Glisson's capsule matrix structure and function is altered in patients with cirrhosis irrespective of aetiology.

BACKGROUND & AIMS: Glisson's capsule is the interstitial connective tissue that surrounds the liver. As part of its normal physiology, it withstands significant daily changes in liver size. The pathophysiology of the capsule in disease is not well understood. The aim of this study was to characterise the changes in capsule matrix, cellular composition, and mechanical properties that occur in liver disease and to determine whether these correlate with disease severity or aetiology.

METHODS

Samples from ten control patients, and six with steatosis, seven with moderate fibrosis, and 37 with cirrhosis were collected from autopsies, intraoperative biopsies, and liver explants. Matrix proteins and cell markers were assessed by staining and second harmonic generation imaging. Mechanical tensile testing was performed on a test frame.

RESULTS

Capsule thickness was significantly increased in cirrhotic samples compared with normal controls irrespective of disease aetiology (70.12 ± 14.16 μm and 231.58 ± 21.82 μm, respectively), whereas steatosis and moderate fibrosis had no effect on thickness (90.91 ± 11.40 μm). Changes in cirrhosis included an increase in cell number (fibroblasts, vascular cells, infiltrating immune cells, and biliary epithelial cells). Key matrix components (collagens 1 and 3, hyaluronan, versican, and elastin) were all deposited in the lower capsule, although only the relative amounts per area of hyaluronan and versican were increased. Organisational features, including crimping and alignment of collagen fibres, were also altered in cirrhosis. Unexpectedly, capsules from cirrhotic livers had decreased resistance to loading compared with controls.

CONCLUSIONS

The liver capsule, similar to the parenchyma, is an active site of disease, demonstrating changes in matrix and cell composition as well as mechanical properties.

IMPACT AND IMPLICATIONS

We assessed the changes in composition and response to stretching of the liver outer sheath, the capsule, in human liver disease. We found an increase in key structural components and numbers of cells as well as a change in matrix organisation of the capsule during the later stages of disease. This allows the diseased capsule to stretch more under any given force, suggesting that it is less stiff than healthy tissue.