Search

Beige/brite adipocytes, which express high levels of uncoupling protein 1 (UCP1) to generate heat using stored triglycerides, are induced under specific stimuli such as cold exposure in inguinal white adipose tissue (iWAT). Although extracellular microenvironments such as extracellular matrix (ECM) stiffness are known to regulate cell behaviors, including cell differentiation into adipocytes, the effect on iWAT cells is unknown. In this study, we show that rigid ECM promotes the cell spreading of iWAT-derived preadipocytes. Furthermore, the expression of UCP1 and other thermogenic genes in iWAT cells is promoted when the cells are cultured on rigid ECM. The expression of mTOR, a kinase known to regulate the differentiation to beige adipocytes, is decreased on rigid substrates. These results suggest that ECM stiffness plays an important role in the differentiation to beige adipocytes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Direct cardiac reprogramming holds great potential for regenerative medicine. However, it remains inefficient, and induced cardiomyocytes (iCMs) generated in vitro are less mature than those in vivo, suggesting that undefined extrinsic factors may regulate cardiac reprogramming. Previous in vitro studies mainly used hard polystyrene dishes, yet the effect of substrate rigidity on cardiac reprogramming remains unclear. Thus, we developed a Matrigel-based hydrogel culture system to determine the roles of matrix stiffness and mechanotransduction in cardiac reprogramming. We found that soft matrix comparable with native myocardium promoted the efficiency and quality of cardiac reprogramming. Mechanistically, soft matrix enhanced cardiac reprogramming via inhibition of integrin, Rho/ROCK, actomyosin, and YAP/TAZ signaling and suppression of fibroblast programs, which were activated on rigid substrates. Soft substrate further enhanced cardiac reprogramming with Sendai virus vectors via YAP/TAZ suppression, increasing the reprogramming efficiency up to ∼15%. Thus, mechanotransduction could provide new targets for improving cardiac reprogramming., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)

The physical properties of the extracellular matrix (ECM), such as stiffness, are involved in the determination of the characteristics of cancer cells, including chemotherapy sensitivity. Resistance to chemotherapy is often linked to dysfunction of tumor suppressor p53; however, it remains elusive whether the ECM microenvironment interferes with p53 activation in cancer cells. Here, we show that, in MCF-7 breast cancer cells, extracellular stiffness influences p53 activation induced by the antitumor drug doxorubicin. Cell growth inhibition by doxorubicin was increased in response to ECM rigidity in a p53-dependent manner. The expression of Rho-associated coiled coil-containing protein kinase (ROCK) 2, which induces the activation of myosin II, was significantly higher when cells were cultured on stiffer ECM substrates. Knockdown of ROCK2 expression or pharmacological inhibition of ROCK decreased doxorubicin-induced p53 activation. Our results suggest that a soft ECM causes downregulation of ROCK2 expression, which drives resistance to chemotherapy by repressing p53 activation., Competing Interests: The authors declare that there is no conflict of interests regarding the publication of this paper.

Although extracellular matrix (ECM) stiffness is an important aspect of the extracellular microenvironment and is known to direct the lineage specification of stem cells and affect cancer progression, the molecular mechanisms that sense ECM stiffness have not yet been elucidated. In this study, we show that the proline-rich linker (PRL) region of vinculin and the PRL-region-binding protein vinexin are involved in sensing the stiffness of ECM substrates. A rigid substrate increases the level of cytoskeleton-associated vinculin, and the fraction of vinculin stably localizing at focal adhesions (FAs) is larger on rigid ECM than on soft ECM. Mutations in the PRL region or the depletion of vinexin expression impair these responses to ECM stiffness. Furthermore, vinexin depletion impairs the stiffness-dependent regulation of cell migration. These results suggest that the interaction of the PRL region of vinculin with vinexin α plays a crucial role in sensing ECM stiffness and in mechanotransduction.

In this study, a simple combined method consisting of floating and anchored collagen gel in a ligament or tendon equivalent culture system was used to produce the oriented fibrils in fibroblast-populated collagen matrices (FPCMs) during the remodeling and contraction of the collagen gel. Orientation of the collagen fibrils along single axis occurred over the whole area of the floating section and most of the fibroblasts were elongated and aligned along the oriented collagen fibrils, whereas no significant orientation of fibrils was observed in normally contracted FPCMs by the floating method. Higher elasticity and enhanced mechanical strength were obtained using our simple method compared with normally contracted floating FPCMs. The Young's modulus and the breaking point of the FPCMs were dependent on the initial cell densities. This simple method will be applied as a convenient bioreactor to study cellular processes of the fibroblasts in the tissues with highly oriented fibrils such as ligaments or tendons., ((c) 2006 Wiley Periodicals, Inc.)

Extracellular matrix (ECM) plays important roles in tissue engineering because cellular growth and differentiation, in the two-dimensional cell culture as well as in the three-dimensional space of the developing organism, require ECM with which the cells can interact. Especially, the bioartificial liver-assist device or regeneration of the liver-tissue substitutes for liver tissue engineering requires a suitable ECM for hepatocyte culture because hepatocytes are anchorage-dependent cells and are highly sensitive to the ECM milieu for the maintenance of their viability and differentiated functions. Galactose-carrying synthetic ECMs derived from synthetic polymers and natural polymers bind hepatocytes through a receptor-mediated mechanism, resulting in enhanced hepatocyte functions. Attachment and functions of hepatocytes were affected by physico-chemical properties including ECM geometry as well as the type, density and orientation of galactose. Also, cellular environment, medium composition and dynamic culture system influenced liver-specific functions of hepatocytes beside ECM.

Development of spatial pattern and form is one of the central issues in embryology and is included under the general name of morphogenesis. Recently, many investigations have revealed how does development occurs by each embryonic stem cell or which Genes play a crucial role for morphogenesis. However, still fundamental question is unclear; such as how does each cell recognize spatial information or which kind of information guides each cell to the suitable place. Approximately, we have 6x10(13) cells in our body. If each frame of reference of each cell is included in the gene, gene must have included more than 6x10(13) of information to inform each cell where they are. We could simply suggest this kind of the idea is quite wrong because we know genes are few enough to include such informations. Recently, it has been suggested that interaction between intracellular and extracellular fiber play crucial roll for morphogenesis. The fibers inside cell are quite complicated but well organized the system, and fibers outside of the cell are comparatively very simple fiber. Each of the fibers is well studied, but quantitative investigation of their interaction is lacking although importance is suggested by many researchers. A major problem is lacking of new method or technique. In our topics, we would like to introduce how intracellular and extracellular fiber generate morphogenesis and how we could investigate them using new technique for tissue engineering, one of the promising field of applied cell biology.

Galactose moiety as the hepatocyte anchorage was covalently coupled with chitosan for the development of synthetic extracellular matrix. Hepatocytes adhesion to galactosylated chitosan (GC)-coated polystyrene (PS) dish became as high as 94.7% after 2 h incubation whereas the hepatocytes adhesion to chitosan-coated PS dish was 69.1%, indication of galactose-specific recognition between GC molecules and asialoglycoprotein receptors of hepatocytes. The DNA synthesis of the hepatocytes adhered to GC-coated dish was increased in the presence of epidermal growth factor (EGF) at low concentration of GC (0.05 microg/ml) whereas the DNA synthesis of the hepatocytes adhered to GC-coated dish was decreased in the presence of EGF at high concentration of GC (5 microg/ml). The spreading shapes of the hepatocytes adhered to the surface in the presence of EGF at low concentration of GC (0.05 microg/ml) were enhanced than in the absence of EGF. The hepatocytes adhered to the surface at high concentration of GC (5 microg/ml) showed round shapes and exhibited many spheroid formation after 24 h in the presence of EGF.

Abstract: In liver tissue engineering, the development of appropriate extracellular matrix (ECM) is important because hepatocytes are anchorage-dependent cells and they rapidly lose liver-specific functions and viability in vitro. Therefore, it is very important to regulate galactose-mediated hepatocyte recognition to enhance selective interactions between galactose-carrying polymers and hepatocytes and liver-specific functions. In this review, to regulate hepatocyte behaviors by galactose-carrying polymers, the effect of physico-chemical properties of galactose-carrying polymers, cellular environment, medium composition and dynamic culture system were explained. Moreover, to understand the regulation mechanism of hepatocyte behaviors by galactose-carrying polymers, intracellular signal transduction in the hepatocytes by galactose-carrying polymers was also discussed. [Copyright &y& Elsevier]