Selective enrichment of hepatocytes from mouse embryonic stem cells with a culture system containing cholestatic serum

In vitro differentiation effect of CCL4-induced liver injured mice serum on bone marrow-derived mesenchymal stem cells toward hepatocytes like cells

Liver dysfunction is a major health problem worldwide. Stem cells therapy has opened up new avenues for researches to treat liver diseases due to their multi lineage differentiation. As mesenchymal stem cells (MSCs) can be differentiated into hepatic lineages in the presence of different exogenous factors, the current study aimed to investigate the impact of carbon tetrachloride (CCl₄) induced liver injured mice serum on MSCs differentiation toward hepatocytes in vitro. Male Balb/c mice were treated for liver injury with CCl₄ as determined through biochemical tests spectrophotometrically and different growth factors (EGF, HGF) quantification through Sandwich ELISA in both normal and CCl₄-induced liver injured mice serum. Mice bone marrow derived-MSCs at second passage were treated with normal and CCl₄-induced liver injured mice serum. After 7 days, serum treated MSCs were investigated for hepatocytes like characteristics through RT-PCR. Serum biochemical tests (Bilirubin, ALT and ALP) and sandwich ELISA results of EGF and HGF showed marked increase in CCl₄ treated mice serum as compared to normal mice serum_. Periodic acid Schiff's staining and urea assay kit confirmed high level of glycogen storage and urea production in cells treated with CCl₄-induced liver injured mice serum. RT-PCR results of CCl₄-induced liver injured mice serum treated cells also showed expression of hepatic markers (Albumin, Cyto-8, Cyto-18, and Cyto-19). This study confirmed that CCl₄-induced liver injured serum treatment can differentiate MSCs into hepatocyte-like cells in vitro.

Mesenchymal Stem Cells Pretreated with HGF and FGF4 Can Reduce Liver Fibrosis in Mice

Stem cells have opened a new avenue to treat liver fibrosis. We investigated in vitro and in vivo the effect of cytokine (HGF and FGF4) pretreated MSCs in reduction of CCl4 liver injury. Mouse MSCs were pretreated with cytokines to improve their ability to reduce CCl4 injury. In vitro we gave CCl4 injury to mouse hepatocytes and cocultured it with untreated and cytokines pretreated MSCs. For in vivo study we labeled MSCs with PKH-26 and transplanted them into CCl4 injured mice by direct injection into liver. In vitro data showed that cytokines pretreated MSCs significantly reduce LDH level and apoptotic markers in CCl4 injured hepatocytes cocultured model. Furthermore the cytokines pretreated MSCs also improved cell viability and enhanced hepatic and antiapoptotic markers in injured hepatocytes cocultured model as compared to untreated MSCs. In vivo data in cytokines pretreated group demonstrated greater homing of MSCs in liver, restored glycogen storage, and significant reduction in collagen, alkaline phosphatase, and bilirubin levels. TUNEL assay and real time PCR also supported our hypothesis. Therefore, cytokines pretreated MSCs were shown to have a better therapeutic potential on reduction of liver injury. These results demonstrated the potential utility of this novel idea of cytokines pretreated MSCs for the treatment of liver fibrosis.

In vitro hepatic trans-differentiation of human mesenchymal stem cells using sera from congestive/ischemic liver during cardiac failure

Cellular therapy for end-stage liver failures using human mesenchymal stem cells (hMSCs)-derived hepatocytes is a potential alternative to liver transplantation. Hepatic trans-differentiation of hMSCs is routinely accomplished by induction with commercially available recombinant growth factors, which is of limited clinical applications. In the present study, we have evaluated the potential of sera from cardiac-failure-associated congestive/ischemic liver patients for hepatic trans-differentiation of hMSCs. Results from such experiments were confirmed through morphological changes and expression of hepatocyte-specific markers at molecular and cellular level. Furthermore, the process of mesenchymal-to-epithelial transition during hepatic trans-differentiation of hMSCs was confirmed by elevated expression of E-Cadherin and down-regulation of Snail. The functionality of hMSCs-derived hepatocytes was validated by various liver function tests such as albumin synthesis, urea release, glycogen accumulation and presence of a drug inducible cytochrome P450 system. Based on these findings, we conclude that sera from congestive/ischemic liver during cardiac failure support a liver specific microenvironment for effective hepatic trans-differentiation of hMSCs in vitro.

Dynamic tracking of stem cells in an acute liver failure model

AIM: To investigate a dual labeling technique, which would enable real-time monitoring of transplanted embryonic stem cell (ESC) kinetics, as well as long-term tracking.

METHODS: Liver damage was induced in C57/BL6 male mice (n = 40) by acetaminophen (APAP) 300 mg/kg administered intraperitoneally. Green fluorescence protein (GFP) positive C57/BL6 mouse ESCs were stained with the near-infrared fluorescent lipophilic tracer 1,1-dioctadecyl-3,3,3,3-tetramethylindotricarbocyanine iodide (DiR) immediately before transplantation into the spleen. Each of the animals in the cell therapy group (n = 20) received 5 × 10⁶ ESCs 4 h following treatment with APAP. The control group (n = 20) received the vehicle only. The distribution and dynamics of the cells were monitored in real-time with the IVIS Lumina-2 at 30 min post transplantation, then at 3, 12, 24, 48 and 72 h, and after one and 2 wk. Immunohistochemical examination of liver tissue was used to identify expression of GFP and albumin. Plasma alanine aminotransferase (ALT) was measured as an indication of liver damage.

RESULTS: DiR-stained ESCs were easily tracked with the IVIS using the indocyanine green filter due to its high background passband with minimal background autofluorescence. The transplanted cells were confined inside the spleen at 30 min post-transplantation, gradually moved into the splenic vein, and were detectable in parts of the liver at the 3 h time-point. Within 24 h of transplantation, homing of almost 90% of cells was confirmed in the liver. On day three, however, the DiR signal started to fade out, and ex vivo IVIS imaging of different organs allowed signal detection at time-points when the signal could not be detected by in vivo imaging, and confirmed that the highest photon emission was in the liver (P < 0.0001). At 2 wk, the DiRsignal was no longer detectable in vivo; however, immunohistochemistry analysis of constitutively-expressed GFP was used to provide an insight into the distribution of the cells. GFP +ve cells were detected in tissue sections resembling hepatocytes and were dispersed throughout the hepatic parenchyma, with the presence of a larger number of GFP +ve cells incorporated within the sinusoidal endothelial lining. Very faint albumin expression was detected in the transplanted GFP +ve cells at 72 h; however at 2 wk, few cells that were positive for GFP were also strongly positive for albumin. There was a significant improvement in serum levels of ALT, albumin and bilirubin in both groups at 2 wk when compared with the 72 h time-point. In the cell therapy group, serum ALT was significantly (P = 0.016) lower and albumin (P = 0.009) was significantly higher when compared with the control group at the 2 wk time-point; however there was no difference in mortality between the two groups.

CONCLUSION: Dual labeling is an easy to use and cheap method for longitudinal monitoring of distribution, survival and engraftment of transplanted cells, and could be used for cell therapy models.

Strategies to produce hepatocytes and hepatocyte-like cells from pluripotent stem cells

Human embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) are a potent source for unlimited production of hepatocytes and hepatocyte-like cells that may replace primary human hepatocytes in a variety of fields including liver cell therapy, liver tissue engineering, manufacturing bioartificial liver, modeling inherited and chronic liver diseases, drug screening and toxicity testing. Human ESCs are able to spontaneously form embryoid bodies, which then spontaneously differentiate to various tissue-specific cell lineages containing a total of 10-30% albumin-producing hepatocytes and hepatocyte-like cells. Enrichment of embryoid bodies with the definitive endoderm, from which hepatocytes arise, yields increasing the final ratio of hepatocyte population up by 50-65%. Current strategies of the directed differentiation of human ESCs (and iPSCs) to hepatocytes that reproduce liver embryogenesis by sequential stimulation of culturing ESCs with tissue-specific growth factors result in achieving the differentiation rate up to 60-80%. In the future, directed differentiation of human ESCs and iPSCs to hepatocytes should be further optimized towards generating homogeneous cultures of hepatocytes in order to avoid expensive procedures of separation and isolation of hepatocytes and hepatocyte-like cells.

Differentiation of embryonic stem cells into hepatocytes that coexpress coagulation factors VIII and IX

AIM

To establish an efficient culture system to support embryonic stem (ES) cell differentiation into hepatocytes that coexpress F-VIII and F-IX.

METHODS

Mouse E14 ES cells were cultured in differentiation medium containing sodium butyrate (SB), basic fibroblast growth factor (bFGF), and/or bone morphogenetic protein 4 (BMP4) to induce the differentiation of endoderm cells and hepatic progenitor cells. Hepatocyte growth factor, oncostatin M, and dexamethasone were then used to induce the maturation of ES cell-derived hepatocytes. The mRNA expression levels of endoderm-specific genes and hepatocyte-specific genes, including the levels of F-VIII and F-IX, were detected by RT-PCR and real-time PCR during various stages of differentiation. Protein expression was examined by immunofluorescence and Western blot. At the final stage of differentiation, flow cytometry was performed to determine the percentage of cells coexpressing F-VIII and F-IX, and ELISA was used to detect the levels of F-VIII and F-IX protein secreted into the culture medium.

RESULTS

The expression of endoderm-specific and hepatocyte-specific markers was upregulated to highest level in response to the combination of SB, bFGF, and BMP4. Treatment with the three inducers during hepatic progenitor differentiation significantly enhanced the mRNA and protein levels of F-VIII and F-IX in ES cell-derived hepatocytes. More importantly, F-VIII and F-IX were coexpressed with high efficiency at the final stage of differentiation, and they were also secreted into the culture medium.

CONCLUSION

We have established a novel in vitro differentiation protocol for ES-derived hepatocytes that coexpress F-VIII and F-IX that may provide a foundation for stem cell replacement therapy for hemophilia.

Enhanced hepatic differentiation of mesenchymal stem cells after pretreatment with injured liver tissue

Liver failure represents a serious challenge for cell based therapies. Mesenchymal stem cells (MSCs) possess potential for regeneration of fibrotic liver; however, there is a dire need to improve their hepatic differentiation. This study examines a pretreatment strategy to augment the differentiation potential of MSCs towards hepatic lineage. MSCs were isolated from C57BL/6 wild type mice and were characterized by flow cytometry for CD44 (92.4%), CD90 (96.6%), CD105 (94.7%), CD45 (0.8%) and CD34 (1.4%) markers. To improve the differentiation potential of MSCs towards hepatic lineage, cells were pretreated with injured liver tissue in an in-vitro model, which resulted in high expression of albumin, cytokeratin 8, 18, TAT and HNF1α as compared to untreated MSCs. The efficacy of pretreated MSCs was evaluated by preparing in-vivo mouse model with liver fibrosis by intraperitoneal administration of CCl(4). Pretreated MSCs were transplanted in the left lateral lobe of mice with liver fibrosis and showed enhanced localization and differentiation abilities after 1 month. The expression for cytokeratin 8, 18, albumin and Bcl-xl was up-regulated and that of HGF, Bax and Caspase- 3 was down-regulated in animals transplanted with pretreated MSCs. Sirus red staining also confirmed a significant reduction in the fibrotic area in liver tissue transplanted with pretreated MSCs as compared to untreated MSCs and was concomitant with improved serum levels of bilirubin and alkaline phosphatase (ALP). Therefore, it was concluded that pretreatment with injured liver tissue augment homing and hepatic differentiation abilities of MSCs and provides an improved procedure for the treatment of liver fibrosis.

Hepatic differentiation of mouse embryonic stem cells in three-dimensional polymer scaffolds

Embryonic stem cells (ESCs) can have unlimited proliferation potential and the capability to differentiate into almost all types of tissues. The use of ESCs as a novel source of hepatocytes has therefore recently received much attention. To date, however, the efficient and mass differentiation of ESCs into hepatocytes in vitro has been proven to be difficult. In this study, we investigated a three-dimensional (3D) mouse ESC hepatic differentiation system. Cells derived from 5-day-old embryoid bodies were mixed with Matrigel and immediately seeded in a biodegradable polymer scaffold composed of poly-l-lactic acid and polyglycolic acid. Exogenous growth factors and hormones were added sequentially for 20 days to promote hepatic histogenesis. The system enabled spontaneous spheroid formation and mass cultivation of embryoid body-derived cells. The 3D differentiated hepatocyte-like cells were able to express several liver-specific markers and proteins, secrete albumin, store glycogen, and allow the uptake of low-density lipoproteins. These findings suggest that this supportive 3D environment with appropriate inducing factors could provide mouse ESC-derived cells with an environment closely mimicking that of hepatogenesis in vivo.

Effects of sodium butyrate on the differentiation of pancreatic and hepatic progenitor cells from mouse embryonic stem cells

Recently significant progress has been made in differentiating embryonic stem (ES) cells toward pancreatic cells. However, little is known about the generation and identification of pancreatic progenitor cells from ES cells. Here we explored the influence of sodium butyrate on pancreatic progenitor differentiation, and investigated the different effects of sodium butyrate on pancreatic and hepatic progenitor formation. Our results indicated that different concentration and exposure time of sodium butyrate led to different differentiating trends of ES cells. A relatively lower concentration of sodium butyrate with shorter exposure time induced more pancreatic progenitor cell formation. When stimulated by a higher concentration and longer exposure time of sodium butyrate, ES cells differentiated toward hepatic progenitor cells rather than pancreatic progenitor cells. These progenitor cells could further mature into pancreatic and hepatic cells with the supplement of exogenous inducing factors. The resulting pancreatic cells expressed specific markers such as insulin and C-peptide, and were capable of insulin secretion in response to glucose stimulation. The differentiated hepatocytes were characterized by the expression of a number of liver-associated genes and proteins, and had the capability of glycogen storage. Thus, the current study demonstrated that sodium butyrate played different roles in inducing ES cells toward pancreatic or hepatic progenitor cells. These progenitor cells could be further induced into mature pancreatic cells and hepatocytes. This finding may facilitate the understanding of pancreatic and hepatic cell differentiation from ES cells, and provide a potential source of transplantable cells for cell-replacement therapies.

Sodium butyrate and dexamethasone promote exocrine pancreatic gene expression in mouse embryonic stem cells

AIM

The feasibility of inducing endocrine pancreatic differentiation of embryonic stem (ES) cells has been well documented. However, whether ES cells possess the potential for exocrine pancreatic differentiation requires further exploration. Here, we investigated whether sodium butyrate and glucocorticoids were conducive to the exocrine pancreatic differentiation of ES cells.

METHODS

E14 mouse ES cells were cultured in suspension to form embryoid bodies (EBs). These EBs were cultured in differentiating medium containing varying concentrations of sodium butyrate. The effects of activinA and dexamethasone (Dex) on exocrine differentiation were also explored. Finally, the combination of sodium butyrate, activinA, and Dex was used to promote the differentiation of exocrine pancreatic cells. Specific exocrine pancreatic gene expression was detected by reverse transcription polymerase chain reaction (RT-PCR) and amylase expression was examined by immunofluorescence staining. Flow cytometry analysis was also performed to determine the percentage of amylase-positive cells after the treatment with activinA, sodium butyrate, and Dex.

RESULTS

Exposure of ES cells to 1 mmol/L sodium butyrate for 5 days promoted exocrine pancreatic gene expression. Further combination with Dex and other pancreatic-inducing factors, such as activinA, significantly enhanced the mRNA and protein levels of exocrine pancreatic markers. Additionally, flow cytometry revealed that approximately 17% of the final differentiated cells were amylase-positive.

CONCLUSION

These data indicate that the exocrine pancreatic differentiation of ES cells can be induced by activinA, sodium butyrate, and Dex, providing a potential tool for studying pancreatic differentiation and pancreas-related diseases.