Hepatocyte growth factor exerts a proliferative effect on oval cells through the PI3K/AKT signaling pathway

Bone morphogenetic protein-4 induced rat hepatic progenitor cell (WB-F344 cell) differentiation toward hepatocyte lineage

Hepatic progenitor cells are local stem cells in the liver and they can be differentiated into either hepatocytes or cholangiocytes depending on different stimulations. These stimulations include extracellular growth factors and intracellular transcription factors. Bone morphogenetic protein 4 (BMP4) is a member of transforming growth factor beta (TGF-beta) superfamily and was first identified as growth factor to induce ectopic bone formation from skeletal muscle. Role of BMP4 in the liver is still unclear especially its role in hepatic progenitor cells (HPCs) differentiation. BMP4 was used to stimulate rat HPCs (WB-F344 cells) and differentiation of WB-F344 cells was investigated by reverse transcriptase polymerase chain reaction (RT-PCR) and Western blot analysis. Both adenovirus delivered BMP4 and recombinant BMP4 were able to induce expression of hepatocyte markers such as albumin, TAT-1, and G6Pase but not cholangiocyte markers such as beta4-integrin and CK19. BMP4 induced differentiation of WB-F344 cells toward hepatocytes was mediated by increase in phosphorylation of Smad1 and ERK1/2. Moreover, BMP4 also stimulated expression of transcription factor--C/EBP-alpha, which involved in differentiation of WB-F344 cells toward hepatocytes. BMP4 is able to stimulate WB-F344 cells differentiation toward hepatocyte lineage.

Serum levels of stem cell factor and their clinical significances in patients with severe hepatitis

AIM: To investigate the serum levels of stem cell factor (SCF) and their clinical significances in patients with severe hepatitis.

METHODS: A total of 45 hepatitis patients (including 15 cases of acute hepatitis, 16 cases of chronic hepatitis and 14 cases of severe hepatitis) and 15 healthy subjects (as controls) were collected from our hospital . The severe hepatitis patients were divided into survival subgroup (n = 4) and death subgroup (n = 10). Serum levels of SCF were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS: The levels of serum SCF were significantly higher in severe hepatitis than those in acute hepatitis, chronic hepatitis and the controls (2403.1 ± 42.8 ng/L vs 2354.9 ± 19.0 ng/L, 2376.7 ± 16.4 ng/L, 2358.4 ± 16.0 ng/L; all P < 0.05), and also higher in the death subgroup than those in the survival subgroup (2418.1 ± 50.7 ng/L vs 2376.3 ± 11.7 ng/L, P < 0.05). The levels of serum SCF showed significantly positive correlation (r = 0.38, P < 0.01) with those of hepatocyte growth factor (HGF) and significantly negative correlation with those of albumin and prothrombin time activity (PTA).

CONCLUSION: Serum levels of SCF may reflect the degree of hepatic injury and the prognosis of severe hepatitis patients, indicating that stem cells may be required for liver regeneration in severe hepatitis patients.

Hepatic non-parenchymal cells and extracellular matrix participate in oval cell-mediated liver regeneration

AIM: To elucidate the interaction between non-parenchymal cells, extracellular matrix and oval cells during the restituting process of liver injury induced by partial hepatectomy (PH).

METHODS: We examined the localization of oval cells, non-parenchymal cells, and the extracellular matrix components using immunohistochemical and double immunofluorescent analysis during the proliferation and differentiation of oval cells in N-2-acetylaminofluorene (2-AAF)/PH rat model.

RESULTS: By day 2 after PH, small oval cells began to proliferate around the portal area. Most of stellate cells and laminin were present along the hepatic sinusoids in the periportal area. Kupffer cells and fibronectin markedly increased in the whole hepatic lobule. From day 4 to 9, oval cells spread further into hepatic parenchyma, closely associated with stellate cells, fibronectin and laminin. Kupffer cells admixed with oval cells by day 6 and then decreased in the periportal zone. From day 12 to 15, most of hepatic stellate cells (HSCs), laminin and fibronectin located around the small hepatocyte nodus, and minority of them appeared in the nodus. Kupffer cells were mainly limited in the pericentral sinusoids. After day 18, the normal liver lobule structures began to recover.

CONCLUSION: Local hepatic microenvironment may participate in the oval cell-mediated liver regeneration through the cell-cell and cell-matrix interactions.

Establishment and characterization of hepatic stem-like cell lines from normal adult rat liver

The liver is a unique organ with the potential to regenerate from injury. Hepatic stem cells contribute to liver regeneration when surviving hepatocytes in injured liver are unable to proliferate. To investigate the mechanism of liver regeneration in vitro, we established hepatic stem cell lines named HY1, HY2 and HY3, derived from a healthy liver of adult rat. HY cells showed an expression pattern similar to oval cells, and efficiently induced hepatic differentiation following sequential treatment with type I collagen, transforming growth factor-beta1 (TGF-beta1), and hepatocyte growth factor (HGF) or oncostatin M (OSM). These results suggested that HY cells are liver stem cells representing an excellent tool for in vitro studies on liver regeneration.

MetMAb, the one-armed 5D5 anti-c-Met antibody, inhibits orthotopic pancreatic tumor growth and improves survival

The hepatocyte growth factor (HGF) and its receptor, c-Met, have been implicated in driving proliferation, invasion, and poor prognosis in pancreatic cancer. Here, we investigated the expression of HGF and c-Met in primary pancreatic cancers and described in vitro and in vivo models in which MetMAb, a monovalent antibody against c-Met, was evaluated. First, expression of HGF and MET mRNA was analyzed in 59 primary pancreatic cancers and 51 normal samples, showing that both factors are highly expressed in pancreatic cancer. We next examined HGF responsiveness in pancreatic cancer lines to select lines that proliferate in response to HGF. Based on these studies, two lines were selected for further in vivo model development: BxPC-3 (c-Met(+), HGF(-)) and KP4 (c-Met(+), HGF(+)) cells. As BxPC-3 cells are responsive to exogenous HGF, s.c. tumor xenografts were grown in a paracrine manner with purified human HGF provided by osmotic pumps, wherein MetMAb treatment significantly inhibited tumor growth. KP4 cells are autocrine for HGF and c-Met, and MetMAb strongly inhibited s.c. tumor growth. To better model pancreatic cancer and to enable long-term survival studies, an orthotopic model of KP4 was established. MetMAb significantly inhibited orthotopic KP4 tumor growth in 4-week studies monitored by ultrasound and also improved survival in 90-day studies. MetMAb significantly reduced c-Met phosphorylation in orthotopic KP4 tumors with a concomitant decrease in Ki-67 staining. These data suggest that the HGF/c-Met axis plays an important role in the progression of pancreatic cancer and that targeting c-Met therein may have therapeutic value.

Ezrin expression is associated with hepatocellular carcinoma possibly derived from progenitor cells and early recurrence after surgical resection

Heterogeneous biological characteristics of hepatocellular carcinoma may be attributed to the cellular origin of the tumor. Patients with hepatocellular carcinoma probably derived from hepatic progenitor cells had early tumor recurrence after surgical resection or liver transplantation, suggesting that these tumors have aggressive characteristics. Ezrin, a member of the ERM (ezrin-radixin-moesin) cytoskeleton-associated protein family, is highly expressed in several types of human cancers and correlations between its immunoreactivity and patient outcome have been shown. In this study, ezrin expression, as well as cytokeratin19 and cytokeratin 7 expression, which are regarded as progenitor cell/ductular markers were immunohistochemically assessed in cases of hepatocellular carcinoma. In normal livers, ezrin expression was not found in any cell types, whereas cytokeratin 7 and cytokeratin 19 were exclusively stained in bile duct cells. In contrast, in livers with chronic hepatitis or cirrhosis, positive ezrin expression was observed in ductular reactions with strong intensity and intermediate hepatobiliary cells with various intensity. Of 77 cases of hepatocellular carcinoma, 28 (36%) had positive ezrin expression, 32 (42%) had cytokeratin 7 expression, and 11 (14%) had cytokeratin 19 expression. Ezrin expression in hepatocellular carcinoma was significantly associated with cytokeratin 19 expression, but not with cytokeratin 7 expression. Patients with ezrin-positive hepatocellular carcinoma had a significantly higher prevalence of elevated serum alpha-fetoprotein. Patients with immunohistochemical ezrin-positive hepatocellular carcinoma demonstrated significantly shorter recurrence-free and overall survival compared to patients with ezrin-negative hepatocellular carcinoma. Multivariate analysis revealed positive ezrin expression and multiple tumors to be independently associated with early recurrence in patients with hepatocellular carcinoma after curative surgical resection. These results suggested that hepatocellular carcinoma with ezrin expression might be at least partly derived from hepatic progenitor cells. Measurement of ezrin expression might be used to identify patients with an increased risk of early recurrence.

PI3K/Akt activation is critical for early hepatic regeneration after partial hepatectomy

Hepatic resection is associated with rapid proliferation and regeneration of the remnant liver. Phosphatidylinositol 3-kinase (PI3K), composed of a p85alpha regulatory and a p110alpha catalytic subunit, participates in multiple cellular processes, including cell growth and survival; however, the role of PI3K in liver regeneration has not been clearly delineated. In this study, we used the potent PI3K inhibitor wortmannin and small interfering RNA (siRNA) targeting the p85alpha and p110alpha subunits to determine whether total or selective PI3K inhibition would abrogate the proliferative response of the liver after partial hepatectomy in mice. Hepatic resection is associated with an induction in PI3K activity; total PI3K blockade with wortmannin and selective inhibition of p85alpha or p110alpha with siRNA resulted in a significant decrease in hepatocyte proliferation, especially at the earliest time points. Fewer macrophages and Kupffer cells were present in the regenerating liver of mice treated with wortmannin or siRNA to p85alpha or p110alpha, as reflected by a paucity of F4/80-positive cells. Additionally, PI3K inhibition led to an aberrant architecture in the regenerating hepatocytes characterized by vacuolization, lipid deposition, and glycogen accumulation; these changes were not noted in the sham livers. Our data demonstrate that PI3K/Akt pathway activation plays a critical role in the early regenerative response of the liver after resection; inhibition of this pathway markedly abrogates the normal hepatic regenerative response, most likely by inhibiting macrophage infiltration and cytokine elaboration and thus hepatocyte priming for replication.

Deletion of the Met tyrosine kinase in liver progenitor oval cells increases sensitivity to apoptosis in vitro

The hepatocyte growth factor (HGF)/Met signaling system is essential for liver development, homeostasis, and function. In this study, we took advantage of a liver-specific, Met-conditional knockout mouse generated in our laboratory to address the molecular mechanisms of HGF/Met signaling in adult liver progenitor cell (oval cell) biology. For this purpose, we isolated oval cells from 3,5-diethoxycarbonyl-1,4-dihydro-collidine-treated Met(flx/flx) mice and established oval cell-derived cell lines that carried either functional (Met(flx/flx)) or a nonfunctional (Met(-/-)) met gene using virus-mediated Cre-loxP recombination. Oval cells lacking Met tyrosine kinase activity displayed neither Met phosphorylation nor activation of downstream targets and were refractory to HGF stimulation. Although Met(-/-) and Met(flx/flx) cells proliferated at similar rates under 10% serum, Met-deficient cells demonstrated decreased cell viability and were more prone to apoptosis when challenged with either serum starvation or the pro-apoptotic cytokine transforming growth factor-beta. Treatment with HGF reduced transforming growth factor-beta-mediated cell death in Met(flx/flx) but not Met(-/-) cells. Importantly, Met(flx/flx) and Met(-/-) cells both constitutively expressed hgf, and conditioned medium from serum-starved oval cells exhibited anti-apoptotic activity in Met(flx/flx) cells. Furthermore, serum-starved Met(flx/flx) cells showed persistent activation of the Met tyrosine kinase, suggesting HGF/Met autocrine regulation. In conclusion, these data reveal a critical, functional role for Met in oval cell survival through an autocrine mechanism.

Signaling networks in hepatic oval cell activation

Oval cells are hypothesized to be the progeny of intrahepatic stem cells, also referred to as adult liver stem cells. The mechanisms by which these cells are activated to proliferate and differentiate during liver regeneration is important for the development of new therapies to treat liver disease. Oval cell activation is the first step in progenitor-dependent liver regeneration in response to certain types of injury. This review describes what is currently known about the factors involved in oval cell activation, proliferation, migration, and differentiation.

Stretch-Induced Alveolar Type II Cell Apoptosis

Apoptosis of alveolar type II (ATII) cells in response to high-amplitude mechanical stretch represents an important mechanism of ventilation-induced lung injury. Previously, it was demonstrated in an in vitro model that stretch-induced ATII cell apoptosis was prevented by angiotensin-converting enzyme (ACE) inhibitors. This study investigates the mechanism by which ACE inhibitors prevent stretch-induced apoptosis and elucidates the role of bradykinin as an endogenous anti-apoptotic factor. Rat ATII cells cultured on flexible membranes were subjected to cyclic stretch (40 cycles/min; 30% increase in surface area) and compared with static controls. Angiotensinogen, the bradykinin precursor T-kininogen, and bradykinin receptor expression were measured by RT-PCR; Angiotensin II and phosphoinositol 3 OH-kinase (PI3K) activity (as phospho-Akt) were measured by enzyme-linked immunosorbent assay; and Bcl-2 and Bcl-X(L) were measured by Western blot. Stretch did not influence angiotensinogen expression or induce angiotensin II generation. The angiotensin II receptor antagonist saralasin did not prevent stretch-induced apoptosis, whereas ACE inhibitors did. Stretch reduced ATII cell bradykinin release (T-kininogen expression and bradykinin supernatant concentration), and subsequently led to reduced PI3K activity and decreased concentrations of the anti-apoptotic proteins Bcl-2/Bcl-X(L). Bradykinin substitution or addition of keratinocyte or hepatocyte growth factor prevented stretch-induced decrease in PI3K activity and Bcl-2/Bcl-X(L) and reduced stretch-induced apoptosis. Mechanical stretch impairs a constitutively expressed, autocrine anti-apoptotic ATII cell survival signal involving bradykinin-mediated stimulation of the PI3K-Akt-Bcl-2/Bcl-X(L) pathway. Restoration of this pathway prevents stretch-induced apoptosis. This may be beneficial when mechanical ventilation cannot completely avoid alveolar overdistension to maintain oxygenation.

Ischemic preconditioning enhances regenerative capacity of hepatocytes in long-term ischemically damaged rat livers

BACKGROUND AND AIMS

Ischemic preconditioning (IPC) protects tissues against ischemia and reperfusion (I/R) injury. The aim of this study was to examine the impact of IPC on protection and regeneration of hepatocytes after prolonged I/R injury.

METHODS

A rat model of segmental (70%) hepatic ischemia was used to determine the effect of 10-min IPC preceding 40, 60, 90, or 120 min of liver ischemia. The effect was assessed by comparing cytolysis markers and necrotic areas of the liver, as well as the regenerative capacity of hepatocytes using the proliferating cell nuclear antigen labeling index (PCNA-LI) and weight of the ischemic liver lobe. Protein kinase B/Akt (Akt) and caspase-9 were investigated immunohistochemically to determine the effect of IPC on activation of survival and anti-apoptotic signals.

RESULTS

In the model of 40 min I/R, which resulted in focal necrosis of the liver, IPC significantly protected against I/R injury by reducing the area of focal necrosis, level of PCNA-LI and immunoreactivities to Akt and caspase-9. In contrast, IPC did not prevent ischemic damage in the 90- and 120-min ischemic model with massive liver necrosis. However, IPC enhanced the regenerative capacity of the remaining hepatocytes with higher levels of PCNA-LI, number of Akt-positive cells and mean weight of the liver lobe postoperatively than in the controls.

CONCLUSIONS

In a model of focal necrosis of the liver, IPC protected hepatocytes against I/R injury. In addition, in a model of massive necrosis, IPC maintained the regenerative capacity of the remaining hepatocytes by enhancing the survival signals.

"AKT"ing lessons for stem cells: regulation of cardiac myocyte and progenitor cell proliferation

Cardiac development and postnatal growth depend on activation of AKT, but initial strategies to improve myocardial repair using AKT were stymied by undesirable corollary alterations in myocardial structure and function. These unfortunate precedents were based on high-level expression of constitutively activated AKT, predominantly in the cytoplasm of the cell. Based on subsequent studies establishing that activated AKT accumulates in the nucleus, we reasoned that the location of AKT, not simply the activity level, would be a critical determinant of the phenotypic outcome resulting from AKT activation. Using myocardial-specific expression of nuclear-targeted AKT (AKT/nuc), the proliferation of myocardial stem and progenitor cell populations is enhanced, casting new light on the implementation of AKT activity as a molecular interventional approach for treatment of cardiomyopathic damage resulting from acute injury, chronic stress, or the debilitating changes of aging.

Major HGF-mediated regenerative pathways are similarly affected in human and canine cirrhosis

Background

The availability of non-rodent animal models for human cirrhosis is limited. We investigated whether privately-owned dogs (Canis familiaris) are potential model animals for liver disease focusing on regenerative pathways. Several forms of canine hepatitis were examined: Acute Hepatitis (AH), Chronic Hepatitis (CH), Lobular Dissecting Hepatitis (LDH, a specific form of micronodulair cirrhosis), and Cirrhosis (CIRR). Canine cirrhotic samples were compared to human liver samples from cirrhotic stages of alcoholic liver disease (hALC) and chronic hepatitis C infection (hHC).

Results

Canine specific mRNA expression of the regenerative hepatocyte growth factor (HGF) signaling pathway and relevant down-stream pathways were measured by semi-quantitative PCR and Western blot (STAT3, PKB, ERK1/2, and p38-MAPK). In all canine groups, levels of c-MET mRNA (proto-oncogenic receptor for HGF) were significantly decreased (p < 0.05). Surprisingly, ERK1/2 and p38-MAPK were increased in CH and LDH. In the human liver samples Western blotting indicated a high homology of down-stream pathways between different etiologies (hALC and hHC). Similarly activated pathways were found in CIRR, hALC, and hHC.

Conclusion

In canine hepatitis and cirrhosis the major regenerative downstream pathways were activated. Signaling pathways are similarly activated in human cirrhotic liver samples, irrespective of the differences in etiology in the human samples (alcohol abuse and HCV-infection). Therefore, canine hepatitis and cirrhosis could be an important clinical model to evaluate novel interventions prior to human clinical trials.

Putative human liver progenitor cells in explanted liver

BACKGROUND/AIMS

Hepatocyte progenitors have frequently been cultured from rodents but reports from human liver are rare.

METHODS

Non-parenchymal cell fraction isolated from 19 explant livers (removed at orthotopic liver transplantation for acute or chronic liver disease) and histologically normal human liver was cultured.

RESULTS

Proliferating epithelioid colonies were identifiable after 2-3 weeks culture as a very rare event (<1 per million cells plated) expressing mRNAs and protein antigens of mixed hepatocytic/biliary phenotype. Colony survival could be prolonged by transduction of the catalytic sub-unit of telomerase. Hepatocyte growth factor, epidermal growth factor and oncostatin M did not further enhance hepatocytic differentiation. The expression of markers associated with hepatocyte precursor status was investigated by flow cytometry. Cells expressing the stem cell-associated markers CD133 and CD117 were identified at low frequency. The proportion of cells expressing the integrin CD49f was higher in diseased liver than in normal liver, but the proportion expressing the hepatocyte growth factor receptor c-met was lower. Successful enrichment of plated populations for progenitors was not achieved.

CONCLUSION

Although there is clear histological evidence of hepatocyte precursors in human explant livers, predictable culture of such cells with differentiation toward mature hepatocyte phenotype remains elusive.

Hepatocyte growth factor promotes colonic epithelial regeneration via Akt signaling

Hepatocyte growth factor (HGF) can promote the regeneration of injured organs, including HGF gene therapy by electroporation (EP) for liver injury. In this study, we investigated the effect of HGF on dextran sulfate sodium-induced colitis and tried to clarify the regenerative mechanisms of colonic epithelial cells and the signaling pathway involved. Colitis was induced by dextran sulfate sodium in mice, together with HGF gene transfer by EP. On day 10, the colitis was evaluated histologically and by Western blot analysis. The colonic epithelial cell line MCE301 was exposed to HGF protein, and its proliferation and activated signaling pathway were analyzed. In vivo, the histological score improved and the number of Ki-67-positive epithelial cells increased in the HGF-treated mice compared with the controls. Western blot analysis showed enhanced expression of phospho-Akt in the HGF-treated mice compared with the controls. In vitro, HGF stimulated the proliferation of MCE301 cells. There was enhanced phospho-Akt expression for more than 48 h after HGF stimulation, although phospho-ERK1/2 was enhanced for only 10 min. LY-294002 or Akt small interfering RNA suppressed cell proliferation induced by HGF. Thus HGF induces the proliferation of colonic epithelial cells via the phosphatidylinositol 3-kinase/Akt signaling pathway. HGF gene therapy can attenuate acute colitis via epithelial cell proliferation through the PI3K/Akt pathway. These data suggested that HGF gene therapy by EP may be effective for the regeneration and repair of injured epithelial cells in inflammatory bowel disease.

FLJ10540-elicited cell transformation is through the activation of PI3-kinase/AKT pathway

A significant challenge in the post-genomic era is how to prioritize differentially expressed and uncharacterized novel genes found in hepatocellular carcinoma (HCC) microarray profiling. One such category is cell cycle regulated genes that have only evolved in higher organisms but not in lower eukaryotic cells. Characterization of these genes may reveal some novel human cancer-specific abnormalities. A novel transcript, FLJ10540 was identified. FLJ10540 is overexpressed in HCC as examined by quantitative reverse transcription-polymerase chain reaction and immunohistochemistry. The patients with higher FLJ10540 expression had a poor survival than those with lower FLJ10540 expression. Functional characterization indicates that FLJ10540 displays a number of characteristics associated with an oncogene, including anchorage-independent growth, enhanced cell growth at low serum levels and induction of tumorigenesis in nude mice. FLJ10540-elicited cell transformation is mediated by activation of the phosphatidylinositol 3'-kinase (PI3K)/AKT pathway. Moreover, FLJ10540 forms a complex with PI3K and can activate PI3K activity, which provides a mechanistic basis for FLJ10540-mediated oncogenesis. Together, using a combination of bioinformatics searches and empirical data, we have identified a novel oncogene, FLJ10540, which is conserved only in higher organisms. The finding raises the possibility that FLJ10540 is a potential new therapeutic target for HCC treatment. These findings may contribute to the development of new therapeutic strategies that are able to block the PI3K/AKT pathway in cancer cells.

The hypoxic environment in tumor-stromal cells accelerates pancreatic cancer progression via the activation of paracrine hepatocyte growth factor/c-Met signaling

BACKGROUND

Pancreatic cancer is one of the representative solid tumors, in which the hypoxic microenvironment plays a crucial role in malignant progression. We previously demonstrated that tumor-stromal interaction under hypoxia enhances the invasiveness of pancreatic cancer cells through hepatocyte growth factor (HGF)/c-Met signaling.

METHODS

We investigated the immunohistochemical expression of hypoxia inducible factor-1alpha (HIF-1alpha) c-Met, and HGF in both cancer and stromal cells using 41 pancreatic cancer tissue specimens, and tried to identify any correlations with the clinical features and survival.

RESULTS

Positive staining for HIF-1alpha was observed in both pancreatic cancer and the surrounding stromal cells in more than 30% of the cases, and it significantly correlated with lymph node metastasis (P < .05). A significant correlation was observed between the expression of HIF-1alpha and HGF in stromal cells (P < .05). In addition, the c-Met expression in cancer cells was found to significantly correlate with the HGF expression in not only cancer but also stromal cells. The disease-free survival rates of the patients with HIF-1alpha in cancer, stromal, c-Met in cancer, and an HGF expression in stromal cells was significantly worse than those without such expressions (P < .05).

CONCLUSIONS

These data suggest that the HGF/c-Met signaling via HIF-1alpha ?may therefore negatively affect the prognosis in patients with pancreatic cancer, and targeting tumor stroma under hypoxia might thus be potentially useful as a novel therapy for this cancer.

Effect of hepatocyte growth factor on methionine adenosyltransferase genes and growth is cell density-dependent in HepG2 cells

Hepatocyte growth factor (HGF) is a potent hepatocyte mitogen but its effect in liver cancer is conflicting. Methionine adenosyltransferase (MAT) is an essential enzyme encoded by two genes (MAT1A and MAT2A), while a third gene (MAT2beta) encodes for a subunit that regulates the MAT2A-encoded isoenzyme. MAT1A is silenced while MAT2A and MAT2beta are induced in hepatocellular carcinoma (HCC). The current work examined expression of HGF/c-met in HCC and whether HGF regulates MAT genes and growth in HepG2 cells. We found the mRNA levels of HGF and c-met are markedly increased in HCC. To study the influence of cell density, HepG2 cells were plated under high-density (HD) or low-density (LD) and treated with HGF (10 ng/ml). Cell density had a dramatic effect on MAT1A expression, being nearly undetectable at LD to a ninefold induction under HD. Cell density also determined the effect of HGF. At HD, HGF increased the mRNA levels of p21 and p27, while lowering the levels of MAT genes, cyclin A, and c-met. At LD, HGF increased the mRNA levels of cyclin A, MAT2A, MAT2beta, and c-met. Consistently, HGF inhibits growth under HD but stimulates growth under LD. HGF induced sustained high ERK activation under HD as compared to LD. In summary, HGF induces genes favoring growth and is mitogenic when HepG2 cells are plated under LD; however, the opposite occurs under HD. This involves cell density-dependent differences in HGF-induced ERK activation. This may explain why HGF is mitogenic only when there is loss of cell-cell contact in vivo.

Liver regeneration: mechanisms, mysteries and more

BACKGROUND

Liver regeneration remains a fascinating topic, still partly clouded to many as to the exact cellular and molecular mechanisms that bring about this phenomenon. It is an area, therefore, of active research today. This review looks at the recent published reports that have led to a greater understanding of this process.

METHODS

A database search was carried out on Medline search using the terms liver regeneration with no linguistic limitations from 1966 to 2006.

RESULTS

There are two randomized controlled trials on the topic and most data and information have come from experimental studies in animals.

CONCLUSION

Liver regeneration is a complex, tightly controlled process involving many inflammatory cells growth factors and hormones. More information about it is awaited in studies on humans.

HGF enhanced proliferation and differentiation of dental pulp cells

Hepatocyte growth factor (HGF) is mesenchymal-derived growth factor acting through a transmembrane tyrosine kinase receptor, c-met. HGF has multiple effects on different cells. However, its function in dentinogenesis remains unclear. In this study, the expression of HGF in human dental pulp cells (DPCs) in vitro was studied by immunostaining and RT-PCR. The effect of HGF on DPCs proliferation was determined by MTT, while its effect on cell differentiation was analyzed using ALPase activity, and further confirmed with ALP and DSPP mRNA and protein expression. Immunostaining revealed that HGF was found mainly in the cytoplasm of DPCs. RT-PCR analysis showed that both HGF and c-met were expressed from the DPCs. Exogenous addition of HGF enhanced proliferation and differentiation of DPCs by up-regulating CREB, ELK-1, and PPAR-gamma. U0126, an ERK/MAPK inhibitor, inhibited the effects of HGF on DPCs. It was concluded that HGF stimulated both proliferation and differentiation of DPCs, at least partially through the ERK/MAPK pathway.

X-Linked inhibitor of apoptosis protein expression level in colorectal cancer is regulated by hepatocyte growth factor/C-met pathway via Akt signaling

PURPOSE

The inhibitor of the apoptosis protein (IAP) family members, such as the X-linked IAP (XIAP), survivin, and livin, are essential for cell survival and antiapoptosis in colorectal cancer cells. We hypothesized that the hepatocyte growth factor (HGF) activation in colorectal cancer via c-Met receptor regulates IAP proteins through Akt signaling.

EXPERIMENTAL DESIGN

The level of IAPs and C-Met mRNA expression was assessed using a quantitative real-time reverse transcriptase-PCR (RT-PCR) assay on colorectal normal mucosa (n = 13), adenomas (n = 6), and colorectal cancer tumors (n = 50). The role of HGF/C-Met pathway through Akt and XIAP was investigated by small interfering RNA (siRNA) and quantitative RT-PCR analysis of colorectal cancer lines.

RESULTS

Of the IAPs, only XIAP showed significant correlation to tumor development and progression. XIAP mRNA level in primary colorectal cancer was significantly higher than that in colorectal normal mucosa (P = 0.01); liver metastases was significantly higher than primary colorectal cancer tumors (P = 0.04); and primary colorectal cancer N1/N2 cases were significantly higher than N0 cases (P = 0.008). HGF stimulation of colorectal cancer lines enhanced XIAP mRNA expression but not other IAPs. Activation of XIAP expression by HGF was inhibited by siRNA targeting Akt1 and Akt2.

CONCLUSIONS

Activation of C-MET enhances XIAP through the Akt pathway. XIAP up-regulation was shown to be correlated to colorectal cancer tumor progression. The Akt-XIAP pathway may be a potential molecular target for regulating colorectal cancer progression.

Hepatocyte growth factor accelerates the proliferation of hepatic oval cells and possibly promotes the differentiation in a 2-acetylaminofluorene/partial hepatectomy model in rats

BACKGROUND

Hepatocyte growth factor (HGF) is the primary agent promoting the proliferation of mature hepatocytes. The purpose of the present paper was to clarify the effects of HGF on the proliferation and differentiation of hepatic oval cells using a 2-acetylaminofluorene/partial hepatectomy (2-AAF/PH) model in rats.

METHODS

Recombinant human HGF (0.2 mg/day) was administered to 2-AAF/PH rats for 7 days using osmotic pumps intraperitoneally implanted in conjunction with hepatectomy (day zero).

RESULTS

Periportal basophilic areas consisting of oval cells were significantly enlarged by treatment with HGF on day 8. In control animals, expression of alpha-fetoprotein (AFP) in the liver was gradually upregulated, leading a marked increase on day 12. In HGF-treated rats, AFP expression was stimulated at an earlier date and decreased to an undetectable level on day 12. Conversely, expression of albumin transcripts, which was stimulated by HGF-treatment at a later date, continued to increase even after HGF administration ceased, leading to an extremely high level on day 12. Moreover, treatment with HGF also stimulated the expression of hepatocyte nuclear factor-1alpha and -4alpha at an early date.

CONCLUSIONS

These results indicate that, besides the proliferation of hepatic oval cells, HGF possibly promotes the differentiation to hepatocytes in vivo, suggesting that recombinant human HGF accelerates the regeneration of severely damaged livers, a situation in which the proliferation of mature hepatocytes is impaired.

Adult stem cells and cancer stem cells: tie in or tear apart?

Stem cell research is one of the new frontiers of medical science. Because of the unique self-renewable ability and powerful potential to differentiate, stem cells can be viewed as the mother of all cells in the body and have been investigated as a possible tool for reversing the degeneration and damage on organs. Recently, successful isolating cancerous stem cells from leukemia, breast and brain cancers provide a new target for eliminate cancer; however, it hints an increasing caution in using adult stem cells for organ repair. Cancerous stem cells share the same properties of self-renewal and differentiation with normal stem cells, with the addition of similar phenotype of adult stem cells isolated from the same tissue. Some believe that cancerous stem cells are derived from mutation of the normal stem cells, whereas others suspect it to be from different origins. Further investigation of the intrinsic factor underlying the behavior of adult stem cells and cancerous stem cells will shed light on both the fields of tissue engineering and cancer therapy. In this review, recent progresses in the studies of adult stem cells and cancerous stem cells are summarized to facilitate a better understanding and elicit much attention in this field.

Dual effects of adenovirus-mediated thrombopoietin gene transfer on hepatic oval cell proliferation and platelet counts

Thrombopoietin (TPO) is the growth factor for megakaryocytes and platelets, however, it also acts as a potent regulator of stem cell proliferation. To examine the significance of TPO expression in proliferation of hepatic oval cells, the effect of adenovirus-mediated TPO gene transfer into livers of the Solt-Farber model, which mimics the condition where liver regeneration is impaired, was examined. Hepatic TPO mRNA peaked its expression at 2 days after gene transduction and then gradually decreased. The peripheral platelet number began to increase at 4 days (P<0.05) and reached its plateau at 9 days (P<0.01). Oval cells expressed c-Mpl, a receptor for TPO as well as immature hematopoietic and hepatocytic surface markers such as CD34 and AFP. The proliferating cell nuclear antigen-positive oval cells in rats into which adenovirus-TPO gene was transferred at 7 and 9 days were significantly greater than those in adenovirus-LacZ gene transferred (P<0.05, each), and the total numbers of oval cells in the adenovirus-TPO gene transferred at 9 and 13 days were also significantly greater than those in adenovirus-LacZ gene transferred (P<0.05, each). Expression of SCF protein was increased at 4, 7, and 9 days by TPO gene administration and that of c-Kit was increased at 4 and 7 days. These data suggest that adenovirus-mediated TPO gene transfer stimulated oval cell proliferation in liver as well as increasing peripheral platelet counts, emphasizing the significance of the TPO/c-Mpl system in proliferation of hepatic oval cells.

Differentiation of mouse embryonic stem cells into hepatocytes in vitro

AIM: To explore a method for the differentiation of embryonic stem (ES) cells into hepatocytes in vitro.

METHODS: ES cells were cultured on the feeder layer of mouse embryonic fibroblasts (MEF) in the medium containing leukemia inhibitory factor (LIF). The inductive factors, such as acid-fibroblast growth factor (acid-FGF), HGF, oncostatin M (OSM), Dex and ITS mixture (5 g/L insulin, 5 g/L transferring, 5 mg/L selenic acid), were added at day 9, 12, 12, 15 of induction. The activity of alkaline phosphatase (ALP) was detected by cytochemical method and visualized by NBT/BCIP. Albumin (ALB) and CK18 were examined by immunohistochemistry and DAB staining.

RESULTS: ALP was positive in the undifferentiated ES cells. Four days after induction, embryonid bodies came into formation. After the inductive factors were added, ES cells were differentiated into single morphological cells like epithelium. ALB and CK18 were positive in some differentiated cells.

CONCLUSION: Embryonic stem cells can be selectively differentiated into hepatocytes in vitro.

Differentiation of rat bone marrow cells cultured on artificial basement membrane containing extracellular matrix into a liver cell lineage

BACKGROUND/AIMS

Bone marrow (BM) cells have been shown to be capable of differentiating into a liver cell lineage in vitro. However, their differentiation and proliferation is poor, and the cell characteristics are poorly understood.

METHODS

We cultured rat BM cells on an artificial basement membrane containing extracellular matrix (ECM) with hepatocyte growth factor (HGF). The expression of mRNA for liver-specific genes was analyzed by reverse transcription PCR. The expression of albumin and Musashi-1 by cultured cells was analyzed using a fluorescence-activated cell sorter (FACS). The proportions of albumin-positive cells when culture was performed with different concentrations of HGF were analyzed by FACS.

RESULTS

On culture day 21, polygonal cells proliferated and formed cell colonies. These cells expressed mRNA for all the liver-specific genes analyzed, and showed heterogeneous differentiation, some cells expressing albumin, others expressing Musashi-1. Albumin-positive differentiated cells were large and rich in intracellular structures, while Musashi-1-positive undifferentiated cells had the opposite characteristics. Culturing cells with higher concentrations of HGF induced an increased proportion of albumin-positive cells.

CONCLUSIONS

The results suggest that cell culture on an ECM with a high concentration of HGF increases the extent to which BM cells differentiate into a liver cell lineage and proliferate in vitro.

Involvement of HGF/SF-Met signaling in prostate adenocarcinoma cells: evidence for alternative mechanisms leading to a metastatic phenotype in Pr-14c

BACKGROUND

Hepatocyte growth factor/scatter factor (HGF/SF) facilitates intercellular communication between the epithelial carcinoma and its surrounding stromal tissue during metastatic invasion through interaction with its proto-oncogenic receptor, Met, found on carcinoma cells. This study utilizes the C31/Tag transgenic mouse prostate cancer cell line model in an attempt to characterize the interaction between HGF/SF and Met on the metastatic potential of prostate cancer.

METHODS

Exogenous HGF was supplied to the prostate adenocarcinoma cell line (Pr-14) and metastatic cell line (Pr-14c) to evaluate mitogenicity by proliferation assays, morphological characteristics on an extracellular matrix substrate, and motogenic properties using the scatter assay, invasion chambers, and zymogram studies to analyze secretory enzymes produced by the cell lines.

RESULTS

RNA and protein analyses show that the cell lines express similar amounts of Met. Pr-14 cells have an increased growth rate following HGF/SF treatment, whereas the metastatic Pr-14c cells show little change. Morphological studies of Pr-14c cells on extracellular matrix demonstrate negligible changes when compared to the tubular formation of Pr-14 cells after HGF/SF stimulation. Motility studies of the metastatic cells following HGF/SF treatment reveal a potentially faulty signaling pathway downstream of Met activation in the metastatic prostate cells.

CONCLUSIONS

Our studies suggest that proliferation, invasion, and cell morphological characteristics may be induced independently from the HGF/SF-Met pathway in C31/Tag metastatic prostate cancer cells.

Aging is associated with decreased pancreatic acinar cell regeneration and phosphatidylinositol 3-kinase/Akt activation

BACKGROUND & AIMS

The effects of aging on pancreatic acinar cell proliferation have not been clearly defined. Phosphatidylinositol 3-kinase (PI3K)-mediated phosphorylation of Akt is a critical step for proliferation of various cell types and insulin secretion from pancreatic endocrine cells; however, its role in acinar cell proliferation is not known. The purpose of this study was to (1) delineate the effects of aging on pancreatic regeneration after partial pancreatectomy (Px) and (2) define the involvement of the PI3K/Akt pathway in pancreatic regeneration.

METHODS

Following partial Px, pancreatic regeneration and activation of the PI3K pathway were compared in young and aged mice. Activation of the PI3K/Akt pathway was evaluated by Akt phosphorylation (pAkt). The role of the PI3K pathway in pancreatic regeneration after partial Px was assessed by effects of a pharmacologic PI3K inhibitor wortmannin or small interfering RNA (siRNA) to the p85alpha regulatory subunit. To confirm further the critical role of the PI3K/Akt pathway in pancreatic acinar cell proliferation, IGF-1-mediated cell proliferation was determined in cultured acinar cells pretreated with wortmannin or p85alpha siRNA.

RESULTS

Pancreatic regeneration and pAkt expression after partial Px were significantly decreased with aging. Treatment with wortmannin or p85alpha siRNA reduced pancreatic regeneration after partial Px. The IGF-1-mediated cell proliferation in vitro was completely blocked by wortmannin or p85alpha siRNA but not by the MEK/ERK inhibitor PD98059.

CONCLUSIONS

PI3K/Akt activation plays a critical role in the regeneration of pancreatic acini after resection. Furthermore, pancreatic regeneration is markedly attenuated in the aged pancreas most likely because of decreased PI3K/Akt activation.

Oncostatin M inhibits proliferation of rat oval cells, OC15-5, inducing differentiation into hepatocytes

Oval cells of the liver participate in liver regeneration when hepatocytes are prevented from proliferating in response to liver damage. To clarify the role of oncostatin M (OSM) in the liver regeneration involving oval cells, we examined the expression of OSM and OSM-specific receptor (OSM-R) in the liver undergoing regeneration in the 2-acetylaminofluorene/partial hepatectomy model. Expression levels of OSM-R changed in correlation to the number of oval cells, and its expression was exclusively observed in oval cells. On the other hand, OSM was expressed in both oval cells and Kupffer cells. To examine the effect of OSM on the growth and differentiation of oval cells, rat oval cells (OC15-5) were incubated in conditioned medium of 293T cells expressing rat OSM cDNA. This resulted in suppression of growth, changes in morphology (microvilli and large cytoplasm with developed organelles), and expression of hepatocyte markers (albumin, tyrosine amino transferase, and tryptophan oxygenase). The effects of the conditioned medium with rat OSM were abrogated by introducing a small interfering RNA specifically targeting rat OSM-R into OC15-5 cells. These results indicate that OSM is a key mediator for inducing differentiation of OC15-5 cells into hepatocytes and suggest that the OSM/OSM-R system is pivotal in the differentiation of oval cells into hepatocytes, thereby promoting liver regeneration.

Synergistic induction of hepatocyte growth factor in human skin fibroblasts by the inflammatory cytokines interleukin-1 and interferon-γ

Hepatocyte growth factor (HGF) is one of the vital factors for wound healing. HGF expression markedly increases in wounded skin and is mainly localized in dermal fibroblasts. HGF expression level in human dermal fibroblasts in vitro, however, is low and thus may be stimulated by some factors in the process of wound healing. Candidates of the factors are inflammatory cytokines released by polymorphonuclear and mononuclear cells infiltrating the wounded area, but HGF production in human dermal fibroblasts is only slightly induced by interleukin (IL)-1, tumor necrosis factor (TNF)-alpha or interferon (IFN)-gamma. We here report that a combination of IL-1beta and IFN-gamma or a combination of TNF-alpha and IFN-gamma very markedly induced HGF production. The synergistic effect of the former was more marked than that of the latter. Synergistic effects of IL-1beta and IFN-gamma were observed at more than 10 pg/ml and 10 IU/ml, respectively, and were detectable as early as 12 h after addition. Neither IFN-alpha nor IFN-beta was able to replace IFN-gamma. HGF mRNA expression was also synergistically upregulated by IL-1beta and IFN-gamma. IL-1beta plus IFN-gamma-induced synergistic production of HGF was potently inhibited by treatment of cells with the extracellular signal-regulated kinase (ERK) kinase inhibitor PD98059 and the p38 inhibitor SB203580 but not by the c-Jun N-terminal kinase (JNK) inhibitor SP600125. Taken together, our results indicate that a combination of IL-1beta and IFN-gamma synergistically induced HGF production in human dermal fibroblasts and suggest that activation of ERK and p38 but not of JNK is involved in the synergistic effect.

Activation of TEC and STAT3 after partial hepatectomy or hepatocytic growth factor stimulation

AIM: To study the activation of TEC and STAT3 in the hepatocyte after partial hepatectomy (PH) or hepatocytic growth factor (HGF) stimulation in the mice.

METHODS: Mice of SPF degree and WB F-344 cell (liver stem cell line) were used in this study. In vivo and in vitro experimental models of PH and HGF stimulation were established respectively. Immunoprecipitation (IP) and immunoblotting (IB) were used to observe the phosphorylation level and time of TEC and STAT3. On the other hand, electrophoretic mobility shift assay (EMSA) was used to detect the binding ability of STAT3 DNA.

RESULTS: TEC and STAT3 were both inducibly phosphorylated in one hour after PH or HGF stimulation. Ten to twenty minutes after PH, levels of TEC and STAT3 reached the peak. About 10 min after HGF stimulation, TEC phosphorylation level reached maximum value and about 30 min STAT3 phosphorylation level reached peak value. Meanwhlie, STAT3 DNA binding activity was enhanced both In vivo and in vitro experiments.

CONCLUSION: After PH or HGF-stimulation, both TEC and STAT3 are quickly phosphorylated in one hour, and they synergically affect the early proliferation of hepatocytes.

Liver regeneration: from myth to mechanism

The unusual regenerative properties of the liver are a logical adaptation by organisms, as the liver is the main detoxifying organ of the body and is likely to be injured by ingested toxins. The numerous cytokine- and growth-factor-mediated pathways that are involved in regulating liver regeneration are being successfully dissected using molecular and genetic approaches. So what is known about this process at present and which questions remain?

Function of oval cells in hepatocellular carcinoma in rats

AIM: To study oval cells pathological characteristics and relationship with the occurrence of hepatocellular carcinoma (HCC); to observe the form and structural characteristics of oval cells; to explore the expression characteristics of C-kit, PCNA mRNA and c-myc gene during the occurrence and development of HCC and the effect of ulinastatin (UTI) on C-kit and PCNA expression.

METHODS: One hundred and twenty-five SD rats fed on 3,3'-diaminobenzidine (DAB) to construct HCC models were divided into control group, cancer-inducing group and UTI intervention group. In each group, rat liver samples were collected at weeks 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22 and 24 respectively to study pathological distribution characteristics of oval cells in the process of carcinogenesis under optical microscope. Oval cells were separated by the methods of improved density gradient centrifugation and their structural characteristics were observed under optical microscope and electronic microscope respectively; the oval cells expressing C-kit and PCNA in the collected samples were observed by the methods of immunohistochemistry and image analysis and the expression of c-myc mRNA was also detected by reverse transcription polymerase chain reaction (RT-PCR).

RESULTS: Oval cells proliferated firstly in the portal area then gradually migrated into hepatic parenchyma in the inducing group and intervention group. The oval cells distributed inside and outside the carcinoma nodes. The oval cells presented the characteristics of undifferentiated cells: a high ratio of nucleolus and cellular plasm and obvious nucleoli, rare organelle in plasm. Only a few mitochondria and endoplasmic reticulum and some villus-like apophysis on surface of cells could be seen. Cells stained with C-kit and PCNA antibody were mainly oval cells distributed in the portal area. The expression of c-myc mRNA increased with the progression of HCC. However, in the intervention group, UTI could retard its increase.

CONCLUSION: Oval cells work throughout the development of HCC, and might play important roles in this process. c-myc gene may be a kind of promoter gene of HCC, and play a key role in hepatic injury and development of HCC. UTI could retard the occurrence of HCC.

Hepatocyte-specific Pten deficiency results in steatohepatitis and hepatocellular carcinomas

PTEN is a tumor suppressor gene mutated in many human cancers, and its expression is reduced or absent in almost half of hepatoma patients. We used the Cre-loxP system to generate a hepatocyte-specific null mutation of Pten in mice (AlbCrePten(flox/flox) mice). AlbCrePten(flox/flox) mice showed massive hepatomegaly and steatohepatitis with triglyceride accumulation, a phenotype similar to human nonalcoholic steatohepatitis. Adipocyte-specific genes were induced in mutant hepatocytes, implying adipogenic-like transformation of these cells. Genes involved in lipogenesis and beta-oxidation were also induced, possibly as a result of elevated levels of the transactivating factors PPARgamma and SREBP1c. Importantly, the loss of Pten function in the liver led to tumorigenesis, with 47% of AlbCrePten(flox/flox) livers developing liver cell adenomas by 44 weeks of age. By 74-78 weeks of age, 100% of AlbCrePten(flox/flox) livers showed adenomas and 66% had hepatocellular carcinomas. AlbCrePten(flox/flox) mice also showed insulin hypersensitivity. In vitro, AlbCrePten(flox/flox) hepatocytes were hyperproliferative and showed increased hyperoxidation with abnormal activation of protein kinase B and MAPK. Pten is thus an important regulator of lipogenesis, glucose metabolism, hepatocyte homeostasis, and tumorigenesis in the liver.

Keratinocyte Growth Factor Stimulates Alveolar Type II Cell Proliferation through the Extracellular Signal–Regulated Kinase and Phosphatidylinositol 3-OH Kinase Pathways

Keratinocyte growth factor (KGF or FGF-7) stimulates alveolar type II cell proliferation, but little is known about the signaling pathways involved. We investigated the role of the ERK (p42/44 mitogen activated protein [MAP] kinase) and phosphatidylinositol 3-OH kinase (PI3 kinase) pathways on alveolar type II cell proliferation and differentiation. Rat type II cells were cultured on tissue culture plastic and Matrigel in the presence or absence of KGF and specific chemical inhibitors PD98059, LY294002, and rapamycin at various concentrations. Proliferation was measured by thymidine incorporation and DNA quantitation, and differentiation was measured by expression of surfactant protein A and alkaline phosphatase. We demonstrate that KGF activates distal effectors of the PI3 kinase pathway, PKB/Akt, and p70S6 kinase, as well as p42/44 MAP kinase proteins. Inhibition of these pathways with PD98059, LY294002, or rapamycin inhibited type II cell proliferation but had no significant effect on differentiation. KGF did not activate the c-Jun kinase or p38 MAP kinase pathways. We conclude that the p42/44 MAP kinase and PI3 kinase pathways are important in regulating alveolar type II cell proliferation in response to KGF.

Hepatocyte-specific Pten deficiency results in steatohepatitis and hepatocellular carcinomas

PTEN is a tumor suppressor gene mutated in many human cancers, and its expression is reduced or absent in almost half of hepatoma patients. We used the Cre-loxP system to generate a hepatocyte-specific null mutation of Pten in mice (AlbCrePten(flox/flox) mice). AlbCrePten(flox/flox) mice showed massive hepatomegaly and steatohepatitis with triglyceride accumulation, a phenotype similar to human nonalcoholic steatohepatitis. Adipocyte-specific genes were induced in mutant hepatocytes, implying adipogenic-like transformation of these cells. Genes involved in lipogenesis and beta-oxidation were also induced, possibly as a result of elevated levels of the transactivating factors PPARgamma and SREBP1c. Importantly, the loss of Pten function in the liver led to tumorigenesis, with 47% of AlbCrePten(flox/flox) livers developing liver cell adenomas by 44 weeks of age. By 74-78 weeks of age, 100% of AlbCrePten(flox/flox) livers showed adenomas and 66% had hepatocellular carcinomas. AlbCrePten(flox/flox) mice also showed insulin hypersensitivity. In vitro, AlbCrePten(flox/flox) hepatocytes were hyperproliferative and showed increased hyperoxidation with abnormal activation of protein kinase B and MAPK. Pten is thus an important regulator of lipogenesis, glucose metabolism, hepatocyte homeostasis, and tumorigenesis in the liver.

Differentiation of adult bone marrow CD45-CD117- stem cells into hepatocyte in vitro

AIM: To observe whether the CD117-CD45- bone marrow cell can differentiate into the cells with characters of hepatocyte by the stimulation of hepatocyte growth factor (HGF)and fibroblast growth factor-4 (FGF4), and to explore the acting mechanism of the growth factors.

METHODS: Bone marrow cells were from the stern or ilium of 4 healthy volunteers between 4-40 years old. CD117-CD45- bone marrow cells separated by magnetic cell sorting method, cultured in DMEM medium with FGF4, HGF, FGF4+ HGF or no growth factor were divided into four groups: groups A, B, C, and D accordingly. Cells were collected on d 0, 7, 14, 21, and 28 for detecting the hepatocyte markers: AFP, CK18, albumin by immunocytochemistry, glycogen by PAS staining and c-met, FGFR2 mRNA by RT-PCR.

RESULTS: The specific markers of hepatocyte were positive in groups A, B and C but not in group D. C-met and FGFR2 mRNA expressed at a low level in the cells newly isolated or cultured in the medium without growth factor, but at increasing level after cutured with growth factor.

CONCLUSION: HGF and FGF4 can induce CD45-CD117- differentiate into hepatocyte-like cells. The effect of growth factor on cell differentiation is probably by the positive regulation between the growth factor and its receptor.