Engineering an in vitro air-blood barrier by 3D bioprinting

Intensive efforts in recent years to develop and commercialize in vitro alternatives in the field of risk assessment have yielded new promising two- and three dimensional (3D) cell culture models. Nevertheless, a realistic 3D in vitro alveolar model is not available yet. Here we report on the biofabrication of the human air-blood tissue barrier analogue composed of an endothelial cell, basement membrane and epithelial cell layer by using a bioprinting technology. In contrary to the manual method, we demonstrate that this technique enables automatized and reproducible creation of thinner and more homogeneous cell layers, which is required for an optimal air-blood tissue barrier. This bioprinting platform will offer an excellent tool to engineer an advanced 3D lung model for high-throughput screening for safety assessment and drug efficacy testing.

Establishment of a novel intervertebral disc/endplate culture model: analysis of an ex vivo in vitro whole-organ rabbit culture system

STUDY DESIGN: Ex vivo in vitro study evaluating a novel intervertebral disc/endplate culture system. OBJECTIVES: To establish a whole-organ intervertebral disc culture model for the study of disc degeneration in vitro, including the characterization of basic cell and organ function. SUMMARY OF BACKGROUND DATA: With current in vivo models for the study of disc and endplate degeneration, it remains difficult to investigate the complex disc metabolism and signaling cascades. In contrast, more controlled but simplified in vitro systems using isolated cells or disc fragments are difficult to culture due to the unconstrained conditions, with often-observed cell death or cell dedifferentiation. Therefore, there is a demand for a controlled culture model with preserved cell function that offers the possibility to investigate disc and endplate pathologies in a structurally intact organ. METHODS: Naturally constrained intervertebral disc/endplate units from rabbits were cultured in multi-well plates. Cell viability, metabolic activity, matrix composition, and matrix gene expression profile were monitored using the Live/Dead cell viability test (Invitrogen, Basel, Switzerland), tetrazolium salt reduction (WST-8), proteoglycan and deoxyribonucleic acid quantification assays, and quantitative polymerase chain reaction. RESULTS: Viability and organ integrity were preserved for at least 4 weeks, while proteoglycan and deoxyribonucleic acid content decreased slightly, and matrix genes exhibited a degenerative profile with up-regulation of type I collagen and suppression of collagen type II and aggrecan genes. Additionally, cell metabolic activity was reduced to one third of the initial value. CONCLUSIONS: Naturally constrained intervertebral rabbit discs could be cultured for several weeks without losing cell viability. Structural integrity and matrix composition were retained. However, the organ responded to the artificial environment with a degenerative gene expression pattern and decreased metabolic rate. Therefore, the described system serves as a promising in vitro model to study disc degeneration in a whole organ.

Synthetic versus natural curcumin: bioequivalence in an in vitro oral mucositis model

BACKGROUND Curcumin (CUR) is a dietary spice and food colorant (E100). Its potent anti-inflammatory activity by inhibiting the activation of Nuclear Factor-kappaB is well established. METHODS The aim of this study was to compare natural purified CUR (nCUR) with synthetically manufactured CUR (sCUR) with respect to their capacity to inhibit detrimental effects in an in vitro model of oral mucositis. The hypothesis was to demonstrate bioequivalence of nCUR and sCUR. RESULTS The purity of sCUR was HPLC-confirmed. Adherence and invasion assays for bacteria to human pharyngeal epithelial cells demonstrated equivalence of nCUR and sCUR. Standard assays also demonstrated an identical inhibitory effect on pro-inflammatory cytokine/chemokine secretion (e.g., interleukin-8, interleukin-6) by Detroit pharyngeal cells exposed to bacterial stimuli. There was bioequivalence of sCUR and nCUR with respect to their antibacterial effects against various pharyngeal species. CONCLUSION nCUR and sCUR are equipotent in in vitro assays mimicking aspects of oral mucositis. The advantages of sCUR include that it is odorless and tasteless, more easily soluble in DMSO, and that it is a single, highly purified molecule, lacking the batch-to-batch variation of CUR content in nCUR. sCUR is a promising agent for the development of an oral anti-mucositis agent.

Topical curcumin can inhibit deleterious effects of upper respiratory tract bacteria on human oropharyngeal cells in vitro: potential role for patients with cancer therapy induced mucositis?

Curcumin exerts its anti-inflammatory activity via inhibition of nuclear factor κB. Oropharyngeal epithelia and residing bacteria closely interact in inflammation and infection. This in vitro model investigated the effects of curcumin on bacterial survival, adherence to, and invasion of upper respiratory tract epithelia, and studied its anti-inflammatory effect. We aimed to establish a model, which could offer insights into the host-pathogen interaction in cancer therapy induced mucositis.

Percutaneous aortic valve replacement: valvuloplasty studies in vitro

Valvuloplasty of the aortic valve is currently used in selected patients for severe calcified aortic valve disease, but clinical effectiveness is low and complication rate remains high. In this study, the total particle load after valvuloplasty and the embolization risk of calcific debris into the coronary arteries was analyzed in an in vitro model.

Primary bovine synoviocyte cultures: a useful tool for in vitro drug testing?

The aim of the study was to evaluate bovine synoviocyte culture as an in vitro model to test new intra-articular drugs. The inflammatory reaction pattern of synoviocytes as compared to fibroblasts was studied over nine passages. Expression of pro-inflammatory cytokines was assessed after stimulation with lipopolysaccharide. Immunohistochemical markers were used to identify synoviocyte populations. Primary synoviocytes expressed markedly higher amounts of interleukin-1beta mRNA and tumour necrosis factor-alpha mRNA than fibroblasts after stimulation. This difference was lost over two passages. CD68-positive macrophage-like synoviocytes diminished over three passages, which may explain the reduced pro-inflammatory cytokine response. Primary bovine synoviocytes appear to be an appropriate and optimised model for testing novel drugs for cattle, because their response may more closely reflect in vivo tissue responses compared to cultured cell lines.

Pulmonary surfactant coating of multi-walled carbon nanotubes (MWCNTs) influences their oxidative and pro-inflammatory potential in vitro

Background Increasing concern has been expressed regarding the potential adverse health effects that may be associated with human exposure to inhaled multi-walled carbon nanotubes (MWCNTs). Thus it is imperative that an understanding as to the underlying mechanisms and the identification of the key factors involved in adverse effects are gained. In the alveoli, MWCNTs first interact with the pulmonary surfactant. At this interface, proteins and lipids of the pulmonary surfactant bind to MWCNTs, affecting their surface characteristics. Aim of the present study was to investigate if the pre-coating of MWCNTs with pulmonary surfactant has an influence on potential adverse effects, upon both (i) human monocyte derived macrophages (MDM) monocultures, and (ii) a sophisticated in vitro model of the human epithelial airway barrier. Both in vitro systems were exposed to MWCNTs either pre-coated with a porcine pulmonary surfactant (Curosurf) or not. The effect of MWCNTs surface charge was also investigated in terms of amino (−NH2) and carboxyl (−COOH) surface modifications. Results Pre-coating of MWCNTs with Curosurf affects their oxidative potential by increasing the reactive oxygen species levels and decreasing intracellular glutathione depletion in MDM as well as decreases the release of Tumour necrosis factor alpha (TNF-α). In addition, an induction of apoptosis was observed after exposure to Curosurf pre-coated MWCNTs. In triple cell-co cultures the release of Interleukin-8 (IL-8) was increased after exposure to Curosurf pre-coated MWCNTs. Effects of the MWCNTs functionalizations were minor in both MDM and triple cell co-cultures. Conclusions The present study clearly indicates that the pre-coating of MWCNTs with pulmonary surfactant more than the functionalization of the tubes is a key factor in determining their ability to cause oxidative stress, cytokine/chemokine release and apoptosis. Thus the coating of nano-objects with pulmonary surfactant should be considered for future lung in vitro risk assessment studies. Keywords: Multi-walled carbon nanotubes (MWCNTs); Pulmonary surfactant (Curosurf); Macrophages; Epithelial cells; Dendritic cells; Triple cell co-culture; Pro-inflammatory and oxidative reactions

SFRP-4 abrogates Wnt-3a-induced beta-catenin and Akt/PKB signalling and reverses a Wnt-3a-imposed inhibition of in vitro mammary differentiation

ABSTRACT: BACKGROUND: Conserved Wnt ligands are critical for signalling during development; however, various factors modulate their activity. Among these factors are the Secreted Frizzled-Related Proteins (SFRP). We previously isolated the SFRP-4 gene from an involuting rat mammary gland and later showed that transgenic mice inappropriately expressing SFRP-4 during lactation exhibited a high level of apoptosis with reduced survival of progeny. RESULTS: In order to address the questions related to the mechanism of Wnt signalling and its inhibition by SFRP-4 which we report here, we employed partially-purified Wnt-3a in a co-culture model system. Ectopic expression of SFRP-4 was accomplished by infection with a pBabepuro construct. The co-cultures comprised Line 31E mouse mammary secretory epithelial cells and Line 30F, undifferentiated, fibroblast-like mouse mammary cells. In vitro differentiation of such co-cultures can be demonstrated by induction of the beta-casein gene in response to lactogenic hormones.We show here that treatment of cells with partially-purified Wnt-3a initiates Dvl-3, Akt/PKB and GSK-3beta hyperphosphorylation and beta-catenin activation. Furthermore, while up-regulating the cyclin D1 and connexin-43 genes and elevating transepithelial resistance of Line 31E cell monolayers, Wnt-3a treatment abrogates differentiation of co-cultures in response to the lactogenic hormones prolactin, insulin and glucocorticoid. Cells which express SFRP-4, however, are largely unaffected by Wnt-3a stimulation. Since a physical association between Wnt-3a and SFRP-4 could be demonstrated with immunoprecipitation/Western blotting experiments, this interaction, presumably owing to the Frizzled homology region typical of all SFRPs, explains the refractory response to Wnt-3a which was observed. CONCLUSION: This study demonstrates that Wnt-3a treatment activates the Wnt signalling pathway and interferes with in vitro differentiation of mammary co-cultures to beta-casein production in response to lactogenic hormones. Similarly, in another measure of differentiation, following Wnt-3a treatment mammary epithelial cells could be shown to up-regulate the cyclin D1 and connexin-43 genes while phenotypically they show increased transepithelial resistance across the cell monolayer. All these behavioural changes can be blocked in mammary epithelial cells expressing SFRP-4. Thus, our data illustrate in an in vitro model a mechanism by which SFRP-4 can modulate a differentiation response to Wnt-3a.

Reassembling a system from the sensor to cerebral representation: the olfactory system in vitro.

An odorant's code is represented by activity in a dispersed ensemble of olfactory sensory neurons in the nose, activation of a specific combination of groups of mitral cells in the olfactory bulb and is considered to be mapped at divergent locations in the olfactory cortex. We present here an in vitro model of the mammalian olfactory system developed to gain easy access to all stations of the olfactory pathway. Mouse olfactory epithelial explants are cocultured with a brain slice that includes the olfactory bulb and olfactory cortex areas and maintains the central olfactory pathway intact and functional. Organotypicity of bulb and cortex is preserved and mitral cell axons can be traced to their target areas. Calcium imaging shows propagation of mitral cell activity to the piriform cortex. Long term coculturing with postnatal olfactory epithelial explants restores the peripheral olfactory pathway. Olfactory receptor neurons renew and progressively acquire a mature phenotype. Axons of olfactory receptor neurons grow out of the explant and rewire into the olfactory bulb. The extent of reinnervation exhibits features of a postlesion recovery. Functional imaging confirms the recovery of part of the peripheral olfactory pathway and shows that activity elicited in olfactory receptor neurons or the olfactory nerves is synaptically propagated into olfactory cortex areas. This model is the first attempt to reassemble a sensory system in culture, from the peripheral sensor to the site of cortical representation. It will increase our knowledge on how neuronal circuits in the central olfactory areas integrate sensory input and counterbalance damage.

Local changes in neocortical circuit dynamics coincide with the spread of seizures to thalamus in a model of epilepsy

During the generalization of epileptic seizures, pathological activity in one brain area recruits distant brain structures into joint synchronous discharges. However, it remains unknown whether specific changes in local circuit activity are related to the aberrant recruitment of anatomically distant structures into epileptiform discharges. Further, it is not known whether aberrant areas recruit or entrain healthy ones into pathological activity. Here we study the dynamics of local circuit activity during the spread of epileptiform discharges in the zero-magnesium in vitro model of epilepsy. We employ high-speed multi-photon imaging in combination with dual whole-cell recordings in acute thalamocortical (TC) slices of the juvenile mouse to characterize the generalization of epileptic activity between neocortex and thalamus. We find that, although both structures are exposed to zero-magnesium, the initial onset of focal epileptiform discharge occurs in cortex. This suggests that local recurrent connectivity that is particularly prevalent in cortex is important for the initiation of seizure activity. Subsequent recruitment of thalamus into joint, generalized discharges is coincident with an increase in the coherence of local cortical circuit activity that itself does not depend on thalamus. Finally, the intensity of population discharges is positively correlated between both brain areas. This suggests that during and after seizure generalization not only the timing but also the amplitude of epileptiform discharges in thalamus is entrained by cortex. Together these results suggest a central role of neocortical activity for the onset and the structure of pathological recruitment of thalamus into joint synchronous epileptiform discharges.

In vitro study to simulate the intracardiac magnetohydrodynamic effect

PURPOSE Blood flow causes induced voltages via the magnetohydrodynamic (MHD) effect distorting electrograms (EGMs) made during magnetic resonance imaging. To investigate the MHD effect in this context MHD voltages occurring inside the human heart were simulated in an in vitro model system inside a 1.5 T MR system. METHODS The model was developed to produce MHD signals similar to those produced by intracardiac flow and to acquire them using standard clinical equipment. Additionally, a new approach to estimate MHD distortions on intracardiac electrograms is proposed based on the analytical calculation of the MHD signal from MR phase contrast data. RESULTS The recorded MHD signals were similar in magnitude to intracardiac signals that would be measured by an electrogram of the left ventricle. The dependency of MHD signals on magnetic field strength and electrode separation was well reflected by an analytical model. MHD signals reconstructed from MR flow data were in excellent agreement with the MHD signal measured by clinical equipment. CONCLUSION The in vitro model allows investigation of MHD effects on intracardiac electrograms. A phase contrast MR scan was successfully applied to characterize and estimate the MHD distortion on intracardiac signals allowing correction of these effects. Magn Reson Med, 2014. © 2014 Wiley Periodicals, Inc.

Besnoitia besnoiti lytic cycle in vitro and differences in invasion and intracellular proliferation among isolates

Background Bovine besnoitiosis, caused by the protozoan Besnoitia besnoiti, reduces productivity and fertility of affected herds. Besnoitiosis continues to expand in Europe and no effective control tools are currently available. Experimental models are urgently needed. Herein, we describe for the first time the kinetics of standardised in vitro models for the B. besnoiti lytic cycle. This will aid to study the pathogenesis of the disease, in the screening for vaccine targets and drugs potentially useful for the treatment of besnoitiosis. Methods We compared invasion and proliferation of one B. tarandi (from Finland) and seven B. besnoiti isolates (Bb-Spain1, Bb-Spain2, Bb-Israel, Bb-Evora03, Bb-Ger1, Bb-France, Bb-Italy2) in MARC-145 cell culture. Host cell invasion was studied at 4, 6, 8 and 24 h post infection (hpi), and proliferation characteristics were compared at 24, 48, 72, 96, 120, and 144 hpi. Results In Besnoitia spp., the key parameters that determine the sequential adhesion-invasion, proliferation and egress steps are clearly distinct from those in the related apicomplexans Toxoplasma gondii and Neospora caninum. Besnoitia spp. host cell invasion is a rather slow process, since only 50 % of parasites were found intracellular after 3–6 h of exposure to host cells, and invasion still took place after 24 h. Invasion efficacy was significantly higher for Bb-France, Bb-Evora03 and Bb-Israel. In addition, the time span for endodyogeny to take place was as long as 18–35 h. Bb-Israel and B. tarandi isolates were most prolific, as determined by the tachyzoite yield at 72 hpi. The total tachyzoite yield could not be predicted neither by invasion-related parameters (velocity and half time invasion) nor by proliferation parameters (lag phase and doubling time (dT)). The lytic cycle of Besnoitia was asynchronous as evidenced by the presence of three different plaque-forming tachyzoite categories (lysis plaques, large and small parasitophorous vacuoles). Conclusions This study provides first insights into the lytic cycle of B. besnoiti isolates and a standardised in vitro model that allows screening of drug candidates for the treatment of besnoitiosis.

Modeling immune functions of the mouse blood-cerebrospinal fluid barrier in vitro: primary rather than immortalized mouse choroid plexus epithelial cells are suited to study immune cell migration across this brain barrier.

BACKGROUND The blood-cerebrospinal fluid barrier (BCSFB) established by the choroid plexus (CP) epithelium has been recognized as a potential entry site of immune cells into the central nervous system during immunosurveillance and neuroinflammation. The location of the choroid plexus impedes in vivo analysis of immune cell trafficking across the BCSFB. Thus, research on cellular and molecular mechanisms of immune cell migration across the BCSFB is largely limited to in vitro models. In addition to forming contact-inhibited epithelial monolayers that express adhesion molecules, the optimal in vitro model must establish a tight permeability barrier as this influences immune cell diapedesis. METHODS We compared cell line models of the mouse BCSFB derived from the Immortomouse(®) and the ECPC4 line to primary mouse choroid plexus epithelial cell (pmCPEC) cultures for their ability to establish differentiated and tight in vitro models of the BCSFB. RESULTS We found that inducible cell line models established from the Immortomouse(®) or the ECPC4 tumor cell line did not express characteristic epithelial proteins such as cytokeratin and E-cadherin and failed to reproducibly establish contact-inhibited epithelial monolayers that formed a tight permeability barrier. In contrast, cultures of highly-purified pmCPECs expressed cytokeratin and displayed mature BCSFB characteristic junctional complexes as visualized by the junctional localization of E-cadherin, β-catenin and claudins-1, -2, -3 and -11. pmCPECs formed a tight barrier with low permeability and high electrical resistance. When grown in inverted filter cultures, pmCPECs were suitable to study T cell migration from the basolateral to the apical side of the BCSFB, thus correctly modelling in vivo migration of immune cells from the blood to the CSF. CONCLUSIONS Our study excludes inducible and tumor cell line mouse models as suitable to study immune functions of the BCSFB in vitro. Rather, we introduce here an in vitro inverted filter model of the primary mouse BCSFB suited to study the cellular and molecular mechanisms mediating immune cell migration across the BCSFB during immunosurveillance and neuroinflammation.

An in vitro triple cell co-culture model with primary cells mimicking the human alveolar epithelial barrier

A triple cell co-culture model was recently established by the authors, consisting of either A549 or 16HBE14o- epithelial cells, human blood monocyte-derived macrophages and dendritic cells, which offers the possibility to study the interaction of xenobiotics with those cells. The 16HBE14o- containing co-culture model mimics the airway epithelial barrier, whereas the A549 co-cultures mimic the alveolar type II-like epithelial barrier. The goal of the present work was to establish a new triple cell co-culture model composed of primary alveolar type I-like cells isolated from human lung biopsies (hAEpC) representing a more realistic alveolar epithelial barrier wall, since type I epithelial cells cover >93% of the alveolar surface. Monocultures of A549 and 16HBE14o- were morphologically and functionally compared with the hAEpC using laser scanning microscopy, as well as transmission electron microscopy, and by determining the epithelial integrity. The triple cell co-cultures were characterized using the same methods. It could be shown that the epithelial integrity of hAEpC (mean ± SD, 1180 ± 188 Ω cm(2)) was higher than in A549 (172 ± 59 Ω cm(2)) but similar to 16HBE14o- cells (1469 ± 156 Ω cm(2)). The triple cell co-culture model with hAEpC (1113 ± 30 Ω cm(2)) showed the highest integrity compared to the ones with A549 (93 ± 14 Ω cm(2)) and 16HBE14o- (558 ± 267 Ω cm(2)). The tight junction protein zonula occludens-1 in hAEpC and 16HBE14o- were more regularly expressed but not in A549. The epithelial alveolar model with hAEpC combined with two immune cells (i.e. macrophages and dendritic cells) will offer a novel and more realistic cell co-culture system to study possible cell interactions of inhaled xenobiotics and their toxic potential on the human alveolar type I epithelial wall.