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1.
Hepatology ; 2024 Jul 02.
Article in English | MEDLINE | ID: mdl-38954820

ABSTRACT

Alpha-1 antitrypsin deficiency (A1ATD) is a life-threatening condition caused by inheritance of the SERPINA1 'Z' genetic variant (PiZ) driving AAT protein misfolding in hepatocytes. There remain no approved medicines for this disease. Here, we report the results of a small molecule screen performed in patient derived iPSC-hepatocytes that identified Leucine-rich repeat kinase-2 (LRRK2) as a potentially new therapeutic target. Of the commercially available LRRK2 inhibitors tested, we identified CZC-25146, a candidate with favorable pharmacokinetic properties, as being capable of reducing polymer load, increasing normal AAT secretion, and reducing inflammatory cytokines in both cells and PiZ mice. Mechanistically, this effect was achieved through induction of autophagy. Our findings support the use of CZC-25146 and LRRK2 inhibitors in hepatic proteinopathy research and their further investigation as novel therapeutic candidates for A1ATD.

2.
J Med Virol ; 96(3): e29546, 2024 Mar.
Article in English | MEDLINE | ID: mdl-38516804

ABSTRACT

Tapasin, a crucial molecular chaperone involved viral antigen processing and presentation, plays an important role in antivirus immunity. However, its impact on T cell differentiation in the context of virus clearance remains unclear. In this study, we employed induced pluripotent stem cells to differentiate into hepatocyte-like cell, which were subsequently inserted to the inverted colloidal crystal scaffolds, thus establishing a hepatocyte organoid (HO). By inoculating hepatitis B virus (HBV) particles in the system, we successfully engineered a robust in vitro HBV infection model for at least 3 weeks. Furthermore, we aimed to explore the effects of lentivirus-mediated short hairpin RNA (shRNA) targeting human Tapasin on the differentiation and antiviral function of CD8+ T cells. Specifically, we transfected dendritic cells (DCs) with Tapasin-shRNA and cocultured with T cells. The results demonstrated that Tapasin-shRNA transfected DCs effectively suppressed T cell proliferation and impeded HBV-specific cytotoxic T lymphocyte responses. Our investigation also revealed the role of mTOR pathway activation in reducing autophagy activity within CD8+ T cells. Expressions of autophagy-related proteins, beclin-1, LC3II/LC3I were decreased and PI3K/AKT/mTOR activity was increased in Tapasin-shRNA group. Collectively, our findings elucidate that shRNA targeting the Tapasin gene within DCs inhibits T cell differentiation by reducing autophagy activity to hamper viral clearance in the HBV-infected HO.


Subject(s)
Dendritic Cells , Hepatitis B , Membrane Transport Proteins , Humans , Autophagy/genetics , CD8-Positive T-Lymphocytes/metabolism , Dendritic Cells/metabolism , Down-Regulation , Hepatitis B/metabolism , Hepatitis B Core Antigens/genetics , Hepatitis B virus , Hepatocytes/metabolism , Induced Pluripotent Stem Cells , Membrane Transport Proteins/genetics , Membrane Transport Proteins/metabolism , Phosphatidylinositol 3-Kinases/metabolism , RNA, Small Interfering/genetics , TOR Serine-Threonine Kinases/genetics , TOR Serine-Threonine Kinases/metabolism , Organoids/metabolism , Organoids/virology
3.
Biomaterials ; 293: 121982, 2023 02.
Article in English | MEDLINE | ID: mdl-36640555

ABSTRACT

Human pluripotent stem cell-derived hepatocytes (hPSC-Heps) may be suitable for treating liver diseases, but differentiation protocols often fail to yield adult-like cells. We hypothesised that replicating healthy liver niche biochemical and biophysical cues would produce hepatocytes with desired metabolic functionality. Using 2D synthetic hydrogels which independently control mechanical properties and biochemical cues, we found that culturing hPSC-Heps on surfaces matching the stiffness of fibrotic liver tissue upregulated expression of genes for RGD-binding integrins, and increased expression of YAP/TAZ and their transcriptional targets. Alternatively, culture on soft, healthy liver-like substrates drove increases in cytochrome p450 activity and ureagenesis. Knockdown of ITGB1 or reducing RGD-motif-containing peptide concentration in stiff hydrogels reduced YAP activity and improved metabolic functionality; however, on soft substrates, reducing RGD concentration had the opposite effect. Furthermore, targeting YAP activity with verteporfin or forskolin increased cytochrome p450 activity, with forskolin dramatically enhancing urea synthesis. hPSC-Heps could also be successfully encapsulated within RGD peptide-containing hydrogels without negatively impacting hepatic functionality, and compared to 2D cultures, 3D cultured hPSC-Heps secreted significantly less fetal liver-associated alpha-fetoprotein, suggesting furthered differentiation. Our platform overcomes technical hurdles in replicating the liver niche, and allowed us to identify a role for YAP/TAZ-mediated mechanosensing in hPSC-Hep differentiation.


Subject(s)
Hepatocytes , Oligopeptides , Humans , Colforsin/metabolism , Colforsin/pharmacology , Cell Differentiation , Oligopeptides/pharmacology , Oligopeptides/metabolism , Cytochrome P-450 Enzyme System/metabolism , Cytochrome P-450 Enzyme System/pharmacology , Hydrogels/chemistry
4.
Nat Metab ; 4(12): 1812-1829, 2022 12.
Article in English | MEDLINE | ID: mdl-36536133

ABSTRACT

RNA alternative splicing (AS) expands the regulatory potential of eukaryotic genomes. The mechanisms regulating liver-specific AS profiles and their contribution to liver function are poorly understood. Here, we identify a key role for the splicing factor RNA-binding Fox protein 2 (RBFOX2) in maintaining cholesterol homeostasis in a lipogenic environment in the liver. Using enhanced individual-nucleotide-resolution ultra-violet cross-linking and immunoprecipitation, we identify physiologically relevant targets of RBFOX2 in mouse liver, including the scavenger receptor class B type I (Scarb1). RBFOX2 function is decreased in the liver in diet-induced obesity, causing a Scarb1 isoform switch and alteration of hepatocyte lipid homeostasis. Our findings demonstrate that specific AS programmes actively maintain liver physiology, and underlie the lipotoxic effects of obesogenic diets when dysregulated. Splice-switching oligonucleotides targeting this network alleviate obesity-induced inflammation in the liver and promote an anti-atherogenic lipoprotein profile in the blood, underscoring the potential of isoform-specific RNA therapeutics for treating metabolism-associated diseases.


Subject(s)
Alternative Splicing , RNA-Binding Proteins , Mice , Animals , Alternative Splicing/genetics , RNA Splicing Factors/genetics , RNA Splicing Factors/metabolism , RNA-Binding Proteins/genetics , RNA-Binding Proteins/metabolism , Protein Isoforms/genetics , Protein Isoforms/metabolism , RNA/genetics , Liver/metabolism , Homeostasis , Cholesterol/metabolism , Scavenger Receptors, Class B/genetics , Scavenger Receptors, Class B/metabolism
5.
JHEP Rep ; 4(4): 100446, 2022 Apr.
Article in English | MEDLINE | ID: mdl-35284810

ABSTRACT

Background & Aims: The truncating mutations in tight junction protein 2 (TJP2) cause progressive cholestasis, liver failure, and hepatocyte carcinogenesis. Due to the lack of effective model systems, there are no targeted medications for the liver pathology with TJP2 deficiency. We leveraged the technologies of patient-specific induced pluripotent stem cells (iPSC) and CRISPR genome-editing, and we aim to establish a disease model which recapitulates phenotypes of patients with TJP2 deficiency. Methods: We differentiated iPSC to hepatocyte-like cells (iHep) on the Transwell membrane in a polarized monolayer. Immunofluorescent staining of polarity markers was detected by a confocal microscope. The epithelial barrier function and bile acid transport of bile canaliculi were quantified between the two chambers of Transwell. The morphology of bile canaliculi was measured in iHep cultured in the Matrigel sandwich system using a fluorescent probe and live-confocal imaging. Results: The iHep differentiated from iPSC with TJP2 mutations exhibited intracellular inclusions of disrupted apical membrane structures, distorted canalicular networks, altered distribution of apical and basolateral markers/transporters. The directional bile acid transport of bile canaliculi was compromised in the mutant hepatocytes, resembling the disease phenotypes observed in the liver of patients. Conclusions: Our iPSC-derived in vitro hepatocyte system revealed canalicular membrane disruption in TJP2 deficient hepatocytes and demonstrated the ability to model cholestatic disease with TJP2 deficiency to serve as a platform for further pathophysiologic study and drug discovery. Lay summary: We investigated a genetic liver disease, progressive familial intrahepatic cholestasis (PFIC), which causes severe liver disease in newborns and infants due to a lack of gene called TJP2. By using cutting-edge stem cell technology and genome editing methods, we established a novel disease modeling system in cell culture experiments. Our experiments demonstrated that the lack of TJP2 induced abnormal cell polarity and disrupted bile acid transport. These findings will lead to the subsequent investigation to further understand disease mechanisms and develop an effective treatment.

6.
Acta Biochim Biophys Sin (Shanghai) ; 53(6): 643-651, 2021 May 21.
Article in English | MEDLINE | ID: mdl-33973620

ABSTRACT

The 3D cell culture model is an indispensable tool in the study of liver biology in the field of health and disease and the development of clinically relevant products for liver therapies. The 3D culture model captures critical factors of the microenvironmental niche required by hepatocytes for exhibiting optimal phenotypes, thus enabling the pursuit of a range of preclinical studies that are not entirely feasible in conventional 2D cell models. In this review, we highlight the major attributes associated with and the components needed for the development of a functional 3D liver culture model for a range of applications.


Subject(s)
Cell Culture Techniques/methods , Hepatocytes/metabolism , Liver/cytology , Tissue Engineering/methods , Bioprinting/methods , Extracellular Matrix/metabolism , Humans , Liver Transplantation , Phenotype , Printing, Three-Dimensional , Tissue Scaffolds
7.
Nat Mater ; 20(1): 108-118, 2021 01.
Article in English | MEDLINE | ID: mdl-32958876

ABSTRACT

The maintenance of human skeletal stem cells (hSSCs) and their progeny in bone defects is a major challenge. Here, we report on a transplantable bandage containing a three-dimensional Wnt-induced osteogenic tissue model (WIOTM). This bandage facilitates the long-term viability of hSSCs (8 weeks) and their progeny, and enables bone repair in an in vivo mouse model of critical-sized calvarial defects. The newly forming bone is structurally comparable to mature cortical bone and consists of human and murine cells. Furthermore, we show that the mechanism of WIOTM formation is governed by Wnt-mediated asymmetric cell division of hSSCs. Covalently immobilizing Wnts onto synthetic materials can polarize single dividing hSSCs, orient the spindle and simultaneously generate a Wnt-proximal hSSC and a differentiation-prone Wnt-distal cell. Our results provide insight into the regulation of human osteogenesis and represent a promising approach to deliver human osteogenic constructs that can survive in vivo and contribute to bone repair.


Subject(s)
Bone and Bones/cytology , Cell Division , Osteogenesis , Skull/cytology , Stem Cells/cytology , Tissue Engineering/methods , Wnt Proteins/metabolism , Animals , Humans , Mice , Skull/physiology
8.
Front Bioeng Biotechnol ; 9: 816542, 2021.
Article in English | MEDLINE | ID: mdl-35308825

ABSTRACT

Intra-peritoneal placement of alginate encapsulated human induced pluripotent stem cell-derived hepatocytes (hPSC-Heps) represents a potential new bridging therapy for acute liver failure. One of the rate-limiting steps that needs to be overcome to make such a procedure more efficacious and safer is to reduce the accumulation of fibrotic tissue around the encapsulated cells to allow the free passage of relevant molecules in and out for metabolism. Novel chemical compositions of alginate afford the possibility of achieving this aim. We accordingly used sulfated alginate and demonstrated that this material reduced fibrotic overgrowth whilst not impeding the process of encapsulation nor cell function. Cumulatively, this suggests sulfated alginate could be a more suitable material to encapsulate hPSC-hepatocyte prior to human use.

9.
Nat Mater ; 19(9): 1026-1035, 2020 09.
Article in English | MEDLINE | ID: mdl-32341512

ABSTRACT

The symmetry breaking of protein distribution and cytoskeleton organization is an essential aspect for the development of apicobasal polarity. In embryonic cells this process is largely cell autonomous, while differentiated epithelial cells collectively polarize during epithelium formation. Here, we demonstrate that the de novo polarization of mature hepatocytes does not require the synchronized development of apical poles on neighbouring cells. De novo polarization at the single-cell level by mere contact with the extracellular matrix and immobilized cadherin defining a polarizing axis. The creation of these single-cell liver hemi-canaliculi allows unprecedented imaging resolution and control and over the lumenogenesis process. We show that the density and localization of cadherins along the initial cell-cell contact act as key triggers of the reorganization from lateral to apical actin cortex. The minimal cues necessary to trigger the polarization of hepatocytes enable them to develop asymmetric lumens with ectopic epithelial cells originating from the kidney, breast or colon.


Subject(s)
Biomimetics , Hepatocytes/cytology , Cell Line , Cell Polarity , Humans
10.
Nat Commun ; 10(1): 3350, 2019 07 26.
Article in English | MEDLINE | ID: mdl-31350390

ABSTRACT

The liver parenchyma is composed of hepatocytes and bile duct epithelial cells (BECs). Controversy exists regarding the cellular origin of human liver parenchymal tissue generation during embryonic development, homeostasis or repair. Here we report the existence of a hepatobiliary hybrid progenitor (HHyP) population in human foetal liver using single-cell RNA sequencing. HHyPs are anatomically restricted to the ductal plate of foetal liver and maintain a transcriptional profile distinct from foetal hepatocytes, mature hepatocytes and mature BECs. In addition, molecular heterogeneity within the EpCAM+ population of freshly isolated foetal and adult human liver identifies diverse gene expression signatures of hepatic and biliary lineage potential. Finally, we FACS isolate foetal HHyPs and confirm their hybrid progenitor phenotype in vivo. Our study suggests that hepatobiliary progenitor cells previously identified in mice also exist in humans, and can be distinguished from other parenchymal populations, including mature BECs, by distinct gene expression profiles.


Subject(s)
Liver/cytology , Transcription, Genetic , Antigens, Neoplasm/genetics , Antigens, Neoplasm/metabolism , Cell Adhesion Molecules/genetics , Cell Adhesion Molecules/metabolism , Epithelial Cell Adhesion Molecule/genetics , Epithelial Cell Adhesion Molecule/metabolism , Fetus/metabolism , Hepatocytes/cytology , Hepatocytes/metabolism , Humans , Liver/metabolism , Single-Cell Analysis , Stem Cells/cytology , Stem Cells/metabolism
11.
Stem Cells Transl Med ; 8(2): 124-137, 2019 02.
Article in English | MEDLINE | ID: mdl-30456803

ABSTRACT

Recent advancements in the production of hepatocytes from human pluripotent stem cells (hPSC-Heps) afford tremendous possibilities for treatment of patients with liver disease. Validated current good manufacturing practice (cGMP) lines are an essential prerequisite for such applications but have only recently been established. Whether such cGMP lines are capable of hepatic differentiation is not known. To address this knowledge gap, we examined the proficiency of three recently derived cGMP lines (two hiPSC and one hESC) to differentiate into hepatocytes and their suitability for therapy. hPSC-Heps generated using a chemically defined four-step hepatic differentiation protocol uniformly demonstrated highly reproducible phenotypes and functionality. Seeding into a 3D poly(ethylene glycol)-diacrylate fabricated inverted colloid crystal scaffold converted these immature progenitors into more advanced hepatic tissue structures. Hepatic constructs could also be successfully encapsulated into the immune-privileged material alginate and remained viable as well as functional upon transplantation into immune competent mice. This is the first report we are aware of demonstrating cGMP-compliant hPSCs can generate cells with advanced hepatic function potentially suitable for future therapeutic applications. Stem Cells Translational Medicine 2019;8:124&14.


Subject(s)
Cell- and Tissue-Based Therapy/standards , Hepatocytes/cytology , Pluripotent Stem Cells/cytology , Animals , Cell Culture Techniques/standards , Cell Differentiation/physiology , Cell Line , Humans , Liver/cytology , Mice
12.
Biomaterials ; 182: 299-311, 2018 11.
Article in English | MEDLINE | ID: mdl-30149262

ABSTRACT

Generation of human organoids from induced pluripotent stem cells (iPSCs) offers exciting possibilities for developmental biology, disease modelling and cell therapy. Significant advances towards those goals have been hampered by dependence on animal derived matrices (e.g. Matrigel), immortalized cell lines and resultant structures that are difficult to control or scale. To address these challenges, we aimed to develop a fully defined liver organoid platform using inverted colloid crystal (ICC) whose 3-dimensional mechanical properties could be engineered to recapitulate the extracellular niche sensed by hepatic progenitors during human development. iPSC derived hepatic progenitors (IH) formed organoids most optimally in ICC scaffolds constructed with 140 µm diameter pores coated with type I collagen in a two-step process mimicking liver bud formation. The resultant organoids were closer to adult tissue, compared to 2D and 3D controls, with respect to morphology, gene expression, protein secretion, drug metabolism and viral infection and could integrate, vascularise and function following implantation into livers of immune-deficient mice. Preliminary interrogation of the underpinning mechanisms highlighted the importance of TGFß and hedgehog signalling pathways. The combination of functional relevance with tuneable mechanical properties leads us to propose this bioengineered platform to be ideally suited for a range of future mechanistic and clinical organoid related applications.


Subject(s)
Induced Pluripotent Stem Cells/cytology , Liver/cytology , Organoids/cytology , Polyethylene Glycols/chemistry , Tissue Engineering/methods , Tissue Scaffolds/chemistry , Biocompatible Materials/chemistry , Cells, Cultured , Crystallization , Humans , Induced Pluripotent Stem Cells/metabolism
13.
Stem Cell Reports ; 10(3): 693-702, 2018 03 13.
Article in English | MEDLINE | ID: mdl-29478892

ABSTRACT

Use of hepatocytes derived from induced pluripotent stem cells (i-Heps) is limited by their functional differences in comparison with primary cells. Extracellular niche factors likely play a critical role in bridging this gap. Using image-based characterization (high content analysis; HCA) of freshly isolated hepatocytes from 17 human donors, we devised and validated an algorithm (Hepatocyte Likeness Index; HLI) for comparing the hepatic properties of cells against a physiological gold standard. The HLI was then applied in a targeted screen of extracellular niche factors to identify substrates driving i-Heps closer to the standard. Laminin 411, the top hit, was validated in two additional induced pluripotent stem cell (iPSC) lines, primary tissue, and an in vitro model of α1-antitrypsin deficiency. Cumulatively, these data provide a reference method to control and screen for i-Hep differentiation, identify Laminin 411 as a key niche protein, and underscore the importance of combining substrates, soluble factors, and HCA when developing iPSC applications.


Subject(s)
Induced Pluripotent Stem Cells/metabolism , Laminin/metabolism , Adolescent , Adult , Cell Differentiation/physiology , Female , Hepatocytes/metabolism , Humans , Liver/metabolism , Male , alpha 1-Antitrypsin/metabolism
14.
JCI Insight ; 2(11)2017 Jun 02.
Article in English | MEDLINE | ID: mdl-28570275

ABSTRACT

A major challenge for studying authentic liver cell function and cell replacement therapies is that primary human hepatocytes rapidly lose their advanced function in conventional, 2-dimensional culture platforms. Here, we describe the fabrication of 3-dimensional hexagonally arrayed lobular human liver tissues inspired by the liver's natural architecture. The engineered liver tissues exhibit key features of advanced differentiation, such as human-specific cytochrome P450-mediated drug metabolism and the ability to support efficient infection with patient-derived inoculums of hepatitis C virus. The tissues permit the assessment of antiviral agents and maintain their advanced functions for over 5 months in culture. This extended functionality enabled the prediction of a fatal human-specific hepatotoxicity caused by fialuridine (FIAU), which had escaped detection by preclinical models and short-term clinical studies. The results obtained with the engineered human liver tissue in this study provide proof-of-concept determination of human-specific drug metabolism, demonstrate the ability to support infection with human hepatitis virus derived from an infected patient and subsequent antiviral drug testing against said infection, and facilitate detection of human-specific drug hepatotoxicity associated with late-onset liver failure. Looking forward, the scalability and biocompatibility of the scaffold are also ideal for future cell replacement therapeutic strategies.

15.
Sci Rep ; 6: 37427, 2016 11 29.
Article in English | MEDLINE | ID: mdl-27897167

ABSTRACT

It is well known that a three-dimensional (3D) culture environment and the presence of extracellular matrix (ECM) proteins facilitate hepatocyte viability and maintenance of the liver-specific phenotype in vitro. However, it is not clear whether specific ECM components such as collagen or fibronectin differentially regulate such processes, especially in 3D scaffolds. In this study, a series of ECM-functionalized inverted colloidal crystal (ICC) microporous scaffolds were fabricated and their influence on Huh-7.5 cell proliferation, morphology, hepatic-specific functions, and patterns of gene expression were compared. Both collagen and fibronectin promoted albumin production and liver-specific gene expression of Huh-7.5 cells, compared with the bare ICC scaffold. Interestingly, cells in the fibronectin-functionalized scaffold exhibited different aggregation patterns to those in the collagen-functionalized scaffold, a variation that could be related to the distinct mRNA expression levels of cell adhesion-related genes. Based on these results, we can conclude that different ECM proteins, such as fibronectin and collagen, indeed play distinct roles in the phenotypic regulation of cells cultured in a 3D environment.


Subject(s)
Collagen Type I/pharmacology , Fibronectins/pharmacology , Gene Expression Regulation/drug effects , Hepatocytes/drug effects , Tissue Scaffolds , Actins/genetics , Actins/metabolism , Albumins/genetics , Albumins/metabolism , Cadherins/genetics , Cadherins/metabolism , Cell Culture Techniques , Cell Line, Tumor , Cell Proliferation/drug effects , Cell Survival/drug effects , Collagen Type I/chemistry , Colloids , Cytochrome P-450 CYP3A/genetics , Cytochrome P-450 CYP3A/metabolism , Extracellular Matrix/chemistry , Fibronectins/chemistry , Hepatocyte Nuclear Factor 4/genetics , Hepatocyte Nuclear Factor 4/metabolism , Hepatocytes/cytology , Hepatocytes/physiology , Humans , Integrins/genetics , Integrins/metabolism , Occludin/genetics , Occludin/metabolism , Porosity
16.
J Vis Exp ; (114)2016 Aug 27.
Article in English | MEDLINE | ID: mdl-27684530

ABSTRACT

The ability to maintain hepatocyte function in vitro, for the purpose of testing xenobiotics' cytotoxicity, studying virus infection and developing drugs targeted at the liver, requires a platform in which cells receive proper biochemical and mechanical cues. Recent liver tissue engineering systems have employed three-dimensional (3D) scaffolds composed of synthetic or natural hydrogels, given their high water retention and their ability to provide the mechanical stimuli needed by the cells. There has been growing interest in the inverted colloidal crystal (ICC) scaffold, a recent development, which allows high spatial organization, homotypic and heterotypic cell interaction, as well as cell-extracellular matrix (ECM) interaction. Herein, we describe a protocol to fabricate the ICC scaffold using poly (ethylene glycol) diacrylate (PEGDA) and the particle leaching method. Briefly, a lattice is made from microsphere particles, after which a pre-polymer solution is added, properly polymerized, and the particles are then removed, or leached, using an organic solvent (e.g., tetrahydrofuran). The dissolution of the lattice results in a highly porous scaffold with controlled pore sizes and interconnectivities that allow media to reach cells more easily. This unique structure allows high surface area for the cells to adhere to as well as easy communication between pores, and the ability to coat the PEGDA ICC scaffold with proteins also shows a marked effect on cell performance. We analyze the morphology of the scaffold as well as the hepatocarcinoma cell (Huh-7.5) behavior in terms of viability and function to explore the effect of ICC structure and ECM coatings. Overall, this paper provides a detailed protocol of an emerging scaffold that has wide applications in tissue engineering, especially liver tissue engineering.

17.
Interface Focus ; 4(2): 20130056, 2014 Apr 06.
Article in English | MEDLINE | ID: mdl-24748953

ABSTRACT

During the past two decades, novel biomaterial scaffold for cell attachment and culture has been developed for applications in tissue engineering, biosensing and regeneration medicine. Tissue engineering of blood vessels remains a challenge owing to the complex three-layer histology involved. In order to engineer functional blood vessels, it is essential to recapitulate the characteristics of vascular smooth muscle cells (SMCs) inside the tunica media, which is known to be critical for vasoconstriction and vasodilation of the circulatory system. Until now, there has been a lack of understanding on the mechanotransduction of the SMC layer during the transformation from viable synthetic to quiescent contractile phenotypes. In this study, microfabricated arrays of discontinuous microwalls coated with fluorescence microbeads were developed to probe the mechanotransduction of the SMC layer. First, the system was exploited for stimulating the formation of a highly aligned orientation of SMCs in native tunica medium. Second, atomic force microscopy in combination with regression analysis was applied to measure the elastic modulus of a polyacrylamide gel layer coated on the discontinuous microwall arrays. Third, the conventional traction force assay for single cell measurement was extended for applications in three-dimensional cell aggregates. Then, the biophysical effects of discontinuous microwalls on the mechanotransduction of the SMC layer undergoing cell alignment were probed. Generally, the cooperative multiple cell-cell and cell-microwall interactions were accessed quantitatively by the newly developed assay with the aid of finite-element modelling. The results show that the traction forces of highly aligned cells lying in the middle region between two opposing microwalls were significantly lower than those lying adjacent to the microwalls. Moreover, the spatial distributions of Von Mises stress during the cell alignment process were dependent on the collective cell layer orientation. Immunostaining of the SMC sheet further demonstrated that the collective mechanotransduction induced by three-dimensional topographic cues was correlated with the reduction of actin and vinculin expression. In addition, the online two-dimensional LC-MS/MS analysis verified the modulation of focal adhesion formation under the influence of microwalls through the regulation in the expression of three key cytoskeletal proteins.

18.
Biomed Mater Eng ; 24(2): 1433-45, 2014.
Article in English | MEDLINE | ID: mdl-24642971

ABSTRACT

Thermo-responsive poly(N-isopropylacrylamide) (PIPAAm) with a particular lower critical solution temperature (LCST) have been applied for the non-invasive harvesting of confluent cell layer. Until now, the effect of adhesive ligand on the biophysical responses of cells during cell layer harvesting from PIPAAm has not been elucidated. In this study, the deadhesion kinetics of smooth muscle cells (SMC) on various adhesive ligands immobilized on PIPAAm were investigated. Firstly, the formation of elastin (EL), laminin (LA), hyaluronic acid (HA) and collagen (CL) coating on PIPAAm surfaces were validated with XPS, microBCA assay and AFM. It was shown that EL was most effective in driving cell retraction on PIPAAm surface. Moreover, the highest rate of initial SMC deadhesion on EL-PIPAAm was driven by the formation of stress fibers. Interestingly, HA was most effective in preventing initial SMC detachment from PIPAAm surface in comparison with EL, LA and CL. Also, the adhesion energy of SMC on HA-PIPAAm remained constant, which was two times and six times higher than that on CL-PIPAAm and EL-PIPAAm, respectively from 20 min onward. Overall, the results reported herein pave the way for the engineering of the invasive regeneration/recovery of cells/tissue with adhesive ligand.


Subject(s)
Acrylic Resins/metabolism , Coated Materials, Biocompatible/metabolism , Myocytes, Smooth Muscle/cytology , Acrylic Resins/chemistry , Animals , Cell Adhesion , Cell Line , Coated Materials, Biocompatible/chemistry , Collagen/chemistry , Collagen/metabolism , Elastin/chemistry , Elastin/metabolism , Hyaluronic Acid/chemistry , Hyaluronic Acid/metabolism , Kinetics , Laminin/chemistry , Laminin/metabolism , Ligands , Myocytes, Smooth Muscle/metabolism , Rats , Surface Properties , Temperature
19.
Acta Biomater ; 8(1): 244-52, 2012 Jan.
Article in English | MEDLINE | ID: mdl-21906699

ABSTRACT

In cartilage tissue engineering, hydrogel is widely used as the scaffold for hosting and culturing chondrocyte suspension during neo-tissue formation. In order to develop cultured chondrocytes into a functional cartilage equivalent, the hydrogel must provide an ideal microenvironment for the rapidly proliferating chondrocytes. At the same time, the essential functions of chondrocytes, such as the secretion of type II collagen and glycosaminoglycans, must be maintained. In these studies, we quantitatively characterize the mechanobiology underlying a newly discovered "edge flourish" phenomenon of cultured chondrocytes within a three-dimensional agarose hydrogel, which may ultimately nurture scaffold-free cartilaginous tissue regeneration. First, real-time microscopy was used to track the spatiotemporal distributions of chondrocytes at different focal planes. The chondrocytes were observed to exhibit abundant neo-tissue outgrowth and significant cartilaginous phenotype at the edge of the hydrogel compared to those inside the hydrogel bulk. Secondly, the hydrogel surface stresses induced by the encapsulated chondrocytes were characterized quantitatively in real time using the finite-element method. Finally, the real-time three-dimensional matrix deformations of agarose hydrogel under the influence of chondrocytes were measured using a multiple-particle tracking assay. Our results indicate that the mechanism of the "edge flourish" phenomenon is induced by the oriented outgrowth of chondrocytic isogenous groups located at the edge of hydrogel. These isogenous groups exhibit directed outgrowth towards the surface of the hydrogel and eventually generate substantial surface tension on the interface of hydrogel and medium. Ultimately, the encapsulated chondrocytes closest to the hydrogel/medium interface will spontaneously sprout out of the hydrogel and form a layer of rich proliferative and chondrocytic extracellular matrix secreting chondrocytes at the surface of the hydrogel.


Subject(s)
Cartilage/cytology , Chondrocytes/physiology , Hydrogels/chemistry , Tissue Engineering/methods , Tissue Scaffolds/chemistry , Animals , Biocompatible Materials/chemistry , Cell Culture Techniques/methods , Cells, Cultured , Chondrocytes/cytology , Materials Testing , Sepharose/chemistry , Surface Properties , Swine
20.
J Biomed Mater Res A ; 98(3): 450-60, 2011 Sep 01.
Article in English | MEDLINE | ID: mdl-21661094

ABSTRACT

Epigallocatechin-3-gallate (EGCG), which is the main polyphenolic constituent of green tea, has emerged as a promising candidate for potential applications in selected anticancer therapeutics. Generally, tumor metastasis is known to be correlated with the alterations in cell adhesion and migration of normal cells. Nevertheless, the effect of EGCG on the biophysical responses of tumor cell adhering on extracellular matrix remains obscure. In this study, a thermosenstive poly(N-isopropylacrylamide) (PIPAAm) system was developed to elucidate the potential anti-tumor effect of EGCG on the deadhesion and migration of HepG2 cells. First, both XPS and ELISA validated the coating of laminin (LA) on PIPAAm. Second, a change of nanotopology of LA layer on PIPAAm across the lower solution critical temperature (LCST) was detected with AFM. HepG2 cells seeded on LA-coated PIPAAm surface was shown to go through deadhesion by lowering the temperature below the LCST. Interestingly, EGCG was shown to decelerate the thermally triggered deadhesion of HepG2 cell on LA coated PIPAAm. Moreover, the inhibition of cell deadhesion in EGCG treated cells was shown to be driven by actin remodeling. Interestingly, the modulation of cell deadhesion on LA coated PIPAAm by EGCG leads to the reduction of cell motility as shown by real-time cell migration assay. Overall, the use of PIPAAm system demonstrated the promise of EGCG as anticancer therapy through the suppression of cell deadhesion and migration.


Subject(s)
Acrylamides/chemistry , Anticarcinogenic Agents/pharmacology , Biocompatible Materials/chemistry , Catechin/analogs & derivatives , Cell Movement/drug effects , Polymers/chemistry , Acrylic Resins , Catechin/pharmacology , Cell Adhesion/drug effects , Hep G2 Cells , Humans , Liver Neoplasms/drug therapy , Tea/chemistry , Temperature
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