The construction of a functional liver-tissue equivalent using tissue engineering is a very important goal because the liver is a central organ in the body. However, the construction of functional ...organ-scale liver tissue is impossible because it requires a high-density blood vessel network. In this study, we focused on decellularization technology to solve this problem. Decellularized liver tissue with a fine vascular tree network template was obtained using Triton X-100. The distance between each vascular structure was less than 1 mm. Endothelialization of the blood vessel network with human umbilical vein endothelial cells (HUVECs) was successfully performed without any leakage of HUVECs to the outside of the vessel structure. Furthermore, hepatocytes/spheroids could be located around the blood vessel structure. This study indicates that decellularized liver tissue is a potential scaffold for creating a practical liver tissue using tissue engineering technology.
Growth factors (GFs) are indispensable in regenerative medicine because of their high effectiveness. However, as GFs degenerate easily, the development of a suitable carrier with improved stability ...for GFs is necessary. In this study, we developed a gel-in-oil (G/O) emulsion technology for the transdermal delivery of growth factors. Nanogel particles prepared with heparin-immobilized gelatin that can bind growth factors were dispersed in isopropyl myristate. The particle size of the G/O emulsion could be controlled by changing the surfactant concentration, volume ratio of the water phase to the oil phase, and gelatin concentration. In vitro skin penetration studies showed better penetration through the stratum corneum of fluorescent proteins containing G/O emulsions than of the aqueous solution of GF. Similarly, an in vivo study showed an angiogenesis-inducing effect after transdermal application of GF-immobilized G/O emulsion. Angiogenesis in mice was confirmed owing to both an increased blood vessel network and higher hemoglobin content in the blood. Therefore, the G/O emulsion could be a promising carrier for GFs with better stability and can effectively deliver GFs at the target site.
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•Gel-in-oil (G/O) nanodispersion ensures effective delivery of functional molecules.•G/O could avoid degradation of bFGF at physiological temperature.•Nanogel droplets confirmed increased permeability through the skin.•Transdermal delivery of bFGF loaded G/O nanodispersion induces angiogenesis.
Reconstructed liver has been desired as a liver substitute for transplantation. However, reconstruction of a whole liver has not been achieved because construction of a vascular network at an organ ...scale is very difficult. We focused on decellularized liver (DC-liver) as an artificial scaffold for the construction of a hierarchical vascular network. In this study, we obtained DC-liver and the tubular network structure in which both portal vein and hepatic vein systems remained intact. Furthermore, endothelialization of the tubular structure in DC-liver was achieved, which prevented blood leakage from the tubular structure. In addition, hepatocytes suspended in a collagen sol were injected from the surroundings using a syringe as a suitable procedure for liver cell inoculation. In summary, we developed a base structure consisting of an endothelialized vascular-tree network and hepatocytes for whole liver engineering.
Recently, organ construction has been attempted using decellularized organs. In this study, we used decellularized rat liver to construct liver tissue by recellularization. The right lobe of the rat ...liver was decellularized with 4% Triton X-100 solution, recellularized with 10
rat hepatocytes, and albumin synthesis in the recellularized right lobe was observed. Therefore, we introduce a method of decellularizing rat liver, which retains its fine vascular structure after removal of all the cells, perform organogenesis using the decellularized liver, and evaluate the structural and functional properties of the products.
Cryopreservation is important for enabling long-term cell preservation. However, physical damage due to ice crystal formation and membrane permeation by dimethyl sulfoxide (DMSO) severely affects ...cryopreserved cell viability. To ensure cell survival and functional maintenance after cryopreservation, it is important to protect the cell membrane, the most vulnerable cell component, from freeze-thaw damage. This study aimed to create a glycolipid derivative having a positive interaction with the cell membrane and cytoprotective effects. As a result, we synthesized a novel trehalose derivative, oleyl-trehalose (Oleyl-Treh), composed of trehalose and oleyl groups. Its use led to increased viable cell counts when used with DMSO in a non-cytotoxic concentration range (1.6 nM–16 μM). Oleyl-Treh significantly improved viability and liver-specific functions of hepatocytes after cryopreservation, including albumin secretion, ethoxyresorufin-O-deethylase activity (an indicator of cytochrome P450 family 1 subfamily A member 1 activity), and ammonia metabolism. Oleyl-Treh could localize trehalose to the cell membrane; furthermore, the oleyl group affected cell membrane fluidity and exerted cryoprotective effects. This novel cryoprotective agent, which shows a positive interaction with the cell membrane, provides a unique approach toward cell protection during cryopreservation.
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Liver transplantation plays an important role in the medical field. To improve the quality of a donor liver, there is a need to establish a preservation system to prevent damage and maintain liver ...function. In response to this demand, machine perfusion (MP) has been proposed as a new liver preservation method instead of the conventional static cold storage. There is controversy about the optimal MP temperature of the donor liver. Since the oxygen consumption of the liver differs depending on the temperature, construction of a system that satisfies the oxygen demand of the liver is crucial for optimizing the preservation temperature. In this study, an MP system, which satisfies the oxygen demand of liver at each temperature, was constructed using an index of oxygen supply; the overall volumetric oxygen transfer coefficient, the amount of oxygen retention of perfusate and oxygen saturation. Both subnormothermic MP (SNMP, 20–25 °C) and normothermic MP (NMP, 37 °C) could maintain liver viability at a high level (94%). However, lactate metabolism of the liver during NMP was more active than that during SNMP. Furthermore, the ammonia metabolism of liver after NMP was superior to that after SNMP. Hence, NMP, which maintains the metabolic activity of the liver, is more suitable for preservation of the donor liver than SNMP, which suppresses the metabolic activity. In summary, normothermia is the optimal temperature for liver preservation, and we succeeded in constructing an NMP system that could suppress liver damage and maintain function.
Cell transplantation is a potential alternative for orthotopic liver transplantation because of the chronic donor shortage. Functional liver tissue is needed for cell transplantations. However, large ...functional liver tissue is difficult to construct because of the high oxygen consumption of hepatocytes. In our previous study, we developed a novel method to generate hybrid organoids. In this study, we used fetal liver cells (FLCs) to construct a hybrid organoid. Nucleus numbers, angiogenesis, and albumin production were measured in transplanted samples. Higher cell viability and larger liver tissue was found in FLC-containing samples than in hepatocyte-containing samples. Furthermore, the therapeutic efficiency of FLC-containing samples was evaluated by transplantation into Nagase analbuminemia rats. As a result, an increase in albumin concentration was found in rat blood. In summary, transplantation of a FLC-containing hybrid organoid is a potential approach for cell transplantation.
•We prepared a growth factor-immobilizable gel.•Sufficient angiogenesis was induced by the growth factor-immobilizable gel.•FLCs had higher cell viability than hepatocytes in transplanted samples.•Albumin concentrations increased in NAR blood after FLC transplantation.
Hepatocyte transplantation is a potential therapy for treating various liver diseases. However, oxygen shortage leading to loss of hepatocyte function becomes a limitation following hepatocyte ...transplantation. To overcome this problem, we developed a hybrid organoid, consisting of growth factor (GF)-immobilizable gel particles combined with hepatocytes. Benefits of the hybrid organoid were evaluated in three groups: (i) hybrid organoid consisting of cells and GF-immobilizable gel particles (HG-C); (ii) hybrid organoid consisting of cells and gel particles (G-C); and (iii) cells suspended in collagen (C–C). We found liver-specific functions of HG-C were maintained longer than in the other conditions during in vitro culture. Furthermore, after transplantation, HG-C was effective in maintaining viability of transplanted hepatocytes and promoting angiogenesis around the hepatocytes. In summary, transplantation of HG-C is a potential method for future liver tissue engineering.
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We developed a new oil-based delivery system for transdermal protein delivery, a gel-in-oil (G/O) nanosuspension, where gelatin-based hydrogel was coated with hydrophobic surfactants. ...The high entrapment efficiency of a model protein, phycocyanin (PC), into nano-sized gelatin hydrogel particles was achieved. Spectroscopic evaluation of PC suggested that the G/O nanosuspension could retain the functional form of PC in isopropyl myristate. In vitro skin permeation studies showed that the G/O nanosuspension facilitated the delivery of PC through the stratum corneum of Yucatan micropig skin.
Two-dimensional monolayer culture is the most popular cell culture method. However, the cells may not respond as they do in vivo because the culture conditions are different from in vivo conditions. ...However, hydrogel-embedding culture, which cultures cells in a biocompatible culture substrate, can produce in vivo-like cell responses, but in situ evaluation of cells in a gel is difficult. In this study, we realized an in vivo-like environment in vitro to produce cell responses similar to those in vivo and established an in situ evaluation system for hydrogel-embedded cell responses. The extracellular matrix (ECM)-modeled gel consisted of collagen and heparin (Hep-col) to mimic an in vivo-like environment. The Hep-col gel could immobilize growth factors, which is important for ECM functions. Neural stem/progenitor cells cultured in the Hep-col gel grew and differentiated more actively than in collagen, indicating an in vivo-like environment in the Hep-col gel. Second, a thin-layered gel culture system was developed to realize in situ evaluation of the gel-embedded cells. Cells in a 200-μm-thick gel could be evaluated clearly by a phase-contrast microscope and immunofluorescence staining through reduced optical and diffusional effects. Finally, we found that the neural cells cultured in this system had synaptic connections and neuronal action potentials by immunofluorescence staining and Ca2+ imaging. In conclusion, this culture method may be a valuable evaluation system for neurotoxicity testing.
