Fluid shear triggers microvilli formation via mechanosensitive activation of TRPV6

Transport of Maternally Administered Pharmaceutical Agents Across the Placental Barrier In Vitro

To understand the transport of pharmaceutical agents and their effects on developing fetus, we have created a placental microsystem that mimics structural phenotypes and physiological characteristic of a placental barrier. We have shown the formation of a continuous network of epithelial adherens junctions and endothelial cell-cell junctions confirming the integrity of the placental barrier. More importantly, the formation of elongated microvilli under dynamic flow condition is demonstrated. Fluid shear stress acts as a mechanical cue triggering the microvilli formation. Pharmaceutical agents were administered to the maternal channel, and the concentration of pharmaceutical agents in fetal channel for coculture and control models were evaluated. In fetal channel, the coculture model exhibited about 2.5 and 2.2% of the maternal initial concentration for naltrexone and 6β-naltrexol, respectively. In acellular model, fetal channel showed about 10.5 and 10.3% of the maternal initial concentration for naltrexone and 6β-naltrexol, respectively. Gene expressions of epithelial cells after direct administration of naltrexone and 6β-naltrexol to the maternal channel and endothelial cells after exposure due to transport through placental barrier are also reported.

Functional analysis of human brain endothelium using a microfluidic device integrating a cell culture insert

The blood-brain barrier (BBB) is a specialized brain endothelial barrier structure that regulates the highly selective transport of molecules under continuous blood flow. Recently, various types of BBB-on-chip models have been developed to mimic the microenvironmental cues that regulate the human BBB drug transport. However, technical difficulties in complex microfluidic systems limit their accessibility. Here, we propose a simple and easy-to-handle microfluidic device integrated with a cell culture insert to investigate the functional regulation of the human BBB endothelium in response to fluid shear stress (FSS). Using currently established immortalized human brain microvascular endothelial cells (HBMEC/ci18), we formed a BBB endothelial barrier without the substantial loss of barrier tightness under the relatively low range of FSS (0.1-1 dyn/cm2). Expression levels of key BBB transporters and receptors in the HBMEC/ci18 cells were dynamically changed in response to the FSS, and the effect of FSS reached a plateau around 1 dyn/cm2. Similar responses were observed in the primary HBMECs. Taking advantage of the detachable cell culture insert from the device, the drug efflux activity of P-glycoprotein (P-gp) was analyzed by the bidirectional permeability assay after the perfusion culture of cells. The data revealed that the FSS-stimulated BBB endothelium exhibited the 1.9-fold higher P-gp activity than that of the static culture control. Our microfluidic system coupling with the transwell model provides a functional human BBB endothelium with secured transporter activity, which is useful to investigate the bidirectional transport of drugs and its regulation by FSS.

Chip-based multimodal super-resolution microscopy for histological investigations of cryopreserved tissue sections

Histology involves the observation of structural features in tissues using a microscope. While diffraction-limited optical microscopes are commonly used in histological investigations, their resolving capabilities are insufficient to visualize details at subcellular level. Although a novel set of super-resolution optical microscopy techniques can fulfill the resolution demands in such cases, the system complexity, high operating cost, lack of multi-modality, and low-throughput imaging of these methods limit their wide adoption for histological analysis. In this study, we introduce the photonic chip as a feasible high-throughput microscopy platform for super-resolution imaging of histological samples. Using cryopreserved ultrathin tissue sections of human placenta, mouse kidney, pig heart, and zebrafish eye retina prepared by the Tokuyasu method, we demonstrate diverse imaging capabilities of the photonic chip including total internal reflection fluorescence microscopy, intensity fluctuation-based optical nanoscopy, single-molecule localization microscopy, and correlative light-electron microscopy. Our results validate the photonic chip as a feasible imaging platform for tissue sections and pave the way for the adoption of super-resolution high-throughput multimodal analysis of cryopreserved tissue samples both in research and clinical settings.

Establishment of Trophoblast-Like Tissue Model from Human Pluripotent Stem Cells in Three-Dimensional Culture System

The placenta has a lifelong impact on the health of both the mother and fetus. Despite its significance, human early placental development is poorly understood due to the limited models. The models that can reflect the key features of early human placental development, especially at early gestation, are still lacking. Here, the authors report the generation of trophoblast-like tissue model from human pluripotent stem cells (hPSCs) in three-dimensional (3D) cultures. hPSCs efficiently self-organize into blastocoel-like cavities under defined conditions, which produce different trophoblast subtypes, including cytotrophoblasts (CTBs), syncytiotrophoblasts (STBs), and invasive extravillous trophoblasts (EVTs). The 3D cultures can exhibit microvilli structure and secrete human placenta-specific hormone. Single-cell RNA sequencing analysis further identifies the presence of major cell types of trophoblast-like tissue as existing in vivo. The results reveal the feasibility to establish 3D trophoblast-like tissue model from hPSCs in vitro, which is not obtained by monolayer culture. This new model system can not only facilitate to dissect the underlying mechanisms of early human placental development, but also imply its potential for study in developmental biology and gestational disorders.

Mechanotransduction at the Plasma Membrane-Cytoskeleton Interface

Mechanical cues are crucial for survival, adaptation, and normal homeostasis in virtually every cell type. The transduction of mechanical messages into intracellular biochemical messages is termed mechanotransduction. While significant advances in biochemical signaling have been made in the last few decades, the role of mechanotransduction in physiological and pathological processes has been largely overlooked until recently. In this review, the role of interactions between the cytoskeleton and cell-cell/cell-matrix adhesions in transducing mechanical signals is discussed. In addition, mechanosensors that reside in the cell membrane and the transduction of mechanical signals to the nucleus are discussed. Finally, we describe two examples in which mechanotransduction plays a significant role in normal physiology and disease development. The first example is the role of mechanotransduction in the proliferation and metastasis of cancerous cells. In this system, the role of mechanotransduction in cellular processes, including proliferation, differentiation, and motility, is described. In the second example, the role of mechanotransduction in a mechanically active organ, the gastrointestinal tract, is described. In the gut, mechanotransduction contributes to normal physiology and the development of motility disorders.

Advancements in Microfluidic Systems for the Study of Female Reproductive Biology

The female reproductive tract is a highly complex physiological system that consists of the ovaries, fallopian tubes, uterus, cervix, and vagina. An enhanced understanding of the molecular, cellular, and genetic mechanisms of the tract will allow for the development of more effective assisted reproductive technologies, therapeutics, and screening strategies for female specific disorders. Traditional 2-dimensional and 3-dimensional static culture systems may not always reflect the cellular and physical contexts or physicochemical microenvironment necessary to understand the dynamic exchange that is crucial for the functioning of the reproductive system. Microfluidic systems present a unique opportunity to study the female reproductive tract, as these systems recapitulate the multicellular architecture, contacts between different tissues, and microenvironmental cues that largely influence cell structure, function, behavior, and growth. This review discusses examples, challenges, and benefits of using microfluidic systems to model ovaries, fallopian tubes, endometrium, and placenta. Additionally, this review also briefly discusses the use of these systems in studying the effects of endocrine disrupting chemicals and diseases such as ovarian cancer, preeclampsia, and polycystic ovarian syndrome.

Current understanding of autophagy in intrahepatic cholestasis of pregnancy

Intrahepatic cholestasis of pregnancy (ICP) is the most common liver disease during pregnancy. Manifested with pruritus and elevation in bile acids, the etiology of ICP is still poorly understood. Although ICP is considered relatively benign for the mother, increased rates of adverse fetal outcomes including sudden fetal demise are possible devastating outcomes associated with ICP. Limited understanding of the underlying mechanisms restricted treatment options and managements of ICP. In recent decades, evolving evidence indicated the significance of autophagy in pregnancy and pregnancy complications. Autophagy is an ancient self-defense mechanism which is essential for cell survival, differentiation and development. Autophagy has pivotal roles in embryogenesis, implantation, and maintenance of pregnancy, and is involved in the orchestration of diverse physiological and pathological cellular responses in patients with pregnancy complications. Recent advances in these research fields provide tantalizing targets on autophagy to improve the care of pregnant women. This review summarizes recent advances in understanding autophagy in ICP and its possible roles in the causation and prevention of ICP.

TRPV Protein Family-From Mechanosensing to Cancer Invasion

Biophysical cues from the cellular microenvironment are detected by mechanosensitive machineries that translate physical signals into biochemical signaling cascades. At the crossroads of extracellular space and cell interior are located several ion channel families, including TRP family proteins, that are triggered by mechanical stimuli and drive intracellular signaling pathways through spatio-temporally controlled Ca2+-influx. Mechanosensitive Ca2+-channels, therefore, act as critical components in the rapid transmission of physical signals into biologically compatible information to impact crucial processes during development, morphogenesis and regeneration. Given the mechanosensitive nature of many of the TRP family channels, they must also respond to the biophysical changes along the development of several pathophysiological conditions and have also been linked to cancer progression. In this review, we will focus on the TRPV, vanilloid family of TRP proteins, and their connection to cancer progression through their mechanosensitive nature.

Placental Villous Explant Culture 2.0: Flow Culture Allows Studies Closer to the In Vivo Situation

During pregnancy, freely floating placental villi are adapted to fluid shear stress due to placental perfusion with maternal plasma and blood. In vitro culture of placental villous explants is widely performed under static conditions, hoping the conditions may represent the in utero environment. However, static placental villous explant culture dramatically differs from the in vivo situation. Thus, we established a flow culture system for placental villous explants and compared commonly used static cultured tissue to flow cultured tissue using transmission and scanning electron microscopy, immunohistochemistry, and lactate dehydrogenase (LDH) and human chorionic gonadotropin (hCG) measurements. The data revealed a better structural and biochemical integrity of flow cultured tissue compared to static cultured tissue. Thus, this new flow system can be used to simulate the blood flow from the mother to the placenta and back in the most native-like in vitro system so far and thus can enable novel study designs.

A novel mechanosensitive channel controls osmoregulation, differentiation, and infectivity in Trypanosoma cruzi

The causative agent of Chagas disease undergoes drastic morphological and biochemical modifications as it passes between hosts and transitions from extracellular to intracellular stages. The osmotic and mechanical aspects of these cellular transformations are not understood. Here we identify and characterize a novel mechanosensitive channel in Trypanosoma cruzi (TcMscS) belonging to the superfamily of small-conductance mechanosensitive channels (MscS). TcMscS is activated by membrane tension and forms a large pore permeable to anions, cations, and small osmolytes. The channel changes its location from the contractile vacuole complex in epimastigotes to the plasma membrane as the parasites develop into intracellular amastigotes. TcMscS knockout parasites show significant fitness defects, including increased cell volume, calcium dysregulation, impaired differentiation, and a dramatic decrease in infectivity. Our work provides mechanistic insights into components supporting pathogen adaptation inside the host, thus opening the exploration of mechanosensation as a prerequisite for protozoan infectivity.

Dynamic placenta-on-a-chip model for fetal risk assessment of nanoparticles intended to treat pregnancy-associated diseases

Pregnant women often have to take medication either for pregnancy-related diseases or for previously existing medical conditions. Current maternal medications pose fetal risks due to off target accumulation in the fetus. Nanoparticles, engineered particles in the nanometer scale, have been used for targeted drug delivery to the site of action without off-target effects. This has opened new avenues for treatment of pregnancy-associated diseases while minimizing risks on the fetus. It is therefore instrumental to study the potential transfer of nanoparticles from the mother to the fetus. Due to limitations of in vivo and ex vivo models, an in vitro model mimicking the in vivo situation is essential. Placenta-on-a-chip provides a microphysiological recapitulation of the human placenta. Here, we reviewed the fetal risks associated with current therapeutic approaches during pregnancy, analyzed the advantages and limitations of current models used for nanoparticle assessment, and highlighted the current need for using dynamic placenta-on-a-chip models for assessing the safety of novel nanoparticle-based therapies during pregnancy.

Microfluidic Co-Culture Platform to Recapitulate the Maternal-Placental-Embryonic Axis

Safety assessment of the effects of developmental toxicants on pregnant women is challenging, and systemic effects in embryo-maternal interactions are largely unknown. However, most developmental toxicity studies rely on animal trials, while in vitro platforms that recapitulate the maternal-placental-embryonic axis are missing. Here, the development of a dedicated microfluidic device for co-cultivation of a placental barrier and 3D embryoid bodies to enable systemic toxicity testing at the embryo-maternal interface is reported. The microfluidic platform features simple handling and recuperation of both tissue models, which facilitates post-hoc in-depth analysis at the tissue and single-cell level. Gravity-driven flow enables inter-tissue communication through the liquid phase as well as simple and robust operation and renders the platform parallelizable. As a proof of concept and to demonstrate platform use for systemic embryotoxicity testing in vitro, maternal exposure to plastic microparticles is emulated, and microparticle effects on the embryo-placental co-culture are investigated.

Organ-on-a-chip technology for the study of the female reproductive system

Over the past decade, organs-on-a-chip and microphysiological systems have emerged as a disruptive in vitro technology for biopharmaceutical applications. By enabling new capabilities to engineer physiological living tissues and organ units in the precisely controlled environment of microfabricated devices, these systems offer great promise to advance the frontiers of basic and translational research in biomedical sciences. Here, we review an emerging body of interdisciplinary work directed towards harnessing the power of organ-on-a-chip technology for reproductive biology and medicine. The focus of this topical review is to provide an overview of recent progress in the development of microengineered female reproductive organ models with relevance to drug delivery and discovery. We introduce the engineering design of these advanced in vitro systems and examine their applications in the study of pregnancy, infertility, and reproductive diseases. We also present two case studies that use organ-on-a-chip design principles to model placental drug transport and hormonally regulated crosstalk between multiple female reproductive organs. Finally, we discuss challenges and opportunities for the advancement of reproductive organ-on-a-chip technology.

In vitro models replicating the human intestinal epithelium for absorption and metabolism studies: A systematic review

Absorption, distribution, metabolism and excretion (ADME) studies represent a fundamental step in the early stages of drug discovery. In particular, the absorption of orally administered drugs, which occurs at the intestinal level, has gained attention since poor oral bioavailability often led to failures for new drug approval. In this context, several in vitro preclinical models have been recently developed and optimized to better resemble human physiology in the lab and serve as an animal alternative to accomplish the 3Rs principles. However, numerous models are ineffective in recapitulating the key features of the human small intestine epithelium and lack of prediction potential for drug absorption and metabolism during the preclinical stage. In this review, we provide an overview of in vitro models aimed at mimicking the intestinal barrier for pharmaceutical screening. After briefly describing how the human small intestine works, we present i) conventional 2D synthetic and cell-based systems, ii) 3D models replicating the main features of the intestinal architecture, iii) micro-physiological systems (MPSs) reproducing the dynamic stimuli to which cells are exposed in the native microenvironment. In this review, we will highlight the benefits and drawbacks of the leading intestinal models used for drug absorption and metabolism studies.

Bioengineered Microphysiological Placental Models: Towards Improving Understanding of Pregnancy Health and Disease

Driven by a lack of appropriate human placenta models, recent years have seen the introduction of bioengineered in vitro models to better understand placental health and disease. Thus far, the focus has been on the maternal-foetal barrier. However, there are many other physiologically and pathologically significant aspects of the placenta that would benefit from state-of-the-art bioengineered models, in particular, integrating advanced culture systems with contemporary biological concepts such as organoids. This critical review defines and discusses the key parameters required for the development of physiologically relevant in vitro models of the placenta. Specifically, it highlights the importance of cell type, mechanical forces, and culture microenvironment towards the use of physiologically relevant models to improve the understanding of human placental function and dysfunction.

Collagen I Based Enzymatically Degradable Membranes for Organ-on-a-Chip Barrier Models

Organs-on-chips are microphysiological in vitro models of human organs and tissues that rely on culturing cells in a well-controlled microenvironment that has been engineered to include key physical and biochemical parameters. Some systems contain a single perfused microfluidic channel or a patterned hydrogel, whereas more complex devices typically employ two or more microchannels that are separated by a porous membrane, simulating the tissue interface found in many organ subunits. The membranes are typically made of synthetic and biologically inert materials that are then coated with extracellular matrix (ECM) molecules to enhance cell attachment. However, the majority of the material remains foreign and fails to recapitulate the native microenvironment of the barrier tissue. Here, we study microfluidic devices that integrate a vitrified membrane made of collagen-I hydrogel (VC). The biocompatibility of this membrane was confirmed by growing a healthy population of stem cell derived endothelial cells (iPSC-EC) and immortalized retinal pigment epithelium (ARPE-19) on it and assessing morphology by fluorescence microscopy. Moreover, VC membranes were subjected to biochemical degradation using collagenase II. The effects of this biochemical degradation were characterized by the permeability changes to fluorescein. Topographical changes on the VC membrane after enzymatic degradation were also analyzed using scanning electron microscopy. Altogether, we present a dynamically bioresponsive membrane integrated in an organ-on-chip device with which disease-related ECM remodeling can be studied.

Human TRPV6-pathies caused by gene mutations

The TRP-family of ion channels consists of 27 members in humans. Most TRP channels are non- selective cation channels with the exception of TRPV5 and TRPV6 which exhibit a high permeability for Ca²⁺ ions. A functional channel is formed by 4 identical subunits [1]. A growing number of mutations are present in human TRPV6 genes which alter channel function and can lead to elevated blood levels of the parathyroid hormone accompanied by transient hyperparathyroidism. Recent publications suggest that TRPV6 mutations could also trigger non-alcoholic chronic pancreatitis. This review summarises the consequences of these mutations within the TRPV6 gene.

Advances in Engineering Human Tissue Models

Research in cell biology greatly relies on cell-based in vitro assays and models that facilitate the investigation and understanding of specific biological events and processes under different conditions. The quality of such experimental models and particularly the level at which they represent cell behavior in the native tissue, is of critical importance for our understanding of cell interactions within tissues and organs. Conventionally, in vitro models are based on experimental manipulation of mammalian cells, grown as monolayers on flat, two-dimensional (2D) substrates. Despite the amazing progress and discoveries achieved with flat biology models, our ability to translate biological insights has been limited, since the 2D environment does not reflect the physiological behavior of cells in real tissues. Advances in 3D cell biology and engineering have led to the development of a new generation of cell culture formats that can better recapitulate the in vivo microenvironment, allowing us to examine cells and their interactions in a more biomimetic context. Modern biomedical research has at its disposal novel technological approaches that promote development of more sophisticated and robust tissue engineering in vitro models, including scaffold- or hydrogel-based formats, organotypic cultures, and organs-on-chips. Even though such systems are necessarily simplified to capture a particular range of physiology, their ability to model specific processes of human biology is greatly valued for their potential to close the gap between conventional animal studies and human (patho-) physiology. Here, we review recent advances in 3D biomimetic cultures, focusing on the technological bricks available to develop more physiologically relevant in vitro models of human tissues. By highlighting applications and examples of several physiological and disease models, we identify the limitations and challenges which the field needs to address in order to more effectively incorporate synthetic biomimetic culture platforms into biomedical research.

Development of an Organ-on-a-Chip-Device for Study of Placental Pathologies

The human placenta plays a key role in reproduction and serves as a major interface for maternofetal exchange of nutrients. Study of human placenta pathology presents a great experimental challenge because it is not easily accessible. In this paper, a 3D placenta-on-a-chip model is developed by bioengineering techniques to simulate the placental interface between maternal and fetal blood in vitro. In this model, trophoblasts cells and human umbilical vein endothelial cells are cultured on the opposite sides of a porous polycarbonate membrane, which is sandwiched between two microfluidic channels. Glucose diffusion across this barrier is analyzed under shear flow conditions. Meanwhile, a numerical model of the 3D placenta-on-a-chip model is developed. Numerical results of concentration distributions and the convection-diffusion mass transport is compared to the results obtained from the experiments for validation. Finally, effects of flow rate and membrane porosity on glucose diffusion across the placental barrier are studied using the validated numerical model. The placental model developed here provides a potentially helpful tool to study a variety of other processes at the maternal-fetal interface, for example, effects of drugs or infections like malaria on transport of various substances across the placental barrier.

Cytoskeleton induced the changes of microvilli and mechanical properties in living cells by atomic force microscopy

The cytoskeleton acts as a scaffold for membrane protrusion, such as microvilli. However, the relationship between the characteristics of microvilli and cytoskeleton remains poorly understood under the physiological state. To investigate the role of the cytoskeleton in regulating microvilli and cellular mechanical properties, atomic force microscopy (AFM) was used to detect the dynamic characteristics of microvillus morphology and elastic modulus of living HeLa cells. First, HeLa and MCF-7 cell lines were stained with Fluor-488-phalloidin and microtubules antibody. Then, the microvilli morphology was analyzed by high-resolution images of AFM in situ. Furthermore, changes in elastic modulus were investigated by the force curve of AFM. Fluorescence microscopy and AFM results revealed that destroyed microfilaments led to a smaller microvilli size, whereas the increase in the aggregation and number of microfilaments led to a larger microvilli size. The destruction and aggregation of microfilaments remarkably affected the mechanical properties of HeLa cells. Microtubule-related drugs induced the change of microtubule, but we failed to note significant differences in microvilli morphology and mechanical properties of cells. In summary, our results unraveled the relationship between microfilaments and the structure of microvilli and Young's modulus in living HeLa cells, which would contribute to the further understanding of the physiological function of the cytoskeleton in vivo.

Targeting Mechanotransduction in Osteosarcoma: A Comparative Oncology Perspective

Mechanotransduction is the process in which cells can convert extracellular mechanical stimuli into biochemical changes within a cell. While this a normal process for physiological development and function in many organ systems, tumour cells can exploit this process to promote tumour progression. Here we summarise the current state of knowledge of mechanotransduction in osteosarcoma (OSA), the most common primary bone tumour, referencing both human and canine models and other similar mesenchymal malignancies (e.g., Ewing sarcoma). Specifically, we discuss the mechanical properties of OSA cells, the pathways that these cells utilise to respond to external mechanical cues, and mechanotransduction-targeting strategies tested in OSA so far. We point out gaps in the literature and propose avenues to address them. Understanding how the physical microenvironment influences cell signalling and behaviour will lead to the improved design of strategies to target the mechanical vulnerabilities of OSA cells.

High sucrose diet induces morphological, structural and functional impairments in the renal tubules of Drosophila melanogaster: A model for studying type-2 diabetes mediated renal tubular dysfunction

Continuous feeding of high dietary sugar is strongly associated with type 2 diabetes (T2D) and its secondary complications. Diabetic nephropathy (DN) is a major secondary complication that leads to glomerular and renal tubular dysfunction. The present study is aimed to investigate the effects of chronic exposure of high sugar diet (HSD) on renal tubules. Malpighian tubules (MTs), a renal organ of Drosophila, were used as a model in the study. Feeding of HSD develops T2D condition in Drosophila. The MTs showed structural abnormalities in 20 days of HSD fed flies. Impaired insulin signaling, oxidative stress, enhanced levels of AGE-RAGE and induction of apoptosis were observed in the MTs of these flies. Further, altered expression of transporters, enhanced uric acid level and reduced fluid secretion rate confirmed the impaired function of MTs in these flies. RNA-seq and RT-PCR analyses in the MTs of HSD fed-and control-flies revealed the altered expression of candidate genes that regulate several important pathways including extracellular matrix (ECM), advanced glycation end products-receptor for advanced glycation end products (AGE-RAGE), transforming growth factor β (TGF-β), galactose, starch and sucrose metabolism that are well known mediators of renal tubular dysfunction in DN patients. Disruption of insulin signaling in the MTs also causes renal tubular dysfunction similar to HSD fed flies. Overall, the study suggests that phenotypes observed in the MTs of HSD fed flies recapitulate several hallmarks of renal tubular dysfunction in DN patients. Therefore, we conclude that MTs of HSD fed flies may be used for deciphering the underlying mechanisms of T2D mediated renal tubular dysfunction.

Autoinhibition of TRPV6 Channel and Regulation by PIP2

Transient receptor potential vanilloid 6 (TRPV6), a calcium-selective channel possessing six transmembrane domains (S1-S6) and intracellular N and C termini, plays crucial roles in calcium absorption in epithelia and bone and is involved in human diseases including vitamin-D deficiency, osteoporosis, and cancer. The TRPV6 function and regulation remain poorly understood. Here we show that the TRPV6 intramolecular S4-S5 linker to C-terminal TRP helix (L/C) and N-terminal pre-S1 helix to TRP helix (N/C) interactions, mediated by Arg470:Trp593 and Trp321:Ile597 bonding, respectively, are autoinhibitory and are required for maintaining TRPV6 at basal states. Disruption of either interaction by mutations or blocking peptides activates TRPV6. The N/C interaction depends on the L/C interaction but not reversely. Three cationic residues in S5 or C terminus are involved in binding PIP2 to suppress both interactions thereby activating TRPV6. This study reveals "PIP2 - intramolecular interactions" regulatory mechanism of TRPV6 activation-autoinhibition, which will help elucidating the corresponding mechanisms in other TRP channels.

Inspired by the human placenta: a novel 3D bioprinted membrane system to create barrier models

Barrier organ models need a scaffold structure to create a two compartment culture. Technical filter membranes used most often as scaffolds may impact cell behaviour and present a barrier themselves, ultimately limiting transferability of test results. In this work we present an alternative for technical filter membrane systems: a 3D bioprinted biological membrane in 24 well format. The biological membrane, based on extracellular matrix (ECM), is highly permeable and presents a natural 3D environment for cell culture. Inspired by the human placenta we established a coculture of a trophoblast-derived cell line (BeWo b30), together with primary placental fibroblasts within the biological membrane (simulating villous stroma) and primary human placental endothelial cells-representing three cellular components of the human placental villus. All cell types maintained their cell type specific marker expression after two weeks of coculture on the biological membrane. In permeability assays the trophoblast layer developed a barrier on the biological membrane, which was even more pronounced when cocultured with fibroblasts. In this work we present a filter membrane free scaffold, we characterize its properties and assess its suitability for cell culture and barrier models. Further we show a novel placenta inspired model in a complex bioprinted coculture. In the absence of an artificial filter membrane, we demonstrate barrier architecture and functionality.

Microphysiological systems of the placental barrier

Methods to evaluate maternal-fetal transport across the placental barrier have generally involved clinical observations after-the-fact, ex vivo perfused placenta studies, or in vitro Transwell assays. Given the ethical and technical limitations in these approaches, and the drive to understand fetal development through the lens of transport-induced injury, such as with the examples of thalidomide and Zika Virus, efforts to develop novel approaches to study these phenomena have expanded in recent years. Notably, within the past 10 years, placental barrier models have been developed using hydrogel, bioreactor, organ-on-a-chip, and bioprinting approaches. In this review, we discuss the biology of the placental barrier and endeavors to recapitulate this barrier in vitro using these approaches. We also provide analysis of current limitations to drug discovery in this context, and end with a future outlook.

The unique applicability of the human placenta to the Adverse Outcome Pathway (AOP) concept: the placenta provides fundamental insights into human organ functions at multiple levels of biological organization

Despite the short lifespan of the human placenta, the proper formation and function of the organ is of crucial importance for fetal development. Placental dysfunction increases the risk of complications for mother and child during pregnancy and childbirth and beyond as it predisposes to fetal programming. The placenta is an upstream organ of the fetus. It performs the functions of fetal lungs, liver, intestines, kidneys and glands as long as these organs are not fully functional. Furthermore, it is the only human organ that is non-invasively available either after elective abortion or after birth. This is a crucial point given that the conceptual framework of Adverse Outcome Pathway (AOP) requires data on organ function. In vitro and ex vivo placental studies, combined with epidemiological and clinical data on pregnant women, newborns, and infants can uniquely cover all levels of information needed to develop new AOPs and complement existing AOPs related to reproductive toxicity and beyond. To stimulate further research in this area and to support researchers in future studies dealing with the development of AOPs related to the placenta, this review first gives a brief description of placental structure, placental development and relevant pregnancy diseases. The state of knowledge about the available placental models, their particularities and limitations are briefly discussed. Finally, the use of placental research for the development of AOPs is presented with an illustrative example.

Computational modeling of the interactions between the maternal and fetal circulations in human pregnancy

In pregnancy, fetal growth is supported by its placenta. In turn, the placenta is nourished by maternal blood, delivered from the uterus, in which the vasculature is dramatically transformed to deliver this blood an ever increasing volume throughout gestation. A healthy pregnancy is thus dependent on the development of both the placental and maternal circulations, but also the interface where these physically separate circulations come in close proximity to exchange gases and nutrients between mum and baby. As the system continually evolves during pregnancy, our understanding of normal vascular anatomy, and how this impacts placental exchange function is limited. Understanding this is key to improve our ability to understand, predict, and detect pregnancy pathologies, but presents a number of challenges, due to the inaccessibility of the pregnant uterus to invasive measurements, and limitations in the resolution of imaging modalities safe for use in pregnancy. Computational approaches provide an opportunity to gain new insights into normal and abnormal pregnancy, by connecting observed anatomical changes from high-resolution imaging to function, and providing metrics that can be observed by routine clinical ultrasound. Such advanced modeling brings with it challenges to scale detailed anatomical models to reflect organ level function. This suggests pathways for future research to provide models that provide both physiological insights into pregnancy health, but also are simple enough to guide clinical focus. We the review evolution of computational approaches to understanding the physiology and pathophysiology of pregnancy in the uterus, placenta, and beyond focusing on both opportunities and challenges. This article is categorized under: Reproductive System Diseases >Computational Models.

Go with the Flow-Trophoblasts in Flow Culture

With establishment of uteroplacental blood flow, the perfused fetal chorionic tissue has to deal with fluid shear stress that is produced by hemodynamic forces across different trophoblast subtypes. Amongst many other cell types, trophoblasts are able to sense fluid shear stress through mechanotransduction. Failure in the adaption of trophoblasts to fluid shear stress is suggested to contribute to pregnancy disorders. Thus, in the past twenty years, a significant body of work has been devoted to human- and animal-derived trophoblast culture under microfluidic conditions, using a rather broad range of different fluid shear stress values as well as various different flow systems, ranging from commercially 2D to customized 3D flow culture systems. The great variations in the experimental setup reflect the general heterogeneity in blood flow through different segments of the uteroplacental circulation. While fluid shear stress is moderate in invaded uterine spiral arteries, it drastically declines after entrance of the maternal blood into the wide cavity of the intervillous space. Here, we provide an overview of the increasing body of evidence that substantiates an important influence of maternal blood flow on several aspects of trophoblast physiology, including cellular turnover and differentiation, trophoblast metabolism, as well as endocrine activity, and motility. Future trends in trophoblast flow culture will incorporate the physiological low oxygen conditions in human placental tissue and pulsatile blood flow in the experimental setup. Investigation of trophoblast mechanotransduction and development of mechanosome modulators will be another intriguing future direction.

Physiological and pathological regulation of autophagy in pregnancy

Autophagy exists widely in eukaryotic cells and is regulated by a variety of molecular mechanisms. Its physiological functions include providing energy, maintaining cell homeostasis, and promoting apoptosis of abnormal cells. At present, the regulation of autophagy in tumor, degenerative disease, and cardiovascular disease has attracted much attention. Gradually, the role of autophagy in pregnancy tends to be valued. The previous literature has shown that autophagy can influence the occurrence and maintenance of pregnancy from three aspects: embryo (affecting the process of fertilization and embryonic development and the function of trophoblast cells), maternal (decidualization), and maternal-to-fetal immune crosstalk. Undoubtedly, abnormalities in autophagy levels are associated with a variety of pregnancy complications, such as preeclampsia, fetal growth restriction, and preterm delivery which have been proven by human, animal, and in vitro experiments. The regulation of autophagy is expected to be a target for the treatment of these pregnancy complications. This article reviews the research on autophagy, especially about its physiological and pathological regulation during pregnancy.

A Novel Human Placental Barrier Model Based on Trophoblast Stem Cells Derived from Human Induced Pluripotent Stem Cells

The placenta acts as an interface between the fetus and the expecting mother. Various drugs and environmental pollutants can pass through the human placental barrier and may harm the developing fetus. Currently available in vitro placental barrier models are often inadequate, because they are lacking the functional trophoblast cells. Therefore, we developed and characterized a new human placental model using trophoblast stem cells (TSCs) derived from human induced pluripotent stem cells. Umbilical vein endothelial cells, fibroblast, and TSCs were cocultured using micromesh cell culture technique. These cells formed a tight three-layered structure. This coculture model induced progressive fusion of TSCs and formed a syncytialized epithelium that resembles the in vivo syncytiotrophoblast. Our model allowed the cultured trophoblasts to form microvilli and to reconstitute expression and physiological localization of membrane transport proteins, such as transporter for ATP-binding cassette subfamily B member 1, ATP-binding cassette subfamily C member 3, and glucose transporter-1. Drug permeability assays were performed using five compounds. The results from the permeability assays were comparable to the ones obtained with ex vivo placental models. In conclusion, we developed a novel coculture model mimicking human placenta that provides a useful tool for the studies on transfer of substances between the mother and fetus. Impact statement Compared with the currently available in vitro placental barrier models, a novel three-dimensional coculture placental barrier model presented in this study morphologically and functionally modeled the true placental barrier. The use of human trophoblast stem cells from human induced pluripotent stem cells substantially improved the current model. The use of micromesh sheet as a bioscaffold facilitated the formation of a good multilayer structure, which is closer to the physical appearance of the placenta observed in human.

Uptake of silica particulate drug carriers in an intestine-on-a-chip: towards a better in vitro model of nanoparticulate carrier and mucus interactions

Micro and nano-particulate carriers have potential to increase bioavailability of oral drugs, but must first overcome the mucus barrier of the intestinal epithelium to facilitate absorption and entry to systemic circulation. We report on mucus-silica nanoparticulate carrier interactions in an in vitro intestine-on-a-chip (IOAC) microfluidic model. Caco-2 cells cultured within the IOAC model recapitulate the morphology of the human intestinal epithelium that is currently lacking in traditional static Transwell models. Fine control over the cell culture conditions produced a mucus layer, previously problematic to achieve without employing cell co-culture. The microdevice design also allowed for direct imaging of silica particulate carrier (40-700 nm) uptake through the mucus and cellular monolayer. PEGylated particulate carriers penetrated more readily through the mucus layer compared to non-PEGylated particulate carriers while larger particulate carriers tended to retard particulate carrier penetration through a dense mucus mesh. This was confirmed via imaging flow cytometry and UV-fluorescence spectroscopy. The IOAC also demonstrated the ability to mimic intestinal peristaltic fluidic conditions, which in turn affects the particulate carrier uptake. This in vitro IOAC model has potential to directly elucidate mucus interactions and uptake mechanisms for a range of drug carrier systems.

Organs-On-Chip Models of the Female Reproductive System

Microfluidic-based technology attracts great interest in cell biology and medicine, in virtue of the ability to better mimic the in vivo cell microenvironment compared to conventional macroscale cell culture platforms. Recent Organs-on-chip (OoC) models allow to reproduce in vitro tissue and organ-level functions of living organs and systems. These models have been applied for the study of specific functions of the female reproductive tract, which is composed of several organs interconnected through intricate endocrine pathways and communication mechanisms. To date, a disease and toxicology study of this system has been difficult to perform. Thus, there is a compelling need to develop innovative platforms for the generation of disease model and for performing drug toxicity/screening in vitro studies. This review is focused on the analysis of recently published OoC models that recreate pathological and physiological characteristics of the female reproductive organs and tissues. These models aim to be used to assess changes in metabolic activity of the specific cell types and the effect of exposure to hormonal treatment or chemical substances on some aspects of reproduction and fertility. We examined these models in terms of device specifications, operating procedures, accuracy for studying the biochemical and functional activity of living tissues and the paracrine signalling that occurs within the different tissues. These models represent a powerful tool for understanding important diseases and syndromes affecting women all around the world. Immediate adoption of these models will allow to clarify diseases, causes and adverse events occurring during pregnancy such as pre-eclampsia, infertility or preterm birth, endometriosis and infertility.

Biosensors for Detection of Human Placental Pathologies: A Review of Emerging Technologies and Current Trends

Substantial growth in the biosensor research has enabled novel, sensitive and point-of-care diagnosis of human diseases in the last decade. This paper presents an overview of the research in the field of biosensors that can potentially predict and diagnosis of common placental pathologies. A survey of biomarkers in maternal circulation and their characterization methods is presented, including markers of oxidative stress, angiogenic factors, placental debris, and inflammatory biomarkers that are associated with various pathophysiological processes in the context of pregnancy complications. Novel biosensors enabled by microfluidics technology and nanomaterials is then reviewed. Representative designs of plasmonic and electrochemical biosensors for highly sensitive and multiplexed detection of biomarkers, as well as on-chip sample preparation and sensing for automatic biomarker detection are illustrated. New trends in organ-on-a-chip based placental disease models are highlighted to illustrate the capability of these in vitro disease models in better understanding the complex pathophysiological processes, including mass transfer across the placental barrier, oxidative stress, inflammation, and malaria infection. Biosensor technologies that can be potentially embedded in the placental models for real time, label-free monitoring of these processes and events are suggested. Merger of cell culture in microfluidics and biosensing can provide significant potential for new developments in advanced placental models, and tools for diagnosis, drug screening and efficacy testing.

Serum levels of epithelial-derived mediators and interleukin-4/interleukin-13 signaling after bronchial challenge with Dermatophagoides pteronyssinus in patients with allergic asthma

Allergens are the main trigger that enhances airway type 2 inflammation, and the epithelium is the first line of defense that reacts to its exposure. Therefore, epithelial-derived mediators, such as interleukin (IL)-25, IL-33, thymic stromal lymphopoietin (TSLP) and ezrin, may play a role as alarmins in IL-4/IL-13 signaling in allergic asthma (AA). We investigated the serum levels of IL-25, IL-33, TSLP, ezrin, IL-4 and IL-13, after bronchial challenge with Dermatophagoides pteronyssinus in patients with AA. We examined 18 subjects: nine steroid-free stable patients with AA sensitized to D. pteronyssinus and nine non-atopic healthy subjects (HS). Bronchial allergen challenge was performed using inhaled D. pteronyssinus allergen. IL-4, IL-13, IL-25, IL-33, TSLP and ezrin levels in serum were measured by ELISA at two time points - before and 24 hours after bronchial allergen challenge. The serum levels of IL-25, TSLP and ezrin did not differ between AA and HS groups at baseline. However, after allergen exposure, significant increases in serum levels of IL-25, TSLP and ezrin were observed only in patients with AA. The serum level of IL-33 at baseline was significantly higher in the AA group compared with HS, but the allergen challenge did not provoke an increase of this cytokine in any group. IL-4 and IL-13 levels were significantly higher at baseline in the AA group compared with HS and, after allergen exposure, were significantly increased in the AA group, with no effect on HS. Thus, the epithelial-derived mediators IL-25, TSLP and ezrin, via IL4/IL13 signaling, enhance type 2 inflammation after bronchial challenge with D. pteronyssinus in AA.

Drug transport across the human placenta: review of placenta-on-a-chip and previous approaches

In the past few decades, the placenta became a very controversial topic that has had many researchers and pharmacists discussing the significance of the effects of pharmaceutical drug intake and how it is a possible leading cause towards birth defects. The creation of an in vitro microengineered model of the placenta can be used to replicate the interactions between the mother and fetus, specifically pharmaceutical drug intake reactions. As the field of nanotechnology significantly continues growing, nanotechnology will become more apparent in the study of medicine and other scientific disciplines, specifically microengineering applications. This review is based on past and current research that compares the feasibility and testing of the placenta-on-a-chip microengineered model to the previous and underdeveloped in vivo and ex vivo approaches. The testing of the practicality and effectiveness of the in vitro, in vivo and ex vivo models requires the experimentation of prominent pharmaceutical drugs that most mothers consume during pregnancy. In this case, these drugs need to be studied and tested more often. However, there are challenges associated with the in vitro, in vivo and ex vivo processes when developing a practical placental model, which are discussed in further detail.

Differentiation of derived rabbit trophoblast stem cells under fluid shear stress to mimic the trophoblastic barrier

BACKGROUND

The placenta controls exchanges between the mother and the fetus and therefore fetal development and growth. The maternal environment can lead to disturbance of placental functions, with consequences on the health of the offspring. Since the rabbit placenta is very close to that of humans, rabbit models can provide biomedical data to study human placental function. Yet, to limit the use of animal experiments and to investigate the mechanistic aspects of placental function, we developed a new cell culture model in which rabbit trophoblast cells are differentiated from rabbit trophoblast stem cells.

METHODS

Rabbit trophoblast stems cells were derived from blastocysts and differentiated onto a collagen gel and in the presence of a flow of culture medium to mimic maternal blood flow. Transcriptome analysis was performed on the stem and differentiated cells.

RESULTS

Our culture model allows the differentiation of trophoblast stem cells. In particular, the fluid shear stress enhances microvilli formation on the differentiated cell surface, lipid droplets formation and fusion of cytotrophoblasts into syncytiotrophoblasts. In addition, the transcriptome analysis confirms the early trophoblast identity of the derived stem cells and reveals upregulation of signaling pathways involved in trophoblast differentiation.

CONCLUSION

Thereby, the culture model allows mimicking the in vivo conditions in which maternal blood flow exerts a shear stress on trophoblast cells that influences their phenotype.

GENERAL SIGNIFICANCE

Our culture model can be used to study the differentiation of trophoblast stem cells into cytotrophoblasts and syncytiotrophoblasts, as well as the trophoblast function in physiological and pathological conditions.

Transgelin-2: Biochemical and Clinical Implications in Cancer and Asthma

Transgelin-2 has been regarded as an actin-binding protein that induces actin gelation and regulates actin cytoskeleton. However, transgelin-2 has recently been shown to relax the myosin cytoskeleton of the airway smooth muscle cells by acting as a receptor for extracellular metallothionein-2. From a clinical perspective, these results support transgelin-2 as a promising therapeutic target for diseases such as cancer and asthma. The inhibition of transgelin-2 prevents actin gelation and thereby cancer cell proliferation, invasion, and metastasis. Conversely, the activation of transgelin-2 with specific agonists relaxes airway smooth muscles and reduces pulmonary resistance in asthma. Here, we review new studies on the biochemical properties of transgelin-2 and discuss their clinical implications for the treatment of immune, oncogenic, and respiratory disorders.

Emerging concepts of shear stress in placental development and function

Blood flow, and the force it generates, is critical to placental development and function throughout pregnancy. This mechanical stimulation of cells by the friction generated from flow is called shear stress (SS) and is a fundamental determinant of vascular homeostasis, regulating remodelling and vasomotor tone. This review describes how SS is fundamental to the establishment and regulation of the blood flow through the uteroplacental and fetoplacental circulations. Amongst the most recent findings is that alongside the endothelium, embryonic stem cells and the villous trophoblast are mechanically sensitive. A complex balance of forces is required to enable effective establishment of the uteroplacental circulation, while protecting the embryo and placental villi. SS also generates flow-mediated vasodilatation through the release of endothelial nitric oxide, a process vital for adequate placental blood flow. The identification of SS sensors and the mechanisms governing how the force is converted into biochemical signals is a fast-paced area of research, with multiple cellular components under investigation. For example, the Piezo1 ion channel is mechanosensitive in a variety of tissues including the fetoplacental endothelium. Enhanced Piezo1 activity has been demonstrated in response to the Yoda1 agonist molecule, suggesting the possibility for developing tools to manipulate these channels. Whether such agents might progress to novel therapeutics to improve blood flow through the placenta requires further consideration and research.

Ezrin Orchestrates Signal Transduction in Airway Cells

Ezrin is a critical structural protein that organizes receptor complexes and orchestrates their signal transduction. In this study, we review the ezrin-meditated regulation of critical receptor complexes, including the epidermal growth factor receptor (EGFR), CD44, vascular cell adhesion molecule (VCAM), and the deleted in colorectal cancer (DCC) receptor. We also analyze the ezrin-meditated regulation of critical pathways associated with asthma, such as the RhoA, Rho-associated protein kinase (ROCK), and protein kinase A (cAMP/PKA) pathways. Mounting evidence suggests that ezrin plays a role in controlling airway cell function and potentially contributes to respiratory diseases. Ezrin can participate in asthma pathogenesis by affecting bronchial epithelium repair, T lymphocyte regulation, and the contraction of the airway smooth muscle cells. These studies provide new insights for the design of novel therapeutic strategies for asthma treatment.

Maternal Transient Receptor Potential Vanilloid 6 (Trpv6) Is Involved In Offspring Bone Development

Embryonic growth and bone development depend on placental Ca²⁺ transport across the feto-maternal barrier to supply minerals to the fetus. The individual factors and cellular mechanisms that regulate placental Ca²⁺ transfer, however, are only beginning to emerge. We find that the Ca²⁺ -selective transient receptor potential vanilloid 6 (TRPV6) channel is expressed in trophoblasts of the fetal labyrinth, in the yolk sac, and in the maternal part of the placenta. Lack of functional TRPV6 channels in the mother leads to a reduced Ca²⁺ content in both placenta and embryo. Ca²⁺ uptake in trophoblasts is impaired in the absence of Trpv6. Trpv6-deficient embryos are smaller, have a lower body weight, and shorter and less calcified femurs. The altered cortical bone microarchitecture persists in adulthood. We show that TRPV6's Ca²⁺ -conducting property causes this embryonic and bone phenotype. Our results show that TRPV6 is necessary for the Ca²⁺ uptake in trophoblasts and that TRPV6 deficiency in the placenta leads to reduced embryo growth, minor bone calcification, and impaired bone development. © 2019 American Society for Bone and Mineral Research.

From Petri Dishes to Organ on Chip Platform: The Increasing Importance of Machine Learning and Image Analysis

The increasing interest for microfluidic devices in medicine and biology has opened the way to new time-lapse microscopy era where the amount of images and their acquisition time will become crucial. In this optic, new data analysis algorithms have to be developed in order to extract novel features of cell behavior and cell-cell interactions. In this brief article, we emphasize the potential strength of a new paradigm arising in the integration of microfluidic devices (i.e., organ on chip), time-lapse microscopy analysis, and machine learning approaches. Some snapshots of previous case studies in the context of immunotherapy are included as proof of concepts of the proposed strategies while a visionary description concludes the work foreseeing future research and applicative scenarios.

Perspective: The promise of multi-cellular engineered living systems

Recent technological breakthroughs in our ability to derive and differentiate induced pluripotent stem cells, organoid biology, organ-on-chip assays, and 3-D bioprinting have all contributed to a heightened interest in the design, assembly, and manufacture of living systems with a broad range of potential uses. This white paper summarizes the state of the emerging field of "multi-cellular engineered living systems," which are composed of interacting cell populations. Recent accomplishments are described, focusing on current and potential applications, as well as barriers to future advances, and the outlook for longer term benefits and potential ethical issues that need to be considered.

Perfusable and stretchable 3D culture system for skin-equivalent

This study describes a perfusable and stretchable culture system for a skin-equivalent. The system is comprised of a flexible culture device equipped with connections that fix vascular channels of the skin-equivalent and functions as an interface for an external pump. Furthermore, a stretching apparatus for the culture device can be fabricated using rapid prototyping technologies, which allows for easy modifications of stretching parameters. When cultured under dynamically stretching and perfusion conditions, the skin-equivalent exhibits improved morphology. The epidermal layer becomes thicker and more differentiated than that cultured without the stretching stimuli or under statically-stretched conditions, and the dermal layer was more densely populated with dermal fibroblasts than that cultured without perfusion due to the nutrient and oxygen supply by perfusion via the vascular channels. Therefore, the system is useful for the improvement and biological studies of skin-equivalents.