P-27 cellular effects of in vitro lipid overload on hepatic stellate cells and hepatocytes.

Introduction and Objectives: Hepatic cells undergo different processes in response to the steatogenic input of MAFLD. Hepatic cell culture in steatogenic medium is a useful, reproducible tool intended to elucidate these pathogenic mechanisms. This study aimed to study cellular proliferation, death, and senescence in hepatocytes and hepatic stellate cells (HSC) using a model of steatosis in vitro. Materials and Methods: HepG2 hepatocytes were cultured in RPMI1640 (Control-Hep) and LX-2 HSC in DMEM (Control-LX2). Steatogenic media: either RPMI1640 or DMEM supplemented accordingly: mild steatosis (MS:50µM sodium oleate/sodium palmitate (OA/PA) at 2:1 ratio), severe steatosis (SS:500µM 2OA:1PA). HepG2 or LX-2 cells were preincubated for 24h at 37°C and 5% CO2, then incubated in MS or SS medium for up to 72h. Steatogenic medium was refreshed daily. Viability, mortality, proliferation, and senescence were analyzed. Assays are performed in triplicates. Data: Mean±SD. 2-way ANOVA followed by Tukey. P<0.05. Results: Hepatocytes: MS showed lower viability and proliferation, with increased mortality at 72h and higher senescence from 48h. SS displayed lower viability, and proliferation, with increased mortality but lower senescence from 24h. HSC: MS showed diminished viability and increased mortality (16.0%) at 72h. SS showed lower viability and increased mortality rate (50.0%) from 48h.Proliferation increased in both MS and SS at 24h but decreased by 72h. Cellular senescence was diminished at 24 and 48h in both steatogenic conditions. Conclusions: Steatogenic conditions induced different outcomes in the two cell lines studied. Hepatocyte behavior depends on lipid contents. In MS, increased senescence might be considered a mechanism to avoid damaged-cell proliferation. In SS, increased mortality rate and decreased senescence suggest lipotoxicity and activation of death pathways. In contrast, HSC cultured in steatogenic conditions might turn into the activated state, therefore increasing their proliferation and avoiding other cellular processes, including senescence. Both hepatocyte and HSC outcomes presented here contribute to the pathogenesis of MAFLD.