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

Area of Science:

• Regenerative Medicine
• Tissue Engineering
• Hepatology

Background:

• Subcutaneous transplantation of engineered hepatocyte/fibroblast sheets (EHFSs) is a promising method for creating vascularized subcutaneous human liver tissue (VSLT).
• Understanding the development of liver-specific structures and functions within VSLTs in vivo is crucial for their therapeutic application.

Purpose of the Study:

• To investigate the time-dependent characteristics of VSLT formation, including vascularization, cell adhesion, and the expression of liver-specific genes and functions.
• To assess the therapeutic potential of VSLTs in a mouse model of acute liver failure.

Main Methods:

• Subcutaneous transplantation of EHFSs in mice.
• Analysis of vascular network formation using mouse- and human-origin endothelial cells (mVEGFR2, hVEGFR2).
• Evaluation of liver-specific gene expression (adhesion molecules, transporters, coagulation factors, urea synthesis, metabolism enzymes) and functional activities over time.

Main Results:

• Rapid neovascularization by mouse ECs followed by human ECs led to the formation of thick, multilayered VSLTs, overcoming oxygen supply limitations.
• Significant upregulation of various liver-specific genes, including cell adhesion molecules, transporters, coagulation factors, urea synthesis enzymes, and drug-metabolizing enzymes.
• VSLT-treated mice with subacute hepatic failure survived for at least 7 weeks post-liver damage.

Conclusions:

• EHFS transplantation enables the development of functional VSLTs with robust vascularization and expression of key liver-specific genes and functions.
• Ectopic liver tissue formation in vivo demonstrates potential as a safe and low-invasive therapeutic strategy for liver diseases.
• This study provides critical insights into the in vivo development and functionality of engineered liver tissue for regenerative medicine.