The beneficial paracrine roles of mesenchymal stem cells (MSCs) in tissue repair have potential in therapeutic strategies against various diseases. However, the key therapeutic factors secreted from MSCs and their exact molecular mechanisms of action remain unclear. In this study, the cell-free secretome of umbilical cord-derived MSCs showed significant anti-fibrotic activity in the mouse models of liver fibrosis. The involved action mechanism was the regulation of hepatic stellate cell activation by direct inhibition of the TGF/Smad-signaling. Antagonizing the milk fat globule-EGF factor 8 (MFGE8) activity blocked the anti-fibrotic effects of the MSC secretome in vitro and in vivo. Moreover, MFGE8 was secreted by MSCs from the umbilical cord as well as other tissues, including teeth and bone marrow. Administration of recombinant MFGE8 protein alone had a significant anti-fibrotic effect in two different models of liver fibrosis. Additionally, MFGE8 downregulated TGF type I receptor expression by binding to v3 integrin on HSCs. These findings revealed the potential role of MFGE8 in modulating TGF-signaling. Thus, MFGE8 could serve as a novel therapeutic agent for liver fibrosis. [BMB Reports 2017; 50(2): 58-59]

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Highly homogeneous and functional stem cell-derived hepatocyte-like cells (HLCs) are considered a promising option in the cell-based therapy of liver disease and the development of effective in vitro toxicity screening tools. However, the purity of cells and expression and/or activity of drug metabolizing enzymes in stem cell-derived HLCs are usually too low to be useful for clinical or in vitro applications. Here, we describe a highly optimized hepatic differentiation protocol, which produces >90% (BGO1 and CHA15) albumin-positive HLCs with no purification process from human embryonic stem cell lines. In addition, we show that hepatic enzyme gene expressions and activities were significantly improved by generating 3D spheroidal aggregate of HLCs, compared with 2D HLCs. The 3D differentiation method increased expression of nuclear receptors (NRs) that regulate the proper expression of key hepatic enzymes. Furthermore, significantly increased hepatic functions such as albumin and urea secretion were observed in 3D hepatic spheroids, compared with 2D HLCs. HLCs in the spheroid exhibited morphological and ultrastructural features of normal hepatocytes. Importantly, we show that repeated exposures to xenobiotics facilitated further functional maturation of HLC, as confirmed by increased expression of genes for drug metabolizing enzymes and transcription factors. In conclusion, the 3D culture system with repeated exposures to xenobiotics may be a new strategy for enhancing hepatic metabolizing ability of stem cell-derived HLCs as a cell source for in vitro high-throughput hepatotoxicity models.

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Milk fat globule-EGF factor 8 (MFG-E8) is an anti-inflammatory glycoprotein that mediates a wide spectrum of pathophysiological processes. MFG-E8 has been studied as a key regulator of cancer cell invasion, migration, and proliferation in different tissues and organs. However, potential roles of MFG-E8 in the growth and progression of liver cancer have not been investigated to date. Here, we analyzed 33 human hepatocellular carcinoma (HCC) samples and found that levels of MFG-E8 expression were significantly higher in HCC cells than in normal liver tissues. In addition, our in vitro gain-of-function study in three different HCC cell lines revealed that overexpression of MFG-E8 promoted the proliferation and migration of HCC cells, as determined by RT-qPCR, MTT assays, and wound healing analyses. Conversely, an MFG-E8 loss-of function study showed that proliferation capacity was significantly reduced by MFG-E8 knockdown in HCC cells. Additionally, MFG-E8 activity-neutralizing antibodies profoundly inhibited both migration and proliferation of HCC cells, attenuating their tumorigenic properties. These reductions in migration and proliferation were rescued by treatment of HCC cells with recombinant MFG-E8 protein. Furthermore, an in vivo HCC xenograft study showed that the number of proliferating HCC cells and tumor volume/weight were all significantly increased by MFG-E8 overexpression, compared to control mice. These results clearly show that MFG-E8 plays an important role in HCC progression and may provide a basis for future mechanistic studies and new strategies for the treatment of liver cancer.Cancers 2020, 12, 403 2 of 16 underlying HCC tumorigenesis and identifying novel therapeutic targets are both of great significance in improving the overall prognosis of patients with HCC.Milk fat globule-EGF factor 8 (MFG-E8) is a glycoprotein initially identified as a component of milk fat globules secreted from mammary epithelial cells [3]. Human MFG-E8 consists of an N-terminal EGF-like domain which contains an integrin-binding RGD motif, and two repeated C-terminal discoidin/F5/8C domains that bind phosphatidylserine [3]. Because phosphatidylserine is exposed on the surfaces of apoptotic cells, MFG-E8 has been studied as an opsonin that mediates clearance of dying cells via integrin-expressing phagocytes [4,5]. MFG-E8 is also expressed in many cell types, including mammary epithelial and myoepithelial cells, dendritic cells, endothelial cells, intestinal cells, and retinal epithelial cells. It has been demonstrated that MFG-E8 regulates cellular proliferation, differentiation, and migration under various pathophysiological conditions, including sepsis and age-related diseases [6,7]. We also showed that MFG-E8 is secreted from human umbilical cord mesenchymal stem cells and strongly inhibits the activation of hepatic stellate cells, reducing liver fibrosis both in vitro and in vivo [8].Recent studies have revealed that MFG-E8 is involved in the progression of a variety of tumors, including breast cancer, ovarian canc...