Hepatoblast and mesenchymal cell-specific gene-expression in fetal rat liver and in cultured fetal rat liver cells

Improved Differentiation of hESC-Derived Pancreatic Progenitors by Using Human Fetal Pancreatic Mesenchymal Cells in a Micro-scalable Three-Dimensional Co-culture System

Mesenchymal cells of diverse origins differ in gene and protein expression besides producing varying effects on their organ-matched epithelial cells' maintenance and differentiation capacity. Co-culture with rodent's tissue-specific pancreatic mesenchyme accelerates proliferation, self-renewal, and differentiation of pancreatic epithelial progenitors. Therefore, in our study, the impact of three-dimensional (3D) co-culture of human fetal pancreatic-derived mesenchymal cells (hFP-MCs) with human embryonic stem cell-derived pancreatic progenitors (hESC-PPs) development towards endocrine and beta cells was assessed. Besides, the ability to maintain scalable cultures combining hFP-MCs and hESC-PPs was investigated. hFP-MCs expressed many markers in common with bone marrow-derived mesenchymal stem cells (BM-MSCs). However, they showed higher expression of DESMIN compared to BM-MSCs. After co-culture of hESC-PPs with hFP-MCs, the pancreatic progenitor (PP) spheroids generated in Matrigel had higher expression of NGN3 and INSULIN than BM-MSCs co-culture group, which shows an inductive impact of pancreatic mesenchyme on hESC-PPs beta-cells maturation. Pancreatic aggregates generated by forced aggregation through scalable AggreWell system showed similar features compared to the spheroids. These aggregates, a combination of hFP-MCs and hESC-PPs, can be applied as an appropriate tool for assessing endocrine-niche interactions and developmental processes by mimicking the pancreatic tissue.

Myofibroblasts control the proliferation of fetal hepatoblasts and their differentiated cholangiocytes during the hepatoblast-to-cholangiocyte transition

Mesenchymal cells in the liver provide the microenvironment for hepatoblasts expansion and differentiation. We have previously demonstrated that myofibroblasts (MFs) promoted hepatoblasts differentiation into cholangiocytes, whereas its role in controlling the proliferation of hepatoblasts and their differentiated cholangiocytes remains elusive. Here, we investigated the role of MFs in regulating the proliferation of hepatoblasts and their differentiated cholangiocytes using an indirect coculture system. When cocultured with hepatoblasts, MFs promoted hepatoblasts differentiation into cholangiocytes and inhibited the proliferation and stemness of hepatoblasts. However, when hepatoblasts already differentiated into cholangiocytes, MFs promoted the differentiated cholangiocytes proliferation. In addition, hepatoblast proliferation genes such as hepatocyte growth factor (HGF), insulin-like growth factor-1 and 2 (IGF-1 and 2), midkine 1 (Mdk1), and pleiotrophin (Ptn) expression in MFs were down-regulated compared with their levels in fibroblasts. Our findings uncover the role of MFs in controlling the proliferation of hepatoblasts and their differentiated cholangiocytes, potentially providing a novel therapeutic strategy for cholangiocyte regeneration.

Liver regeneration requires Yap1-TGFβ-dependent epithelial-mesenchymal transition in hepatocytes

BACKGROUND & AIMS

Chronic failure of mechanisms that promote effective regeneration of dead hepatocytes causes replacement of functional hepatic parenchyma with fibrous scar tissue, ultimately resulting in cirrhosis. Therefore, defining and optimizing mechanisms that orchestrate effective regeneration might prevent cirrhosis. We hypothesized that effective regeneration of injured livers requires hepatocytes to evade the growth-inhibitory actions of TGFβ, since TGFβ signaling inhibits mature hepatocyte growth but drives cirrhosis pathogenesis.

METHODS

Wild-type mice underwent 70% partial hepatectomy (PH); TGFβ expression and signaling were evaluated in intact tissue and primary hepatocytes before, during, and after the period of maximal hepatocyte proliferation that occurs from 24-72 h after PH. To determine the role of Yap1 in regulating TGFβ signaling in hepatocytes, studies were repeated after selectively deleting Yap1 from hepatocytes of Yap1^flox/flox mice.

RESULTS

TGFβ expression and hepatocyte nuclear accumulation of pSmad2 and Yap1 increased in parallel with hepatocyte proliferative activity after PH. Proliferative hepatocytes also upregulated Snai1, a pSmad2 target gene that promotes epithelial-to-mesenchymal transition (EMT), suppressed epithelial genes, induced myofibroblast markers, and produced collagen 1α1. Deleting Yap1 from hepatocytes blocked their nuclear accumulation of pSmad2 and EMT-like response, as well as their proliferation.

CONCLUSION

Interactions between the TGFβ and Hippo-Yap signaling pathways stimulate hepatocytes to undergo an EMT-like response that is necessary for them to grow in a TGFβ-enriched microenvironment and regenerate injured livers.

LAY SUMMARY

The adult liver has an extraordinary ability to regenerate after injury despite the accumulation of scar-forming factors that normally block the proliferation and reduce the survival of residual liver cells. We discovered that liver cells manage to escape these growth-inhibitory influences by transiently becoming more like fibroblasts themselves. They do this by reactivating programs that are known to drive tissue growth during fetal development and in many cancers. Understanding how the liver can control programs that are involved in scarring and cancer may help in the development of new treatments for cirrhosis and liver cancer.

Hepatoma SK Hep-1 cells exhibit characteristics of oncogenic mesenchymal stem cells with highly metastatic capacity

BACKGROUND

SK Hep-1 cells (SK cells) derived from a patient with liver adenocarcinoma have been considered a human hepatoma cell line with mesenchymal origin characteristics, however, SK cells do not express liver genes and exhibit liver function, thus, we hypothesized whether mesenchymal cells might contribute to human liver primary cancers. Here, we characterized SK cells and its tumourigenicity.

METHODS AND PRINCIPAL FINDINGS

We found that classical mesenchymal stem cell (MSC) markers were presented on SK cells, but endothelial marker CD31, hematopoietic markers CD34 and CD45 were negative. SK cells are capable of differentiate into adipocytes and osteoblasts as adipose-derived MSC (Ad-MSC) and bone marrow-derived MSC (BM-MSC) do. Importantly, a single SK cell exhibited a substantial tumourigenicity and metastatic capacity in immunodefficient mice. Metastasis not only occurred in circulating organs such as lung, liver, and kidneys, but also in muscle, outer abdomen, and skin. SK cells presented greater in vitro invasive capacity than those of Ad-MSC and BM-MSC. The xenograft cells from subcutaneous and metastatic tumors exhibited a similar tumourigenicity and metastatic capacity, and showed the same relatively homogenous population with MSC characteristics when compared to parental SK cells. SK cells could unlimitedly expand in vitro without losing MSC characteristics, its tumuorigenicity and metastatic capacity, indicating that SK cells are oncogenic MSC with enhanced self-renewal capacity. We believe that this is the first report that human MSC appear to be transformed into cancer stem cells (CSC), and that their derivatives also function as CSCs.

CONCLUSION

Our findings demonstrate that SK cells represent a transformation mechanism of normal MSC into an enhanced self-renewal CSC with metastasis capacity, SK cells and their xenografts represent a same relative homogeneity of CSC with substantial metastatic capacity. Thus, it represents a novel mechanism of tumor initiation, development and metastasis by CSCs of non-epithelial and endothelia origin.

Extending the knowledge in histochemistry and cell biology

Central to modern Histochemistry and Cell Biology stands the need for visualization of cellular and molecular processes. In the past several years, a variety of techniques has been achieved bridging traditional light microscopy, fluorescence microscopy and electron microscopy with powerful software-based post-processing and computer modeling. Researchers now have various tools available to investigate problems of interest from bird's- up to worm's-eye of view, focusing on tissues, cells, proteins or finally single molecules. Applications of new approaches in combination with well-established traditional techniques of mRNA, DNA or protein analysis have led to enlightening and prudent studies which have paved the way toward a better understanding of not only physiological but also pathological processes in the field of cell biology. This review is intended to summarize articles standing for the progress made in "histo-biochemical" techniques and their manifold applications.