Pan, Q.

Overestimation of hematopoietic stem cell frequencies in human liver grafts (Article)

2013-04-10T00:00:00Z

Identification of lineage-uncommitted, long-lived, label-retaining cells in healthy human esophagus and stomach, and in metaplastic esophagus (Article)

2013-04-01T00:00:00Z

Background & Aims: The existence of slowly cycling, adult stem cells has been challenged by the identification of actively cycling cells. We investigated the existence of uncommitted, slowly cycling cells by tracking 5-iodo-2'-deoxyuridine (IdU) label-retaining cells (LRCs) in normal esophagus, Barrett's esophagus (BE), esophageal dysplasia, adenocarcinoma, and healthy stomach tissues from patients. Methods: Four patients (3 undergoing esophagectomy, 1 undergoing esophageal endoscopic mucosal resection for dysplasia and an esophagectomy for esophageal adenocarcinoma) received intravenous infusion of IdU (200 mg/m2 body surface area; maximum dose, 400 mg) over a 30-minute period; the IdU had a circulation half-life of 8 hours. Tissues were collected at 7, 11, 29, and 67 days after infusion, from regions of healthy esophagus, BE, dysplasia, adenocarcinoma, and healthy stomach; they were analyzed by in situ hybridization, flow cytometry, and immunohistochemical analyses. Results: No LRCs were found in dysplasias or adenocarcinomas, but there were significant numbers of LRCs in the base of glands from BE tissue, in the papillae of the basal layer of the esophageal squamous epithelium, and in the neck/isthmus region of healthy stomach. These cells cycled slowly because IdU was retained for at least 67 days and co-labeling with Ki-67 was infrequent. In glands from BE tissues, most cells did not express defensin-5, Muc-2, or chromogranin A, indicating that they were not lineage committed. Some cells labeled for endocrine markers and IdU at 67 days; these cells represented a small population (<0.1%) of epithelial cells at this time point. The epithelial turnover time of the healthy esophageal mucosa was approximately 11 days (twice that of the intestine). Conclusions: LRCs of human esophagus and stomach have many features of stem cells (long lived, slow cycling, uncommitted, and multipotent), and can be found in a recognized stem cell niche. Further analyses of these cells, in healthy and metaplastic epithelia, is required. © 2013 AGA Institute.

Novel Anti-viral Strategies for Hepatitis C (Doctoral Thesis)

2012-02-22T00:00:00Z

HCV is a single‐stranded positive‐sense RNA virus that was first identified in 19891. HCV belongs to the Flaviviridae family and has six major genotypes. According to the estimation of the World Health Organization, approximately 170 million people, 3% of the world population, are HCV positive with 3 to 4 million de novo infections each year. Of the newly infected individuals only approx. 15‐40% will effectively clear the virus and those who fail to do so will develop a chronic and progressive infection. The prevalence is high in Egypt (>10%), Asia (5‐10%) and Southern Europe (1‐2.5%) and is low in the Netherlands (<1%). Chronic hepatitis C is a slowly progressive disease causing no or few symptoms in the initial phase, but 10 to 20% of the patients develop liver cirrhosis over a period of 10 to 30 years. Patients with liver cirrhosis have an annual risk of 1 to 5% to develop liver cancer, in particular hepatocellular carcinoma (HCC). Unfortunately, there are still no effective vaccines or antibodies available for the prevention of infection.

Image-guided radiation therapy for muscle-invasive bladder cancer (Article)

2012-01-01T00:00:00Z

Organ preservation protocols that incorporate chemoradiotherapy have shown good efficacy in bladder cancer. Owing to changes in rectal filling, urinary inflow and subsequent bladder volume with bladder wall deformations, irradiation must take into account interfractional and intrafractional internal target motion. Growing evidence suggests that image guidance during irradiation is essential in order to appropriately treat bladder cancer in this way. We performed a literature search on the imaging techniques and margins used for radiation therapy planning in the context of whole-bladder and partial-bladder irradiation. The most common image-guided radiation therapy (IGRT) method was based on cone-beam CT using anisotropic margins. The role of cine-MRI for the prediction of intraindividual bladder changes, in association with cone-beam CT or ultrasonography, is promising. Drinking protocols, diet and laxatives were used in most cases to minimize large variations in bladder size and shape. IGRT is crucial for avoiding tumor undercoverage and undue toxicity during radiation therapy for bladder cancer. IGRT-based adaptive radiation therapy can be performed using cone-beam CT or ultrasonography: modeling of bladder changes with cine-MRI or other imaging techniques might also be useful for facilitating adaptive radiation therapy with personalized margins.

Hepatic cell-to-cell transmission of small silencing RNA can extend the therapeutic reach of RNA interference (RNAi) (Article)

2011-12-23T00:00:00Z

Background/aims: RNA interference (RNAi), a sequence-specific gene silencing technology triggered by small interfering RNA (siRNA), represents promising new avenues for treatment of various liver diseases including hepatitis C virus (HCV) infection. In plants and invertebrates, RNAi provides an important mechanism of cellular defence against viral pathogens and is dependent on the spread of siRNA to neighbouring cells. A study was undertaken to investigate whether vector-delivered RNAi can transfer between hepatic cells in vitro and in mice, and whether this exchange could extend the therapeutic effect of RNAi against HCV infection. Methods: Transmission of RNAi was investigated in culture by assessing silencing of HCV replication and expression of viral entry receptor CD81 using a human hepatic cell line and primary B lymphocytes transduced with siRNA-expressing vectors. In vivo transmission between hepatic cells was investigated in NOD/SCID mice. Involvement of exosomes was demonstrated by purification, uptake and mass spectrometric analysis. Results: Human and mouse liver cells, as well as primary human B cells, were found to have the ability to exchange small RNAs, including cellular endogenous microRNA and delivered siRNA targeting HCV or CD81. The transmission of RNAi was largely independent of cell contact and partially mediated by exosomes. Evidence of RNAi transmission in vivo was observed in NOD/SCID mice engrafted with human hepatoma cells producing CD81 siRNA, causing suppression of CD81 expression in mouse hepatocytes. Conclusion: Both human and mouse hepatic cells exchange small silencing RNAs, partially mediated by shuttling of exosomes. Transmission of siRNA potentially extends the therapeutic reach of RNAi-based therapies against HCV as well as other liver diseases. Copyright Article author (or their employer) 2011.

Production of multicopy shRNA lentiviral vectors for antiviral therapy. (Article)

2011-07-12T00:00:00Z

For effective RNA interference (RNAi)-based therapies against viral infection, particularly highly mutational viruses like HCV and HIV, combinational strategies that target multiple regions within a viral genome are required to prevent resistance. The use of lentiviral vectors for combinatorial RNAi (coRNAi) offers possibilities to deliver multiple short hairpin RNA (shRNA) sequences simultaneously to individual cells while maintaining high expression levels required to suppress viral replication. By applying coRNAi, one can impart either a protective strategy, i.e., treatment prior to infection, or a long-term treatment postinfection without the eventuality of mutational outgrowth due to incomplete selection pressure. In this chapter, we provide a detailed description of the methods available to create coRNAi vectors and discuss some of the current problems and technical limitations.

Mobilization of hepatic mesenchymal stem cells from human liver grafts (Article)

2011-05-01T00:00:00Z

Extensive studies have demonstrated the potential applications of bone marrow-derived mesenchymal stem cells (BM-MSCs) as regenerative or immunosuppressive treatments in the setting of organ transplantation. The aims of the present study were to explore the presence and mobilization of mesenchymal stem cells (MSCs) in adult human liver grafts and to compare their functional capacities to those of BM-MSCs. The culturing of liver graft preservation fluids (perfusates) or end-stage liver disease tissues resulted in the expansion of MSCs. Liver-derived mesenchymal stem cells (L-MSCs) were equivalent to BM-MSCs in adipogenic and osteogenic differentiation and in wingless-type-stimulated proliferative responses. Moreover, the genome-wide gene expression was very similar, with a 2-fold or greater difference found in only 82 of the 32,321 genes (0.25%). L-MSC differentiation into a hepatocyte lineage was demonstrated in immunodeficient mice and in vitro by the ability to support a hepatitis C virus infection. Furthermore, a subset of engrafted MSCs survived over the long term in vivo and maintained stem cell characteristics. Like BM-MSCs, L-MSCs were found to be immunosuppressive; this was shown by significant inhibition of T cell proliferation. In conclusion, the adult human liver contains an MSC population with a regenerative and immunoregulatory capacity that can potentially contribute to tissue repair and immunomodulation after liver transplantation.

Disturbance of the microRNA pathway by commonly used lentiviral shRNA libraries limits the application for screening host factors involved in hepatitis C virus infection (Article)

2011-04-06T00:00:00Z

RNA interference (RNAi) is widely used as a screening tool for the identification of host genes involved in viral infection. Due to the limitation of raw small interfering RNA (siRNA), we tested two commonly used short hairpin RNA (shRNA) lentiviral libraries to identify host factors involved in hepatitis C virus (HCV) infection. It was found that these shRNA library vectors caused non-specific disturbance of HCV replication that was not due to toxicity or interferon response, but related to the high shRNA levels disturbing the endogenous microRNA biogenesis. The high shRNA levels achieved with these vectors reduced the levels of mature microRNAs, including miR-122 known to promote HCV replication. Our findings extend the caution of potential off-target effects of lentiviral shRNA libraries which appear unsuitable to screen microRNA regulated phenotypes, such as HCV replication.

Ribavirin enhances interferon-stimulated gene transcription by activation of the interferon-stimulated response element (Article)

2011-04-01T00:00:00Z

AAV-mediated gene therapy for liver diseases: The prime candidate for clinical application? (Article)

2011-03-01T00:00:00Z

Introduction: Diseases of the liver represent a major health problem. Often treatments are ineffective, prompting the need for new therapeutic strategies. From extensive preclinical studies, gene therapy in particular mediated by adeno-associated virus (AAV)-derived vectors, has now emerged as the prime candidate for clinical application. AAV-mediated gene therapy for inherited liver diseases has now become a clinical reality, in particular for the treatment of hemophilia B. Areas covered: This review provides a summary of current literature on AAV-mediated gene therapies for both inherited and acquired liver diseases and outlines different strategies to overcome current clinical limitations. The unique properties of AAV over other viral vectors are highlighted as well as the current challenges which are faced for wide-ranging clinical application. Expert opinion: Despite the extensive positive results from animal models, successful application in clinical settings is hampered by immunological barriers. However, immune suppression and other strategies can be employed to overcome these limitations. Given some of their unique advantages, AAV vectors are currently the most obvious candidate for hepatic gene therapy applications, however, serotype-related issues of immune reactivity still represent a formidable barrier for clinical success.

Calcineurin inhibitor tacrolimus does not interfere with the suppression of hepatitis C virus infection by interferon-α (Article)

2010-04-01T00:00:00Z

Immunosuppression considerably affects hepatitis C virus (HCV) recurrence and the outcome of antiviral treatment after liver transplantation. Recent findings have suggested that the calcineurin inhibitor tacrolimus (Tac), unlike cyclosporine A (CsA), interferes with the antiviral activity of interferon-α (IFN-α) in vitro. The aim of this study was to more extensively investigate the effects of calcineurin inhibitors on IFN-α signaling and antiviral activity in subgenomic and infectious HCV models. Treatment with Tac and CsA did not affect Huh7 cell proliferation at doses of 10 to 500 ng/mL; however, it completely inhibited T cell proliferation. In contrast to previous reports, Tac had no effect on IFN-α-stimulated reporter gene expression, even at the dose of 5 μg/mL. Furthermore, in Huh7 subgenomic HCV replicon cells, treatment with Tac had no significant effect on the suppression of viral replication by IFN-α. In the infectious HCV model, treatment with IFN-α effectively inhibited both viral RNA replication and de novo production of virus particles, and neither was attenuated at any concentration of Tac. CsA had no significant effect on IFN-α-stimulated reporter gene expression; however, as shown previously, a combination of CsA (at 500 ng/mL and higher) and IFN-α resulted in enhanced inhibition of viral replication in both the subgenomic and infectious HCV models. In conclusion, our study shows no evidence that Tac or CsA interferes with IFN-α-mediated inhibition of HCV replication and virion production in vitro. Therefore, no further mechanistic arguments have been found to break the clinical controversy about the choice of calcineurin inhibitors during posttransplantation antiviral therapy.

Combined antiviral activity of interferon-α and RNA interference directed against hepatitis C without affecting vector delivery and gene silencing (Article)

2009-07-01T00:00:00Z

The current standard interferon-alpha (IFN-α)-based therapy for chronic hepatitis C virus (HCV) infection is only effective in approximately half of the patients, prompting the need for alternative treatments. RNA interference (RNAi) represents novel approach to combat HCV by sequence-specific targeting of viral or host factors involved in infection. Monotherapy of RNAi, however, may lead to therapeutic resistance by mutational escape of the virus. Here, we proposed that combining lentiviral vector-mediated RNAi and IFN-α could be more effective and avoid therapeutic resistance. In this study, we found that IFN-α treatment did not interfere with RNAi-mediated gene silencing. RNAi and IFN-α act independently on HCV replication showing combined antiviral activity when used simultaneously or sequentially. Transduction of mouse hepatocytes in vivo and in vitro was not effected by IFN-α treatment. In conclusion, RNAi and IFN-α can be effectively combined without cross-interference and may represent a promising combinational strategy for the treatment of hepatitis C.

Prospects of RNAi and microRNA-based therapies for hepatitis C (Article)

2009-06-01T00:00:00Z

Background: RNA interference (RNAi) represents a promising new approach to combat viral infections, and recent developments in the field of gene therapy have increased the feasibility of clinical applications. Objective: to explore the utility of RNAi for the treatment of the ultimately life-threatening liver disease caused by hepatitis C virus (HCV), which affects approximately 170 million people worldwide. Methods: A review of current developments in liver-directed gene delivery and the potential application of RNAi for the treatment of HCV. In addition, the involvement of microRNAs (miRNA) in HCV infection and the potential therapeutic implications are emphasized. Conclusions: RNAi technologies have fuelled rapid progress in the basic understanding of HCV biology and revealed numerous new viral and host-cell factors as potential targets for therapy. Together with the improvement of gene delivery technology and the discovery of the critical role of miRNA in HCV infection, RNAi and miRNA-based antiviral strategies hold great promise for the future.