Microfluidic Culture Research Articles

Cortical Brain Injury Causes Retrograde Degeneration of Afferent Basal Forebrain Cholinergic Neurons via the p75NTR.

Traumatic brain injury elicits neuronal loss at the site of injury and progressive neuronal loss in the penumbra. However, the consequences of TBI on afferent neurons projecting to the injured tissue from distal locations is unknown. Basal forebrain cholinergic neurons (BFCNs) extend long projections to multiple brain regions including the cortex, regulate many cognitive functions and are compromised in numerous neurodegenerative disorders. To determine the consequence of cortical injury on these afferent neurons, we used the Fluid Percussion Injury (FPI) model of traumatic brain injury and assessed the effects on BFCN survival and axon integrity in male and female mice. Survival or death of BF neurons can be regulated by neurotrophins or proneurotrophins, respectively. The injury elicited an induction of proNGF and proBDNF in the cortex, and a loss of BFCNs ipsilateral to the injury compared to sham uninjured mice. p75NTR knockout mice did not show loss of BFCN neurons, indicating a retrograde degenerative effect of the cortical injury on the afferent BFCNs mediated through p75NTR. In contrast, locus coeruleus (LC) neurons which also project throughout the cortex were unaffected by the injury, suggesting specificity in retrograde degeneration after cortical TBI. Proneurotrophins (proNTs) provided directly to basal forebrain axons in microfluidic cultures triggered retrograde axonal degeneration and cell death, which did not occur in the absence of p75NTR. This study shows that after traumatic brain injury, proNTs induced in the injured cortex promote BFCN axonal degeneration and retrograde neuron loss through p75NTR.Significance StatementTBI is well-known to elicit direct neuronal loss at the site of injury and secondary loss in the penumbra, however the effect on afferent neuronal populations that project axons from distal locations such as the basal forebrain, has not been elucidated. Basal forebrain cholinergic neurons (BFCNs) project to a myriad of brain regions and regulate cognitive processes such as learning, attention, and memory, and are compromised in neurodegenerative diseases such as Alzheimer's disease. These neurons constitutively express p75NTR, a receptor that can promote neuronal degeneration following injury. We demonstrate here that cortical injury promotes degeneration of afferent BFCNs, mediated by p75NTR, indicating that TBI causes neuronal loss in brain regions distal to the site of injury via retrograde axonal degeneration.

O-019 Decreased Sperm Motility Associated With Bacterial Vaginosis Modeled in a Human Cervix Chip

Abstract Study question What is the underlying cause of infertility associated with bacterial vaginosis (BV)? Summary answer We provide the first evidence to suggest that BV-associated infertility could be the result of sperm dysfunction induced by exposure to poor cervical microbiome. What is known already Infertility is a global health concern, impacting 186 million individuals worldwide. In 25% of infertile couples the underlying cause remains unexplained. The complex interactions between the host mucosal epithelium, microbiome, and other microenvironmental factors play a significant role in health and disease of the reproductive tract. BV affects 30% of reproductive-aged women and is linked to overgrowth of pathogenic Gardnerella vaginalis bacteria. BV has a strong association with infertility, but it is not clear whether the resulting changes in the vaginal microbiome play a causal role, and as such BV screening is not currently included in infertility evaluation or treatment Study design, size, duration Female reproductive tract protective factors such as cervical mucus helps sperm retain their ability to fertilize for days compared to hours in suspension. We previously leveraged human organ-on-a-chip microfluidic culture technology to develop a physiological in vitro model of human cervix (Cervix Chip) that is lined with primary cervical epithelium interfaced with stromal fibroblasts. The epithelium forms a functional tissue barrier and produces mucus with compositional, biophysical, and hormone-responsive properties similar to the living cervix. Participants/materials, setting, methods We used 2D culture of sperm and bacteria as a screening and validated the effect of the identified bacteria on physiological in vitro Cervix Chip. A BV consortium containing E2 and E4 Gardnerella vaginalis bacteria was co-cultured with the Cervix Chip for 48 hours before adding human sperm samples. The motility of fluorescently labeled sperm was non-invasively evaluated in live chips using time-lapse imaging and quantitatively analyzed to obtain the percentage of motile sperm. Main results and the role of chance We initially analyzed the effects of bacterial co-cultur L. crispatus (optimal) or G. vaginalis (suboptimal) bacteria on sperm motility using a conventional 2D culture system. We observed a significant drop in sperm motility within 2 hours when exposed to G. vaginalis compared to L. crispatus or the control condition (no bacteria). We have established sperm staining and live tracking on Cervix Chip. Motile sperm was tracked on Cervix Chip for more than 7 days compared to 12 hours in suspension. We then tested this effect on-chip and observed that co-culture of live sperm with dysbiotic Cervix Chip (infected with G. vaginalis) resulted in a significant reduction in the sperm motility within 24 hours after exposure compared to the sperm exposed to the chips without bacteria. The dysbiotic Cervix Chip also exhibited a disease phenotype with elevated levels of proinflammatory cytokines including IL-1α, IL-1β, IL-6, IL-8, and TNF-α in the effluents of the chip's epithelial channel as well as significantly reduced thickness of the cervical mucus layer that correlated with reduced sperm motility. This finding is consistent with the observation that successful fertility is often associated with the quality of cervical mucus, which can be compromised in the BV dysbiotic condition. Limitations, reasons for caution Primary cervical epithelium cells used in the study were sourced from a single donor. Frozen sperm samples prepared for intrauterine insemination were used in the study Wider implications of the findings Our study suggests that infertility related to BV may be caused by sperm dysfunction, and BV screening should be considered in patients with unexplained infertility. We propose a model that can be used to identify dysbiotic conditions in the female reproductive tract that are unfavorable to sperm motility. Trial registration number N/A

Enabling oxygen-controlled microfluidic cultures for spatiotemporal microbial single-cell analysis.

Microfluidic cultivation devices that facilitate O2 control enable unique studies of the complex interplay between environmental O2 availability and microbial physiology at the single-cell level. Therefore, microbial single-cell analysis based on time-lapse microscopy is typically used to resolve microbial behavior at the single-cell level with spatiotemporal resolution. Time-lapse imaging then provides large image-data stacks that can be efficiently analyzed by deep learning analysis techniques, providing new insights into microbiology. This knowledge gain justifies the additional and often laborious microfluidic experiments. Obviously, the integration of on-chip O2 measurement and control during the already complex microfluidic cultivation, and the development of image analysis tools, can be a challenging endeavor. A comprehensive experimental approach to allow spatiotemporal single-cell analysis of living microorganisms under controlled O2 availability is presented here. To this end, a gas-permeable polydimethylsiloxane microfluidic cultivation chip and a low-cost 3D-printed mini-incubator were successfully used to control O2 availability inside microfluidic growth chambers during time-lapse microscopy. Dissolved O2 was monitored by imaging the fluorescence lifetime of the O2-sensitive dye RTDP using FLIM microscopy. The acquired image-data stacks from biological experiments containing phase contrast and fluorescence intensity data were analyzed using in-house developed and open-source image-analysis tools. The resulting oxygen concentration could be dynamically controlled between 0% and 100%. The system was experimentally tested by culturing and analyzing an E. coli strain expressing green fluorescent protein as an indirect intracellular oxygen indicator. The presented system allows for innovative microbiological research on microorganisms and microbial ecology with single-cell resolution.

Tumor Organoid Model and Its Pharmacological Applications in Tumorigenesis Prevention.

Cancer is a leading cause of death and a severe threat to global public health. Organoid, as a novel 3D in vitro model, has been applied in various tumor related studies due to its apparent advantages. The organoid is mainly constructed by Matrigel-depended 3D culture system, Air-Liquid Interface (ALI) culture, and Microfluidic culture or Organ-on-chips platform. For the application in carcinogenesis studies, the organoid model may favor depicting initiative hallmarks and identifying potential intervening targets, investigating driver genes of carcinogenesis, and identifying known or unknown risk or protective factors. In this review, we discussed different organoid construction methods and their properties. We also noted that tumor organoids can portray initiative hallmarks and identify possible intervening targets, as well as explore carcinogenesis driver genes and uncover known or unknown risks or protective factors. Organoid systems have been used to identify tumor-preventive drugs such as oligomeric proanthocyanidins, Vitamin D, n-3 PUFAs, and pomegranate. The current evidence underscores the organoid model's potential importance in developing innovative tumorprevention techniques.

Design and evaluation of a skin-on-a-chip pumpless microfluidic device

The development of microfluidic culture technology facilitates the progress of study of cell and tissue biology. This technology expands the understanding of pathological and physiological changes. A skin chip, as in vitro model, consisting of normal skin tissue with epidermis and dermis layer (full thickness) was developed. Polydimethylsiloxane microchannels with a fed-batched controlled perfusion feeding system were used to create a full-thick ex-vivo human skin on-chip model. The design of a novel skin-on-a-chip model was reported, in which the microchannel structures mimic the architecture of the realistic vascular network as nutrients transporter to the skin layers. Viabilities of full-thick skin samples cultured on the microbioreactor and traditional tissue culture plate revealed that a precise controlled condition provided by the microfluidic enhanced tissue viability at least for seven days. Several advantages in skin sample features under micro-scale-controlled conditions were found such as skin mechanical strength, water adsorption, skin morphology, gene expression, and biopsy longevity. This model can provide an in vitro environment for localizing drug delivery and transdermal drug diffusion studies. The skin on the chip can be a valuable in vitro model for representing the interaction between drugs and skin tissue and a realistic platform for evaluating skin reaction to pharmaceutical materials and cosmetic products.

Abstract 4854: PKM2 Modulates hepatic macrophage regulation of NASH, ferroptosis and HCC through TGF-β signaling

Abstract Background: Non-alcoholic steatohepatitis (NASH) and cirrhosis are major risk factors for hepatocellular carcinoma (HCC), which affects men 2-4 times more than women. In tumors Pyruvate kinase M2 (PKM2), induces aerobic glycolysis (Warburg effect) and proinflammatory and non-apoptotic cell death, ferroptosis. Raised levels of hepatic macrophage PKM2 expression are associated with poor prognosis HCC. We previously found that liver specific TGF-β/SMAD4 knockout mice develop iron deposition and hemochromatosis due to a dramatic loss of hepcidin. Moreover, Smad4+/−Sptbn1+/− mice develop gastrointestinal cancers but only in the presence of an altered microbiome. Recently, we found that liver-specific knockout of a TGF-β/SMAD3/4 adaptor protein, βII-spectrin (LSKO) blocks diet-induced NASH and HCC in mice, as well as in siRNA treated human NASH microfluidic cultures (Sci Transl Med. 2021;13(624): eabk2267). We hypothesized that βII-spectrin modulates PKM2 expression in NASH fatty liver, promoting proinflammatory cytokine release, inflammation and tumorigenesis. In addition, microbiome changes could alter hepcidin function and modulate ferroptosis. Our goal is to understand the molecular mechanism underlying PKM2 driven NASH and HCC. Methods: For our NASH mouse model, we fed SPTBN1Flox (control) and liver-specific βII-spectrin knockout (SPTBN1LSKO) mice a Western diet (WD). Body weight, total cholesterol, and triglyceride concentrations in serum were monitored, and PKM2 expression levels in the liver tissues was analyzed. SPTBN1Flox and SPTBN1LSKO mice were treated with both WD and Diethylnitrosamine (DEN) for HCC, and gut microbiome profiles were performed in these mice. To evaluate PKM2 expression in the NASH-associated HCC mouse model, immunohistochemical labeling was performed on liver tissues of these mice with PKM2-specific antibody. Inflammation, lipidosis and fibrosis were determined with H&E, Oil Red O and Sirius Red staining. Results: We found upregulation of PKM2 expression in NASH and HCC Kupffer cells (WD SPTBN1Flox mice). In contrast, PKM2 expression was markedly reduced in the liver in WD SPTBN1LSKO that blocked NASH and HCC. Interestingly, microbiome profiles were altered and TGF-β/SMAD3-regulated fibrosis as well as expression of inflammatory genes were significantly reduced in LSKO mice, compared to the NASH mice. Conclusions: Our findings suggest that the knockdown of the Smad3/4 adaptor βII-spectrin decreases PKM2 expression in Kupffer cells, thereby suppressing pro-inflammatory cytokine production, blocking NASH-associated HCC. Hepatic macrophages such as Kupffer cells and monocyte-derived macrophages could therefore play a critical role in the ferroptosis-mediated protumor immune microenvironment. In addition, our work provides new insight into potential mechanism for two disorders that affect males more than females, hemochromatosis and HCC. Citation Format: Kazufumi Ohshiro, Krishanu Bhowmick, Xiaochun Yang, Addison Klebanov, Sahara John, Dillon Voss, Adrian Krainer, Lopa Mishra. PKM2 Modulates hepatic macrophage regulation of NASH, ferroptosis and HCC through TGF-β signaling. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4854.

Reliable cell retention of mammalian suspension cells in microfluidic cultivation chambers

Microfluidic cultivation, with its high level of environmental control and spatio-temporal resolution of cellular behavior, is a well-established tool in today’s microfluidics. Yet, reliable retention of (randomly) motile cells inside designated cultivation compartments still represents a limitation, which prohibits systematic single-cell growth studies. To overcome this obstacle, current approaches rely on complex multilayer chips or on-chip valves, which makes their application for a broad community of users infeasible. Here, we present an easy-to-implement cell retention concept to withhold cells inside microfluidic cultivation chambers. By introducing a blocking structure into a cultivation chamber’s entrance and nearly closing it, cells can be manually pushed into the chamber during loading procedures but are unable to leave it autonomously in subsequent long-term cultivation. CFD simulations as well as trace substance experiments confirm sufficient nutrient supply within the chamber. Through preventing recurring cell loss, growth data obtained from Chinese hamster ovary cultivation on colony level perfectly match data determined from single-cell data, which eventually allows reliable high throughput studies of single-cell growth. Due to its transferability to other chamber-based approaches, we strongly believe that our concept is also applicable for a broad range of cellular taxis studies or analyses of directed migration in basic or biomedical research.

Using microfluidic models to evaluate whether monocyte preconditioning plays a role in tumor-associated macrophage mediated resistance to hormone therapy in men with prostate cancer.

228 Background: While men with metastatic castrate-resistant prostate cancer benefit greatly from 2nd generation androgen targeted therapies (ATTs), the utility of these therapies is inevitably limited by the development of resistance. Tumor associated macrophages (TAMs) are a myeloid immune cell population within the prostate tumor microenvironment (TME) that have been shown to play an integral role in development of ATT-resistance. However, the pathways that underlie TAM-mediated ATT resistance remain under investigation. In particular, many TAMs within the TME are derived from circulating monocytes and it is not yet clear whether the pathways driving TAM-mediated resistance are activated exclusively within the TME or if the activation of critical resistance pathways begins while the cells are circulating as monocytes. In this study, we utilized novel microscale technologies to investigate the transcriptome of monocytes and macrophages derived from patients progressing and responding to ATTs as well as the degree to which the macrophages promote ATT resistance in prostate tumor models. Methods: Primary monocytes were isolated from 22 men with prostate cancer who were either progressing or responding to 2ndgeneration ATTs. A portion of the monocytes from each patient were isolated for transcriptome analysis and the rest were differentiated into monocyte-derived macrophages (MDMs). MDMs were then cultured in monoculture or in co-culture with androgen-independent prostate tumor cells (22Rv1 and C42B). Each culture was then left untreated or treated with enzalutamide therapy. Following culture/treatment, each macrophage condition was isolated for transcriptome analysis and tumor cell populations from each condition were evaluated for treatment cytotoxicity. Results: Viability data from MDM-C42B co-culture demonstrated a 20% increase in tumor cell viability following enzalutamide treatment when C42B cells were cultured with primary MDMs from castrate-sensitive patients as compared to MDMs from castrate-resistant patients. Subsequent transcriptome analysis demonstrated key signatures in monocyte/macrophage populations that were associated ATT response. Conclusions: Leveraging a novel microfluidic culture platform known as Stacks, we were able to utilize primary, patient-derived cells to demonstrate that the role of TAMs in ATT resistance within the prostate TME is dependent, at least in part, on factors that are present prior to extravasation into the TME. Transcriptome analysis identified candidate pathways, which may be driving TAM-mediated differences in ATT response. These findings have the potential to lead to future use of circulating monocytes as a predictive biomarker as well as lead to the identification and targeting of ATT resistance pathways in patients.

Paclitaxel effects on axonal localization and vesicular trafficking of NaV1.8.

Patients treated with paclitaxel (PTX) or other antineoplastic agents can experience chemotherapy-induced peripheral neuropathy (CIPN), a debilitating side effect characterized by numbness and pain. PTX interferes with microtubule-based transport, which inhibits tumor growth via cell cycle arrest but can also affect other cellular functions including trafficking of ion channels critical to transduction of stimuli by sensory neurons of the dorsal root ganglia (DRG). We examined the effects of PTX on voltage-gated sodium channel NaV1.8, which is preferentially expressed in DRG neurons, using a microfluidic chamber culture system and chemigenetic labeling to observe anterograde channel transport to the endings of DRG axons in real time. PTX treatment increased the numbers of NaV1.8-containing vesicles traversing the axons. Vesicles in PTX-treated cells exhibited greater average velocity, along with shorter and less frequent pauses along their trajectories. These events were paralleled by greater surface accumulation of NaV1.8 channels at the distal ends of DRG axons. These results were consistent with observations that NaV1.8 is trafficked in the same vesicles containing NaV1.7 channels, which are also involved in pain syndromes in humans and are similarly affected by PTX treatment. However, unlike Nav1.7, we did not detect increased NaV1.8 current density measured at the neuronal soma, suggesting a differential effect of PTX on trafficking of NaV1.8 in soma versus axonal compartments. Therapeutic targeting of axonal vesicular traffic would affect both Nav1.7 and Nav1.8 channels and increase the possibilities of alleviating pain associated with CIPN.

A Scalable, Modular Degasser for Passive In-Line Removal of Bubbles from Biomicrofluidic Devices.

Bubbles are a common cause of microfluidic malfunction, as they can perturb the fluid flow within the micro-sized features of a device. Since gas bubbles form easily within warm cell culture reagents, degassing is often necessary for biomicrofluidic systems. However, fabrication of a microscale degasser that can be used modularly with pre-existing chips may be cumbersome or challenging, especially for labs not equipped for traditional microfabrication, and current commercial options can be expensive. Here, we address the need for an affordable, accessible bubble trap that can be used in-line for continuous perfusion of organs-on-chip and other microfluidic cultures. We converted a previously described, manually fabricated PDMS degasser to allow scaled up, reproducible manufacturing by commercial machining or fused deposition modeling (FDM) 3D printing. After optimization, the machined and 3D printed degassers were found to be stable for >2 weeks under constant perfusion, without leaks. With a ~140 µL chamber volume, trapping capacity was extrapolated to allow for ~5-20 weeks of degassing depending on the rate of bubble formation. The degassers were biocompatible for use with cell culture, and they successfully prevented bubbles from reaching a downstream microfluidic device. Both degasser materials showed little to no leaching. The machined degasser did not absorb reagents, while the FDM printed degasser absorbed a small amount, and both maintained fluidic integrity from 1 µL/min to >1 mL/min of pressure-driven flow. Thus, these degassers can be fabricated in bulk and allow for long-term, efficient bubble removal in a simple microfluidic perfusion set-up.

The "3Ds" of Growing Kidney Organoids: Advances in Nephron Development, Disease Modeling, and Drug Screening.

A kidney organoid is a three-dimensional (3D) cellular aggregate grown from stem cells in vitro that undergoes self-organization, recapitulating aspects of normal renal development to produce nephron structures that resemble the native kidney organ. These miniature kidney-like structures can also be derived from primary patient cells and thus provide simplified context to observe how mutations in kidney-disease-associated genes affect organogenesis and physiological function. In the past several years, advances in kidney organoid technologies have achieved the formation of renal organoids with enhanced numbers of specialized cell types, less heterogeneity, and more architectural complexity. Microfluidic bioreactor culture devices, single-cell transcriptomics, and bioinformatic analyses have accelerated the development of more sophisticated renal organoids and tailored them to become increasingly amenable to high-throughput experimentation. However, many significant challenges remain in realizing the use of kidney organoids for renal replacement therapies. This review presents an overview of the renal organoid field and selected highlights of recent cutting-edge kidney organoid research with a focus on embryonic development, modeling renal disease, and personalized drug screening.

Live tracking metabolic networks and physiological responses within microbial assemblages at single-cell level.

Microbial interactions impact the functioning of both natural and engineered systems, yet our ability to directly monitor these highly dynamic and spatially resolved interactions in living cells is very limited. Here, we developed a synergistic approach coupling single-cell Raman microspectroscopy with 15N2 and 13CO2 stable isotope probing in a microfluidic culture system (RMCS-SIP) for live tracking of the occurrence, rate, and physiological shift of metabolic interactions in active microbial assemblages. Quantitative and robust Raman biomarkers specific for N2 and CO2 fixation in both model and bloom-forming diazotrophic cyanobacteria were established and cross-validated. By designing a prototype microfluidic chip allowing simultaneous microbial cultivation and single-cell Raman acquisition, we achieved temporal tracking of both intercellular (between heterocyst and vegetative cells of cyanobacteria) and interspecies N and C metabolite exchange (from diazotroph to heterotroph). Moreover, single-cell N and C fixation and bidirectional transfer rate in living cells were quantified via SIP-induced characteristic Raman shifts. Remarkably, RMCS captured physiological responses of metabolically active cells to nutrient stimuli through comprehensive metabolic profiling, providing multimodal information on the evolution of microbial interactions and functions under fluctuating conditions. This noninvasive RMCS-SIP is an advantageous approach for live-cell imaging and represents an important advancement in the single-cell microbiology field. This platform can be extended for real-time tracking of a wide range of microbial interactions with single-cell resolution and advances the understanding and manipulation of microbial interactions for societal benefit.

Spatially selective cell treatment and collection for integrative drug testing using hydrodynamic flow focusing and shifting.

Hydrodynamic focusing capable of readily producing and controlling laminar flow facilitates drug treatment of cells in existing microfluidic culture devices. However, to expand applications of such devices to multiparameter drug testing, critical limitations in current hydrodynamic focusing microfluidics must be addressed. Here we describe hydrodynamic focusing and shifting as an advanced microfluidics tool for spatially selective drug delivery and integrative cell-based drug testing. We designed and fabricated a co-flow focusing, three-channel microfluidic device with a wide cell culture chamber. By controlling inlet flow rates of sample and two side solutions, we could generate hydrodynamic focusing and shifting that mediated precise regulation of the path and width of reagent and drug stream in the microfluidic device. We successfully validated a hydrodynamic focusing and shifting approach for spatially selective delivery of DiI, a lipophilic fluorophore, and doxorubicin, a chemotherapeutic agent, to tumor cells in our device. Moreover, subsequent flowing of a trypsin EDTA solution over the cells that were exposed to doxorubicin flow allowed us to selectively collect the treated cells. Our approach enabled downstream high-resolution microscopy of the cell suspension to confirm the nuclear delivery of doxorubicin into the tumor cells. In the device, we could also evaluate in situ the cytotoxic effect of doxorubicin to the tumor cells that were selectively treated by hydrodynamic flow focusing and shifting. These results show that hydrodynamic focusing and shifting enable a fast and robust approach to spatially treat and then collect cells in an optimized microfluidic device, offering an integrative assay tool for efficient drug screening and discovery.

A robust, flow-based, microfluidic device for siRNA-mediated gene knockdown in glioblastoma spheroids

Glioblastoma (GBM) is a deadly disease with a poor prognosis, there is therefore a crucial need for novel therapeutic targets. Current preclinical models of GBM fail to predict clinical outcomes, thus, new translationally relevant models are urgently needed for reliable therapeutic target validation. 3D spheroid culture of cancer cells has been shown to better reflect tumour biology than 2D monolayer culture, as has culturing cells in flow-based microfluidic devices, which mimic key aspects of the tumour microenvironment. Gene knockdown by siRNA is a key preclinical target validation tool, however, siRNA-mediated knockdown of cancer spheroids in microfluidic culture has not yet been demonstrated. Here we describe a simple and robust microfluidic device that can maintain GBM spheroids (U87 cells) for at least 7 days. Via RNA sequencing analysis, we demonstrate that spheroids grown in microfluidic culture are more proliferative than spheroids grown in static plate culture and downregulate genes associated with cell adhesion, potentially offering insights into the metastatic process. Comparison of target gene (PRMT2 and RAB21) knockdown using siRNA between 2D monolayer cultured cells, static spheroid culture and spheroids maintained in the microfluidic device showed that gene expression (as measured by quantitative-PCR) was significantly reduced in all culture systems. Knockdown was most efficient in cells grown in 2D monolayer culture followed by static spheroid culture, but we also demonstrate [Formula: see text] knockdown efficiency using the microfluidic device. In summary, this study describes an easy-to-use microfluidic culture platform and provides evidence that pre-clinical siRNA-mediated target validation studies will be possible in flow systems that mimic tumour physiology.

Opportunities involving microfluidics and 3D culture systems to the in vitro embryo production.

Traditional methods of gamete handling, fertilization, and embryo culture often face limitations in efficiency, consistency, and the ability to closely mimic in vivo conditions. This review explores the opportunities presented by microfluidic and 3D culture systems in overcoming these challenges and enhancing in vitro embryo production. We discuss the basic principles of microfluidics, emphasizing their inherent advantages such as precise control of fluid flow, reduced reagent consumption, and high-throughput capabilities. Furthermore, we delve into microfluidic devices designed for gamete manipulation, in vitro fertilization, and embryo culture, highlighting innovations such as droplet-based microfluidics and on-chip monitoring. Next, we explore the integration of 3D culture systems, including the use of biomimetic scaffolds and organ-on-a-chip platforms, with a particular focus on the oviduct-on-a-chip. Finally, we discuss the potential of these advanced systems to improve embryo production outcomes and advance our understanding of early embryo development. By leveraging the unique capabilities of microfluidics and 3D culture systems, we foresee significant advancements in the efficiency, effectiveness, and clinical success of in vitro embryo production.

Vat photopolymerization 3D printed microfluidic devices for organ-on-a-chip applications.

Organs-on-a-chip, or OoCs, are microfluidic tissue culture devices with micro-scaled architectures that repeatedly achieve biomimicry of biological phenomena. They are well positioned to become the primary pre-clinical testing modality as they possess high translational value. Current methods of fabrication have facilitated the development of many custom OoCs that have generated promising results. However, the reliance on microfabrication and soft lithographic fabrication techniques has limited their prototyping turnover rate and scalability. Additive manufacturing, known commonly as 3D printing, shows promise to expedite this prototyping process, while also making fabrication easier and more reproducible. We briefly introduce common 3D printing modalities before identifying two sub-types of vat photopolymerization - stereolithography (SLA) and digital light processing (DLP) - as the most advantageous fabrication methods for the future of OoC development. We then outline the motivations for shifting to 3D printing, the requirements for 3D printed OoCs to be competitive with the current state of the art, and several considerations for achieving successful 3D printed OoC devices touching on design and fabrication techniques, including a survey of commercial and custom 3D printers and resins. In all, we aim to form a guide for the end-user to facilitate the in-house generation of 3D printed OoCs, along with the future translation of these important devices.

Multispecies biofilm architecture determines bacterial exposure to phages.

Numerous ecological interactions among microbes-for example, competition for space and resources, or interaction among phages and their bacterial hosts-are likely to occur simultaneously in multispecies biofilm communities. While biofilms formed by just a single species occur, multispecies biofilms are thought to be more typical of microbial communities in the natural environment. Previous work has shown that multispecies biofilms can increase, decrease, or have no measurable impact on phage exposure of a host bacterium living alongside another species that the phages cannot target. The reasons underlying this variability are not well understood, and how phage-host encounters change within multispecies biofilms remains mostly unexplored at the cellular spatial scale. Here, we study how the cellular scale architecture of model 2-species biofilms impacts cell-cell and cell-phage interactions controlling larger scale population and community dynamics. Our system consists of dual culture biofilms of Escherichia coli and Vibrio cholerae under exposure to T7 phages, which we study using microfluidic culture, high-resolution confocal microscopy imaging, and detailed image analysis. As shown previously, sufficiently mature biofilms of E. coli can protect themselves from phage exposure via their curli matrix. Before this stage of biofilm structural maturity, E. coli is highly susceptible to phages; however, we show that these bacteria can gain lasting protection against phage exposure if they have become embedded in the bottom layers of highly packed groups of V. cholerae in co-culture. This protection, in turn, is dependent on the cell packing architecture controlled by V. cholerae biofilm matrix secretion. In this manner, E. coli cells that are otherwise susceptible to phage-mediated killing can survive phage exposure in the absence of de novo resistance evolution. While co-culture biofilm formation with V. cholerae can confer phage protection to E. coli, it comes at the cost of competing with V. cholerae and a disruption of normal curli-mediated protection for E. coli even in dual species biofilms grown over long time scales. This work highlights the critical importance of studying multispecies biofilm architecture and its influence on the community dynamics of bacteria and phages.

3D ECM-rich environment sustains the identity of naive human iPSCs.

The establishment of invitro naive human pluripotent stem cell cultures opened new perspectives for the study of early events in human development. The role of several transcription factors and signaling pathways have been characterized during maintenance of human naive pluripotency. However, little is known about the role exerted by the extracellular matrix (ECM) and its three-dimensional (3D) organization. Here, using an unbiased and integrated approach combining microfluidic cultures with transcriptional, proteomic, and secretome analyses, we found that naive, but not primed, hiPSC colonies are characterized by a self-organized ECM-rich microenvironment. Based on this, we developed a 3D culture system that supports robust long-term feeder-free self-renewal of naive hiPSCs and also allows direct and timely developmental morphogenesis simply by modulating the signaling environment. Our study opens new perspectives for future applications of naive hiPSCs to study critical stages of human development in 3D starting from a single cell.

Vaginal microbiome-host interactions modeled in a human vagina-on-a-chip

BackgroundA dominance of non-iners Lactobacillus species in the vaginal microbiome is optimal and strongly associated with gynecological and obstetric health, while the presence of diverse obligate or facultative anaerobic bacteria and a paucity in Lactobacillus species, similar to communities found in bacterial vaginosis (BV), is considered non-optimal and associated with adverse health outcomes. Various therapeutic strategies are being explored to modulate the composition of the vaginal microbiome; however, there is no human model that faithfully reproduces the vaginal epithelial microenvironment for preclinical validation of potential therapeutics or testing hypotheses about vaginal epithelium-microbiome interactions.ResultsHere, we describe an organ-on-a-chip (organ chip) microfluidic culture model of the human vaginal mucosa (vagina chip) that is lined by hormone-sensitive, primary vaginal epithelium interfaced with underlying stromal fibroblasts, which sustains a low physiological oxygen concentration in the epithelial lumen. We show that the Vagina Chip can be used to assess colonization by optimal L. crispatus consortia as well as non-optimal Gardnerella vaginalis-containing consortia, and to measure associated host innate immune responses. Co-culture and growth of the L. crispatus consortia on-chip was accompanied by maintenance of epithelial cell viability, accumulation of D- and L-lactic acid, maintenance of a physiologically relevant low pH, and down regulation of proinflammatory cytokines. In contrast, co-culture of G. vaginalis-containing consortia in the vagina chip resulted in epithelial cell injury, a rise in pH, and upregulation of proinflammatory cytokines.ConclusionThis study demonstrates the potential of applying human organ chip technology to create a preclinical model of the human vaginal mucosa that can be used to better understand interactions between the vaginal microbiome and host tissues, as well as to evaluate the safety and efficacy of live biotherapeutics products.AsSRkJhp7GmswS9e3XcXgrVideo

Oxygen Gradient Induced in Microfluidic Chips Can Be Used as a Model for Liver Zonation

Availability of oxygen plays an important role in tissue organization and cell-type specific metabolism. It is, however, difficult to analyze hypoxia-related adaptations in vitro because of inherent limitations of experimental model systems. In this study, we establish a microfluidic tissue culture protocol to generate hypoxic gradients in vitro, mimicking the conditions found in the liver acinus. To accomplish this, four microfluidic chips, each containing two chambers, were serially connected to obtain eight interconnected chambers. HepG2 hepatocytes were uniformly seeded in each chamber and cultivated under a constant media flow of 50 µL/h for 72 h. HepG2 oxygen consumption under flowing media conditions established a normoxia to hypoxia gradient within the chambers, which was confirmed by oxygen sensors located at the inlet and outlet of the connected microfluidic chips. Expression of Hif1α mRNA and protein was used to indicate hypoxic conditions in the cells and albumin mRNA and protein expression served as a marker for liver acinus-like zonation. Oxygen measurements performed over 72 h showed a change from 17.5% to 15.9% of atmospheric oxygen, which corresponded with a 9.2% oxygen reduction in the medium between chamber1 (inlet) and 8 (outlet) in the connected microfluidic chips after 72 h. Analysis of Hif1α expression and nuclear translocation in HepG2 cells additionally confirmed the hypoxic gradient from chamber1 to chamber8. Moreover, albumin mRNA and protein levels were significantly reduced from chamber1 to chamber8, indicating liver acinus zonation along the oxygen gradient. Taken together, microfluidic cultivation in interconnected chambers provides a new model for analyzing cells in a normoxic to hypoxic gradient in vitro. By using a well-characterized cancer cell line as a homogenous hepatocyte population, we also demonstrate that an approximate 10% reduction in oxygen triggers translocation of Hif1α to the nucleus and reduces albumin production.