Deficiency in the NFAT5/TonEBP osmoregulatory transcription factor does not influence liver regeneration

Abstract

Introduction: Liver regeneration following partial hepatectomy is characterized by marked hepatocellular swelling possibly resulting from osmotic dysequilibrium. The osmoregulatory transcription factor NFAT5 (also designated TonEBP plays a central role in maintaining intracellular water homeostasis in response to osmotic stress. We therefore hypothesized that NFAT5 would influence the regeneration of the liver. Methods: Heterozygous NFAT5 knockout mice (Nfat5+/Δ) were compared with wild-type C57BL/6 mice. 1) Mice were weighed and subjected to midline laparotomy under isoflurane anesthesia, followed by partial hepatectomy. A 64+/−2% resection was achieved by removal of the right median, right lateral and left lobes. Samples were collected from 6 wild-type and 6 heterozygous knockout animals 1, 2, 3, 5, and 7 days post-hepatectomy (n=60 animals). 2) Liver regeneration was quantitated by comparing regenerated liver mass to the calculated approximate total liver mass. 3) Proliferating Cell Nuclear Antigen (PCNA) staining was performed on liver sections obtained at the aforementioned timepoints. 4) NFAT5 mRNA levels were determined at each timepoint using quantitative real-time PCR and compared to GAPDH. 5) Results are expressed as mean +/− SEM. Student t-test was used for statistical analysis. Results: Analysis of calculated pre-hepatectomy liver mass to post-operative liver mass revealed 75% total liver regeneration in both wild-type and Nfat5+/Δmice. Liver to body weight ratios pre- and post-hepatectomy confirmed 75+/−3% regeneration at 7 days. PCNA-positivity in each group was similar 7 days post-hepatectomy. The ratio of NFAT5 to GAPDH mRNA in wild-type mice showed no significant change over the course of regeneration.