Fat-associated lymphoid clusters as expandable niches for ectopic liver development

Area of Science:

• Hepatology
• Immunology
• Regenerative Medicine

Background:

• Hepatocyte transplantation is a promising alternative to whole-organ transplantation.
• Intraportal and intrasplenic routes are common but risky in patients with severe liver disease.
• Intraperitoneal (i.p.) injection offers a less invasive alternative, with lymph nodes identified as potential extrahepatic engraftment sites.

Purpose of the Study:

• To investigate extrahepatic niches for hepatocyte engraftment after i.p. injection.
• To determine if other abdominal niches support transplanted hepatocyte survival and proliferation.
• To explore the potential of these niches for ectopic liver regeneration.

Main Methods:

• Hepatocytes were transplanted into mice via i.p. injection.
• Ectopic liver tissue formation was analyzed in fat-associated lymphoid clusters (FALCs).
• Transcriptome analysis compared ectopic and native liver gene expression.
• FALC formation was manipulated through bone marrow transplantation and induced inflammation.

Main Results:

• Hepatocytes transplanted via i.p. injection engrafted and formed functional ectopic livers within FALCs.
• Ectopic livers exhibited compensatory gene expression, functionally integrating with the native liver.
• FALC presence was crucial for ectopic liver development; bone marrow transplantation restored it in immunodeficient mice.
• Increased FALCs via inflammation improved engraftment and accelerated recovery in a mouse model of liver failure.

Conclusions:

• Abdominal FALCs are essential extrahepatic sites for hepatocyte engraftment following i.p. transplantation.
• FALCs provide an accessible and expandable niche for ectopic liver regeneration.
• Adequate growth stimulus is key for enhancing FALC-mediated ectopic liver regeneration.