Background and aim The lymphatic network plays a major role in maintaining tissue fluid homoeostasis. Therefore several pathological conditions associated with oedema formation result in deficient lymphatic function. However, the role of the lymphatic system in the pathogenesis of ascites and oedema formation in cirrhosis has not been fully clarified. The aim of this study was to investigate whether the inability of the lymphatic system to drain tissue exudate contributes to the oedema observed in cirrhosis.
Methods Cirrhosis was induced in rats by CCl4 inhalation. Lymphatic drainage was evaluated using fluorescent lymphangiography. Expression of endothelial nitric oxide synthase (eNOS) was measured in primary lymphatic endothelial cells (LyECs). Inhibition of eNOS activity in cirrhotic rats with ascites (CH) was carried out by L-NG-methyl-L-arginine (L-NMMA) treatment (0.5 mg/kg/day).
Results The (CH) rats had impaired lymphatic drainage in the splanchnic and peripheral regions compared with the control (CT) rats. LyECs isolated from the CH rats showed a significant increase in eNOS and nitric oxide (NO) production. In addition, the lymphatic vessels of the CH rats showed a significant reduction in smooth muscle cell (SMC) coverage compared with the CT rats. CH rats treated with L-NMMA for 7 days showed a significant improvement in lymphatic drainage and a significant reduction in ascites volume, which were associated with increased plasma volume. This beneficial effect of L-NMMA inhibition was also associated with a significant increase in lymphatic SMC coverage.
Conclusions The upregulation of eNOS in the LyECs of CH rats causes long-term lymphatic remodelling, which is characterised by a loss of SMC lymphatic coverage. The amelioration of this lymphatic abnormality by chronic eNOS inhibition results in improved lymphatic drainage and reduced ascites.
- Nitric oxide
- lymphatic vessels
- endothelial cells
- hepatic fibrosis
- hepatic haemodynamics
- hepatic metastases
- hepatic stellate cell
- smooth muscle
- fluid retention in liver disease
- liver cirrhosis
- hepatic haemodynamics
- hepatic circulation
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Funding This work was supported by grants from the Ministerio de Ciencia e Innovación-Plan Nacional de I+D+I (SAF2007-63069 and SAF2010-19025 to MM-R and SAF2009-08039 to WJ) and AGAUR (2009 SGR 1496 to WJ). MP was supported by MICINN (contract number BES-2007-16909). CIBERehd and CIBER-BBN are financed by the Instituto de Salud Carlos III.
Competing interests None.
Provenance and peer review Not commissioned; externally peer reviewed.