important tool for further studies of P-450-dependent xenobiotic metabolism in a well-defined, liver-derived cellular system.

Fibroblast and hepatocyte behavior on synthetic polymer surfaces

Biodegradable poly(phosphoesters) with varying side group chemistry and copolymers of styrene and methyl vinyl ketone (MVK) with varying degrees of hydrophobicity were used to study the growth and behavior of surface-attached fibroblasts and hepatocytes. Mouse 3T3 fibroblasts and chicken embryo fibroblasts attached and proliferated on all of the polymers tested. Fewer cells attached to copolymers of styrene and MVK than to glass or tissue culture polystyrene controls; cell attachment to several poly(phosphoester) surfaces was indistinguishable from controls. The mean speed of fibroblast migration was faster on surfaces where fewer cells attached (59 to 84 microns/h on low attachment surfaces compared with 40 to 46 microns/h on high attachment surfaces). When surface-attached cells were stained with fluorescently labeled phalloidin, only a fraction of the cells on low attachment surfaces were shown to have prominent arrays of actin filament bundles. Chicken hepatocytes also attached to the polymer surfaces. When a suspension containing a large number of cells was placed over the polymer surfaces, approximately 50% of the hepatocytes attached during the first 9 h. Surprisingly, hepatocyte attachment and viability in culture were relatively insensitive to the chemistry of the synthetic polymer substrates. Cell number increased by about a factor of 2 over the first 48 h of culture, then decreased back to approximately 50% of initial cell number over the next several days. Cell morphology did depend on the chemical structure of the substrates.

Establishment of two new cell lines derived from human breast carcinomas with HER-2/neu amplification

Two human cell lines (UACC-812 and 893), both containing significant amplification of the HER-2/neu gene, were established from biopsy specimens of breast carcinomas. One patient had Stage II breast carcinoma; the other had metastatic disease. Characterisation of these lines has revealed that both are highly aneuploid containing multiple clonal chromosome alterations, have doubling times near 100 h, and are oestrogen and progesterone receptor negative. Electron microscopy demonstrates that both lines contain numerous microvilli, cytoplasmic filaments, multivesicular bodies, and desmosomes. Immunoblot analysis for P-glycoprotein using the monoclonal antibody C219 was negative for both patient cell lines. These relatively rare cell lines may represent a useful model to investigate human breast carcinomas.

Iris-derived melanocytes contain a growth factor that resembles basic fibroblast growth factor

A melanocyte growth stimulating factor has been purified from bovine iris melanocytes and identified as being closely related to the basic form of fibroblast growth factor (bFGF). This conclusion was based on the behavior of the melanocyte-derived growth factor when submitted to heparin-Sepharose affinity chromatography, as well as on its ability to cross-react with bFGF in radioimmuno- and radioreceptor assays. The ability of neutralizing bFGF antibodies to block cell proliferation in response to the melanocyte growth factor further confirms that it is closely related to bFGF. Since melanocytes express the 3.7-kb and 7.0-kb bFGF transcript, the possibility exists that uncontrolled expression of melanocyte-derived bFGF could be involved in the malignant transformation of melanocytes into melanoma cells.

Phenobarbital induction of cytochromes P-450. High-level long-term responsiveness of primary rat hepatocyte cultures to drug induction, and glucocorticoid dependence of the phenobarbital response

The induction of hepatic cytochromes P-450 by phenobarbital (PB) was studied in rat hepatocytes cultured for up to 5 weeks on Vitrogen-coated plates in serum-free modified Chee's medium then exposed to PB (0.75 mM) for an additional 4 days. Immunoblotting analysis indicated that P-450 forms PB4 (IIB1) and PB5 (IIB2) were induced dramatically (greater than 50-fold increase), up to levels nearly as high as those achieved in PB-induced rat liver in vivo. The newly synthesized cytochrome P-450 was enzymically active, as shown by the major induction of the P-450 PB4-dependent steroid 16 beta-hydroxylase and pentoxyresorufin O-dealkylase activities in the PB-induced hepatocyte microsomes (up to 90-fold increase). PB induction of these P-450s was markedly enhanced by the presence of dexamethasone (50 nM-1 microM), which alone was not an affective inducing agent, and was inhibited by greater than 90% by 10% fetal bovine serum. The PB response was also inhibited (greater than 85%) by growth hormone (250 ng/ml), indicating that this hormone probably acts directly on the hepatocyte when it antagonizes the induction of P-450 PB4 in intact rats. In untreated hepatocytes, P-450 RLM2 (IIA2), P-450 3 (IIA1) and NADPH P-450 reductase levels were substantially maintained in the cultures for 10-20 days. The latter two enzymes were also inducible by PB to an extent (3-4 fold elevation) that is comparable with that observed in the liver in vivo. Moreover, P-450c (IA1) and P-450 3 (IIA1) were highly inducible by 3-methylcholanthrene (5 microM; 48 h exposure) even after 3 weeks in culture. In contrast, the male-specific pituitary-regulated P-450 form 2c (IIC11) was rapidly lost upon culturing the hepatocytes, suggesting that supplementation of appropriate hormonal factors may be necessary for its expression. The present hepatocyte culture system exhibits a responsiveness to drug inducers that is qualitatively and quantitatively comparable with that observed in vivo, and should prove valuable for more detailed investigations of the molecular and mechanistic basis of the response to PB and its modulation by endogenous hormones.

Latex nanosphere delivery system (LNDS): novel nanometer-sized carriers of fluorescent dyes and active agents selectively target neuronal subpopulations via uptake and retrograde transport

A wide range of latex particles are described which are capable of carrying high concentrations of fluorescent dyes, drugs, and photoactive agents selectively to subpopulations of neurons in vitro and in vivo. Particle size, charge, and concentration were all found to influence uptake into cultured neurons or retrograde transport in vivo. Chromophore loadings of greater than 14% (w/w) were obtained. Incorporation of a photoactivated dye (chlorin e6) into the polymer did not compromise the ability of the dye to produce singlet oxygen following light exposure. We refer to this unique family of latex particles as the latex nanosphere delivery system (LNDS). The LNDS will be usefull for studies of neuroanatomy and nervous system development, as well as more general areas of biomedical research where it is desirable to selectively label subpopulations of cells. The LNDS also offers a means of providing targeted delivery of drugs or photoactive agents to selected subpopulations of cells; this will allow experimentation not currently possible using any existent methodology.

Progressive incorporation of propidium iodide in cultured mouse neurons correlates with declining electrophysiological status: a fluorescence scale of membrane integrity

We describe a visual assay of neuronal electrophysiologic status for use with cultured neurons, based on the exclusion of propidium iodide (PI) by intact cellular membranes. We use this fluorescent dye, which binds to nucleic acids, at concentrations suitable for long-term exposure to neurons without toxicity. We correlate the progressive loss of resting membrane potential and the progressive inability to generate stimulated action potentials by cultured mouse dorsal root ganglion neurons with increasing incorporation of PI. The scoring system used to gauge incorporation of PI is rapid and highly reproducible using a standard fluorescence microscope. Applications exist for studies of neuronal toxicity, survival, and electrophysiology in vitro.

Mapping neuronal inputs to REM sleep induction sites with carbachol-fluorescent microspheres

The cholinergic agonist carbachol was conjugated to latex microspheres that were fluorescently labeled with rhodamine and used as neuroanatomical probes that show little diffusion from their injection site and retrogradely label neurons projecting to the injection site. Microinjection of this pharmacologically active probe into the gigantocellular field of the cat pontine brain stem caused the awake cats to fall into rapid movement (REM) sleep indistinguishable from that produced by free carbachol. Three-dimensional computer reconstruction of the retrogradely labeled neurons revealed a widely distributed neuronal network in the pontine tegmentum. These pharmacologically active microspheres permit a new precision in the characterization and mapping of neurons associated with the control of behavioral state and of other cholinergic networks.