Hepatocytes maintain their function on basement membrane formed by epithelial cells

Development of a Biomimetic Hydrogel Based on Predifferentiated Mesenchymal Stem-Cell-Derived ECM for Cartilage Tissue Engineering

The use of decellularized extracellular matrix (dECM) as a biomaterial has been an important step forward for the development of functional tissue constructs. In addition to tissues and organs, cell cultures are gaining a lot of attention as an alternative source of dECM. In this work, a novel biomimetic hydrogel is developed based on dECM obtained from mesenchymal stem cells (mdECM) for cartilage tissue engineering. To this end, cells are seeded under specific culture conditions to generate an early chondrogenic extracellular matrix (ECM) providing cues and elements necessary for cartilage development. The composition is determined by quantitative, histological, and mass spectrometry techniques. Moreover, the decellularization process is evaluated by measuring the DNA content and compositional analyses, and the hydrogel is formulated at different concentrations (3% and 6% w/v). Results show that mdECM derived hydrogels possess excellent biocompatibility and suitable physicochemical and mechanical properties for their injectability. Furthermore, it is evidenced that this hydrogel is able to induce chondrogenesis of mesenchymal stem cells (MSCs) without supplemental factors and, furthermore, to form hyaline cartilage-like tissue after in vivo implantation. These findings demonstrate for the first time the potential of this hydrogel based on mdECM for applications in cartilage repair and regeneration.

Hepatocytes and Endothelial Networks in a Fluid-Based In Vitro Model of Liver Drug Metabolism

Drug-induced liver toxicity remains a major cause of drug withdrawal from animal testing and human clinical trials. A functional liver culture model corresponding to the liver is urgently required; however, in previous liver models, it has proven difficult to stably maintain multiple liver functions. Previously reported fluid-based systems have some advantages for hepatocyte culture, but have insufficient liver-specific functions because they simply involve moving conventional hepatocyte cultures from a dish into a fluid-based system. Importantly, these cultures have no liver tissue-specific structures that construct liver-specific cellular polarities, such as apical, basolateral, and basal faces. In this study, we developed a fluid-based system for our liver tissue culture models. The liver tissues that were constructed in our originally designed fluid-based systems represent a tissue culture model for studying hepatic functions. Together, our findings show that by mimicking the structure of the liver in the body, our system effectively maintains multiple liver-specific functions. Impact statement A functional liver culture model corresponding to the liver is urgently required; however, in previous liver models, it has proven difficult to stably maintain multiple liver functions. In this study, we developed a fluid-based system for our liver tissue culture models. The liver tissues that were constructed in our originally designed fluid-based systems represent a tissue culture model for studying hepatic functions. Together, our findings show that by mimicking the structure of the liver in the body, our system effectively maintains multiple liver-specific functions.

Fibrillar Collagen Type I Participates in the Survival and Aggregation of Primary Hepatocytes Cultured on Soft Hydrogels

Liver is an essential organ that carries out multiple functions such as glycogen storage, the synthesis of plasma proteins, and the detoxification of xenobiotics. Hepatocytes are the parenchyma that sustain almost all the functions supported by this organ. Hepatocytes and non-parenchymal cells respond to the mechanical alterations that occur in the extracellular matrix (ECM) caused by organogenesis and regenerating processes. Rearrangements of the ECM modify the composition and mechanical properties that result in specific dedifferentiation programs inside the hepatic cells. Quiescent hepatocytes are embedded in the soft ECM, which contains an important concentration of fibrillar collagens in combination with a basement membrane-associated matrix (BM). This work aims to evaluate the role of fibrillar collagens and BM on actin cytoskeleton organization and the function of rat primary hepatocytes cultured on soft elastic polyacrylamide hydrogels (PAA HGs). We used rat tail collagen type I and Matrigel® as references of fibrillar collagens and BM respectively and mixed different percentages of collagen type I in combination with BM. We also used peptides obtained from decellularized liver matrices (dECM). Remarkably, hepatocytes showed a poor adhesion in the absence of collagen on soft PAA HGs. We demonstrated that collagen type I inhibited apoptosis and activated extracellular signal-regulated kinases 1/2 (ERK1/2) in primary hepatocytes cultured on soft hydrogels. Epidermal growth factor (EGF) was not able to rescue cell viability in conjugated BM but affected cell aggregation in soft PAA HGs conjugated with combinations of different proportions of collagen and BM. Interestingly, actin cytoskeleton was localized and preserved close to plasma membrane (cortical actin) and proximal to intercellular ducts (canaliculi-like structures) in soft conditions; however, albumin protein expression was not preserved, even though primary hepatocytes did not remodel their actin cytoskeleton significantly in soft conditions. This investigation highlights the important role of fibrillar collagens on soft hydrogels for the maintenance of survival and aggregation of the hepatocytes. Data suggest evaluating the conditions that allow the establishment of optimal biomimetic environments for physiology and cell biology studies, where the phenotype of primary cells may be preserved for longer periods of time.

Cultured cell-derived decellularized matrices: a review towards the next decade

Summary of recent progress in cell-derived decellularized matrices preparation and application, with perspectives towards the next decade.

Three-dimensional co-culture of BM-MSCs and eccrine sweat gland cells in Matrigel promotes transdifferentiation of BM-MSCs

Victims with extensive and deep burns are unable to regenerate eccrine sweat glands. Combining of stem cells and biomimetic ECM to generate cell-based 3D tissues is showing promise for tissue repair and regeneration. We co-cultured BrdU-labeled bone marrow-derived mesenchymal stem cells (BM-MSCs) and eccrine sweat gland cells in Matrigel for 2 weeks in vitro and then evaluated for BM-MSCs differentiation into functional eccrine sweat gland cells by morphological assessment and immunohistochemical double staining for BrdU/pancytokeratin, BrdU/ZO-2, BrdU/E-cadherin, BrdU/desmoglein-2, BrdU/Na(+)-K(+)-ATPase α, BrdU/NHE1 and BrdU/CFTR. Cells formed spheroid-like structures in Matrigel, and BrdU-labeled BM-MSCs were involved in the 3D reconstitution of eccrine sweat gland tissues, and the incorporated BM-MSCs expressed an epithelial cell marker (pancytokeratin), epithelial cell junction proteins (ZO-2, E-cadherin and desmoglein-2) and functional proteins of eccrine sweat glands (Na(+)-K(+)-ATPase α, NHE1 and CFTR). In conclusion, three-dimensional co-culture of BM-MSCs and eccrine sweat gland cells in Matrigel promotes the transdifferentiation of BM-MSCs into potentially functional eccrine sweat gland cells.

Decellularized Extracellular Matrix Scaffolds for Cartilage Regeneration

Decellularized extracellular matrix (ECM) is gaining a lot of attention as a biomaterial for tissue engineering applications. This chapter describes the processing techniques for decellularization of cell-derived ECM and protocols for the fabrication of ECM-based scaffolds in the form of hydrogels or fibrous polymer meshes by electrospinning. It describes the protocols to analyze the morphology and presence of collagen in fabricated scaffolds using scanning electron microscope and Picrosirius Red staining respectively. Methods to evaluate the metabolic activity and proliferation of cells (resazurin-based assay and DNA assay, respectively) and gene expression are also presented. Furthermore, histological techniques to analyze the presence of sulfated glycosaminoglycans are also described.

Is hepatitis B-virucidal validation of biocides possible with the use of surrogates?

The hepatitis B virus (HBV) is considered to be a major public health problem worldwide, and a significant number of reports on nosocomial outbreaks of HBV infections have been reported. Prevention of indirect HBV transmission by contaminated objects is only possible through the use of infection-control principles, including the use of chemical biocides, which are proven to render the virus non-infectious. The virucidal activity of biocides against HBV cannot be predicted; therefore, validation of the virucidal action of disinfectants against HBV is essential. However, feasible HBV infectivity assays have not yet been established. Thus, surrogate models have been proposed for testing the efficacy of biocides against HBV. Most of these assays do not correlate with HBV infectivity. Currently, the most promising and feasible assay is the use of the taxonomically related duck hepatitis B virus (DHBV), which belongs to the same Hepadnaviridae virus family. This paper reviews the application of DHBV, which can be propagated in vitro in primary duck embryonic hepatocytes, for the testing of biocides and describes why this model can be used as reliable method to evaluate disinfectants for efficacy against HBV. The susceptibility levels of important biocides, which are often used as ingredients for commercially available disinfectants, are also described.

Molecular mechanisms regulating the establishment of hepatocyte polarity during human hepatic progenitor cell differentiation into a functional hepatocyte-like phenotype

The correct functioning of hepatocytes requires the establishment and maintenance of hepatocyte polarity. However, the mechanisms regulating the generation of hepatocyte polarity are not completely understood. The differentiation of human fetal hepatic progenitor cells (hFHPCs) into functional hepatocytes provides a powerful in vitro model system for studying the molecular mechanisms governing hepatocyte development. In this study, we used a two-stage differentiation protocol to generate functional polarized hepatocyte-like cells (HLCs) from hFHPCs. Global gene expression profiling was performed on triplicate samples of hFHPCs, immature-HLCs and mature-HLCs. When the differential gene expression was compared based on the differentiation stage, a number of genes were identified that might be essential for establishing and maintaining hepatocyte polarity. These genes include those that encode actin filament-binding protein, protein tyrosine kinase activity molecules, and components of signaling pathways, such as PTK7, PARD3, PRKCI and CDC42. Based on known and predicted protein-protein interactions, the candidate genes were assigned to networks and clustered into functional categories. The expression of several of these genes was confirmed using real-time RT-PCR. By inactivating genes using small interfering RNA, we demonstrated that PTK7 and PARD3 promote hepatic polarity formation and affect F-actin organization. These results provide unique insight into the complex process of polarization during hepatocyte differentiation, indicating key genes and signaling molecules governing hepatocyte differentiation.

Modifying three-dimensional scaffolds from novel nanocomposite materials using dissolvable porogen particles for use in liver tissue engineering

Background:

Although hepatocytes have a remarkable regenerative power, the rapidity of acute liver failure makes liver transplantation the only definitive treatment. Attempts to incorporate engineered three-dimensional liver tissue in bioartificial liver devices or in implantable tissue constructs, to treat or bridge patients to self-recovery, were met with many challenges, amongst which is to find suitable polymeric matrices. We studied the feasibility of utilising nanocomposite polymers in three-dimensional scaffolds for hepatocytes.

Materials and methods:

Hepatocytes (HepG2) were seeded on a flat sheet and in three-dimensional scaffolds made of a nanocomposite polymer (Polyhedral Oligomeric Silsesquioxane [POSS]-modified polycaprolactone urea urethane) alone as well as with porogen particles, i.e. glucose, sodium bicarbonate and sodium chloride. The scaffold architecture, cell attachment and morphology were studied with scanning electron microscopy, and we assessed cell viability and functionality.

Results:

Cell attachment to the scaffolds was demonstrated. The scaffold made with glucose particles as porogen showed a narrower range of pore size with higher porosity and better inter-pore communications and seemed to encourage near normal cell morphology. There was a steady increase of albumin secretion throughout the experiment while the control (monolayer cell culture) showed a steep decrease after day 7. At the end of the experiment, there was no significant difference in viability and functionality between the scaffolds and the control.

Conclusion:

In this initial study, porogen particles were used to modify the scaffolds produced from the novel polymer. Although there was no significance against the control in functionality and viability, the demonstrable attachment on scanning electron microscopy suggest potential roles for this polymer and in particular for scaffolds made with glucose particles in liver tissue engineering.

Acetaminophen-induced hepatotoxicity in a liver tissue model consisting of primary hepatocytes assembling around an endothelial cell network

Primary hepatocytes have been used in drug development for the evaluation of hepatotoxicity of candidate compounds. However, the rapid depression of their hepatic characters in vitro must be improved to predict toxicity with higher accuracy. We have hypothesized that a well organized tissue construct that includes nonparenchymal cells and appropriate scaffold material(s) could overcome this difficulty by remediating the viability and physiological function of primary hepatocytes. In this study, we constructed an in vitro liver tissue model, consisting of mouse primary hepatocytes assembling around an endothelial cell network on Engelbreth-Holm-Swarm gel, and examined its response to acetaminophen treatment. The increase in lactate dehydrogenase release after the exposure to acetaminophen was induced earlier in the liver tissue model than in monolayer hepatocytes alone, suggesting that the tissue model was more sensitive to an acetaminophen-induced toxicity. On the basis of our results, we conclude that liver tissue models of this kind may enhance the responses of hepatocytes against xenobiotics via the maintenance of hepatic genes and functions such as cytochrome P450s. These findings will contribute to the development of more accurate systems for evaluating hepatotoxicity.

Metabolic profiling based quantitative evaluation of hepatocellular metabolism in presence of adipocyte derived extracellular matrix

The elucidation of the effect of extracellular matrices on hepatocellular metabolism is critical to understand the mechanism of functional upregulation. We have developed a system using natural extracellular matrices [Adipogel] for enhanced albumin synthesis of rat hepatocyte cultures for a period of 10 days as compared to collagen sandwich cultures. Primary rat hepatocytes isolated from livers of female Lewis rats recover within 4 days of culture from isolation induced injury while function is stabilized at 7 days post-isolation. Thus, the culture period can be classified into three distinct stages viz. recovery stage [day 0–4], pre-stable stage [day 5–7] and the stable stage [day 8–10]. A Metabolic Flux Analysis of primary rat hepatocytes cultured in Adipogel was performed to identify the key metabolic pathways modulated as compared to collagen sandwich cultures. In the recovery stage [day 4], the collagen-soluble Adipogel cultures shows an increase in TriCarboxylic Acid [TCA] cycle fluxes; in the pre-stable stage [day 7], there is an increase in PPP and TCA cycle fluxes while in the stable stage [day 10], there is a significant increase in TCA cycle, urea cycle fluxes and amino acid uptake rates concomitant with increased albumin synthesis rate as compared to collagen sandwich cultures throughout the culture period. Metabolic analysis of the collagen-soluble Adipogel condition reveals significantly higher transamination reaction fluxes, amino acid uptake and albumin synthesis rates for the stable vs. recovery stages of culture. The identification of metabolic pathways modulated for hepatocyte cultures in presence of Adipogel will be a useful step to develop an optimization algorithm to further improve hepatocyte function for Bioartificial Liver Devices. The development of this framework for upregulating hepatocyte function in Bioartificial Liver Devices will facilitate the utilization of an integrated experimental and computational approach for broader applications of Adipogel in tissue e engineering and regenerative medicine.

Effects of extracellular matrices derived from different cell sources on chondrocyte functions

Cell-derived extracellular matrices (ECMs) are a key factor in regulating cell functions in tissue engineering and regenerative medicine. The fact that cells are surrounded by their specific ECM in vivo elicits the need to elucidate the effects of ECM derived from different cell sources on cell functions. Here, three types of ECM were prepared by decellularizing cultured chondrocytes, fibroblasts, and mesenchymal stem cells (MSC) and used for chondrocyte culture to compare their effects on chondrocyte adhesion, proliferation, and differentiation. Chondrocyte adhesion to the chondrocyte-derived ECM was greater than those to the fibroblast- and MSC-derived ECM. Chondrocyte proliferation on the chondrocyte-derived ECM was lower than those on the fibroblast- and MSC-derived ECM. The ECM showed no evident effect on chondrocyte differentiation. The effects of ECM on cell functions depended on the cell source used to prepare the ECM.

Decellularized matrices for tissue engineering

IMPORTANCE OF THE FIELD

Biomimetic scaffolds and substrates of extracellular matrices (ECMs) play an important role in the regulation of cell function and in the guidance of new tissue regeneration, as an ECM has the intrinsic cues necessary to communicate with and dictate to cells.

AREAS COVERED IN THIS REVIEW

This paper reviews the latest developments in ECM scaffolds and substrates obtained from decellularized tissues, organs or cultured cells and their application in tissue engineering. The ECM composition, structure, interaction with surrounding cells, preparation method and usage in the regeneration of various tissues and organs are summarised.

WHAT THE READER WILL GAIN

The advantages and challenges of decellularized matrices are highlighted.

TAKE HOME MESSAGE

Similarity in the composition, microstructure and biomechanical properties of the decellularized scaffolds and substrates to those of the native tissues and organs maximizes the promotion effect in the regeneration of both structural and functional tissues and organs. Simple tissues as well as complicated organs have been decellularized and decellularization methods have been optimized to completely remove the cellular components while keeping the ECM intact.

Bioactive scaffolds for engineering vascularized cardiac tissues

Functional vascularization is a key requirement for the development and function of most tissues, and most critically cardiac muscle. Rapid and irreversible loss of cardiomyocytes during cardiac infarction directly results from the lack of blood supply. Contractile cardiac grafts, engineered using cardiovascular cells in conjunction with biomaterial scaffolds, are an actively studied method for cardiac repair. In this article, we focus on biomaterial scaffolds designed to mediate the development and maturation of vascular networks, by immobilized growth factors. The interactive effects of multiple vasculogenic factors are discussed in the context of cardiac tissue engineering.

In vitro cultivation and cryopreservation of duck embryonic hepatocytes

Hepatitis B-virucidal testing of biocides in quantitative suspension tests using duck hepatitis B virus (DHBV) requires primary duck embryonic hepatocytes for viral propagation. To improve the test system and availability of these cells, commercial culture plates with different growth surfaces were tested for cell cultivation and different approaches for cryopreservation of hepatocyte suspension were examined. After 12 days of culture, the largest amounts of hepatocytes were grown in CellBIND and TTP plates and CellBIND surface showed the lowest tendency of monolayer detachment nearly comparable with collagen 1-coated CELLCOAT plates. For cryopreservation of hepatocyte suspension, the use of growth medium supplemented with fetal calf serum (FCS) and dimethyl sulfoxide (ME(2)SO), FCS supplemented with ME(2)SO or cryosafe-1 as cryoprotective agents provided the highest rates of surviving cells after thawing. The freezing-thawing process did not significantly reduce the susceptibility of hepatocytes to infection with DHBV. In conclusion, plates without collagen 1 such as CellBIND are recommended for cultivation of primary duck embryonic hepatocytes in infectivity experiments of DHBV for virucidal testing of biocides. The use of cryopreserved hepatocytes is possible when freshly isolated cells from the liver of duck embryos are not available.

Role of basement membrane in EMMPRIN/CD147 induction in rat tracheal epithelial cells

Extracellular matrix metalloproteinase inducer (EMMPRIN) is a glycosylated transmembrane protein known to induce matrix metalloproteinases (MMPs). Although the expression of EMMPRIN is physiologically limited to fetal lung epithelium, the transcriptional regulation of this protein remains to be elucidated. We hypothesized that the interaction of epithelial cells with the basement membrane regulates EMMPRIN expression. The basement membrane has highly integrated architecture composed of specific extracellular matrix, such as laminins and type IV collagen, and exhibits multiple functions. We previously developed a structured basement membrane mimic, a synthesized basement membrane (sBM) substratum, in which laminin-111, a unique component of embryonic lungs, is incorporated. In the present study we quantified expression of EMMPRIN mRNA of rat tracheal epithelial cells cultured on sBM, laminin-111, type IV collagen, or laminin-332. EMMPRIN was upregulated on sBM and laminin-111, although this was not accompanied by MMP-9 induction. In contrast, type IV collagen and laminin-332 did not induce EMMPRIN. These findings suggest potential roles for basement membrane in the transcriptional regulation of tracheal epithelial EMMPRIN.

Induced differentiation and maturation of newborn liver cells into functional hepatic tissue in macroporous alginate scaffolds

The present work explores cell cultivation in macroporous alginate scaffolds as a means to reproduce hepatocyte terminal differentiation in vitro. Newborn rat liver cell isolates, consisting of proliferating hepatocytes and progenitors, were seeded at high cell density of 125 x 10(6)/cm(3) within the scaffold and then cultivated for 6 wk in chemically defined medium. Within 3 days, the alginate-seeded cells expressed genes for mature liver enzymes, such as tryptophan oxygenase, secreted a high level of albumin, and performed phase I drug metabolism. The cells formed compacted spheroids, establishing homotypic and heterotypic cell-to-cell interactions. By 6 wk, the spheroids developed into organoids, with an external mature hepatocyte layer covered by a laminin layer encasing inner vimentin-positive cells within a laminin-rich matrix also containing collagen. The hepatocytes presented a distinct apical surface between adjacent cells and a basolateral surface with microvilli facing extracellular matrix deposits. By contrast, viable adherent cells within collagen scaffolds presenting the identical porous structure did not express adult liver enzymes or secrete albumin after 6 wk. This study thus illustrates the benefits of cell cultivation in macroporous alginate scaffolds as an effective promoter for the maturation of newborn liver cells into functional hepatic tissue, capable of maintaining prolonged hepatocellular functions.