Automatic air volume control system for ventilation of two patients using a single ventilator: a large animal model study.

The COVID-19 pandemic outbreak led to a global ventilator shortage. Hence, various strategies for using a single ventilator to support multiple patients have been considered. A device called Ventil previously validated for independent lung ventilation was used in this study to evaluate its usability for shared ventilation. We performed experiments with a total number of 16 animals. Eight pairs of pigs were ventilated by a ventilator or anesthetic machine and by Ventil for up to 27 h. In one experiment, 200 ml of saline was introduced to one subject's lungs to reduce their compliance. The experiments were analyzed in terms of arterial blood gases and respiratory parameters. In addition to the animal study, we performed a series of laboratory experiments with artificial lungs (ALs). The resistance and compliance of one AL (affected) were altered, while the tidal volume (TV) and peak pressure (Ppeak) in the second (unaffected) AL were analyzed. In addition, to assess the risk of transmission of pathogens between AL respiratory tracts, laboratory tests were performed using phantoms of virus particles. The physiological level of analyzed parameters in ventilated animals was maintained, except for CO2 tension, for which a permissive hypercapnia was indicated. Experiments did not lead to injuries in the animal's lungs except for one subject, as indicated by CT scan analysis. In laboratory experiments, changes in TV and Ppeak in the unaffected AL were less than 11%, except for 2 cases where the TV change was 20%. No cross-contamination was found in simulations of pathogen transmission. We conclude that ventilation using Ventil can be considered safe in patients undergoing deep sedation without spontaneous breathing efforts.

Effects of genetically modified human skin fibroblasts, stably overexpressing hepatocyte growth factor, on hepatic functions of cocultured C3A cells.

Diseases leading to terminal hepatic failure are among the most common causes of death worldwide. Transplant of the whole organ is the only effective method to cure liver failure. Unfortunately, this treatment option is not available universally due to the serious shortage of donors. Thus, alternative methods have been developed that are aimed at prolonging the life of patients, including hepatic cells transplantation and bridging therapy based on hybrid bioartificial liver devices. Parenchymal liver cells are highly differentiated and perform many complex functions, such as detoxification and protein synthesis. Unfortunately, isolated hepatocytes display a rapid decline in viability and liver-specific functions. A number of methods have been developed to maintain hepatocytes in their highly differentiated state in vitro, amongst them the most promising being 3D growth scaffolds and decellularized tissues or coculture with other cell types required for the heterotypic cell-cell interactions. Here we present a novel approach to the hepatic cells culture based on the feeder layer cells genetically modified using lentiviral vector to stably produce additional amounts of hepatocyte growth factor and show the positive influence of these coculture conditions on the preservation of the hepatic functions of the liver parenchymal cells' model-C3A cells.

Clinical applications of liver support systems / Kliniczne metody wspomagania niewydolnej watroby.

Liver diseases that lead to its failure are one of the most frequent causes of death worldwide. Taking into account liver's complexity, there are no drug for acute or acute on chronic liver failure treatment. So far the only effective therapy is the liver transplantation. Unfortunately donor shortage is a main problem of this therapy. Due to this fact scientists have been looking for a new alternatives. The most promising are cell transplantation and bioartificial support systems. Without doubt hepatocytes are the best source of cells to use. But isolated human hepatocytes dedifferentiate very quickly and lose their functions ex vivo. Therefore, the new sources of cells, which could replace hepatocytes, are highly sought after. It is believed that, in order to help patients suffering from liver disease, the approach to solve this problem should be considered on different levels.

Liver tissue fragments obtained from males are the most promising source of human hepatocytes for cell-based therapies - Flow cytometric analysis of albumin expression.

Cell-based therapies that could provide an alternative treatment for the end-stage liver disease require an adequate source of functional hepatocytes. There is little scientific evidence for the influence of patient's age, sex, and chemotherapy on the cell isolation efficiency and metabolic activity of the harvested hepatocytes. The purpose of this study was to investigate whether hepatocytes derived from different sources display differential viability and biosynthetic capacity. Liver cells were isolated from 41 different human tissue specimens. Hepatocytes were labeled using specific antibodies and analyzed using flow cytometry. Multiparametric analysis of the acquired data revealed statistically significant differences between some studied groups of patients. Generally, populations of cells isolated from the male specimens had greater percentage of biosynthetically active hepatocytes than those from the female ones regardless of age and previous chemotherapy of the patient. Based on the albumin staining (and partially on the α-1-antitrypsin labeling) after donor liver exclusion (6 out of 41 samples), our results indicated that: 1. samples obtained from males gave a greater percentage of active hepatocytes than those from females (p = 0.034), and 2. specimens from the males after chemotherapy greater than those from the treated females (p = 0.032).

Dried human skin fibroblasts as a new substratum for functional culture of hepatic cells.

The primary hepatocytes culture is still one of the main challenges in toxicology studies in the drug discovery process, development of in vitro models to study liver function, and cell-based therapies. Isolated hepatocytes display a rapid decline in viability and liver-specific functions including albumin production, conversion of ammonia to urea, and activity of the drug metabolizing enzymes. A number of methods have been developed in order to maintain hepatocytes in their highly differentiated state in vitro. Optimization of culture conditions includes a variety of media formulations and supplements, growth surface coating with the components of extracellular matrix or with synthetic polymers, three-dimensional growth scaffolds and decellularized tissues, and coculture with other cell types required for the normal cell-cell interactions. Here we propose a new substratum for hepatic cells made by drying confluent human skin fibroblasts' culture. This growth surface coating, prepared using maximally simplified procedure, combines the advantages of the use of extracellular matrices and growth factors/cytokines secreted by the feeder layer cells. In comparison to the hepatoma cells grown on a regular tissue culture plastic, cells cultured on the dried fibroblasts were able to synthesize albumin in larger quantities and to form greater number of apical vacuoles. Unlike the coculture with the living feeder layer cells, the number of cells grown on the new substratum was not reduced after fourteen days of culture. This fact could make the dried fibroblasts coating an ideal candidate for the substrate for non-dividing human hepatocytes.

Analysis of the cytotoxicity of carbon-based nanoparticles, diamond and graphite, in human glioblastoma and hepatoma cell lines.

Nanoparticles have attracted a great deal of attention as carriers for drug delivery to cancer cells. However, reports on their potential cytotoxicity raise questions of their safety and this matter needs attentive consideration. In this paper, for the first time, the cytotoxic effects of two carbon based nanoparticles, diamond and graphite, on glioblastoma and hepatoma cells were compared. First, we confirmed previous results that diamond nanoparticles are practically nontoxic. Second, graphite nanoparticles exhibited a negative impact on glioblastoma, but not on hepatoma cells. The studied carbon nanoparticles could be a potentially useful tool for therapeutics delivery to the brain tissue with minimal side effects on the hepatocytes. Furthermore, we showed the influence of the nanoparticles on the stable, fluorescently labeled tumor cell lines and concluded that the labeled cells are suitable for drug cytotoxicity tests.

Evaluation of the effects of antibiotics on cytotoxicity of EGFP and DsRed2 fluorescent proteins used for stable cell labeling.

The use of fluorescent markers has proven to be an attractive tool in biological imaging. However, its usefulness may be confined by the cytotoxicity of the fluorescent proteins. In this article, for the first time, we have examined an influence of the antibiotics present in culture medium on cytotoxicity of the EGFP and DsRed2 markers used for whole-cell labeling. Results showed that doxycycline negatively affected albumin synthesis in DsRed2-expressing hepatoma cells, and that both hepatoma cells and human skin fibroblasts, labeled with this protein, were characterized by the lowered growth rates. Thus, the cytotoxic effect of fluorescent markers depends on both protein used for cell labeling and on growth conditions that may cause cell stress.

Generation of fluorescently labeled cell lines, C3A hepatoma cells, and human adult skin fibroblasts to study coculture models.

Hepatic/nonhepatic cell cocultures are widely used in studies on the role of homo- and heterotypic interactions in liver physiology and pathophysiology. In this article, for the first time, establishment of the coculture model employing hepatoma C3A cells and human skin fibroblasts, stably expressing fluorescent markers, is described. Suitability of the model in studying coculture conditions using fluorescence microscopy and flow cytometry was examined. C3A cells spontaneously formed island-like growth patterns surrounded by fibroblasts. The "islands" size and resulting intensity of the homo- and heterotypic interactions can easily be tuned by applying various plated cells ratios. We examined the capability of the hepatoma cells to produce albumin in hepatic/nonhepatic cell cocultures. The enzyme-linked immunosorbent assay (ELISA) tests showed that greater number of fibroblasts in coculture, resulting in smaller sizes of hepatoma "islands," and thus, a larger heterotypic interface, promoted higher albumin synthesis. The use of fluorescently labeled cells in flow cytometry measurements enabled us to separately gate two cell populations and to evaluate protein expression only in/on cells of interest. Flow cytometry confirmed ELISA results indicating the highest albumin production in hepatoma cells cocultured with the greatest number of fibroblasts and the inhibited protein synthesis in coculture with osteosarcoma cells.

Use of HIV as a gene transfer vector.

Despite the extensive research efforts over the past 25 years that have focused on HIV, there is still no cure for AIDS. However, tremendous progress in the understanding of the structure and biology of the HIV virus led to the development of safe and potent HIV-based transgene delivery vectors. These genetic vehicles are referred to as lentiviral vectors. They appear to be better suited for particular applications, such as transgene delivery into stem cells, compared to other viral- and non-viral vectors. This is because Lentivirus-based vectors can efficiently infect nondividing and slowly dividing cells. In the present review article, the current state of understanding of HIV-1 is discussed and the main characteristics that had an impact on vector design are outlined. A historical view on the vector concept is presented to facilitate discussion of recent results in vector engineering in a broader context. Subsequently, a state of the art overview concerning vector construction and vector production is given. This review also touches upon the subject of lentiviral vector safety and related topics that can be helpful in addressing this issue are discussed. Finally, examples of Lentivirus-based gene delivery systems and their applications are presented, with emphasis on animal transgenesis and human gene therapy.

Lentiviral vectors encoding tetracycline-dependent repressors and transactivators for reversible knockdown of gene expression: a comparative study.

BACKGROUND: RNA interference (RNAi)-mediated by the expression of short hairpin RNAs (shRNAs) has emerged as a powerful experimental tool for reverse genetic studies in mammalian cells. A number of recent reports have described approaches allowing regulated production of shRNAs based on modified RNA polymerase II (Pol II) or RNA polymerase III (Pol III) promoters, controlled by drug-responsive transactivators or repressors such as tetracycline (Tet)-dependent transactivators and repressors. However, the usefulness of these approaches is often times limited, caused by inefficient delivery and/or expression of shRNA-encoding sequences in target cells and/or poor design of shRNAs sequences. With a view toward optimizing Tet-regulated shRNA expression in mammalian cells, we compared the capacity of a variety of hybrid Pol III promoters to express short shRNAs in target cells following lentivirus-mediated delivery of shRNA-encoding cassettes. RESULTS: RNAi-mediated knockdown of gene expression in target cells, controlled by a modified Tet-repressor (TetR) in the presence of doxycycline (Dox) was robust. Expression of shRNAs from engineered human U6 (hU6) promoters containing a single tetracycline operator (TO) sequence between the proximal sequence element (PSE) and the TATA box, or an improved second-generation Tet-responsive promoter element (TRE) placed upstream of the promoter was tight and reversible as judged using quantitative protein measurements. We also established and tested a novel hU6 promoter system in which the distal sequence element (DSE) of the hU6 promoter was replaced with a second-generation TRE. In this system, positive regulation of shRNA production is mediated by novel Tet-dependent transactivators bearing transactivation domains derived from the human Sp1 transcription factor. CONCLUSION: Our modified lentiviral vector system resulted in tight and reversible knockdown of target gene expression in unsorted cell populations. Tightly regulated target gene knockdown was observed with vectors containing either a single TO sequence or a second-generation TRE using carefully controlled transduction conditions. We expect these vectors to ultimately find applications for tight and reversible RNAi in mammalian cells in vivo.

Tight control of transgene expression by lentivirus vectors containing second-generation tetracycline-responsive promoters.

BACKGROUND: The goal of this study was to design improved regulatable lentivirus vector systems. The aim was to design tetracycline (tet)-regulatable lentivirus vectors based on the Tet-on system displaying low background expression in the absence of the doxycycline (DOX) inducer and high transgene expression levels in the presence of DOX. METHODS: We constructed a binary lentivirus vector system that is composed of a self-inactivating (SIN) lentivirus vector bearing inducible first- or second-generation tet-responsive promoter elements (TREs) driving expression of a transgene and a second lentivirus vector encoding a reverse tetracycline-controlled transactivator (rtTA) that activates transgene expression from the TRE in the presence of DOX. RESULTS: We evaluated a number of different rtTAs and found rtTA2S-M2 to induce the highest levels of transgene expression. Regulated transgene expression was stable in human breast carcinoma cells implanted into nude mice for up to 11 weeks. In an attempt to minimize background expression levels, the chicken beta-globin cHS4 insulator element was cloned into the 3' long terminal repeat (LTR) of the transgene transfer vector. The cHS4 insulator element reduced background expression but expression levels following DOX addition were lower than those observed with vectors lacking an insulator sequence. In a second strategy, vectors bearing second-generation TREs harboring repositioned tetracycline operator elements were used. Such vectors displayed greatly reduced leakiness in the absence of DOX and induced transgene expression levels were up to 522-fold above those seen in the absence of DOX. CONCLUSIONS: Inducible lentivirus vectors bearing insulators or second-generation TREs will likely prove useful for applications demanding the lowest levels of background expression.