Stimulation of oval cell and hepatocyte proliferation by exogenous bombesin and neurotensin in partially hepatectomized rats

Abstract

Aim: To investigate the effect of the neuropeptides bombesin (BBS) and neurotensin (NT) on oval cell proliferation in partially hepatectomized rats not pretreated with a known hepatocyte inhibitor.

Methods: Seventy male Wistar rats were randomly divided into five groups: I = controls, II = sham operated, III = partial hepatectomy 70% (PHx), IV = PHx + BBS (30 μg/kg per day), V = PHx + NT (300 μg/kg per day). Forty eight hours after liver resection, portal endotoxin levels and hepatic glutathione redox state were determined. α-fetoprotein (AFP) mRNA (in situ hybridisation), cytokeratin-19 and Ki67 antigen expression (immunohistochemistry) and apoptosis (TUNEL) were evaluated on liver tissue samples. Cells with morphological features of oval cells that were cytokeratin-19 (+) and AFP mRNA (+) were scored in morphometric analysis and their proliferation was recorded. In addition, the proliferation and apoptotic rates of hepatocytes were determined.

Results: In the control and sham operated groups, oval cells were significantly less compared to groups III, IV and V (P < 0.001). The neuropeptides BBS and NT significantly increased the proliferation of oval cells compared to group III (P < 0.001). In addition, BBS and NT induced a significant increase of hepatocyte proliferation (P < 0.001), whereas it decreased their apoptotic activity (P < 0.001) compared to group III. BBS and NT significantly decreased portal endotoxemia (P < 0.001) and increased the hepatic GSH: GSSG ratio (P < 0.05 and P < 0.001, respectively) compared to group III.

Conclusion: BBS and NT stimulated oval cell proliferation in a model of liver regeneration, without use of concomitant suppression of hepatocyte proliferation as oval cell activation stimuli, and improved the hepatocyte regenerative response. This peptides-induced combined stimulation of oval cell and hepatocyte proliferation might serve as a possible treatment modality for several liver diseases.

Keywords: Apoptosis; Hepatic progenitor cells; Liver regeneration; Oval cells; Oxidative stress; Partial hepatectomy; Proliferation.

Figure 1

Microphotographs showing expression of CK19 from oval cells (arrows) in livers of group III (A) and group IV (B) and α-fetoprotein mRNA expression from oval cells (arrows) in group III (C) and group IV (D). In group IV there is higher oval cell presence as demonstrated by both markers [CK19: streptavidin biotin peroxidase (A) × 250, (B) × 100, α-fetoprotein mRNA: in situ hybridization × 250]. PT: Portal tract.

Figure 2

Microphotographs showing Ki67 (+) hepatocytes (arrows) from livers of group III (A) and group IV (B) and TUNEL (+) hepatocytes (arrows) in group III (C) and group IV (D). In group IV there are more Ki67 (+) hepatocytes (streptavidin biotin peroxidase × 100) and less TUNEL (+) hepatocytes (streptavidin biotin peroxidase and hematoxylin eosin × 250). PT: Portal tract.