Signalling pathways involved in the process of mesenchymal stem cells differentiating into hepatocytes

Leveraging stem cells to combat hepatitis: a comprehensive review of recent studies

Hepatitis is a significant global public health concern, with viral infections being the most common cause of liver inflammation. Antiviral medications are the primary treatments used to suppress the virus and prevent liver damage. However, the high cost of these drugs and the lack of awareness and stigma surrounding the disease create challenges in managing hepatitis. Stem cell therapy has arisen as a promising therapeutic strategy for hepatitis by virtue of its regenerative and immunomodulatory characteristics. Stem cells have the exceptional capacity to develop into numerous cell types and facilitate tissue regeneration, rendering them a highly promising therapeutic avenue for hepatitis. In animal models, stem cell therapy has demonstrated worthy results by reducing liver inflammation and improving liver function. Furthermore, clinical trials have been undertaken to assess the safety and effectiveness of stem cell therapy in individuals with hepatitis. This review aims to explore the involvement of stem cells in treating hepatitis and highlight the findings from studies conducted on both animals and humans. The objective of this review is to primarily concentrate on the ongoing and future clinical trials that assess the application of stem cell therapy in the context of hepatitis, including the transplantation of autologous bone marrow-derived stem cells, human induced pluripotent stem cells, and other mesenchymal stem cells. In addition, this review will explore the potential merits and constraints linked to stem cell therapy for hepatitis, as well as its prospective implications in the management of this disease.

Schisandrin B promotes hepatic differentiation from human umbilical cord mesenchymal stem cells

Human umbilical cord mesenchymal stem cells (UC-MSCs)-derived hepatocyte-like cells (HLCs) have shown great promise in the treatment of liver diseases. However, most current induction protocols yield hepatocyte-like cells with limited function as compared with primary hepatocytes. Schisandrin B (Sch B) is one of the main components of Schisandra chinensis, which can prevent fibrosis progression and promote liver cell regeneration. Herein, we investigated the effects of Sch B on hepatic differentiation of UC-MSCs. We found that treatment with 10 μM Sch B from the second stage of the differentiation process increased hepatic marker levels and hepatic function. Additionally, RNA-seq analysis revealed that Sch B promoted hepatic differentiation via activating the JAK2/STAT3 pathway. When transplanted HLCs into mice with CCL4-induced liver fibrosis, Sch B-treated HLCs exhibited significant therapeutic effects. This study provides an optimized hepatic differentiation protocol for UC-MSCs based on Sch B, yielding functioning cells for liver disease treatment.

Mechanisms of Action of Mesenchymal Stem Cells in Metabolic-Associated Fatty Liver Disease

Metabolic-associated fatty liver disease (MAFLD) is currently the most common chronic liver disease worldwide. However, its pathophysiological mechanism is complicated, and currently, it has no FDA-approved pharmacological therapies. In recent years, mesenchymal stem cell (MSC) therapy has attracted increasing attention in the treatment of hepatic diseases. MSCs are multipotent stromal cells that originated from mesoderm mesenchyme, which have self-renewal and multipotent differentiation capability. Recent experiments and studies have found that MSCs have the latent capacity to be used for MAFLD treatment. MSCs have the potential to differentiate into hepatocytes, which could be induced into hepatocyte-like cells (HLCs) with liver-specific morphology and function under appropriate conditions to promote liver tissue regeneration. They can also reduce liver tissue injury and reverse the development of MAFLD by regulating immune response, antifibrotic activities, and lipid metabolism. Moreover, several advantages are attributed to MSC-derived exosomes (MSC-exosomes), such as targeted delivery, reliable reparability, and poor immunogenicity. After entering the target cells, MSC-exosomes help regulate cell function and signal transduction; thus, it is expected to become an emerging treatment for MAFLD. In this review, we comprehensively discussed the roles of MSCs in MAFLD, main signaling pathways of MSCs that affect MAFLD, and mechanisms of MSC-exosomes on MAFLD.

Interplay of matrix stiffness and stress relaxation in directing osteogenic differentiation of mesenchymal stem cells

The aim of this study is to investigate the impact of the stiffness and stress relaxation of poly(acrylamide-co-acrylic acid) hydrogels on the osteogenic differentiation of human mesenchymal stem cells (hMSCs). Varying the amount of the crosslinker and the ratio between the monomers enabled the obtainment of hydrogels with controlled mechanical properties, as characterized using unconfined compression and atomic force microscopy (AFM). Subsequently, the surface of the hydrogels was functionalized with a mimetic peptide of the BMP-2 protein, in order to favor the osteogenic differentiation of hMSCs. Finally, hMSCs were cultured on the hydrogels with different stiffness and stress relaxation: 15 kPa - 15%, 60 kPa - 15%, 140 kPa - 15%, 100 kPa - 30%, and 140 kPa - 70%. The cells on hydrogels with stiffnesses from 60 kPa to 140 kPa presented a star-like shape, typical of osteocytes, which has only been reported by our group for two-dimensional substrates. Then, the extent of hMSC differentiation was evaluated by using immunofluorescence and by quantifying the expression of both osteoblast markers (Runx-2 and osteopontin) and osteocyte markers (E11, DMP1, and sclerostin). It was found that a stiffness of 60 kPa led to a higher expression of osteocyte markers as compared to stiffnesses of 15 and 140 kPa. Finally, the strongest expression of osteoblast and osteocyte differentiation markers was observed for the hydrogel with a high relaxation of 70% and a stiffness of 140 kPa.

Mesenchymal stromal cells (MSCs) and their exosome in acute liver failure (ALF): a comprehensive review

Recently, mesenchymal stromal cells (MSCs) and their derivative exosome have become a promising approach in the context of liver diseases therapy, in particular, acute liver failure (ALF). In addition to their differentiation into hepatocytes in vivo, which is partially involved in liver regeneration, MSCs support liver regeneration as a result of their appreciated competencies, such as antiapoptotic, immunomodulatory, antifibrotic, and also antioxidant attributes. Further, MSCs-secreted molecules inspire hepatocyte proliferation in vivo, facilitating damaged tissue recovery in ALF. Given these properties, various MSCs-based approaches have evolved and resulted in encouraging outcomes in ALF animal models and also displayed safety and also modest efficacy in human studies, providing a new avenue for ALF therapy. Irrespective of MSCs-derived exosome, MSCs-based strategies in ALF include administration of native MSCs, genetically modified MSCs, pretreated MSCs, MSCs delivery using biomaterials, and also MSCs in combination with and other therapeutic molecules or modalities. Herein, we will deliver an overview regarding the therapeutic effects of the MSCs and their exosomes in ALF. As well, we will discuss recent progress in preclinical and clinical studies and current challenges in MSCs-based therapies in ALF, with a special focus on in vivo reports.

Current Status and Challenges of Human Induced Pluripotent Stem Cell-Derived Liver Models in Drug Discovery

The pharmaceutical industry is in high need of efficient and relevant in vitro liver models, which can be incorporated in their drug discovery pipelines to identify potential drugs and their toxicity profiles. Current liver models often rely on cancer cell lines or primary cells, which both have major limitations. However, the development of human induced pluripotent stem cells (hiPSCs) has created a new opportunity for liver disease modeling, drug discovery and liver toxicity research. hiPSCs can be differentiated to any cell of interest, which makes them good candidates for disease modeling and drug discovery. Moreover, hiPSCs, unlike primary cells, can be easily genome-edited, allowing the creation of reporter lines or isogenic controls for patient-derived hiPSCs. Unfortunately, even though liver progeny from hiPSCs has characteristics similar to their in vivo counterparts, the differentiation of iPSCs to fully mature progeny remains highly challenging and is a major obstacle for the full exploitation of these models by pharmaceutical industries. In this review, we discuss current liver-cell differentiation protocols and in vitro iPSC-based liver models that could be used for disease modeling and drug discovery. Furthermore, we will discuss the challenges that still need to be overcome to allow for the successful implementation of these models into pharmaceutical drug discovery platforms.

Functional Recellularization of Acellular Rat Liver Scaffold by Induced Pluripotent Stem Cells: Molecular Evidence for Wnt/B-Catenin Upregulation

BACKGROUND

Liver transplantation remains the only viable therapy for liver failure but has a severely restricted utility. Here, we aimed to decellularize rat livers to form acellular 3D bio-scaffolds suitable for seeding with induced pluripotent cells (iPSCs) as a tool to investigate the role of Wnt/β-catenin signaling in liver development and generation.

METHODS

Dissected rat livers were randomly divided into three groups: I (control); II (decellularized scaffolds) and III (recellularized scaffolds). Liver decellularization was established via an adapted perfusion procedure and assessed through the measurement of extracellular matrix (ECM) proteins and DNA content. Liver recellularization was assessed through histological examination and measurement of transcript levels of Wnt/β-catenin pathway, hepatogenesis, liver-specific microRNAs and growth factors essential for liver development. Adult rat liver decellularization was confirmed by the maintenance of ECM proteins and persistence of growth factors essential for liver regeneration.

RESULTS

iPSCs seeded rat decellularized livers displayed upregulated transcript expression of Wnt/β-catenin pathway-related, growth factors, and liver specification genes. Further, recellularized livers displayed restored liver-specific functions including albumin secretion and urea synthesis.

CONCLUSION

This establishes proof-of-principle for the generation of three-dimensional liver organ scaffolds as grafts and functional re-establishment.

Advancements in stem cell-derived hepatocyte-like cell models for hepatotoxicity testing

Drug-induced liver injury (DILI) is one of the leading causes of clinical trial failures and high drug attrition rates. Currently, the commonly used hepatocyte models include primary human hepatocytes (PHHs), animal models, and hepatic cell lines. However, these models have disadvantages that include species-specific differences or inconvenient cell extraction methods. Therefore, a novel, inexpensive, efficient, and accurate model that can be applied to drug screening is urgently needed. Owing to their self-renewable ability, source abundance, and multipotent competence, stem cells are stable sources of drug hepatotoxicity screening models. Because 3D culture can mimic the in vivo microenvironment more accurately than can 2D culture, the former is commonly used for hepatocyte culture and drug screening. In this review, we introduce the different sources of stem cells used to generate hepatocyte-like cells and the models for hepatotoxicity testing that use stem cell-derived hepatocyte-like cells.

Genetic modification by overexpression of target gene in mesenchymal stromal cell for treating liver diseases

Different hepatoxic factors cause irreversible liver injury, leading to liver failure, cirrhosis, and cancer in mammals. Liver transplantation is the only effective strategy, which can improve the prognosis of patients with end-stage liver diseases, but it is limited by liver donor shortage, expensive costs, liver graft rejection and dysfunction, and recurring liver failure. Recently, mesenchymal stromal cells (MSCs) isolated from various tissues are regarded as the main stem cell type with therapeutic effects in liver diseases because of their hepatogenic differentiation, anti-inflammatory, immuoregulatory, anti-apoptotic, antifibrotic, and antitumor capacities. To further improve the therapeutic effects of MSCs, multiple studies showed that genetically engineered MSCs have increased regenerative capacities and are able to more effectively inhibit cell death. Moreover, they are able to secrete therapeutic proteins for attenuating liver injury in liver diseases. In this review, we mainly focus on gene overexpression for reprogramming MSCs to increase their therapeutic effects in treating various liver diseases. We described the potential mechanisms of MSCs with gene overexpression in attenuating liver injury, and we recommend further expansion of experiments to discover more gene targets and optimized gene delivery methods for MSC-based regenerative medicine. We also discussed the potential hurdles in genetic engineering MSCs. In conclusion, we highlight that we need to overcome all scientific hurdles before genetically modified MSC therapy can be translated into clinical practices for patients with liver diseases.

ATSC transplantation contributes to liver regeneration following paracetamol-induced acute liver injury through differentiation into hepatic-like cells

INTRODUCTION

Drug-induced liver injury (DILI) is a leading cause of acute liver injury (ALI). Acetaminophen (also termed paracetamol), can often be found in drugs that may be abused (i.e., prescription for pain relief). Animal experiments have shown that mesenchymal stem cell transplantation can ameliorate or even reverse hepatic injury.

MATERIAL AND METHODS

ALI was induced in Wistar rats using paracetamol. ATSCs were transplanted via the intravenous, portal vein, or intrahepatic route directly onto the liver parenchyma. Histological evaluation was conducted to assess drug-induced injury following transplantation. Fluorescence in situ hybridization (FISH) was used to verify the location of stem cells on the liver parenchyma. The effect of those cells on liver regeneration was tested by immunohistochemistry for hepatic growth factor (HGF). In addition, reverse transcription-quantitative PCR (qRT-PCR) was used to assess hepatic growth factor (HGF), hepatic nuclear factor 4α (HNF4α), cytochrome P450 1A2 (CYP1A2) and α-fetoprotein (AFP) mRNA expression.

RESULTS

Immunohistochemical staining for HGF was stronger in the transplanted groups than that in the control group (P<0.001). HNF4α and HGF mRNA levels were increased on day 7 following transplantation (P<0.001 and P=0.009, respectively). CYP1A2 mRNA levels were also increased (P=0.013) in the intravenous groups, while AFP levels were higher in the intrahepatic groups (P=0.006). ATSC transplantation attenuates ALI injury and promotes liver regeneration. Furthermore, expression of specific hepatic enzymes points to ATSC hepatic differentiation.

CONCLUSION

The study showed the positive effects of transplanted adipose tissue stem cells (ATSCs) on liver regeneration (LG) through hepatotrophic factors. Furthermore, increased expression of hepatic specific proteins was recorded in ATSC transplanted groups that indicate stem cells differentiation into hepatic cells.

A time-resolved multi-omic atlas of the developing mouse liver

Liver organogenesis and development are composed of a series of complex, well-orchestrated events. Identifying key factors and pathways governing liver development will help elucidate the physiological and pathological processes including those of cancer. We conducted multidimensional omics measurements including protein, mRNA, and transcription factor (TF) DNA-binding activity for mouse liver tissues collected from embryonic day 12.5 (E12.5) to postnatal week 8 (W8), encompassing major developmental stages. These data sets reveal dynamic changes of core liver functions and canonical signaling pathways governing development at both mRNA and protein levels. The TF DNA-binding activity data set highlights the importance of TF activity in early embryonic development. A comparison between mouse liver development and human hepatocellular carcinoma (HCC) proteomic profiles reveal that more aggressive tumors are characterized with the activation of early embryonic development pathways, whereas less aggressive ones maintain liver function-related pathways that are elevated in the mature liver. This work offers a panoramic view of mouse liver development and provides a rich resource to explore in-depth functional characterization.

Pre-treatments enhance the therapeutic effects of mesenchymal stem cells in liver diseases

Liver diseases caused by viral infection, alcohol abuse and metabolic disorders can progress to end‐stage liver failure, liver cirrhosis and liver cancer, which are a growing cause of death worldwide. Although liver transplantation and hepatocyte transplantation are useful strategies to promote liver regeneration, they are limited by scarce sources of organs and hepatocytes. Mesenchymal stem cells (MSCs) restore liver injury after hepatogenic differentiation and exert immunomodulatory, anti‐inflammatory, antifibrotic, antioxidative stress and antiapoptotic effects on liver cells in vivo. After isolation and culture in vitro, MSCs are faced with nutrient and oxygen deprivation, and external growth factors maintain MSC capacities for further applications. In addition, MSCs are placed in a harsh microenvironment, and anoikis and inflammation after transplantation in vivo significantly decrease their regenerative capacity. Pre‐treatment with chemical agents, hypoxia, an inflammatory microenvironment and gene modification can protect MSCs against injury, and pre‐treated MSCs show improved hepatogenic differentiation, homing capacity, survival and paracrine effects in vitro and in vivo in regard to attenuating liver injury. In this review, we mainly focus on pre‐treatments and the underlying mechanisms for improving the therapeutic effects of MSCs in various liver diseases. Thus, we provide evidence for the development of MSC‐based cell therapy to prevent acute or chronic liver injury. Mesenchymal stem cells have potential as a therapeutic to prolong the survival of patients with end‐stage liver diseases in the near future.

Human amniotic membrane conditioned medium inhibits proliferation and modulates related microRNAs expression in hepatocarcinoma cells

The placental stem cells have called the focus of attention for their therapeutic potential to treat different diseases, including cancer. There is plenty evidence about the antiproliferative, antiangiogenic and proapoptotic properties of the amniotic membrane. Liver cancer is the fifth cause of cancer in the world, with a poor prognosis and survival. Alternative treatments to radio- or chemotherapy have been searched. In this work we aimed to study the antiproliferative properties of the human amniotic membrane conditioned medium (AM-CM) in hepatocarcinoma cells. In addition, we have analyzed the regulation of pro and antiOncomiRs expression involved in hepatocarcinoma physiology. We have determined by ³H-thymidine incorporation assay that AM-CM inhibits DNA synthesis in HepG2 cells after 72 h of treatment. AM-CM pure or diluted at 50% and 25% also diminished HepG2 and HuH-7 cells viability and cell number. Furthermore, AM-CM induced cell cycle arrest in G2/M. When proliferation mechanisms were analyzed we found that AM-CM reduced the expression of both Cyclin D1 mRNA and protein. Nuclear expression of Ki-67 was also reduced. We observed that this CM was able to promote the expression of p53 and p21 mRNA and proteins, leading to cell growth arrest. Moreover, AM-CM induced an increase in nuclear p21 localization, observed by immunofluorescence. As p53 levels were increased, Mdm-2 expression was downregulated. Interestingly, HepG2 and HuH-7 cells treatment with AM-CM during 24 and 72 h produced an upregulation of antiOncomiRs 15a and 210, and a downregulation of proOncomiRs 206 and 145. We provide new evidence about the promising novel applications of human amniotic membrane in liver cancer.

Construction of multicellular aggregate by E-cadherin coated microparticles enhancing the hepatic specific differentiation of mesenchymal stem cells

The differentiation of human mesenchymal stem cells (hMSCs) into hepatocyte-like cells in vitroprovides a promising candidate for cell therapy of liver diseases, and cell aggregates have been proposed to improve the efficiency of expansion and differentiation. Previously, we engineered multicellular aggregates incorporating human E-cadherin fusion protein (hE-cad-Fc)-coated poly(lactic-co-glycolic acid) (PLGA) microparticles (hE-cad-PLGAs), and a significant improvement was obtained in both cellular proliferation of and cytokine secretion by hMSCs. In this study, hepatic differentiation of hMSCs was induced by a biomimetic microenvironment consisting of these engineered aggregates and a cocktail of specific cytokines. The ratio of hE-cad-PLGAs to hMSCs in engineered hMSCs aggregates was optimized to 1:3 for hepatic differentiation. The expressions of hepatic-specific markers were significantly promoted, and cell polarity and activated drug metabolism enzymes were established in MSC/hE-cad-PLGA aggregates compared with MSC and MSC/PLGA aggregates. Moreover, the expressions of stemness and definitive endoderm markers confirmed effectively induced endoderm differentiation in MSC/hE-cad-PLGA aggregates, which was consistent with the pattern of embryonic development. After pre-differentiation for 1 week, the MSC/hE-cad-PLGA aggregates continuously progressed the hepatic phenotype expression in healthy rat peritoneum. Therefore, the biomimetic microenvironment constructed by hE-cad-PLGAs in engineered multicellular aggregates was able to promote the process of endoderm differentiation and the subsequent hepatic differentiation of hMSCs. It would be appropriate for applied research in hepatotoxic drug screening and cell-based treatment of liver diseases. By optimizing with other cytokine cocktail, the engineered multicellular aggregates can be applied to the construction of other endoderm-derived organs. STATEMENT OF SIGNIFICANCE: The differentiation of mesenchymal stem cells (MSCs) into hepatocyte-like cells in vitroprovides a promising for cell therapy for liver diseases, and cell aggregates have been proposed to improve the expansion and differentiation efficiency. Here, engineered multicellular aggregates were constructed by E-cadherin modified microparticles (hE-cad-PLGAs) construct a biomimetic microenvironment to promote the process of endoderm differentiation and the subsequent hepatic differentiation of hMSCs. Furthermore, after pre-differentiation for 1 week, the MSC/hE-cad-PLGA aggregates continuously progressed the hepatic phenotype expression in healthy rat peritoneum. Therefore, engineered multicellular aggregates with hE-cad-PLGAs would be appropriate for applied research in hepatotoxic drug screening and cell-based treatment of liver diseases, and provide a promising method in the construction of other endoderm-derived organs.

Technological advancements for the development of stem cell-based models for hepatotoxicity testing

Stem cells are characterized by their self-renewal capacity and their ability to differentiate into multiple cell types of the human body. Using directed differentiation strategies, stem cells can now be converted into hepatocyte-like cells (HLCs) and therefore, represent a unique cell source for toxicological applications in vitro. However, the acquired hepatic functionality of stem cell-derived HLCs is still significantly inferior to primary human hepatocytes. One of the main reasons for this is that most in vitro models use traditional two-dimensional (2D) setups where the flat substrata cannot properly mimic the physiology of the human liver. Therefore, 2D-setups are progressively being replaced by more advanced culture systems, which attempt to replicate the natural liver microenvironment, in which stem cells can better differentiate towards HLCs. This review highlights the most recent cell culture systems, including scaffold-free and scaffold-based three-dimensional (3D) technologies and microfluidics that can be employed for culture and hepatic differentiation of stem cells intended for hepatotoxicity testing. These methodologies have shown to improve in vitro liver cell functionality according to the in vivo liver physiology and allow to establish stem cell-based hepatic in vitro platforms for the accurate evaluation of xenobiotics.

Remodeling of Glycosaminoglycans During Differentiation of Adult Human Bone Mesenchymal Stromal Cells Toward Hepatocytes

There is a critical need to generate functional hepatocytes to aid in liver repair and regeneration upon availability of a renewable, and potentially personalized, source of human hepatocytes (hHEP). Currently, the vast majority of primary hHEP are obtained from human tissue through cadavers. Recent advances in stem cell differentiation have opened up the possibility to obtain fully functional hepatocytes from embryonic or induced pluripotent stem cells, or adult stem cells. With respect to the latter, human bone marrow mesenchymal stromal cells (hBMSCs) can serve as a source of autogenetic and allogenic multipotent stem cells for liver repair and regeneration. A major aspect of hBMSC differentiation is the extracellular matrix (ECM) composition and, in particular, the role of glycosaminoglycans (GAGs) in the differentiation process. In this study, we examine the influence of four distinct culture conditions/protocols (T1-T4) on GAG composition and hepatic markers. α-Fetoprotein and hepatocyte nuclear factor-4α were expressed continually over 21 days of differentiation, as indicated by real time quantitative PCR analysis, while albumin (ALB) expression did not begin until day 21. Hepatocyte growth factor (HGF) appears to be more effective than activin A in promoting hepatic-like cells through the mesenchymal-epithelial transition, perhaps due to the former binding to the HGF receptor to form a unique complex that diversifies the biological functions of HGF. Of the four protocols tested, uniform hepatocyte-like morphological changes, ALB secretion, and glycogen storage were found to be highest with protocol T2, which involves both early- and late-stage combinations of growth factors. The total GAG profile of the hBMSC ECM is rich in heparan sulfate (HS) and hyaluronan, both of which fluctuate during differentiation. The GAG profile of primary hHEP showed an HS-rich ECM, and thus, it may be possible to guide hBMSC differentiation to more mature hepatocytes by controlling the GAG profile expressed by differentiating cells.

Zebularine Promotes Hepatic Differentiation of Rabbit Bone Marrow Mesenchymal Stem Cells by Interfering with p38 MAPK Signaling

Demethylating agent zebularine is reported to be capable of inducing differentiation of stem cells by activation of methylated genes, though its function in hepatocyte differentiation is unclear. p38 signal pathway is involved in differentiation of hepatocytes and regulating of DNA methyltransferases 1 (DNMT1) expression. However, little is known about the impact of zebularine on bone marrow mesenchymal stem cells (BMMSCs) and p38 signaling during hepatic differentiation. The present study investigated the effects of zebularine on hepatic differentiation of rabbit BMMSCs, as well as the role of p38 on DNMT1 and hepatic differentiation, with the aim of developing a novel strategy for improving derivation of hepatocytes. BMMSCs were treated with zebularine at concentrations of 10, 20, 50, and 100 μM in the presence of hepatocyte growth factor; changes in the levels of hepatic-specific alpha-fetoprotein and albumin were detected and determined by RT-PCR, WB, and immunofluorescence staining. Expression of DNMT1 and phosphorylated p38 as well as urea production and ICG metabolism was also analyzed. Zebularine at concentrations of 10, 20, and 50 μM could not affect cell viability after 48 h. Zebularine treatment leads to an inhibition of DNMT activity and increase of hepatic-specific proteins alpha-fetoprotein and albumin in BMMSCs in vitro; zebularine addition also induced expression of urea production of and ICG metabolism. p38 signal was activated in BMMSCs simulated with HGF; inhibition of p38 facilitated the synthesis of DNMT1 and albumin in cells. Zebularine restrained DNMT1 and phosphorylated p38 which were induced by HGF. Therefore, this study demonstrated that treatment with zebularine exhibited terminal hepatic differentiation of BMMSCs in vitro in association with hepatocyte growth factor; p38 pathway at least partially participates in zebularine-induced hepatic differentiation of rabbit BMMSCs.

Ultrasound Irradiation Combined with Hepatocyte Growth Factor Accelerate the Hepatic Differentiation of Human Bone Marrow Mesenchymal Stem Cells

This study investigated the impact of ultrasound (US) irradiation on the hepatic differentiation of human bone marrow mesenchymal stem cells (hBMSCs) induced by hepatocyte growth factor (HGF) and the possible mechanisms. We treated hBMSCs, using HGF with and without US irradiation. Cell viability and stem cell surface markers were analyzed. Hepatocyte-like cell markers and functional markers including α-fetoprotein (αFP/AFP), cytokeratin 18 (CK18), albumin (ALB) and glycogen content were analyzed at the time point of day 1, 3 and 5 after treatment. The involvement of Wnt/β-catenin signaling pathway was evaluated as well. The results showed that the US treatment at 1.0 W/cm² or 1.5 W/cm² for 30 s or 60 s conditions yielded favorable cell viability and engendered stem cell differentiation. At day 5, the expressions of AFP, CK18, ALB and the glycogen content were significantly elevated in the US-treated group at both messenger ribonucleic acid and protein levels (all p <0.05), in comparison with HGF and control groups. Among all the US treated groups, the expression levels of specific hepatic markers in the (1.5 W/cm² for 60 s) group were the highest. Furthermore, Wnt1, β-Catenin, c-Myc and Cyclin D1 were significantly increased after US irradiation (all p <0.05), and the enhancements of c-Myc and Cyclin D1 could be obviously impaired by the inhibitor ICG-001 (p <0.05, p <0.05), in accordance with decreased ALB and CK18 expression and glycogen content (all p <0.05). In conclusion, US irradiation was able to promote the hBMSCs' differentiation mediated by HGF in vitro safely, easily and controllably. The activation of Wnt/β-catenin signaling pathway was involved in this process. US irradiation could serve as a potentially beneficial tool for the research and application of stem cell differentiation.

Organ reconstruction: Dream or reality for the future

The relevance of research on reconstructed organs is justified by the lack of organs available for transplant and the growing needs for the ageing population. The development of a reconstructed organ involves two parallel complementary steps: de-cellularization of the organ with the need to maintain the structural integrity of the extracellular matrix and vascular network and re-cellularization of the scaffold with stem cells or resident cells.Whole organ engineering for liver, heart, lung or kidneys, is particularly difficult because of the structural complexity of organs and heterogeneity of cells. Rodent, porcine and rhesus monkey organs have been de-cellularized to obtain a scaffold with preserved extracellular matrix and vascular network. As concern the cells for re-cellularization, embryonic, foetal, adult, progenitor stem cells and also iPS have been proposed.Heart construction could be an alternative option for the treatment of cardiac insufficiency. It is based on the use of an extra-cellular matrix coming from an animal's heart and seeded with cells likely to reconstruct a normal cardiac function. Though de-cellularization techniques now seem controlled, the issues posed by the selection of cells capable of generating the various components of cardiac tissue are not settled yet. In addition, the recolonisation of the matrix does not only depend on the phenotype of cells that are used, but it is also impacted by the nature of biochemical signals emitted.Recent researches have shown that it is possible to use decellularized whole liver treated by detergents as scaffold, which keeps the entire network of blood vessels and the integrated extracellular matrix (ECM). Beside of decellularized whole organ scaffold seeding cells selected to repopulate a decellularized liver scaffold are critical for the function of the bioengineered liver. At present, potential cell sources are hepatocyte, and mesenchymal stem cells.Pulmonary regeneration using engineering approaches is complex. In fact, several types of local progenitor cells that contribute to cell repair have been described at different levels of the respiratory tract. Moving towards the alveoles, one finds bronchioalveolar stem cells as well as epithelial cells and pneumocytes. A promising option to increase the donor organ pool is to use allogeneic or xenogeneic decellularized lungs as a scaffold to engineer functional lung tissue ex vivo.The kidney is certainly one of the most difficult organs to reconstruct due to its complex nature and the heterogeneous nature of the cells. There is relatively little research on auto-construction, and experiments have been performed on rats, pigs and monkeys.Nevertheless, before these therapeutic approaches can be applied in clinical practice, many researches are necessary to understand and in particular the behaviour of cells on the decellularized organs as well as the mechanisms of their interaction with the microenvironment. Current knowledges allow optimism for the future but definitive answers can only be given after long term animal studies and controlled clinical studies.

Oncostatin M in William's E medium is suitable for initiation of hepatocyte differentiation in human induced pluripotent stem cells

William's E (WE) is a suitable medium for the differentiation of human induced pluripotent stem (iPS) cells to the hepatocyte lineage. The aim of the present study was to investigate various growth factors in their ability to promote hepatocyte differentiation of iPS cells in WE medium. Human iPS 201B7 cells were cultured in WE medium supplemented with growth factors, and mRNA expression levels and promoter activities of α‑fetoprotein (AFP) and albumin were examined by reverse transcription‑quantitative polymerase chain reaction and luciferase assay, respectively. In addition, time course analysis of AFP mRNA expression was performed in 201B7 cells cultured in WE medium supplemented with oncostatin M. The results demonstrated that mRNA expression levels of AFP were significantly elevated by most growth factors tested as supplements in WE medium, except all‑trans retinoic acid, compared with cells cultured in ReproFF (a medium that maintains pluripotency). The highest increase in AFP mRNA expression levels was observed by oncostatin M stimulation. Albumin mRNA expression levels were increased by all‑trans retinoic acid and insulin‑transferrin‑selenium supplementation in WE medium compared with cells cultured in ReproFF. Oncostatin M supplementation significantly stimulated the promoter activity of the AFP gene, but no growth factor tested significantly stimulated the promoter activity of the albumin gene. By time course analysis, significant increase of AFP mRNA expression was observed on the sixth day post‑stimulation, compared with cells cultured in WE medium alone. In conclusion, the present study demonstrated that oncostatin M supplementation in WE medium was sufficient to initiate hepatocyte differentiation in iPS cells.

Echinococcus-Host Interactions at Cellular and Molecular Levels

The potentially lethal zoonotic diseases alveolar and cystic echinococcosis are caused by the metacestode larval stages of the tapeworms Echinococcus multilocularis and Echinococcus granulosus, respectively. In both cases, metacestode growth and proliferation occurs within the inner organs of mammalian hosts, which is associated with complex molecular host-parasite interactions that regulate nutrient uptake by the parasite as well as metacestode persistence and development. Using in vitro cultivation systems for parasite larvae, and informed by recently released, comprehensive genome and transcriptome data for both parasites, these molecular host-parasite interactions have been subject to significant research during recent years. In this review, we discuss progress in this field, with emphasis on parasite development and proliferation. We review host-parasite interaction mechanisms that occur early during an infection, when the invading oncosphere stage undergoes a metamorphosis towards the metacestode, and outline the decisive role of parasite stem cells during this process. We also discuss special features of metacestode morphology, and how this parasite stage takes up nutrients from the host, utilizing newly evolved or expanded gene families. We comprehensively review mechanisms of host-parasite cross-communication via evolutionarily conserved signalling systems and how the parasite signalling systems might be exploited for the development of novel chemotherapeutics. Finally, we point to an urgent need for the development of functional genomic techniques in this parasite, which will be imperative for hypothesis-driven analyses into Echinococcus stem cell biology, developmental mechanisms and immunomodulatory activities, which are all highly relevant for the development of anti-infective measures.

Mesenchymal Stem Cells after Polytrauma: Actor and Target

Mesenchymal stem cells (MSCs) are multipotent cells that are considered indispensable in regeneration processes after tissue trauma. MSCs are recruited to damaged areas via several chemoattractant pathways where they function as “actors” in the healing process by the secretion of manifold pro- and anti-inflammatory, antimicrobial, pro- and anticoagulatory, and trophic/angiogenic factors, but also by proliferation and differentiation into the required cells. On the other hand, MSCs represent “targets” during the pathophysiological conditions after severe trauma, when excessively generated inflammatory mediators, complement activation factors, and damage- and pathogen-associated molecular patterns challenge MSCs and alter their functionality. This in turn leads to complement opsonization, lysis, clearance by macrophages, and reduced migratory and regenerative abilities which culminate in impaired tissue repair. We summarize relevant cellular and signaling mechanisms and provide an up-to-date overview about promising future therapeutic MSC strategies in the context of severe tissue trauma.

Promising Therapy Candidates for Liver Fibrosis

Liver fibrosis is a wound-healing process in response to repeated and chronic injury to hepatocytes and/or cholangiocytes. Ongoing hepatocyte apoptosis or necrosis lead to increase in ROS production and decrease in antioxidant activity, which recruits inflammatory cells from the blood and activate hepatic stellate cells (HSCs) changing to myofibroblasts. Injury to cholangiocytes also recruits inflammatory cells to the liver and activates portal fibroblasts in the portal area, which release molecules to activate and amplify cholangiocytes. No matter what origin of myofibroblasts, either HSCs or portal fibroblasts, they share similar characteristics, including being positive for α-smooth muscle actin and producing extracellular matrix. Based on the extensive pathogenesis knowledge of liver fibrosis, therapeutic strategies have been designed to target each step of this process, including hepatocyte apoptosis, cholangiocyte proliferation, inflammation, and activation of myofibroblasts to deposit extracellular matrix, yet the current therapies are still in early-phase clinical development. There is an urgent need to translate the molecular mechanism of liver fibrosis to effective and potent reagents or therapies in human.

Stem Cells and Regenerative Medicine: Myth or Reality of the 21th Century

Since the 1960s and the therapeutic use of hematopoietic stem cells of bone marrow origin, there has been an increasing interest in the study of undifferentiated progenitors that have the ability to proliferate and differentiate into various tissues. Stem cells (SC) with different potency can be isolated and characterised. Despite the promise of embryonic stem cells, in many cases, adult or even fetal stem cells provide a more interesting approach for clinical applications. It is undeniable that mesenchymal stem cells (MSC) from bone marrow, adipose tissue, or Wharton's Jelly are of potential interest for clinical applications in regenerative medicine because they are easily available without ethical problems for their uses. During the last 10 years, these multipotent cells have generated considerable interest and have particularly been shown to escape to allogeneic immune response and be capable of immunomodulatory activity. These properties may be of a great interest for regenerative medicine. Different clinical applications are under study (cardiac insufficiency, atherosclerosis, stroke, bone and cartilage deterioration, diabetes, urology, liver, ophthalmology, and organ's reconstruction). This review focuses mainly on tissue and organ regeneration using SC and in particular MSC.

Sepsis: From Pathophysiology to Individualized Patient Care

Sepsis has become a major health economic issue, with more patients dying in hospitals due to sepsis related complications compared to breast and colorectal cancer together. Despite extensive research in order to improve outcome in sepsis over the last few decades, results of large multicenter studies were by-and-large very disappointing. This fiasco can be explained by several factors, but one of the most important reasons is the uncertain definition of sepsis resulting in very heterogeneous patient populations, and the lack of understanding of pathophysiology, which is mainly based on the imbalance in the host-immune response. However, this heroic research work has not been in vain. Putting the results of positive and negative studies into context, we can now approach sepsis in a different concept, which may lead us to new perspectives in diagnostics and treatment. While decision making based on conventional sepsis definitions can inevitably lead to false judgment due to the heterogeneity of patients, new concepts based on currently gained knowledge in immunology may help to tailor assessment and treatment of these patients to their actual needs. Summarizing where we stand at present and what the future may hold are the purpose of this review.