The role of matrix metalloproteinases in patients with pulmonary hypertension: data from a prospective study

BACKGROUND

Despite several therapies, pulmonary hypertension (PH) is still a severe disease which can lead to right heart failure. Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) are involved in cardiac and vascular remodeling in PH. Therefore, these biomarkers play an important role in PH patients. This study investigated whether TIMP-4, MMP-2, and N-terminal Pro-B-Type Natriuretic Peptide (NT-proBNP) plasma levels are useful in assessing the severity of PH and other clinical or echocardiographic parameters.

METHODS

The concentrations of MMP-2, TIMP-4, and NT-proBNP in 68 PH patients were compared with those of 12 controls without PH. All patients underwent a physical examination, echocardiography, and were checked for the presence of cardiovascular risk factors; also, plasma concentrations of MMP-2, TIMP-4, NT-proBNP, total cholesterol, and triglycerides were determined.

RESULTS

In PH patients, significantly elevated plasma levels of TIMP-4 (PH: 2877.99 ± 1363.78 pg/ml, control: 2028.38 ± 762.67 pg/ml, p = 0.0068) and NT-proBNP ( PH: 2405.00 pg/ml-5423.47 ± 6703.38 pg/ml, control: 411.0000 pg/ml-421.75 ± 315.37 pg/ml, p = 0.01) were detected. We also observed that MMP-2 and NT-proBNP were significantly increased in patients with higher WHO functional class (p = 0.001 for MMP-2, p = 0.008 for NT-proBNP), higher pressure in the pulmonary artery (p = 0.002 for MMP-2, p = 0.001 for NT-proBNP), and more severe tricuspid regurgitation (p = 0.001 for MMP-2, p = 0.009 for NT-proBNP). TIMP-4 was elevated in patients with more severe pressure in the pulmonary artery (p = 0.006).

CONCLUSIONS

The plasma levels of TIMP-4 and NT-proBNP are higher in PH patients. MMP-2 and NT-proBNP correlates with different PH parameters severity (WHO functional class, sPAP severity, TV regurgitation severity). Therefore, plasmatic levels of MMP-2 and NT-proBNP at this kind of patients reflect disease severity and may have a prognostic role. MMP-2 can help assess the beneficial effects of PH pharmacotherapy on tissue remodeling. These remodeling biomarkers may not have a diagnostic value but they have the potential to predict survival. Nevertheless, a greater understanding of the involvement of MMPs in PH is mandatory to further explore the prognostic role and the possibilities of therapeutic MMP inhibition in PH.

COVA1-18 neutralizing antibody protects against SARS-CoV-2 in three preclinical models

One year into the Coronavirus Disease 2019 (COVID-19) pandemic caused by Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2), effective treatments are still needed 1-3 . Monoclonal antibodies, given alone or as part of a therapeutic cocktail, have shown promising results in patients, raising the hope that they could play an important role in preventing clinical deterioration in severely ill or in exposed, high risk individuals 4-6 . Here, we evaluated the prophylactic and therapeutic effect of COVA1-18 in vivo , a neutralizing antibody isolated from a convalescent patient 7 and highly potent against the B.1.1.7. isolate 8,9 . In both prophylactic and therapeutic settings, SARS-CoV-2 remained undetectable in the lungs of COVA1-18 treated hACE2 mice. Therapeutic treatment also caused a dramatic reduction in viral loads in the lungs of Syrian hamsters. When administered at 10 mg kg - 1 one day prior to a high dose SARS-CoV-2 challenge in cynomolgus macaques, COVA1-18 had a very strong antiviral activity in the upper respiratory compartments with an estimated reduction in viral infectivity of more than 95%, and prevented lymphopenia and extensive lung lesions. Modelling and experimental findings demonstrate that COVA1-18 has a strong antiviral activity in three different preclinical models and could be a valuable candidate for further clinical evaluation.

[Complications of volar locking plates used to treat distal radius fractures]

About 10 years after volar locking plates were introduced to treat acute distal radius fractures, several papers have reported short-term complications. The aim of this paper was to report our complication rate over a 2-year period and to compare it to the literature. We found similar complication rates despite different classification systems. Because of the prospective nature of our study, we were able to demonstrate that extra-articular and/or intra-articular scores exceeding 8 points on a 12-points scale were statistically associated with more complications, irrespective of the patient's overall health and age.

Rugby morphologies: "bigger and taller", reflects an early directional selection

AIM

The aim of this paper was to investigate the changes over time in anthropometric parameters of young and adult rugby players in France.

METHODS

Age, mass and height were collected for 2051 French elite rugby players participating in the championship during the 1988-1989 and the 2008-2009 seasons. The same variables were collected for the best 145 juniors (under 21 years) and 448 U15 (under 15 years) French players for these seasons. Changes in anthropometric parameters were compared according to age, category (back vs. forwards) and season.

RESULTS

Over 20 years, adult French rugby backs and forwards have become heavier by 12 kg and 12.3 kg, taller by 5.4 cm and 2.9 cm, respectively. Junior players also became taller and heavier, 6 cm and 9.9 kg for backs and 4.4 cm and 11.1 kg for forwards. U15 backs have gained 5.1 cm and 6.5 kg, and forwards earned 4.7 cm and 4.7 kg.

CONCLUSION

Rugby players have become taller and heavier. Their current morphology is the product of a long process of competition and selection. This study demonstrates that this selection of the "large sizes" is already present at a young age.

Promoting effect of rapeseed proteins and peptides on Sf9 insect cell growth

The Baculovirus Expression Vector System has become widely used for the production of recombinant proteins for research and diagnostics. Serum-free culture media able to support high cell densities have been developed for the large scale culture of insect cells. While serum elimination aims at avoiding the risks associated with the introduction of an ill defined component of bovine origin, additives such as protein hydrolysates from animal sources are still used. An alternative could be the supplementation of culture media with protein hydrolysates derived from plants. In this study, we describe the replacement of lactalbumin hydrolysate with a laboratory produced hydrolysate of rapeseed proteins. Its effect on Sf9 cell growth kinetics, substrate consumption and by-product formation in low-serum or serum-free medium was evaluated. Cells were unable to grow in the presence of a rapeseed protein hydrolysate generated by PTN 3.0 Special((R)) enzyme and containing only 24% of peptides under 1 kDa in size. On the other hand, serum-free medium supplementation with a rapeseed protein hydrolysate obtained with Orientase 90N((R)) enzyme had a strong growth promoting effect, leading to a 60% increase in maximal cell density without affecting cell metabolism. This significant positive effect could be explained by the higher degree of hydrolysis of this digest, with 74% of peptides under 1 kDa in size.

Stimulation of monoclonal antibody production of hybridoma cells by butyrate: evaluation of a feeding strategy and characterization of cell behaviour

Experiments, earlier performed in our laboratory, showedthe stimulating effect of butyric acid on monoclonalantibody production by hybridoma cells. Itssimulaneous inhibitory effect on cell growth canhowever compensate for this, so that no increase ofmonoclonal antibody titer might be obtained. We showin this article an experiment with addition of butyricacid in the middle of the growth phase of a batchculture, as a strategy to take real profit of such anaddition by a significant increase of final monoclonalantibody concentration. Indeed, in this way asignificant cell density could be obtained before theaddition of butyric acid, while the remaining culturetime was still sufficiently long for its action,resulting in a two fold increase of final monoclonalantibody titer. The experiment was carried out in a 2 L bioreactor, showing the real practical interest ofsuch an addition for the large scale production ofproteins. Furthermore, analysis of the produced IgG bySDS-PAGE and Western blot did not reveal structuralchanges after stimulation by butyric acid. An originalpoint of our study is the characterization of the cellbehaviour, by flow cytometry and other relatedtechniques, leading to a better insight in the effectof the butyric acid addition on cell growth andmonoclonal antibody production. Although there existsa lot of knowledge about the effects of butyrate oncells in the field of molecular biology, our article isat our knowledge one of the first to show some of itseffects on cell behaviour in bioreactor culture,carried out under perfectly defined and controlledconditions, and with the aim to stimulate monoclonalantibody production.

Characterization of Vero cell growth and death in bioreactor with serum-containing and serum-free media

The density of viable cells in a culture results from a balance between cell proliferation and cell death. The aim of this study was to characterize and compare these two phenomena in Vero cell cultures in one serum containing medium (ScA) and one serum free medium (SfB) in bioreactors. Cell growth was evaluated by cell counting(after crystal violet staining) and cell cycle analysis. Necrosis and apoptosis were characterized and quantified by measuring the release of LDH, trypan blue exclusion,annex in V-FITC/PI staining and TUNEL assay. ScA supported a higher maximal viable-cell density(2.3 x 10(6) vs. 1.8 x 10(6) cells ml(-1)). However, cell cycle analysis showed that cell division was more active in SfB than in ScA. LDH release in the supernatant increased much earlier in SfB than in ScA (one vs. five days), but trypan blue counts showed no apparent difference in the viability of the cultures. Apoptosis, evidenced by annexin V-FITC/PI staining, could be detected in the population of suspension cells detached from microcarriers, but not among adherent cells; positivity of the TUNEL assay occurred later than that of the annexin V-FITC/PI staining. Our data indicate that the lower cell yield in SfB,compared with that in ScA, results from a higher cell death rate. Apparently, cells die from apoptosis followed by secondary necrosis.

Na-butyrate increases the production and alpha2,6-sialylation of recombinant interferon-gamma expressed by alpha2,6- sialyltransferase engineered CHO cells

A non-human like glycosylation pattern in human recombinant glycoproteins expressed by animal cells may compromise their use as therapeutic drugs. In order to correct the CHO glycosylation machinery, a CHO cell line producing recombinant human interferon- gamma (IFN) was transformed to replace the endogenous pseudogene with a functional copy of the enzyme alpha2,6-sialyltransferase (alpha2,6-ST). Both the parental and the modified CHO cell line were propagated in serum-free batch culture with or without 1 mM sodium butyrate. Although Na-butyrate inhibited cell growth, IFN concentration was increased twofold. The IFN sialylation status was determined using linkage specific sialidases and HPLC. Under non- induced conditions, IFN expressed by alpha2,6-engineered cells contained 68% of the total sialic acids in the alpha2,6- conformation and the overall molar ratio of sialic acids to IFN was 2.3. Sodium butyrate addition increased twofold the molar ratio of total sialic acids to IFN and 82% of total sialic acids on IFN were in the alpha2,6-conformation. In contrast, no effect of the sodium butyrate was noticed on the sialylation of the IFN secreted by the alpha2,6-ST deficient parental cell line. This study deals for the first time with the effect of Na-butyrate on CHO cells engineered to produce human like sialylation.

Hybridoma cell behaviour in continuous culture under hyperosmotic stress

In this paper, we propose an alternative strategy to the ones proposed before (Oh et al., 1993; Øyaas et al., 1994a) to get real increases of global final antibody titer and production at hyperosmotic stress, by reducing the detrimental effect of such a stress on cell growth, and conserving the stimulating effect on antibody production. It consists of cultivating the cells in continuous culture and increasing the osmolality stepwise. In this way, the cells could progressively adapt to the higher osmolality at each step and antibody titers could be nearly doubled at 370 and 400 mOsm kg-1, compared to the standard osmolality of 335 mOsm kg-1. Surprisingly, the stimulation of antibody production was not confirmed for higher osmolalities, 425 and 450 mOsm kg- 1, despite the minor negative effect on cell growth. Intracellular IgG analysis by flow cytometry revealed at these osmolalities a significant population of non-producing cells. However, even when taking into account this non-producing population, a stimulating effect on antibody production could not be shown at these highest osmolalities. It seems to us that osmolality has a significant effect on the appearance of these non-producing cells, since they were not observed in continuous cultures at standard osmolality, of comparable duration and at an even higher dilution rate. The appearance of the non-producing cells coincides furthermore with modifications of the synthesised antibody, as shown by electrophoretic techniques. It is however not really clear if these two observations reflect actually the same phenomenon. Hyperosmolality affects the cell behaviour in continuous culture in multiple ways, independently of the growth rate, counting all at least partially for the observed stimulation of antibody production: acceleration of the amino acid, and in particular the glutamine metabolism, increase of the cell volume, increase of the intracellular pH and accumulation of cells in the G1 cell cycle phase.

Influence of the rapeseed protein hydrolysis process on CHO cell growth

Different protein hydrolysates were prepared from enzymatic hydrolyses of a rapeseed isolate (>90% protein content) using different commercial enzymes of non-animal origin. The extent of hydrolysis was controlled to produce hydrolysates corresponding to various degrees of hydrolysis (DH) from 5 to 30. These hydrolysates were characterized according to their solubility and size peptide pattern. Different growth behaviours of Chinese Hamster Ovary cells were observed when these various hydrolysates were added in serum-free medium containing transferrin, albumin and insulin. Hydrolysates from low degree of hydrolysis generally did not exhibit significant positive effect on cell growth; conversely hydrolysates from extensive hydrolysis, corresponding to a major low molecular size peptides content, usually allowed an increase of the maximal cell density. However, depending on the enzyme used, the supplementation with hydrolysates corresponding to a high degree of hydrolysis and composed of at least 70% peptides with a molecular size under 1kDa, led to different maximal cell density values, indicating the importance of enzyme specificity and consequently the nature of the released peptides. This result showed that the positive influence of the rapeseed hydrolysates on cell growth was not only due to a nutritional support tied to the addition of small peptides but may be related to the presence of peptides exhibiting growth or survival factor effects. Furthermore, total substitution of proteins (transferrin, albumin and insulin) in the cell culture medium by some rapeseed hydrolysates appeared to be a promising alternative to improve the cell growth in protein-free media.

Influence of intracellular nucleotide and nucleotide sugar contents on recombinant interferon-gamma glycosylation during batch and fed-batch cultures of CHO cells

Both the macroheterogeneity of recombinant human IFN-gamma produced by CHO cells and intracellular levels of nucleotides and sugar nucleotides, have been characterized during batch and fed-batch cultures carried out in different media. Whereas PF-BDM medium was capable to maintain a high percentage of the doubly- glycosylated glycoforms all over the process, mono-glycosylated and non-glycosylated forms increased during the batch culture using SF-RPMI medium. Intracellular level of UTP was higher in PF-BDM all over the batch culture compared to the SF-RPMI process. UDP-Gal accumulated only during the culture performed in PF-BDM medium, probably as a consequence of the reduced UDP-Glc synthesis flux in SF-RPMI medium. When the recombinant CHO cells were cultivated in fed-batch mode, the UTP level remained at a relatively high value in serum-containing RPMI and its titer increased during the fed-phase indicating an excess of biosynthesis. Besides, an accumulation of UDP-Gal occurred as well. Those results all together indicate that UTP and UDP-Glc syntheses in CHO cells cultivated in SF-RPMI medium in batch process, could be limiting during the glycosylation processes of the recombinant IFN-gamma. At last, the determination of the energetic status of the cells over the three studied processes suggested that a relationship between the adenylate energy charge and the glycosylation macroheterogeneity of the recombinant IFN-gamma may exist.

Intracellular nucleotide and nucleotide sugar contents of cultured CHO cells determined by a fast, sensitive, and high-resolution ion-pair RP-HPLC

Analysis of intracellular nucleotide and nucleotide sugar contents is essential in studying protein glycosylation of mammalian cells. Nucleotides and nucleotide sugars are the donor substrates of glycosyltransferases, and nucleotides are involved in cellular energy metabolism and its regulation. A sensitive and reproducible ion-pair reverse-phase high-performance liquid chromatography (RP-HPLC) method has been developed, allowing the direct and simultaneous detection and quantification of some essential nucleotides and nucleotide sugars. After a perchloric acid extraction, 13 molecules (8 nucleotides and 5 nucleotide sugars) were separated, including activated sugars such as UDP-glucose, UDP-galactose, GDP-mannose, UDP-N-acetylglucosamine, and UDP-N-acetylgalactosamine. To validate the analytical parameters, the reproducibility, linearity of calibration curves, detection limits, and recovery were evaluated for standard mixtures and cell extracts. The developed method is capable of resolving picomolar quantities of nucleotides and nucleotide sugars in a single chromatographic run. The HPLC method was then applied to quantify intracellular levels of nucleotides and nucleotide sugars of Chinese hamster ovary (CHO) cells cultivated in a bioreactor batch process. Evolutions of the titers of nucleotides and nucleotide sugars during the batch process are discussed.

Use of flow cytometry to monitor infection and recombinant human alpha-1,3/4 fucosyltransferase production in baculovirus infected Sf9 cell cultures

This paper describes the setup and the use of a flow cytometric method for monitoring Sf9 insect cell infection by a recombinant baculovirus expressing the human alpha1,3/4 fucosyltransferase Fuc-TIII. Using side scattered light coupled to green fluorescence detection after immunolabeling of the recombinant protein, this method made it possible to monitor baculovirus infection of Sf9 cells grown in batch cultures and infected at different cell densities and multiplicities of infection. The method was able to precisely assess the extent of infection of the insect cells from 60 h postinfection. In asynchronously infected Sf9 cell cultures, the two-step infection process (primary and secondary infection) was well-characterized using this technique. Finally, a reduced sensitivity to baculovirus infection was observed for cells infected at the end of the growth phase compared to the cells infected during exponential growth phase.

Amino acids metabolism by VO 208 hybridoma cells: some aspects of the culture process and medium composition influence

In the present study an approach has been developed in order to examine the consequence of essential and non essential amino acid supplementation on VO208 hybridoma cells behaviour. The effect of amino acid enrichment has been studied taking into account the culture process, i.e., batch or continuous culture mode and the medium composition, i.e., a home made serum-free medium or a serum containing one. A group of 4 amino acids, i.e., Ser, Pro, Gly and Arg presented atypical evolution pattern of their extracellular concentration depending on the type of the medium and on the culture mode. Some amino acids were probably involved in the limitation of the cellular proliferation. Met was one of the amino acids that appears to may have been at limiting concentration in all cases. In continuous culture mode, an enrichment of amino acids resulted in a rapid improvement of the viable cell density in both media, with or without the presence of serum. For most amino acids, supplementation during continuous culture induced an increase of the amino acid uptake rate. A comparative analysis of amino acids utilisation, depending on the culture conditions studied in the present study, has been performed in order to propose an overall picture of amino acids metabolism by VO 208 Hybridoma cell line.

A new Chinese hamster ovary cell line expressing alpha2,6-sialyltransferase used as universal host for the production of human-like sialylated recombinant glycoproteins

Chinese hamster ovary (CHO) cells are widely employed to produce glycosylated recombinant proteins. Our group as well as others have demonstrated that the sialylation defect of CHO cells can be corrected by transfecting the alpha2,6-sialyltransferase (alpha2,6-ST) cDNA. Glycoproteins produced by such CHO cells display both alpha2,6- and alpha2,3-linked terminal sialic acid residues, similar to human glycoproteins. Here, we have established a CHO cell line stably expressing alpha2,6-ST, providing a universal host for further transfections of human genes. Several relevant parameters of the universal host cell line were studied, demonstrating that the alpha2,6-ST transgene was stably integrated into the CHO cell genome, that transgene expression was stable in the absence of selective pressure, that the recombinant sialyltransferase was correctly localized in the Golgi and, finally, that the bioreactor growth parameters of the universal host were comparable to those of the parental cell line. A second step consisted in the stable transfection into the universal host of cDNAs for human glycoproteins of therapeutic interest, i.e. interferon-gamma and the tissue inhibitor of metalloproteinases-1. Interferon-gamma purified from the universal host carried 40.4% alpha2,6- and 59.6% alpha2,3-sialic acid residues and showed improved pharmacokinetics in clearance studies when compared to interferon-gamma produced by normal CHO cells.

[Role of flexible mini-ureteroscopes in diseases of the upper urinary tract]

INTRODUCTION

The management of upper urinary tract disease has been improved by miniaturization of endoscopes. Our objective was to assess the value of flexible mini-ureteroscopes for the diagnosis and treatment of upper urinary tract lesions.

PATIENTS AND METHODS

33 consecutive patients (mean age: 49 +/- 16 years; 23 men) underwent first-line flexible ureteroscopy for upper urinary tract disease, consisting of: stones: 21, filling defect: 6, stenosis: 3, haematuria: 2, positive cytology: 1 and situated in the kidney + renal pelvis: 14 or ureter: 19. The 21 stones were situated in: the calyx: 5, renal pelvis: 1, lumbar ureter: 8, iliac ureter: 3, pelvic ureter: 4. Their mean dimensions were 9.7 +/- 4 x 5.3 +/- 2.3 mm. Previous treatment had failed for 13 stones. There 7.5 F flexible ureteroscopes of various brands were used.

RESULTS

All patients were operated under general anaesthesia. Antegrade ureteroscopy was performed in 2 patients. Advancement of the ureteroscope was considered to be difficult in 5 cases, including the 2 antegrade cases. 13 stones were fragmented by hydroelectric waves. The mean duration of ureteroscopy was 40 +/- 15 min. The mean hospital stay was 2.8 +/- 1 days. There was no intraoperative or perioperative morbidity. Ureteroscopy was considered to be successful in 27 cases (82%) and a failure in 6 cases: fragmentation: 3 and progression: 3. Fifteen patients were reviewed after more than one month (3 +/- 2 months) with no morbidity.

CONCLUSION

Ureteroscopy with flexible mini-ureteroscopes is an effective, reproducible and minimally traumatic diagnostic and therapeutic technique. It is particularly useful for lesions situated above the iliac vessels and is indicated for diagnostic assessment and stones, but also upper tract malformations and strictures.

Development and validation of a methodology for intracellular pH measurements of hybridoma cells under bioreactor culture conditions

The intracellular pH (pH(i)) is an important factor in the regulation of different cellular processes. It might therefore be used as a marker of the physiological state of cells cultivated in a bioreactor environment. We developed and validated therefore a methodology that permits a reproducible and reliable pH(i) measurement under such bioreactor culture conditions, contrary to earlier reported measurements, carried out on cells resuspended in buffers under nongrowth conditions. The hybridoma cells were sampled from the culture, stained with the pH-sensitive dye BCECF-AM (BCECF = 2',7'-bis-carboxyethyl-5,6-carboxyfluorescein), and analyzed by flow cytometry. Such a measurement is perfectible to changes of the cells between the moment of sampling and of final analysis on the flow cytometer. All intermittent steps were for this reason studied in detail, either to determine the optimal conditions to be used or to characterize their influence on the final pH(i) value measured. Additional experiments were carried out, showing the representativeness of the measured pH(i) value for the pH(i) the cells possess really in the culture at the moment of sampling.

Intracellular pH monitoring as a tool for the study of hybridoma cell behavior in batch and continuous bioreactor cultures

We show in this paper the results obtained when studying the behavior of hybridoma cells by monitoring of the pHi during batch and continuous bioreactor cultures. A first set of experiments, consisting of a batch culture and a continuous culture at variable dilution rate, was set up under normal physiological operating conditions. Significant pHi variations were measured during these cultures. For the batch culture, maximal pHi values around 7.60 were associated with the middle of the growth phase, while lower values were found in the culture beginning and during the decay phase, respectively 7.47 and 7.40. For the continuous culture, pHi increased with increasing dilution rate, ranging between 7.40 and 7. 60 for dilution rates between 0.010 and 0.040 h-1. These pHi variations were found for both cultures to be linked to variations of the specific growth rate of the cells. The observed link between pHi and cell growth provided us a general framework for the study of the effect of suboptimal operating conditions on cell behavior, all having a particular interest in animal cell culture technology. First, our results indicate that a decrease of the medium pH of its normal value of 7.00 to 6.70 did not necessarily result in cytoplasmic acidification, at least not after prolonged exposition times in continuous culture, and this despite a pronounced growth inhibitory effect. This effect can therefore rather be explained by the combination of the increased demand for maintenance energy associated with the higher DeltapH gradient maintained across the cell membrane and the decreased supply of energy, in particular via the glucose metabolism. Second, our results indicate that also increased ammonium ion concentrations do not lower pHi. This observation, together with the results of batch cultures carried out at a more alkaline pH, indicates that the form NH3, and not the form NH4+, has a negative effect on cell growth of our hybridoma cell line. Third, in the case of an osmolality increase, a significant pHi increase was observed, with mean values of 7.35 at the lower osmolalities 335 and 370 mOsm/kg and 7.45 at the higher osmolalities of 400, 425, and 450 mOsm/kg. This higher pHi might account at least partially for the increased monoclonal antibody production observed at hyperosmolality and coincided furthermore with a faster glutamine consumption rate.

Insulin utilization and kinetic effect on hybridoma metabolism in batch and continuous cultures

This paper discusses the insulin utilization kinetics and the effect of its concentration during batch and continuous mass cultures of the murine VO208 hybridoma cells, using a home-made serum-free medium. Our results show that insulin is utilized by the cells, with a specific rate of 1 relative units (RU) per 10(9) cells per h in batch culture. In continuous reactor running at different insulin levels, this consumption rate is observed to vary from 0.13 to 0.55 RU per 10(9) cells per h when the insulin activity increases from 0.3 to 35 RU l-1 and then to stabilize for higher insulin levels until 110 RU l-1. A low insulin amount in the medium around 0.01 RU l-1, which is near physiological levels, is found sufficient to promote the cell growth. Interestingly, we observe that too high insulin levels, above 25 RU l-1, induce a reduction of the cell density due to an inhibitory effect on the maximal specific cell growth rate. Furthermore, the specific rate of MAb production is found to be independent of the insulin amount in the medium.

Production of a membrane-bound protein, the human gamma-glutamyl transferase, by CHO cells cultivated on microcarriers, in aggregates and in suspension

Recombinant Chinese Hamster Ovary (CHO) cells, engineered for the production of human gamma-glutamyl transferase (GGT), have been grown on Cytodex 1 microcarriers, as aggregates, or as single cells in suspension after adaptation. GGT is a membrane bound enzyme which was not secreted during the culture period. The maximal enzyme activity was found to be directly related to the achieved maximal cell density. Culture of CHO on microcarriers yielded the fastest growth, with a specific growth rate of 0.04 h-1, the highest cell density (near 1.3 x 10(6) cells ml-1), and the highest enzyme activity around 300 mU ml-1, which corresponded to a specific cellular level of 20 mU 10(-5) cells. GGT could also be produced by growing CHO cells in suspension as single cells or as aggregates. Under these conditions, however, the specific CHO growth rate was significantly slower and the GGT level per cell was divided by a factor 6. Growing CHO cells without microcarriers also resulted in differences in cell metabolism, with a higher conversion yield of glutamine into ammonia, and a higher cell lysis. The catalytic kinetic constants of the enzyme were found identical for the three culture systems.

Software sensors for the monitoring of perfusion cultures: evaluation of the hybridoma density and the medium composition from glucose concentration measurements

New software sensors based on the Extended Kalman Filter technique have been developed for the monitoring of animal cell perfusion cultures. They use a kinetic model describing the growth, death and metabolism of hybridoma cells as a function of the medium composition. The model was initially validated on a batch culture and found to correctly predict the continuous perfusion culture kinetics, except for the production of ammonia and lactate. Using the measurement of a single component in the culture medium, in this case glucose, the Extended Kalman Filter provides an excellent evaluation of the time variation of the concentrations of living and dead cells, of glutamine and antibodies, during the whole perfusion culture for a retained cell density rising from 1 to 11 x 10(6) cells.ml-1 inside the reactor.

Induction of recombinant human gamma-glutamyl transferase by sodium butyrate in transfected V79 and CHO Chinese hamster cells

Sodium butyrate was used to enhance biosynthesis rates of recombinant human gamma-glutamyl transferase (GGT) expressed under the control of the SV40 or the cytomegalovirus immediate early promoter, respectively, in transfected V79 and CHO Chinese hamster cell lines. Maximal induction of GGT specific activity in butyrate-treated cells ranged from 3 to 5-fold and resulted from a strong increase in the GGT mRNA ratio. We also observed that maximal transcription level in V79 cells occurred within 12 hr of treatment, whilst the cell proliferation was transiently arrested. Despite its processing requirements, induced GGT exhibited unchanged catalytic and physico-chemical features relative to human serum or hepatoma enzyme, thus appearing as an excellent model for further studies on human GGT.

Determination of cell lysis and death kinetics in continuous hybridoma cultures from the measurement of lactate dehydrogenase release

The death of the hybridoma VO 208 in a continuous culture at pH 7 and 6.8 was investigated by measuring both the appearance of visible dead cells which do not exclude the trypan blue dye and the release of lactate dehydrogenase (LDH) in the culture medium. The intracellular LDH was found to be completely released either when live cells lysed or when they were transformed into visible dead cells. No significant lysis of blue dead cells could be observed at the two different pH. Using a LDH balance over the culture system, cell lysis was found negligible at pH 7, but accounted for 20% of the total cell death at pH 6.8. A methodology is proposed to evaluate the rate constants of hybridoma lysis and total death. For the investigated cell line in continuous culture, the calculated total cell death rate constant was found to increase from 0.002 h-1 to 0.01 h-1 when decreasing the pH from 7 to 6.8.

Lactate dehydrogenase (LDH) activity of the cultured eukaryotic cells as marker of the number of dead cells in the medium [corrected]

One significant problem in monitoring a culture's evolution is to assess change in cell viability. We have demonstrated that LDH release could be a good indicator of cellular damage of many cell lines, especially during shear stress or sonication. Moreover, we have found a significant correlation between the number of dead cells, determined by Trypan Blue staining, and LDH activity measurements in the supernatant of hybridoma strains, whatever the culture conditions. We have also shown that when viability is still near 100% no LDH is released even at high cell concentrations. Therefore, LDH should serve as a potential marker of cell injury and death.

Comparison of specific rates of hybridoma growth and metabolism in batch and continuous cultures

For the mouse hybridoma cell line VO 208, kinetics of growth, consumption of glucose and glutamine, and production of lactate, ammonia and antibodies were compared in batch and continuous cultures. At a given specific growth rate, different metabolic activities were observed: a 40% lower glucose and glutamine consumption rate, but a 70% higher antibody production rate in continuous than in batch culture. Much higher metabolic rates were also measured during the initial lag phase of the batch culture. When representing the variation of the specific antibody production rate as a function of the specific growth rate, there was a positive association between growth and antibody production in the batch culture, but a negative association during the transient phase of the continuous culture. The kinetic differences between cellular metabolism in batch and continuous cultures may be the result of modifications in the physiology and metabolism of cells which, in continuous cultures, were extensively exposed to glucose limitations.

Influence of inoculum age on hybridoma culture kinetics

To determine the influence of the inoculum age on the kinetics of hybridoma growth and metabolism, spinner flasks have been inoculated with cells previously propagated in T flasks for 43, 52, 62 and 71 hr respectively. Increasing the age of the inoculum is found to result in a longer lag phase, in a lower maximum specific growth rate and in a reduced maximal cell density. During the growth phase specific rates of glucose and glutamine uptake and of ammonia and lactate production are similar. However, with the older inoculum, much higher metabolic activities are observed during the lag phase. The production of antibodies is delayed with increasing inoculum age, but the final antibody concentrations are similar, which indicates a higher specific antibody production rate when inoculating with older cells.

Gamma-glutamyltransferase from human hepatoma cell lines: purification and cell culture of HepG2 on microcarriers

After screening different human hepatoma cell lines, we observed that both HepG2 and PLC/PRF/5 naturally produced large amounts of gamma-glutamyltransferase. We optimized HepG2 cell culture conditions and observed that higher cell densities were obtained when cells were cultured on microcarriers, particularly when Cytodex 3 was used and that cell growth was optimal when DMEM, the basic medium, was supplemented with 5% fetal calf serum and 6 mmol/l glutamine. These culture conditions allowed us to produce the highest amounts of GGT after about 150 h of culture. The GGT obtained from HepG2 cells was partially purified and some of its physico-chemical properties characterized. Successive Con A gel chromatography separated the activity into two peaks, suggesting that GGT from HepG2 is not uniformly glycosylated. Papain-treated HepG2 GGT showed a Mr of about 120 kDa and migrated as a single-chain protein in SDS-PAGE. Immunological and kinetic properties of the GGT were similar to other human GGTs (liver, kidney and serum). It appears that HepG2 GGT could be a source for the preparation of a human enzyme reference material.

[Gougerot-Sjögren syndrome in patients with sarcoidosis]

Three patients with eye and salivary dryness presenting the scintigraphic and histological features of Sjogren's syndrome and also suffering from sarcoïdosis, are reported. The authors stress the rarity of clinically indentifiable dry oculo-salivary syndromes whilst routine scintigraphy of the principle salivary glands using technetium 99 m often reveals altered salivary function. They consider that the primary feature in the development of this dry salivary syndrome consists of fibro-inflammatory lesions of the glandular interstitium, seen in specimens of the glands of the labial mucosae, which are sequelae of the initial sarcoid infiltration. They point out that Sjogren's syndrome occurring in relation with sarcoïdosis has certain special features. These include its appearance in relatively young subjects, the minimal symptoms, the non-essential presence of inflammatory signs and the absence of associated connective tissue disorder.