Endotoxin contamination in fetal bovine serum and its influence on tumor necrosis factor production by macrophage-like cells J774.1 cultured in the presence of the serum

Media matters: culture medium-dependent hypervariable phenotype of mesenchymal stromal cells

BACKGROUND

Despite a long history of investigation and sustained efforts in clinical testing, the number of market authorisations for mesenchymal stromal cell (MSC) therapies remains limited, with none approved by the United States Food and Drug Administration. Several barriers are impeding the clinical progression of MSC therapies, to the forefront of these is a lack of standardised manufacturing protocols which is further compounded by an absence of biologically meaningful characterisation and release assays. A look at clinical trial registries demonstrates the diversity of MSC expansion protocols with variabilities in cell source, isolation method and expansion medium, among other culture variables, making it extraordinarily difficult to compare study outcomes. Current identification and characterisation standards are insufficient; they are not specific to MSCs and do not indicate cell function or therapeutic action.

METHODS

This work analysed the influence of five widely used culture media formulations on the colony-forming potential, proliferation kinetics, trilineage differentiation potential and immunomodulatory potential of human bone marrow-derived MSCs (BM-MSCs). The surface marker expression profiles were also characterised using a high-content flow cytometry screening panel of 243 markers.

RESULTS

Significant differences in the biological attributes of BM-MSCs including clonogenicity, proliferation, differentiation propensity and immunomodulatory capacity were revealed in response to the composition of the culture medium. Despite their biological differences, all cell preparations uniformly and strongly expressed the standard positive markers proposed for BM-MSCs: CD73, CD90 and CD105. Immunophenotypic profiling revealed that the culture medium also had a significant influence on the surface proteome, with one-third of tested markers exhibiting variable expression profiles. Principal component analysis demonstrated that BM-MSCs isolated and expanded in a proprietary xeno- and serum-free medium displayed the most consistent cell phenotypes with little variability between donors compared to platelet lysate and foetal bovine serum-containing media.

CONCLUSIONS

These data suggest that media composition has a highly significant impact on the biological attributes of MSCs, but standard surface marker tests conceal these differences. The results indicate a need for (1) standardised approaches to manufacturing, with an essential focus on defined media and (2) new biologically relevant tests for MSC characterisation and product release.

Sensitive detection of lipopolysaccharides by monitoring of interleukin-10 secretion from human PBMCs

Lipopolysaccharide (LPS) contaminations may falsify immunological experiments and are crucial for pharmaceutical products because they cause life-threatening immune reactions. Here, we present interleukin-10 (IL-10) as a reliable marker to measure LPS contents when the readout of pro-inflammatory cytokines is not favored. This animal free source assay is able to detect LPS with a limit of detection (LOD) of 0.024 EU/ml by monitoring IL-10 secretions from isolated human peripheral blood mononuclear cells (PBMCs).

Cytoprotective Effects of Human Platelet Lysate during the Xeno-Free Culture of Human Donor Corneas

We evaluated the suitability of 2% human platelet lysate medium (2%HPL) as a replacement for 2% fetal bovine serum medium (2%FBS) for the xeno-free organ culture of human donor corneas. A total of 32 corneas from 16 human donors were cultured in 2%FBS for 3 days (TP1), then evaluated using phase contrast microscopy (endothelial cell density (ECD) and cell morphology). Following an additional 25-day culture period (TP2) in either 2%FBS or 2%HPL, the pairs were again compared using microscopy; then stroma and Descemet membrane/endothelium (DmE) were processed for next generation sequencing (NGS). At TP2 the ECD was higher in the 2%HPL group (2179 ± 288 cells/mm²) compared to 2%FBS (2113 ± 331 cells/mm²; p = 0.03), and endothelial cell loss was lower (ECL HPL = -0.7% vs. FBS = -3.8%; p = 0.01). There were no significant differences in cell morphology between TP1 and 2, or between 2%HPL and 2%FBS. NGS showed the differential expression of 1644 genes in endothelial cells and 217 genes in stromal cells. It was found that 2%HPL led to the upregulation of cytoprotective, anti-inflammatory and anti-fibrotic genes (HMOX1, SERPINE1, ANGPTL4, LEFTY2, GADD45B, PLIN2, PTX3, GFRA1/2), and the downregulation of pro-inflammatory/apoptotic genes (e.g., CXCL14, SIK1B, PLK5, PPP2R3B, FABP5, MAL, GATA3). 2%HPL is a suitable xeno-free substitution for 2%FBS in human cornea organ culture, inducing less ECL and producing potentially beneficial alterations in gene expression.

Interactions of Bacterial Toxin CNF1 and Host JAK1/2 Driven by Liquid-Liquid Phase Separation Enhance Macrophage Polarization

Urinary tract infections (UTIs) are a global public health concern, which is mainly caused by uropathogenic Escherichia coli (UPEC). Cytotoxic necrotizing factor 1 (CNF1) is a key UPEC toxin and regulates multiple host cellular processes through activating the Rho GTPases; however, the effect of CNF1 on macrophage polarization remains unknown. Here, we found that CNF1 promoted M1 macrophage polarization through regulating NF-κB and JAK-STAT1 signaling pathways in kidney at an early stage of acute UTIs. Notably, we identified CNF1 could directly interact with JAK1/2 through its domain without Rho GTPases activation, which induced JAK1/2 phosphorylation, subsequent STAT1 activation and M1 polarization. Moreover, CNF1 exhibited liquid-liquid phase separation (LLPS) to induce a CNF1-JAK1/2 complex, promoting macrophage reprogramming. These findings highlight the LLPS-dependent and Rho GTPase-independent effect of CNF1 as an adaptor on interfering with host cell signals.

Harnessing the Natural Healing Power of Colostrum: Bovine Milk-Derived Extracellular Vesicles from Colostrum Facilitating the Transition from Inflammation to Tissue Regeneration for Accelerating Cutaneous Wound Healing

As wound healing is an extremely complicated process, consisting of a cascade of interlocking biological events, successful wound healing requires a multifaceted approach to support appropriate and rapid transitions from the inflammatory to proliferative and remodeling phases. In this regard, here the potential use of bovine milk extracellular vesicles (EVs) to enhance wound healing is investigated. The results show that milk EVs promote fibroblast proliferation, migration, and endothelial tube formation. In particular, milk EVs derived from colostrum (Colos EVs) contain various anti-inflammatory factors facilitating the transition from inflammation to proliferation phase, as well as factors for tissue remodeling and angiogenesis. In an excisional wound mouse model, Colos EVs promote re-epithelialization, activate angiogenesis, and enhance extracellular matrix maturation. Interestingly, Colos EVs are further found to be quite resistant to freeze-drying procedures, maintaining their original characteristics and efficacy for wound repair after lyophilization. These findings on the superior stability and excellent activity of milk Colos EVs indicate that they hold great promise to be developed as anti-inflammatory therapeutics, especially for the treatment of cutaneous wounds.

Virome Characterization in Commercial Bovine Serum Batches-A Potentially Needed Testing Strategy for Biological Products

Bovine serum has been widely used as a universal supplement in culture media and other applications, including the manufacture of biological products and the production of synthetic meat. Currently, commercial bovine serum is tested for possible viral contaminants following regional guidelines. Regulatory agencies’ established tests focused on detecting selected animal origin viruses and are based on virus isolation, immunofluorescence, and hemadsorption assays. However, these tests may fail to detect new or emerging viruses in biological products. High-throughput sequencing is a powerful option since no prior knowledge of the viral targets is required. In the present study, we evaluate the virome of seven commercial batches of bovine serum from Mexico (one batch), New Zealand (two batches), and the United States (four batches) using a specific preparation and enrichment method for pooled samples and sequencing using an Illumina platform. A variety of circular replicase-encoding single-stranded (CRESS) DNA families (Genomoviridae, Circoviridae, and Smacoviridae) was identified. Additionally, CrAssphage, a recently discovered group of bacteriophage correlated with fecal contamination, was identified in 85% of the tested batches. Furthermore, sequences representing viral families with single-stranded DNA (Parvoviridae), double-stranded DNA (Polyomaviridae and Adenoviridae), single-stranded RNA (Flaviviridae, Picornaviridae, and Retroviridae), and double-stranded RNA (Reoviridae) were identified. These results support that high-throughput sequencing associated with viral enrichment is a robust tool and should be considered an additional layer of safety when testing pooled biologicals to detect viral contaminants overlooked by the current testing protocols.

Crocetin Exerts Its Anti-inflammatory Property in LPS-Induced RAW264.7 Cells Potentially via Modulation on the Crosstalk between MEK1/JNK/NF-κB/iNOS Pathway and Nrf2/HO-1 Pathway

Crocetin is a main bioactive component with a carotenoid skeleton in Gardenia jasminoides, a typical traditional Chinese medicine with a long history in Southeast Asia. Crocetin is being commonly consumed as spices, dyes, and food colorants. Recent pharmacological studies had implied that crocetin may possess potent anti-inflammatory properties; however, the underlying molecular mechanism is not fully elucidated. In the present study, the regulatory effect of crocetin on redox balance was systematically investigated in lipopolysaccharide- (LPS-) stimulated RAW264.7 cells. The results showed that crocetin dose-dependently inhibited LPS-induced nitric oxide production and inducible nitric oxide synthase (iNOS) expression in RAW264.7 cells. Molecular data revealed that crocetin exerted its anti-inflammatory property by inhibiting the MEK1/JNK/NF-κB/iNOS pathway and activating the Nrf2/HO-1 pathway. The shRNA-knockdown (KD) of MEK1 and ERK1 confirmed that the activation of MEK1 and inhibition of JNK mediated the anti-inflammatory effect of crocetin. Moreover, the pull-down assay and computational molecule docking showed that crocetin could directly bind to MEK1 and JNK1/2. It is noticed that both KD and knockout (KO) of HO-1 gene blocked this action. More detailed data have shown that HO-1-KO blocked the inhibition of p-IκB-α by crocetin. These data indicated that crocetin exerted its anti-inflammatory property via modulating the crosstalk between the MEK1/JNK/NF-κB/iNOS pathway and the Nrf2/HO-1 pathway, highlighting HO-1 as a major player. Therefore, the present study reveals that crocetin can act as a potential candidate for redox-balancing modulation in charge of its anti-inflammatory and chemopreventive effect, which strengthens its potency in the subsequent clinic application in the near future.

Human platelet lysate as a replacement for fetal bovine serum in human corneal stromal keratocyte and fibroblast culture

The isolation and propagation of primary human corneal stromal keratocytes (CSK) are crucial for cellular research and corneal tissue engineering. However, this delicate cell type easily transforms into stromal fibroblasts (SF) and scar inducing myofibroblasts (Myo‐SF). Current protocols mainly rely on xenogeneic fetal bovine serum (FBS). Human platelet lysate (hPL) could be a viable, potentially autologous, alternative. We found high cell survival with both supplements in CSK and SF. Cell numbers and Ki67+ ratios increased with higher fractions of hPL and FBS in CSK and SF. We detected a loss in CSK marker expression (Col8A2, ALDH3A1 and LUM) with increasing fractions of FBS and hPL in CSK and SF. The expression of the Myo‐SF marker SMA increased with higher amounts of FBS but decreased with incremental hPL substitution in both cell types, implying an antifibrotic effect of hPL. Immunohistochemistry confirmed the RT‐PCR findings. bFGF and HGF were only found in hPL and could be responsible for suppressing the Myo‐SF conversion. Considering all findings, we propose 0.5% hPL as a suitable substitution in CSK culture, as this xeno‐free component efficiently preserved CSK characteristics, with non‐inferiority in terms of cell viability, cell number and proliferation in comparison to the established 0.5% FBS protocol.

Alternative to FBS in animal cell culture - An overview and future perspective

Fetal bovine serum (FBS) is a widely used growth supplement in the in vitro culturing of animal and human cells, tissues and organs, notably due to the occurrence of abundant micro- and macronutrients, along with growth factors. Over the years, increasing demand, high price, batch-to-batch variability in quality and composition, increasing ethical concerns lead to the search for an alternative to FBS. Several approaches have been suggested and employed in the past, but none is implemented as widely as FBS, and each supplement has its own disadvantages. In this review, we described the importance of FBS in cell culture, discussed the issues associated with FBS use and presented the efforts made in the recent past to reduce or replace FBS. The potential of four different alternative sources to FBS, namely, bovine ocular fluid, sericin protein, human platelet lysate and earthworm heat inactivated coelomic fluid was evaluated. In the end, we present the conceptual perspective using the Human Platelet Lysate (HPL) and earthworm Heat Inactivated Coelomic Fluid (HI-CF) combination to alternate FBS and its context in scientific and economic impacts.

Endotoxin Contamination and Reaction Interfering Substances in the Plant Extract Library

Endotoxin is an unintentional contaminant that has numerous activities and can affect various biological experiments using cells. In this study, we measured the endotoxin activity of samples from a plant extract library (PEL) and determined their degrees of contamination. Endotoxin was detected in approx. 48% (n = 139) and approx. 4% (n = 5) of field-collected and crude drug samples, respectively, and in concentrations >5.0 EU/mL in some samples. The concentrations of endotoxin that affect cells in vitro vary depending on the target cell type. Although the degree of contamination varied in the present study, it was considered to have little effect on the cell experiments. More than 150 PEL samples had problems with reaction courses or recovery rates of Limulus amoebocyte lysate (LAL) tests. In the LAL tests, using three plant extracts [Sanguisorba officinalis L. (Rosaceae), Oenothera biennis L. (Onagraceae), and Lythrum salicaria L. (Lythraceae)], the polyphenolic compounds in the plant extracts affected LAL test and their effects differed depending on the plant species. When the 16 single polyphenol compounds were added to the LAL tests, the compounds with caffeoyl and pyrogallol moieties were found to affect the LAL reaction course and recovery rate. Furthermore, none of the compounds had any effects at concentrations of 1 µM. Because the plant extracts contained analogs of various polyphenolic compounds, they were presumed to actually act synergistically. Our findings demonstrated that attention must be paid to the recovery rate and reaction process of LAL tests with samples containing polyphenolic compounds.

Mogroside V inhibits LPS-induced COX-2 expression/ROS production and overexpression of HO-1 by blocking phosphorylation of AKT1 in RAW264.7 cells

Momordica grosvenori is a valuable edible plant with medicinal purposes, and it is widely used in medicated diets and traditional Chinese medicine in Asia. Mogroside V (MV), the main bioactive component from M. grosvenori, is commonly used as a natural sweetener. M. grosvenori extracts have been reported to exert potent anti-inflammatory property, however the underlying molecular mechanism still remains unknown. In the present study, the biological effect of MV in inflammation was investigated in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. The ELISA and western blot analysis results showed that MV significantly inhibited LPS-induced prostaglandin E2 (PGE2) production and cyclooxygenase-2 (COX-2) expression. MV markedly decreased the phosphorylation of IκB-α, increased IκB-α, and reduced nuclear p-65 and C/EBPδ. Furthermore, MV attenuated LPS-induced phosphorylation of MAPKs and AKT1, and only the phosphorylation status of AKT1 was found to be consistent with the expression trend of COX-2. Moreover, MV reduced ROS level and restored overexpressed HO-1 and AP-1 to basal level, which can be markedly reversed by AKT1 inhibitor LY294002. These results revealed that AKT1 plays a key role in LPS-induced COX-2 expression, and acts as a mediator to keep the redox balance in LPS-stimulated RAW264.7 cells. MV exerts anti-inflammatory property by blocking AKT1-mediated NF-κB and C/EBPδ activation, ROS generation and AP-1/ HO-1 expression. Therefore, the present study indicated that MV has a significant chemopreventive effect on the inflammatory lesions and suggested that AKT1 is a potential specific target of MV for relieving inflammation.

A novel serum free primary astrocyte culture method that mimic quiescent astrocyte phenotype

BACKGROUND

Primary astrocyte cultures have been used for decades to study astrocyte functions in health and disease. The current primary astrocyte cultures are mostly maintained in serum-containing medium which produces astrocytes with a reactive phenotype as compared to in vivo quiescent astrocytes. The aim of this study was to establish a serum-free astrocyte culture medium that maintains primary astrocytes in a quiescent state.

NEW METHOD

Serum free astrocyte base medium (ABM) supplemented with basic fibroblast growth factor 2 (FGF2) and epidermal growth factor (EGF) (ABM-FGF2-EGF) or serum supplemented DMEM (MD-10%FBS) was used to culture primary astrocytes isolated from cerebral cortex of postnatal day 1 C57BL/6 mice.

RESULTS

Compared to astrocytes cultured in MD-10%FBS medium, astrocytes in ABM-FGF2-EGF had higher process bearing morphologies similar to in vivo astrocytes. Western blot, immunostaining, quantitative polymerase chain reaction and metabolic assays revealed that astrocytes maintained in ABM-FGF2-EGF had enhanced glycolytic metabolism, higher glycogen content, lower GFAP expression, increased glutamine synthase, and glutamate transporter-1 mRNA levels as compared to astrocytes cultured in MD-10% FBS medium.

COMPARISON TO EXISTING METHODS

These observations suggest that astrocytes cultured in ABM-FGF2-EGF media compared to the usual FBS media promote quiescent and biosynthetic phenotype similar to in vivo astrocytes.

CONCLUSION

This media provides a novel method for studying astrocytes functions in vitro under physiological and pathological conditions.

The pro-inflammatory stimulus of zinc- and copper-containing welding fumes in whole blood assay via protein tyrosine phosphatase 1B inhibition

An asymptomatic systemic inflammation after exposure to zinc- and copper-containing welding fumes has been described as mild form of metal fume fever in recent studies. Since chronic systemic inflammation leads to a higher cardiovascular risk, examining the inflammation with the underlying pathomechanism is necessary to estimate and hopefully prevent long-term effects of welding. We established a whole blood assay to investigate the effects of zinc- and copper-containing welding fume particles on the blood immune response. Increased levels of IL-6, IL-8, TNFα and IL-1β determined after 24 hours of exposure indicated an acute systemic inflammatory reaction. In vitro increases of IL-6 were comparable to in vivo increases of serum IL-6 levels in a study with welding fume exposure of human subjects. Inhibition of PTP1B was identified as one pathway responsible for the effects of zinc- and copper-containing welding fumes and therefore welding fume fever. In conclusion, the whole blood assay is a reliable and feasible method to investigate effects of zinc- and copper-containing welding fumes on the immune system and as a surrogate for systemic inflammation and welding fume fever. Future research can utilize whole blood assays to reduce and partially replace human exposure studies for further investigations of welding fume fever.

Development of reference metal and metal oxide engineered nanomaterials for nanotoxicology research using high throughput and precision flame spray synthesis approaches

There is a growing need to develop and characterize reference metal and metal oxide engineered nanomaterials (ENMs) of high purity and tunable intrinsic properties suitable for nanotoxicology research. Here a high throughput (volume) and precision flame spray pyrolysis (FSP) approach coupled with state-of-the-art characterization techniques are utilized to generate such reference ENMs. The lab-based and industrially relevant FSP system, termed as Versatile Engineered Nanomaterials Generation System (VENGES), synthesizes the metals and metal oxides, at high throughput manner with controlled properties, such as primary particle size, aggregate diameter, shape, crystallinity, stoichiometry and surface chemistry. A nanopanel of nine reference ENMs (silica, silver, silver supported on silica, alumina, ceria and iron oxide) was synthesized and characterized using combined electron microscopy, advanced spectroscopic techniques and physical analyses (e.g., BET, XRD, TEM, pycnometry, XPS, ICP-MS and FTIR). ENMs show a high degree of chemical purity and stoichiometry, and low content of carbon residuals, and are sterile and free of bacteria and endotoxins. Further, their colloidal properties and their implication in in-vitro dosimetry have been also investigated in both environmental and test biological media. The suitability of reference ENMs and protocols developed in this study brings forth new arenas to generate reliable and reproducible toxicological data in an effort to reduce conflicting and contradicting inter-laboratory data on relative toxic effects of ENMs.

Platelet lysate as a novel serum-free media supplement for the culture of equine bone marrow-derived mesenchymal stem cells

Background

Mesenchymal stem cells (MSCs) produced for clinical purposes rely on culture media containing fetal bovine serum (FBS) which is xenogeneic and has the potential to significantly alter the MSC phenotype, rendering these cells immunogenic. As a result of bovine-derived exogenous proteins expressed on the cell surface, MSCs may be recognized by the host immune system as non-self and be rejected. Platelet lysate (PL) may obviate some of these concerns and shows promising results in human medicine as a possible alternative to FBS. Our goal was to evaluate the use of equine platelet lysate (ePL) pooled from donor horses in place of FBS to culture equine MSCs. We hypothesized that ePL, produced following apheresis, will function as the sole media supplement to accelerate the expansion of equine bone marrow-derived MSCs without altering their phenotype and their immunomodulatory capacity.

Methods

Platelet concentrate was obtained via plateletpheresis and ePL were produced via freeze-thaw and centrifugation cycles. Population doublings (PD) and doubling time (DT) of bone marrow-derived MSCs (n = 3) cultured with FBS or ePL media were calculated. Cell viability, immunophenotypic analysis, and trilineage differentiation capacity of MSCs were assessed accordingly. To assess the ability of MSCs to modulate inflammatory responses, E. coli lipopolysaccharide (LPS)-stimulated monocytes were cocultured with MSCs cultured in the two different media formulations, and cell culture supernatants were assayed for the production of tumor necrosis factor (TNF)-α.

Results

Our results showed that MSCs cultured in ePL media exhibited similar proliferation rates (PD and DT) compared with those cultured in FBS at individual time points. MSCs cultured in ePL showed a statistically significant increased viability following a single washing step, expressed similar levels of MSC markers compared to FBS, and were able to differentiate towards the three lineages. Finally, MSCs cultured in ePL efficiently suppressed the release of TNF-α when exposed to LPS-stimulated monocytes similar to those cultured in FBS.

Conclusion

ePL has the potential to be used for the expansion of MSCs before clinical application, avoiding the concerns associated with the use of FBS.

Effect of Native and Modified Apolipoprotein A-I on DNA Synthesis in Cultures of Different Cells

Culturing of bone marrow cells in serum-free RPMI-1640 medium for 24 h was accompanied by a decrease in the rate of [3H]-thymidine incorporation into DNA. Addition of native apolipoprotein A-I (apoA-I) or plasma LDL and HDL to the culture medium increased this parameter. In contrast to native apoA-I, its modified form decelerated DNA synthesis in bone marrow cells. A similar inhibitory effect of modified protein was observed in cultures of human embryonic kidney cells (HEK293) and in rapidly proliferating mouse macrophage cell line ANA-1. The only exclusion was human myeloid cell line U937: neither native nor modified apoA-I affected DNA synthesis in these cells. Thus, the regulatory effects of apoA-I are tissue-specific; this protein can produce either stimulatory or inhibitory effect on DNA biosynthesis in cells depending on its conformation.

Innate immune responses of equine monocytes cultured in equine platelet lysate

Platelet lysate (PL) has been extensively used for the laboratory expansion of human mesenchymal stem cells (MSC) in order to avoid fetal bovine serum (FBS) which has been associated with immune-mediated host reactions and transmission of bovine-origin microbial contaminants. Before suggesting the routine use of PL for MSC culture, we wanted to further investigate whether PL alone might trigger inflammatory responses when exposed to reactive white blood cells such as monocytes. Our objectives were to evaluate the inflammatory profile of equine monocytes cultured with equine PL (ePL) and to determine if ePL can modulate the expression of inflammatory cytokines in lipopolysaccharide (LPS)-stimulated monocytes. In a first experiment, equine monocytes were isolated and incubated with donor horse serum (DHS), FBS, six individual donors ePL or pooled ePL from all horses. In a second experiment, monocytes were stimulated with E. coli LPS in the presence of 1, 5 or 10% DHS and/or pooled ePL. After 6h of incubation, cell culture supernatants were assayed via ELISA for production of the pro-inflammatory cytokines tumor necrosis factor alpha (TNF-α) and Interleukin 1β (IL-1β) as well as for the anti-inflammatory Interleukin 10 (IL-10). Equine monocytes incubated with pooled ePL produced significantly less TNF-α and significantly more IL-10 than monocytes incubated in FBS. A statistically significant difference was not identified for the production of IL-1β. The second experiment showed that pooled ePL added to LPS-stimulated equine monocytes resulted in a significant reduction in TNF-α and IL-1β production. IL-10 production was not significantly upregulated by the addition of ePL to LPS-stimulated monocytes. Finally, the addition of ePL to LPS-stimulated monocytes in the presence of various concentrations of DHS resulted to statistically significant decrease of TNF-α and IL-1β compared to the control groups. This is the first study to demonstrate that ePL suppresses the release of pro-inflammatory cytokines from stimulated equine monocytes. These results encourage further exploration of PL as a homologous media substitute for FBS but also opens the possibility of investigating its use as means to suppress cell-mediated inflammation.

Platelet lysate obtained via plateletpheresis performed in standing and awake equine donors

BACKGROUND

Platelet preparations containing growth factors, attachment factors, and enzymes are appealing to enhance healing of injured tissues and as an alternative to xenogenic serum in cell culture media. Plateletpheresis is commonly used to collect platelets in human medicine but has not been validated in horses.

STUDY DESIGN AND METHODS

Plateletpheresis to collect platelet concentrate was performed on six female, mixed breed, chemically restrained horses using commercially available apheresis equipment. Before and immediately after plateletpheresis, we performed physical examinations and collected blood for chemistry and coagulation panels and then again at 8, 16, 24, and 48 hours after the procedure. To produce platelet lysate, the platelet concentrate underwent two freeze-thaw cycles followed by centrifugation and filtration processing. The platelet lysate was then analyzed for cellular debris, fibrinogen, and growth factors.

RESULTS

The collected platelet concentration contained a mean platelet yield of 390 × 10³ /μL. Donor platelet count decreased from a mean of 193 × 10³ /μL to 138 × 10³ /μL after plateletpheresis, but no individual was at risk for hemorrhage. Pooled platelet lysate had minimal cellular residue and contained growth factor concentrations at 6.1 ng/mL for transforming growth factor-β1, at 3.5 ng/mL for platelet-derived growth factor-BB, and at 13.8 ng/mL for vascular endothelial growth factor-A.

CONCLUSION

Plateletpheresis using commercially available apheresis equipment is a feasible option for collecting platelet concentrate from equine donors. The lysate generated from the apheresis product contains growth factors and has potential to be used as a fetal bovine serum substitute for cell culture.

Investigation into the interaction of recombinant human serum albumin with Re-lipopolysaccharide and lipid A

The interaction of bacterial endotoxins, deep rough mutant lipopolysaccharide LPS Re and the `endotoxic principle' lipid A, with recombinant human serum albumin (rHSA) was investigated with a variety of physical techniques and biological assays. With Fourier-transform infrared spectroscopy and differential scanning calorimetry, the influence of albumin on the acyl chain melting behavior of the endotoxins was measured. Also, the effect on the functional groups of the endotoxins, in particular with respect to their orientation, was studied, including competition experiments with polymyxin B. Furthermore, the influence of endotoxin binding to rHSA on the protein's secondary structure was investigated. The results indicate a non-electrostatic binding with no change of the backbone orientation of LPS and only a slight change of the secondary structure of rHSA. Correspondingly, the amount of charge neutralization of the endotoxins due to rHSA measured by the electrophoretic mobility exhibited only a slight reduction of the surface potential. From these measurements and isothermal titration calorimetry, the lipid:protein binding stoichiometry was estimated to [LPS]:[rHSA], 10:1 molar. The determination of the aggregate structure of the endotoxins by X-ray small-angle scattering exhibited a complex change of a cubic into a non-lamellar structure. No influence of rHSA on endotoxin intercalation into phospholipid liposomes induced by lipopolysaccharide-binding protein could be detected by fluorescence resonance energy transfer. Finally, the LPS-induced cytokine production of human mononuclear cells was only slightly increased at high molar rHSA excess, while the coagulation of amebocyte lysate in the Limulus test yielded a complex change due to rHSA binding of LPS.

Depleting extracellular vesicles from fetal bovine serum alters proliferation and differentiation of skeletal muscle cells in vitro

Background

Fetal bovine serum (FBS) contains a wide range of growth factors, hormones, vitamins, amino acids, fatty acids and trace elements required for cell growth. It was shown that animal sera contain also extracellular vesicles (EVs) with important biological properties; thus we wondered whether EVs present in FBS would influence muscle cell phenotype.

EVs were removed from sera by ultracentrifugation (18 h). C2C12, L6 and human primary myoblasts, were grown either in classical media (CM) or in EVs-depleted media. Differentiation was induced by replacing the culture medium either with CM or EV-depleted media. qRT-PCR of relevant genes and miRNA involved in proliferation, differentiation, energy metabolism and EVs formation and secretion were performed.

Results

Growth of myoblasts in EV-free media during proliferation produces the most unfavorable situation for proper myotube formation, when considering C212 and human myoblasts. Removing EVs from serum committed myoblasts to differentiate precociously (induction of myogenin and decreased expression of myomiR involved in myogenesis). C2C12 and human myoblasts, grown constantly in EV-depleted media during proliferation and differentiation, formed less myotubes than in CM. They had a reduced level of myogenin and a strong increase in myostatin expression, a negative regulator of muscle cell differentiation that affects myotube size. This situation was not reversed when confluent myoblasts were switched to CM for differentiation. Like C2C12 and human cells, L6 formed less myotubes in EVs-depleted media. However, as they do not express myostatin, L6 myotubes were larger and expressed higher level of CKTM2 compared to myotubes grown in CM suggesting that they had reached a higher level of differentiation.

Conclusions

Researchers studying the role of muscle EVs in culture conditions should consider that depleting EVs from serum alters the phenotype of muscle cells. Interestingly, the cross-talk between myoblasts and myotubes during myogenesis (Forterre 2014, PLoS One. 2014 Jan 2;9(1):e84153) can be recapitulate by using FBS-EVs as well. This implies that EVs can transfer specific signals to cells from unrelated species and that part of serum EV composition is evolutionarily conserved (e.g.; myomiR are detected in FBS-EVs). EVs in body fluids could have an unsuspected function during embryogenesis and in regulation of cellular processes such as hypertrophy and hyperplasia.

Electronic supplementary material

The online version of this article (doi:10.1186/s12896-016-0262-0) contains supplementary material, which is available to authorized users.

Influence of the culture medium on the production of nitric oxide and expression of inducible nitric oxide synthase by activated macrophages in vitro

Macrophages play an important role in immune and inflammatory responses, and have been extensively studied in vitro using culture media such as RPMI1640 medium, Dulbecco's modified Eagle medium (DMEM), and Ham's F-12 medium (F-12). We found that the activation phenotypes of a murine macrophage-like cell line, J774.1/JA-4, were obviously different in two distinct culture media (F-12 and DMEM), both of which were supplemented with 10% of the same fetal bovine serum (FBS). Among these phenotypes, nitric oxide (NO) production as well as inducible NO synthase (iNOS) expression, induced by lipopolysaccharide (LPS) and interferon-γ (IFN-γ), were remarkably different. iNOS expression was higher in the macrophages cultured in DMEM than in F-12 for 20 h, while no significant differences were shown in NO production between in F-12 and DMEM. It might be the reason why DMEM have reduced NO production by the induced iNOS. Besides, [Formula: see text]-generating activity, and production of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) in the activated macrophages were also different between the cultures in F-12 and DMEM. These results suggest that F-12 and DMEM contain certain components responsible for modification of macrophage activation processes and/or macrophage functions. Our present results provide evidence that the choice of culture medium is important in the study and analysis of macrophage activation.

MSRV envelope protein is a potent, endogenous and pathogenic agonist of human toll-like receptor 4: Relevance of GNbAC1 in multiple sclerosis treatment

Multiple sclerosis associated retrovirus envelope protein (MSRV-Env) was repeatedly detected in brain lesions and blood of multiple sclerosis (MS) patients. We performed the first pharmacological characterisation of MSRV-Env on recombinant and native human TLR4. MSRV-Env is a full and highly potent TLR4 agonist of endogenous origin. MSRV-Env induces TLR4-dependent pro-inflammatory stimulation of immune cells in vitro and in vivo, and impairs oligodendrocytes precursor cells differentiation to myelinating oligodendrocytes. MSRV-Env may play a role in chronic inflammation and impaired remyelination in MS. GNbAC1, a selective monoclonal antibody, antagonizes MSRV-Env pathogenic effects and represents an innovative therapeutic approach of MS.

Generation of mucosal dendritic cells from bone marrow reveals a critical role of retinoic acid

It is unknown how dendritic cells (DCs) become specialized as mucosal DCs and maintain intestinal homeostasis. We report that a subset of bone marrow cells freshly isolated from C57BL/6 mice express the retinoic acid (RA)-synthesizing enzyme aldehyde dehydrogenase family 1, subfamily A2 (ALDH1a2) and are capable of providing RA to DC precursors in the bone marrow microenvironment. RA induced bone marrow-derived DCs to express CCR9 and ALDH1a2 and conferred upon them mucosal DC functions, including induction of Foxp3(+) regulatory T cells, IgA-secreting B cells, and gut-homing molecules. This response of DCs to RA was dependent on a narrow time window and stringent dose effect. RA promoted bone marrow-derived DC production of bioactive TGF-β by inhibiting suppressor of cytokine signaling 3 expression and thereby enhancing STAT3 activation. These RA effects were evident in vivo, in that mucosal DCs from vitamin A-deficient mice had reduced mucosal DC function, namely failure to induce Foxp3(+) regulatory T cells. Furthermore, MyD88 signaling enhanced RA-educated DC ALDH1a2 expression and was required for optimal TGF-β production. These data indicate that RA plays a critical role in the generation of mucosal DCs from bone marrow and in their functional activity.

Cytokine induction by pyrogens: comparison of whole blood, mononuclear cells, and TLR-transfectants

Given the shortcomings in the measurement of pyrogenic contamination of pharmaceuticals and/or test substances by means of the rabbit pyrogen test and the Limulus amoebocyte lysate (LAL) test, several in vitro pyrogen tests have been developed based on the measurement of cytokine production by monocytes. In this study we measured cytokine production (IL-6, IL-8, IL-1beta, and TNF) in diluted whole blood (WB), mononuclear cells (MNC), and HEK cells stably transfected with CD14 and Toll-like Receptor-2 (TLR2) or TLR4, after stimulation with both standard pyrogens and contaminated substances. Our study demonstrated that in MNC, IL-6 production was more sensitive to pyrogen stimulation than IL-1beta and TNF production. The sensitivity of WB IL-8 production for pyrogens was comparable with that of MNC IL-6 production, but higher than WB IL-6 production. MNC IL-8 production as readout for pyrogenic stimulation was not useful due to high background IL-8 production. Surprisingly, contaminated culture media potently stimulated WB IL-8 production, but not MNC IL-6 production. Finally, the value of TLR-transfected HEK cells in the detection of pyrogenic contamination as well as the role of IL-10 in interindividual differences in cytokine production, is discussed. To summarize, the results presented herein together with literature data indicate that the measurement of WB IL-8 production may represent an advantageous alternative to the measurement of MNC IL-6 production, for the detection of pyrogenic contamination of pharmaceuticals.

Development of low endotoxin gelatin for regenerative medicine

The basic concept of tissue engineering, an actively applied technology in regenerative medicine, is the coordination between cells, scaffolds, and proliferation factors. Collagen and gelatin are materials that have mostly been used as scaffolds because of their excellent affinity for cells, they are biodegradable, and their ability to form gel. However, very few of the collagen or gelatin preparations used as tissue engineering material have been prepared with low levels of endotoxin, which may trigger fever, shock and a fall in blood pressure even in very minute quantities. Therefore we decided to decrease the content of endotoxin in gelatin so that this biomaterial is not harmful to the body but still maintains its properties, namely, bioaffinity and biodegradation for use in the fields of cell culture and regenerative medicine. In this paper, we describe a method whereby endotoxin could be removed from gelatin solution by using an ultrafiltration membrane with a molecular weight cut-off of 100 kDa and low endotoxin gelatin, endotoxin activity in 0.1% gelatin solution was below 0.03 EU/ml, was obtained as the resulting filtrate solution.

Proinflammatory changes in human umbilical cord vein endothelial cells can be induced neither by native nor by modified CRP

The role of C-reactive protein (CRP) in atherosclerosis is controversial. It is not clear, either, if the presumed endothelium-activating effect of CRP resides in native CRP (nCRP) or in a conformational isoform of CRP known as modified CRP (mCRP). In the present study we evaluated and compared the effect of nCRP, recombinant modified CRP (rmCRP) and urea-modified CRP (umCRP) on human umbilical vein endothelial cells (HUVECs). CRP preparations were carefully analyzed by biochemical, immunological and cell biological methods in order to avoid endotoxin or sodium azide contamination as well as inappropriate conformational changes, which together had possibly been the main reason for the previously published controversial results. Neither nCRP nor mCRP showed significant cytotoxicity up to 100 microg ml(-1) at 24 h but high concentrations of CRPs induced cell death at 48 h. rmCRP but not nCRP nor umCRP showed membrane binding to HUVEC by confocal microscopy. However, none of the CRP forms induced intercellular cell adhesion molecule-1, vascular cell adhesion molecule-1, E-selectin expression or IL-8 production. Monocyte chemotactic protein-1 production was weakly inhibited by high concentration of both nCRP and rmCRP, analyzed by sandwich ELISA. Neither nCRP nor mCRP could induce pro-inflammatory changes in the phenotype of HUVECs. Therefore, our present findings do not support the notion that different isoforms of CRP alone have significant effects on inflammation of the vessel wall via an interaction with endothelial cells (ECs), although one cannot exclude the possibility that there may be significant differences among various types of ECs in the response to CRP.

Synergistic activation of macrophages via CD40 and TLR9 results in T cell independent antitumor effects

We have previously shown that macrophages (Mphi) can be activated by CD40 ligation to become cytotoxic against tumor cells in vitro. Here we show that treatment of mice with agonistic anti-CD40 mAb (anti-CD40) induced up-regulation of intracellular TLR9 in Mphi and primed them to respond to CpG-containing oligodeoxynucleotides (CpG), resulting in synergistic activation. The synergy between anti-CD40 and CpG was evidenced by increased production of IFN-gamma, IL-12, TNF-alpha, and NO by Mphi, as well as by augmented apoptogenic effects of Mphi against tumor cells in vitro. The activation of cytotoxic Mphi after anti-CD40 plus CpG treatment was dependent on IFN-gamma but not TNF-alpha or NO, and did not require T cells and NK cells. Anti-CD40 and CpG also synergized in vivo in retardation of tumor growth in both immunocompetent and immunodeficient mice. Inactivation of Mphi in SCID/beige mice by silica treatment abrogated the antitumor effect. Taken together, our results show that Mphi can be activated via CD40/TLR9 ligation to kill tumor cells in vitro and inhibit tumor growth in vivo even in immunocompromised tumor-bearing hosts, indicating that this Mphi-based immunotherapeutic strategy may be appropriate for clinical testing.

Inhibition of lipopolysaccharide-induced cyclooxygenase-2 transcription by 6-(methylsulfinyl) hexyl isothiocyanate, a chemopreventive compound from Wasabia japonica (Miq.) Matsumura, in mouse macrophages

6-(Methylsulfinyl)hexyl isothiocyanate (6-MITC) is a chemopreventive compound occurring in Wasabi (Wasabia japonica (Miq.) Matsumura), which is a very popular pungent spice in Japan. We investigated the effects of 6-MITC on the expression of cyclooxygenase-2 (COX-2) in lipopolysaccharide (LPS)-activated murine macrophage RAW264 cells. Treatment with 6-MITC suppressed LPS-mediated induction of COX-2 protein in a dose-dependent manner. Transfections with various COX-2 promoter reporter constructs revealed that the inhibitory effects of 6-MITC on COX-2 gene expression were directed by the core promoter elements including nuclear factor kappaB (NF-kappaB), CCAAT/enhancer-binding protein (C/EBP) and cyclic AMP-response element (CRE) sites. Western blotting analysis showed that 6-MITC inhibited LPS-induced activation of MAPK (ERK, p38 kinase and JNK) and transcriptional factors (CREB, c-Jun and C/EBPdelta) binding the core elements of COX-2 promoter, substantiating the involvement of these signal transduction pathways in the regulation of COX-2 expression by 6-MITC. Moreover, Western blotting experiments with MAPK-specific inhibitors (U0126 for MEK1/2, SB203580 for p38 kinase and SP600125 for JNK) demonstrated that 6-MITC suppressed LPS-induced COX-2 expression by blocking the activation of JNK-mediated AP-1 and ERK/p38 kinase-mediated CREB or C/EBPdelta. Finally, the structure-activity study revealed that the inhibitory potency of methylsulfinyl isothiocyanates (MITCs) depended on the methyl chain length. These findings demonstrate for the first time that 6-MITC is an effective agent to attenuate COX-2 production, and enhance our understanding of the anti-inflammation properties of 6-MITC.

CD40 ligation activates murine macrophages via an IFN-gamma-dependent mechanism resulting in tumor cell destruction in vitro

We have shown previously that agonistic anti-CD40 mAb induced T cell-independent antitumor effects in vivo. In this study, we investigated mechanisms of macrophage activation with anti-CD40 mAb treatment, assessed by the antitumor action of macrophages in vitro. Intraperitoneal injection of anti-CD40 mAb into C57BL/6 mice resulted in activation of peritoneal macrophages capable of suppressing B16 melanoma cell proliferation in vitro, an effect that was greatly enhanced by LPS and observed against several murine and human tumor cell lines. Anti-CD40 mAb also primed macrophages in vitro to mediate cytostatic effects in the presence of LPS. The tumoristatic effect of CD40 ligation-activated macrophages was associated with apoptosis and killing of tumor cells. Activation of macrophages by anti-CD40 mAb required endogenous IFN-gamma because priming of macrophages by anti-CD40 mAb was abrogated in the presence of anti-IFN-gamma mAb, as well as in IFN-gamma-knockout mice. Macrophages obtained either from C57BL/6 mice depleted of T and NK cells by Ab treatment, or from scid/beige mice, were still activated by anti-CD40 mAb to mediate cytostatic activity. These results argued against the role of NK and T cells as the sole source of exogenous IFN-gamma for macrophage activation and suggested that anti-CD40 mAb-activated macrophages could produce IFN-gamma. We confirmed this hypothesis by detecting intracytoplasmic IFN-gamma in macrophages activated with anti-CD40 mAb in vivo or in vitro. IFN-gamma production by macrophages was dependent on IL-12. Taken together, the results show that murine macrophages are activated directly by anti-CD40 mAb to secrete IFN-gamma and mediate tumor cell destruction.

Identification of estrogen receptor beta expression in Chinese hamster ovary (CHO) cells and comparison of estrogen-responsive gene transcription in cells adapted to serum-free media

Most cultured cell lines require addition of serum to the medium to maintain their proliferative capacity. For studies examining the cellular effects of estrogens serum is charcoal-stripped to remove steroids. Nonetheless, addition of the selective estrogen receptor modulator (SERM) 4-hydroxytamoxifen (4-OHT) inhibits the basal transcriptional activity of estrogen receptors alpha or beta (ERalpha or ERbeta) in transfected cells. We tested the hypothesis that elimination of serum from the culture medium will block 4-OHT's repression of basal activity. Chinese hamster ovary (CHO-K1) cells adapted to serum-free medium exhibited estrogen responsiveness that was identical with that of the cells grown in serum-containing media. 4-OHT-suppressed basal transcription of an estrogen response element (ERE)-reporter in ERalpha-transfected cells even in the absence of serum, indicating that the 4-OHT suppressive activity is not mediated by blocking ER interaction with serum estrogens. We speculate that 4-OHT-ER recruits co-repressors to suppress basal transcription. We discovered that CHO-K1 cells express ERalpha and ERbeta mRNA. However only ERbeta protein was expressed and use of ERbeta-selective 2,3-bis(4-hydroxy-phenyl)propionitrile (DPN) and ERalpha-selective 4-propyl-1,3,5-tris(4-hydroxy-phenyl)pyrazole) (PPT) revealed that only ERbeta was transcriptionally active. In conclusion, growing CHO-K1 in serum-free medium does not impact the estrogen responsiveness and this cell line expresses functional ERbeta.