Time‐dependent structural and functional characterization of subcutaneous human liver tissue

Regenerative medicine for the hepatobiliary system: A review

Liver transplantation, the only proven treatment for end-stage liver disease and acute liver failure, is hampered by the scarcity of donors. Regenerative medicine provides an alternative therapeutic approach. Tremendous efforts dedicated to liver regenerative medicine include the delivery of transplantable cells, microtissues, and bioengineered whole livers via tissue engineering and the maintenance of partial liver function via extracorporeal support. This brief review summarizes the current status of regenerative medicine for the hepatobiliary system. For liver regenerative medicine, the focus is on strategies for expansion of transplantable hepatocytes, generation of hepatocyte-like cells, and therapeutic potential of engineered tissues in liver disease models. For biliary regenerative medicine, the discussion concentrates on the methods for generation of cholangiocyte-like cells and strategies in the treatment of biliary disease. Significant advances have been made in large-scale and long-term expansion of liver cells. The development of tissue engineering and stem cell induction technology holds great promise for the future treatment of hepatobiliary diseases. The application of regenerative medicine in liver still lacks extensive animal experiments. Therefore, a large number of preclinical studies are necessary to provide sufficient evidence for their therapeutic effectiveness. Much remains to be done for the treatment of hepatobiliary diseases with regenerative medicine.

Regenerative medicine for the upper gastrointestinal tract

The main surgical strategy for gastrointestinal tract malignancy is en bloc resection, which consists of not only resection of the involved organs but also simultaneous resection of the surrounding or adjacent mesenteries that contain lymph vessels and nodes. After resection of the diseased organs, the defect of the gastrointestinal conduit is replaced with organs located downstream, such as the stomach and jejunum. However, esophageal and gastric reconstruction using these natural substitutes is associated with a diminished quality of life due to the loss of the reserve function, damage to the antireflux barrier, and dumping syndrome. Thus, replacement of the deficit after resection with the patient's own regenerated tissue to compensate for the lost function and tissue using regenerative medicine will be an ideal treatment. Many researchers have been trying to construct artificial organs through tissue engineering techniques; however, none have yet succeeded in growing a whole organ because of the complicated functions these organs perform, such as the processing and absorption of nutrients. While exciting results have been reported with regard to tissue engineering techniques concerning the upper gastrointestinal tract, such as the esophagus and stomach, most of these achievements have been observed in animal models, and few successful approaches in the clinical setting have been reported for the replacement of mucosal defects. We review the recent progress in regenerative medicine in relation to the upper gastrointestinal tract, such as the esophagus and stomach. We also focus on the functional capacity of regenerated tissue and its role as a culture system to recapitulate the mechanisms underlying infectious disease. With the emergence of technology such as the fabrication of decellularized constructs, organoids and cell sheet medicine, collaboration between gastrointestinal surgery and regenerative medicine is expected to help establish novel therapeutic modalities in the future.

A Gelatin Hydrogel Nonwoven Fabric Facilitates Metabolic Activity of Multilayered Cell Sheets

IMPACT STATEMENT

This study introduces the utility of gelatin hydrogel nonwoven fabrics (GHNFs) for cell sheet engineering. The GHNF had the mechanical property strong enough to hold by forceps even in the swollen condition. The cell sheet harvest and transfer processes were performed simpler and faster than those without using the GHNF. The GHNF facilitates the metabolic activity of three-layered cell sheets, and the cell migration from cell sheets into the GHNF was observed. The GHNF is a promising material used to support cell sheets during the process of assemble formulation and contributes to the improved biological functions of tissue-like cell constructs.

In vitro and in vivo fabrication of stable human hepatocyte tissue in combination with normal fibroblasts derived from donors of various ages

In order to establish a minimally invasive and safe liver regenerative technology, a technique for fabricating liver tissue possessing a vascular network was developed by subcutaneously transplanting a cell sheet composed of primary human hepatocytes and normal fibroblasts. However, differences in fibroblast characteristics owing to donor age may threaten the stability of liver tissue regenerated via this technology. Herein we describe the influence of fibroblasts from multiple donors on the fabrication of engineered human hepatocyte tissues invitro and in vivo. Primary human hepatocytes were cultured with seven strains of fibroblasts derived from the skins of donors of various ages, ranging from a fetus (12 weeks) to the elderly (69 years). Engineered hepatocyte sheets were successfully harvested for all strains. At 2 weeks after the subcutaneous transplantation of the hepatocyte sheets into mice, the highest human albumin (hALB) serum concentration was noted in the mouse containing fibroblasts from a 12 year old (TIG-118). Since the platelet-derived growth factor subunit B (PDGFB) gene expression of TIG-118 cells was significantly higher than that in the other cells, PDGFB may be considered to play an important role in the initial subcutaneous engraftment of primary human hepatocytes. Even though hALB concentration exhibited a parabolic tendency with age, there was no statistically significant difference noted within 6-8 weeks after transplantation. The present study demonstrates that this technology can produce consistent and stable hepatocyte sheets that exhibit long-term survival and liver-specific functionality in vivo regardless of the fibroblast donor age.