Ito cells in lysosomal storage disorders. An ultrastructural study.

Area of Science:

• Hepatology
• Cell Biology
• Biochemistry

Background:

• Ito cells (ICs) are hepatic stellate cells involved in lipid metabolism and storage.
• Previous research suggested minimal or absent lysosomal storage in ICs.
• Lysosomal storage diseases (LSDs) involve the accumulation of undegraded material within lysosomes.

Purpose of the Study:

• To ultrastructurally evaluate lysosomal hypertrophy and hyperplasia in liver Ito cells across various lysosomal storage diseases.
• To determine the extent of lysosomal storage in ICs and its correlation with disease type and severity.

Main Methods:

• Ultrastructural analysis of liver biopsy specimens from patients with diagnosed LSDs.
• Identification and characterization of lysosomal storage within Ito cells using electron microscopy.
• Comparison of storage extent in ICs with involvement of other hepatic cell types, particularly fibroblasts.

Main Results:

• Lysosomal storage was confirmed in Ito cells in Niemann-Pick disease types A and B, Wolman's disease, GM1 gangliosidosis, mucopolysaccharidosis, and multiple sulfatase deficiency.
• Storage in Type C Niemann-Pick disease was minimal, except in cases with significant liver symptoms.
• The degree of lysosomal storage in ICs correlated with the involvement of non-specific fibroblasts, suggesting a shared storage mechanism within the fibroblastic population.

Conclusions:

• Ito cells exhibit lysosomal hypertrophy and hyperplasia in a range of lysosomal storage diseases.
• The findings challenge previous assumptions about the absence of lysosomal storage in ICs.
• Ito cell involvement appears to reflect broader storage phenomena within the hepatic fibroblastic compartment.