Search

The application of cell-based therapeutics requires development of refined and scalable culture processes. Stirred tank bioreactors facilitate growth of human mesenchymal stromal cells (hMSC) while meeting these needs. A process for expansion of hMSCs in a 50 L bioreactor was developed. Parameters evaluated include agitation rate, pH and dissolved oxygen (DO) control set-points, and media formulation. The pH and DO levels were determined empirically in 3 L bioreactors prior to implementation at the 50 L scale. The agitation operating range for microcarrier cultures in the 50 L bioreactor was calculated based on theoretical and empirical analyses of solid suspension and shear limitations. Additionally, small-scale experiments demonstrated that hMSC growth was improved in αMEM supplemented with human platelet lysate in comparison to DMEM supplemented with FBS. A 43-fold expansion of harvested hMSCs was achieved in 11 days in a 50 L bioreactor incorporating these process improvements. Cells expanded in the bioreactor exhibited the expected surface marker expression, trilineage differentiation potential, T cell growth inhibition and indoleamine 2,3-dioxygenase inducibility. The results highlight that identification of optimal pH, DO, agitation rates and culture medium for microcarrier-based bioreactor expansion of adherent cells is paramount to developing a platform to support cell-based therapies.

The long-term outlook for regenerative medicine predicts an increased need for scalable cell expansion technologies that utilize non-animal derived materials and are compatible with the limited number of downstream processing steps required for cell-based therapies. As more stem cell therapeutics progress through clinical testing, current in vitro culture methods using planar vessels are proving cumbersome to scale. Therefore, alternative processes are under investigation. Many human mesenchymal stem/stromal cell (hMSC) bioreactor-based manufacturing processes, in particular, are complicated by the requirement to separate cells from microcarriers with high cell yield and viability whilst maintaining target phenotypic and functional characteristics. Here we review currently available technologies and ongoing development for the expansion of cellular therapeutics, with focus on allogeneic hMSCs and microcarrier-based processes. Upstream challenges include the interplay between the cell culture substrate and media formulation, sourcing of high quality animal-free reagents, and considerations for the use of microcarriers in stirred-tank systems. Complications in downstream processes include harvest approaches for separation of cells from microcarriers and volume reduction.

We aimed to assess the effectiveness of ‘Paesaggi di Prevenzione’, a school-based prevention program delivered by trained teachers and designed to tackle smoking, alcohol misuse, dietary risks, and physical inactivity in adolescence. We evaluated the program between 2010 and 2013 with a two-arm, parallel-group, multicentre cluster randomized controlled trial in which schools were the units of randomization. We collected data on health-compromising behaviours using self-reported measurements of behaviour frequency administered before and after program implementation. We used multivariable mixed-effects logistic regression models to estimate program effects on health-compromising behaviours. The analysis sample included 3410 middle school students and 1651 high school students. Among middle school students, mean age at baseline was 12 years (standard deviation [SD] 0.5 years), 51% were boys, and 41% had high socioeconomic status [SES] (defined as having at least one parent/guardian with university level education). In high school students, mean age at baseline was 14 years (SD 0.7 years), 56% were boys, and 31% had high SES. The program did not have effects on smoking, alcohol misuse, and physical activity. The program had iatrogenic effects in regard to some eating behaviours, resulting in (i) lower odds of fruit consumption among middle-school students (odds ratio [OR] 0.82; 95% confidence interval [CI] 0.68–0.99) and (ii) lower odds of having breakfast every day in high-school students at the post-intervention measurement (OR 0.76; 95%CI 0.58–0.99) but not at one-year follow-up (OR 0.94; 95%CI 0.69–1.28). Due to the possibility of unintended effects, we advise against disseminating ‘Paesaggi di Prevenzione’ in its present form. Trial registration ISRCTN00953701

Several potent, cell permeable 4-aryl-dihydropyrimidinones have been identified as inhibitors of FATP4. Lipophilic ester substituents at the 5-position and substitution at the para-position (optimal groups being -NO(2) and CF(3)) of the 4-aryl group led to active compounds. In two cases racemates were resolved and the S enantiomers shown to have higher potencies.

Background & Aims: Fatty acid transport protein 5 (FATP5/Slc27a5) has been shown to be a multifunctional protein that in vitro increases both uptake of fluorescently labeled long-chain fatty acid (LCFA) analogues and bile acid/coenzyme A ligase activity on overexpression. The aim of this study was to further investigate the diverse roles of FATP5 in vivo. Methods: We studied FATP5 expression and localization in liver of C57BL/6 mice in detail. Furthermore, we created a FATP5 knockout mouse model and characterized changes in hepatic lipid metabolism (this report) and bile metabolism (the accompanying report by Hubbard et al). Results: FATP5 is exclusively expressed by the liver and localized to the basal plasma membrane of hepatocytes, congruent with a role in LCFA uptake from the circulation. Overexpression of FATP5 in mammalian cells increased the uptake of 14 C-oleate. Conversely, FATP5 deletion significantly reduced LCFA uptake by hepatocytes isolated from FATP5 knockout animals. Moreover, FATP5 deletion resulted in lower hepatic triglyceride and free fatty acid content despite increased expression of fatty acid synthetase and also caused a redistribution of lipids from liver to other LCFA-metabolizing tissues. Detailed analysis of the hepatic lipom of FATP5 knockout livers showed quantitative and qualitative alterations in line with a decreased uptake of dietary LCFAs and increased de novo synthesis. Conclusions: Our findings support the hypothesis that efficient hepatocellular uptake of LCFAs, and thus liver lipid homeostasis in general, is largely a protein-mediated process requiring FATP5. These new insights into the physiological role of FATP5 should lead to an improved understanding of liver function and disease.

Insulin resistance in skeletal muscle plays a major role in the development of type 2 diabetes and may be causally associated with increases in intramuscular fatty acid metabolites. Fatty acid transport protein 1 (FATP1) is an acyl-CoA synthetase highly expressed in skeletal muscle and modulates fatty acid uptake and metabolism by converting fatty acids into fatty acyl-CoA. To investigate the role of FATP1 in glucose homeostasis and in the pathogenesis of insulin resistance, we examined the effect of acute lipid infusion or chronic high-fat feeding on insulin action in FATP1 KO mice. Whole-body adiposity, adipose tissue expression of adiponectin, intramuscular fatty acid metabolites, and insulin sensitivity were not altered in FATP1 KO mice fed a regular chow diet. In contrast, FATP1 deletion protected the KO mice from fat-induced insulin resistance and intramuscular accumulation of fatty acyl-CoA without alteration in whole-body adiposity. These findings demonstrate an important role of intramuscular fatty acid metabolites in causing insulin resistance and suggest that FATP1 may be a novel therapeutic target for the treatment of insulin resistance and type 2 diabetes.

Fatty acid transport protein-4 (FATP4) is the major FATP in the small intestine. We previously demonstrated, using in vitro antisense experiments, that FATP4 is required for fatty acid uptake into intestinal epithelial cells. To further examine the physiological role of FATP4, mice carrying a targeted deletion of FATP4 were generated. Deletion of one allele of FATP4 resulted in 48% reduction of FATP4 protein levels and a 40% reduction of fatty acid uptake by isolated enterocytes. However, loss of one FATP4 allele did not cause any detectable effects on fat absorption on either a normal or a high fat diet. Deletion of both FATP4 alleles resulted in embryonic lethality as crosses between heterozygous FATP4 parents resulted in no homozygous offspring; furthermore, no homozygous embryos were detected as early as day 9.5 of gestation. Early embryonic lethality has been observed with deletion of other genes involved in lipid absorption in the small intestine, namely microsomal triglyceride transfer protein and apolipoprotein B, and has been attributed to a requirement for fat absorption early in embryonic development across the visceral endoderm. In mice, the extraembryonic endoderm supplies nutrients to the embryo prior to development of a chorioallantoic placenta. In wild-type mice we found that FATP4 protein is highly expressed by the epithelial cells of the visceral endoderm and localized to the brush-border membrane of extraembryonic endodermal cells. This localization is consistent with a role for FATP4 in fat absorption in early embryogenesis and suggests a novel requirement for FATP4 function during development.

While intestinal transport systems for metabolites such as carbohydrates have been well characterized, the molecular mechanisms of fatty acid (FA) transport across the apical plasmalemma of enterocytes have remained largely unclear. Here, we show that FATP4, a member of a large family of FA transport proteins (FATPs), is expressed at high levels on the apical side of mature enterocytes in the small intestine. Further, overexpression of FATP4 in 293 cells facilitates uptake of long chain FAs with the same specificity as enterocytes, while reduction of FATP4 expression in primary enterocytes by antisense oligonucleotides inhibits FA uptake by 50%. This suggests that FATP4 is the principal fatty acid transporter in enterocytes and may constitute a novel target for antiobesity therapy.

E. coli recombinant expression systems that utilize lac operon control elements to modulate gene expression are known to produce some amount of uninduced (leaky) gene expression. Previously, we showed that high levels of uninduced gene expression was a major cause of instability in the pET expression system. We show here that the pET system, in which the phage T7 RNA polymerase gene is expressed via lac operon control elements, exhibits leaky expression that increases markedly as cells grown in complex medium enter stationary phase. Moreover, we found that this phenomenon occurs with the chromosomal lac operon as well. Further investigation revealed that stationary phase leaky expression requires cyclic AMP, and that substantial leaky expression could be effected in log phase cells by adding cyclic AMP and acetate at pH6.0. Finally, a comparison of otherwise isogenic cya and wild-type hosts showed that expression stability and plasmid maintenance in the cya host is greatly enhanced, even when cells are passaged repeatedly in non-selection medium. These findings both provide a method to enhance the stability of lac-based recombinant expression systems, and suggest that derepression of the lac operon in the absence of inducer may be part of a general cellular response to nutrient limitation.

The long-term view of regenerative medicine therapies predicts an increased need for expansion solutions that ease scalability, utilize animal origin-free materials and are compatible with limited downstream processing steps. As more cell therapeutics progress through clinical testing, current in vitro culture methods are proving cumbersome to scale and lack robustness. Moreover, high quality animal origin-free reagents and downstream processing devices support the future implementation of large scale manufacturing solutions that will be required following clinical success. Here, we describe the implementation of single use bioreactors and high quality media for expansion of cell therapies. We include examples from allogeneic mesenchymal stem cells and autologous T cells. The presentation will review solutions addressing animal origin-free expansion of cells within the context of different upstream process development steps as well as scaling and downstream processing with good cell quality, high recovery, high viability and good activity. Start to finish solutions for expansion and harvest, including high quality reagents, are key enabling technologies for success in commercializing cell therapies.

Human dihydroorotate dehydrogenase (huDHODH) is essential for de novo biosynthesis of pyrimidines and the target of two immunosuppressive drugs, brequinar and the leflunomide metabolite A77-1726 (Chen et al., 1992; Davis et al., 1996). Using a T7 RNA polymerase expression system, we produced huDHODH as a fusion protein containing an amino-terminal decahistidine tag. Escherichia coli growth and expression conditions were optimized to enhance huDHODH solubility and to permit purification of the enzyme in the absence of detergent. Soluble huDHODH, purified by a simple two-step procedure, was catalytically active, monomeric, and contained a flavin mononucleotide (FMN) cofactor in a 1:1 FMN/protein molar ratio. Kinetic analysis showed that huDHODH uses a two site ping-pong mechanism, where DHO is oxidized at one site and the second substrate, ubiquinone, is reduced at the other. This result is consistent with the mechanism proposed for bovine liver DHODH (Hines and Johnston, 1989).