The morphological and immunocytochemical evaluation of primary rat hepatocytes undergoing spontaneous cell death: modulation by the nitric oxide donor S-nitroso-N-acetylpenicillamine

Primary hepatocytes and their cultures in liver apoptosis research

Apoptosis not only plays a key role in physiological demise of defunct hepatocytes, but is also associated with a plethora of acute and chronic liver diseases as well as with hepatotoxicity. The present paper focuses on the modelling of this mode of programmed cell death in primary hepatocyte cultures. Particular attention is paid to the activation of spontaneous apoptosis during the isolation of hepatocytes from the liver, its progressive manifestation upon the subsequent establishment of cell cultures and simultaneously to strategies to counteract this deleterious process. In addition, currently applied approaches to experimentally induce controlled apoptosis in this in vitro setting for mechanistic research purposes and thereby its detection using relevant biomarkers are reviewed.

Pre-conditioned mesenchymal stem cells ameliorate renal ischemic injury in rats by augmented survival and engraftment

Background

Ischemia is the major cause of acute kidney injury (AKI), associated with high mortality and morbidity. Mesenchymal stem cells (MSCs) have multilineage differentiation potential and can be a potent therapeutic option for the cure of AKI.

Methods

MSCs were cultured in four groups SNAP (S-nitroso N-acetyl penicillamine), SNAP + Methylene Blue (MB), MB and a control for in vitro analysis. Cultured MSCs were pre-conditioned with either SNAP (100 μM) or MB (1 μM) or both for 6 hours. Renal ischemia was induced in four groups (as in in vitro study) of rats by clamping the left renal padicle for 45 minutes and then different pre-conditioned stem cells were transplanted.

Results

We report that pre-conditioning of MSCs with SNAP enhances their proliferation, survival and engraftment in ischemic kidney. Rat MSCs pre-conditioned with SNAP decreased cell apoptosis and increased proliferation and cytoprotective genes’ expression in vitro. Our in vivo data showed enhanced survival and engraftment, proliferation, reduction in fibrosis, significant improvement in renal function and higher expression of pro-survival and pro-angiogenic factors in ischemic renal tissue in SNAP pre-conditioned group of animals. Cytoprotective effects of SNAP pre-conditioning were abrogated by MB, an inhibitor of nitric oxide synthase (NOS) and guanylate cyclase.

Conclusion

The results of these studies demonstrate that SNAP pre-conditioning might be useful to enhance therapeutic potential of MSCs in attenuating renal ischemia reperfusion injury.

Characterization of spontaneous cell death in monolayer cultures of primary hepatocytes

Monolayer cultures of primary hepatocytes, isolated from freshly removed livers, represent widely used in vitro tools in the area of liver physiology and pathology, pharmacology and toxicology. However, a major shortcoming of these systems is that they cope with dedifferentiation, which is accompanied by spontaneous cell death. The goal of the present study was to elucidate the mechanisms that drive the process of self-generated cell demise in primary hepatocyte cultures. For this purpose, isolated rat hepatocytes were cultivated under conventional conditions, and the occurrence of apoptosis and necrosis was monitored during 4 days by performing a set of acknowledged cell death assays. These included examination of cell morphology by light microscopy, quantification of apoptotic and necrotic cell populations by Hoechst 33342 and propidium iodide in situ staining, assessment of apoptotic and necrotic activities by measuring caspase 3-like activity and extracellular leakage of lactate dehydrogenase, and studying the expression of apoptosis regulators through immunoblot analysis. In essence, two cell death peaks were observed, namely shortly after cell seeding and in the final stages of the cultivation period, both involving apoptotic and necrotic actions. The outcome of this study not only sheds new light onto the molecular processes that underlie spontaneous cell death in primary hepatocyte cultures, but also opens perspectives for the establishment of strategies to increase cell survival in these popular in vitro systems.

Enrichment of hepatocyte-like cells with upregulated metabolic and differentiated function derived from embryonic stem cells using S-NitrosoAcetylPenicillamine

The generation of a large number of fully functional hepatocytes from a renewable cell source can provide an unlimited resource for bioartificial liver devices and cell replacement therapies. We have established a directed differentiation system using sodium butyrate treatment to generate an enriched population of hepatocyte-like cells from embryonic stem cells. A metabolic analysis of the hepatocyte populations revealed glycolytic and mitochondrial phenotypes similar to mouse hepatoma cells, implying that these cells represent an immature hepatocyte phenotype. To mediate further differentiation, S-NitrosoAcetylPenicillamine (SNAP), a nitric oxide donor, was utilized to induce mitochondrial development in the precursor populations. A comparative analysis of the different treated populations showed that 500microM SNAP treatment resulted in the generation of an enriched population of metabolically mature hepatocyte-like cells with increased differentiated function. Specifically, 500microM SNAP treatment increased glucose consumption, lactate production rates, mitochondrial mass, and potential as compared to untreated populations. In addition, functional analysis revealed that intracellular albumin content, urea secretion rates, and cytochrome P450 7a1 promoter activity were increased in the treated population. The methodology described here to generate an enriched population of metabolically and functionally mature hepatocyte-like cells may have potential implications in drug discovery and regenerative medicine.