Abstract
IntroductionMesenchymal stem/stromal cells (MSCs) improve the metabolic function of co-cultured hepatocytes. The present study aimed to further enhance the trophic effects of co-culture with hepatocytes using hypoxic preconditioning (HPc) of the MSCs and also to investigate the underlying molecular mechanisms involved.MethodsHuman adipose tissue-derived MSCs were subjected to hypoxia (2 % O2; HPc) or normoxia (20 % O2) for 24 h and then co-cultured with isolated human hepatocytes. Assays of metabolic function and apoptosis were performed to investigate the hepatotrophic and anti-apoptotic effects of co-culture. Indirect co-cultures and co-culture with MSC-conditioned medium investigated the role of paracrine factors in the hepatotrophic effects of co-culture. Reactive oxygen species (ROS) activity was antagonised with N-acetylcysteine to investigate whether HPc potentiated the effects of MSCs by intracellular ROS-dependent mechanisms. Tumour necrosis factor (TNF)-α, transforming growth factor (TGF)-β1, and extracellular collagen production was determined and CASP9 and BAX/BCL-2 signalling pathways analysed to investigate the role of soluble factors, extracellular matrix deposition, and apoptosis-associated gene signalling in the effects of co-culture.ResultsHPc potentiated the hepatotrophic and anti-apoptotic effects of co-culture by ROS-dependent mechanisms. There was increased MSC TGF-β1 production, and enhanced MSC deposition of extracellular collagen, with reduced synthesis of TNF-α, as well as a downregulation of the expression of pro-apoptotic CASP9, BAX, BID and BLK genes and upregulated expression of anti-apoptotic BCL-2 in hepatocytes.ConclusionsHPc potentiated the trophic and anti-apoptotic effects of MSCs on hepatocytes via mechanisms including intracellular ROS, autocrine TGF-β, extracellular collagen and caspase and BAX/BCL-2 signalling pathways.Electronic supplementary materialThe online version of this article (doi:10.1186/s13287-015-0218-7) contains supplementary material, which is available to authorized users.
Highlights
Mesenchymal stem/stromal cells (MSCs) improve the metabolic function of co-cultured hepatocytes
Whilst it is possible that isolated primary human hepatocytes become unresponsive to soluble trophic and anti-apoptotic factors released from MSCs, our results suggest that the hepatotrophic effect of co-culture and hypoxic preconditioning (HPc)-induced potentiative effects are primarily mediated by synergistic effects of extracellular matrix (ECM) and direct cell–cell interaction
In conclusion, MSCs have trophic, anti-apoptotic, prosurvival, and protective effects on co-cultured hepatocytes, which are significantly enhanced by HPc
Summary
Mesenchymal stem/stromal cells (MSCs) improve the metabolic function of co-cultured hepatocytes. The present study aimed to further enhance the trophic effects of co-culture with hepatocytes using hypoxic preconditioning (HPc) of the MSCs and to investigate the underlying molecular mechanisms involved. Mesenchymal stem cells (MSCs) have been shown to have a supportive effect on hepatocytes in long-term co-culture in vitro [3]. MSCs maintain and improve co-cultured hepatocyte morphology and metabolic function by the synergistic effects of soluble factors, extracellular matrix (ECM), and cell–cell communication [4,5,6,7]. HPc can rejuvenate aged adipose tissue-derived MSCs by upregulating the gene expression of pro-angiogenic factors, including VEGF, placental growth factor and hepatocyte growth factor [11]
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