Elastin Fiber Accumulation in Liver Correlates with the Development of Hepatocellular Carcinoma

Abstract

Background & aims: The fibrosis stage, which is evaluated by the distribution pattern of collagen fibers, is a major predictor for the development of hepatocellular carcinoma (HCC) for patients with hepatitis C. Meanwhile, the role of elastin fibers has not yet been elucidated. The present study was conducted to determine the significance of quantifying both collagen and elastin fibers.

Methods: We enrolled 189 consecutive patients with hepatitis C and advanced fibrosis. Using Elastica van Gieson-stained whole-slide images of pretreatment liver biopsies, collagen and elastin fibers were evaluated pixel by pixel (0.46 μm/pixel) using an automated computational method. Consequently, fiber amount and cumulative incidences of HCC within 3 years were analyzed.

Results: There was a significant correlation between collagen and elastin fibers, whereas variation in elastin fiber was greater than in collagen fiber. Both collagen fiber (p = 0.008) and elastin fiber (p < 0.001) were significantly correlated with F stage. In total, 30 patients developed HCC during follow-up. Patients who have higher elastin fiber (p = 0.002) in addition to higher collagen fiber (p = 0.05) showed significantly higher incidences of HCC. With regard to elastin fiber, this difference remained significant in F3 patients. Furthermore, for patients with a higher collagen fiber amount, higher elastin was a significant predictor for HCC development (p = 0.02).

Conclusions: Computational analysis is a novel technique for quantification of fibers with the added value of conventional staging. Elastin fiber is a predictor for the development of HCC independently of collagen fiber and F stage.

Fig 1. Representative cases of fiber quantification.

Panel (A) and (B) show representative cases of automated fiber quantification. Both cases were diagnosed as F4 by METAVIR staging system. After automated color classification, collagen fiber was depicted as red color whereas elastin fiber was depicted as blue color. Case 1 is a patient with relatively low elastin proportional area, who showed 14.1% of collagen and 2.5% of elastin. On the contrary, case 2 is a patient with a higher elastin, who showed 6.5% of collagen and 4.8% of elastin.

Fig 2. Box plot of fibers content distribution according to F stage.

Both collagen fibers (A) and elastin fibers (B) differed significantly between F3 and F4. Gray boxes indicate interquartile ranges, and horizontal lines indicate the median value.

Fig 3. Relationship between collagen fibers and elastin fibers.

Panel (A) shows a scatter plot of the significant correlation between collagen and elastin. As the collagen increase, the variance of elastin also increases. Panel (B) shows a scatter plot classified by F stage. A circle indicates an F3 patient, whereas a triangle indicates an F4 patient. The solid line is the trend line for F3 patients, whereas the broken line is the trend line for F4 patients.

Fig 4. Cumulative incidence of HCC according to fiber content.

On panel (A), the cumulative incidence of HCC is compared between patients with high elastin (solid line) and low elastin (broken line). On panel (B), the cumulative incidence of HCC is compared between patients with high collagen (solid line) and low collagen (broken line). Vertical lines indicate censored cases. On panel (C), the cumulative incidence of HCC is compared in three groups divided by collagen and elastin content.

Fig 5. Cumulative incidence of HCC according to fiber content after stratification.

Panel (A) compares the cumulative incidence of HCC in patients with high elastin (solid line) and low elastin (broken line) after stratification by METAVIR F stage. Panel (B) compares the cumulative incidence of HCC in patients with high collagen (solid line) and low collagen (broken line) after stratification by METAVIR F stage. Vertical lines indicate censored cases. Panel (C) shows the cumulative incidence of HCC after stratification by collagen. Low and high collagen were separated by median value.