L Bühler

University of Geneva, Genève, GE, Switzerland

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Publications (157)342.91 Total impact

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    ABSTRACT: Mesenchymal stem cell (MSC) transplantation was shown to be effective for the treatment of liver fibrosis, but the mechanisms of action are not yet fully understood. We transplanted encapsulated human MSCs in two mouse models of liver fibrosis to determine the mechanisms of the protective effect.
    Journal of Hepatology. 10/2014;
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    ABSTRACT: Advanced surgical procedures have traditionally been a domain of open surgery. However, minimally invasive approaches are evolving with the development of robotic technology which appears capable to overcome technical limitations of conventional laparoscopy. While traditionally perceived as impossible indications for minimally invasive surgery, reports on robotic organ transplantations have surfaced with promising results.
    Revue médicale suisse. 06/2014; 10(435):1356-60.
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    ABSTRACT: Regenerative medicine aims to replace a body function or specific cell loss. It includes therapies at the forefront of modem medicine, issuing from translational biomedical research. Transplantation of organs and cells has revolutionized the management of patients for whom medical treatment is a failure. Unfortunately, organ shortage is limiting treatment possibility. As an example, among the 15,000 patients with type I diabetes in Switzerland, only approximately 30 can receive a pancreas or an islet transplant per year. Second example, 500 patients die each year in Switzerland from alcoholic cirrhosis because no treatment is available. Transplantation of islet cells, hepatocytes, mesenchymal stem cells or dopaminergic neurons represents hope fora therapy available for large populations of patients.
    Revue médicale suisse. 06/2014; 10(435):1350-5.
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    ABSTRACT: Magnetic resonance imaging (MRI) gadolinium-perfusion was applied in simulated Donation after Cardiac Death (DCD) in porcine kidneys to measure intrarenal perfusion. Adenosine triphosphate (ATP) resynthesis during oxygenated hypothermic perfusion was compared to evaluate the "ex vivo organ viability". Adenine nucleotide (AN) was measured by P nuclear magnetic resonance (NMR) spectroscopy. Whereas this latter technique requires sophisticated hardware, gadolinium-perfusion can be realized using any standard proton-MRI scanner. The aim of this work was to establish a correlation between the two methods. Twenty-two porcine kidneys presenting up to 90 min warm ischemia were perfused with oxygenation at 4°C using our magnetic resonance-compatible machine. During the perfusion, P NMR spectroscopy and gadolinium-perfusion sequences were performed. Measures obtained from the gadolinium-perfusion were the speed of elimination of the cortical gadolinium and the presence or absence of a corticomedullar shunt. For ATP resynthesis analysis, P chemical shift imaging was acquired and analyzed. All the kidneys have been submitted to histologic examination. ATP resynthesis was observed in all organs presenting a cortical gadolinium elimination slope of (-) 23° or greater. In organs with lower gadolinium elimination, no AN or only precursors were detected. This study reveals a link between the two methods and demonstrates ex vivo viability in 93% of the analyzed kidneys. Benefits and side effects of both methods are discussed. Oxygenated hypothermic perfusion enables the evaluation of kidneys in DCD simulated situation; gadolinium-perfusion can be introduced into any center equipped with a proton-MRI scanner allowing results superposable with ATP measurement.
    Transplantation 01/2014; 97(2):148-53. · 3.78 Impact Factor
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    ABSTRACT: Bone marrow was recently proposed as an alternative and potentially immune-privileged site for pancreatic islet transplantation. The aim of the present study was to assess the survival and rejection mechanisms of free and encapsulated xenogeneic islets transplanted into the medullary cavity of the femur, or under the kidney capsule of streptozotocin-induced diabetic C57BL/6 mice. The median survival of free rat islets transplanted into the bone marrow or under the kidney capsule was 9 and 14 days, respectively, whereas that of free human islets was shorter, 7 days (bone marrow) and 10 days (kidney capsule). Infiltrating CD8+ T cells and redistributed CD4+ T cells, and macrophages were detected around the transplanted islets in bone sections. Recipient mouse splenocytes proliferated in response to donor rat stimulator cells. One month after transplantation under both kidney capsule or into bone marrow, encapsulated rat islets had induced a similar degree of fibrotic reaction and still contained insulin positive cells. In conclusion, we successfully established a small animal model for xenogeneic islet transplantation into the bone marrow. The rejection of xenogeneic islets was associated with local and systemic T cell responses and macrophage recruitment. Although there was no evidence for immune-privilege, the bone marrow may represent a feasible site for encapsulated xenogeneic islet transplantation.
    PLoS ONE 01/2014; 9(3):e91268. · 3.53 Impact Factor
  • 12/2013; 7(1).
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    ABSTRACT: Minimally invasive approaches for cholecystectomy are evolving in a surge for the best possible clinical outcome for the patients. As one of the most recent developments, a robotic set of instrumentation to be used with the da Vinci Si Surgical System has been developed to overcome some of the technical challenges of manual single incision laparoscopy. From February 2011 to February 2013, all consecutive robotic single site cholecystectomies (RSSC) were prospectively collected in a dedicated database. Demographic, intra- and postoperative data of all patients that underwent RSSC at our institution were analyzed. Data were evaluated for the overall patient cohort as well as after stratification according to patient BMI (body mass index) and surgeon's experience. During the study period, 82 patients underwent robotic single site cholecystectomy at our institution. The dominating preoperative diagnosis was cholelithiasis. Mean overall operative time was 91 min. Intraoperative complications occurred in 2.4% of cases. One conversion to open surgery due to the intraoperative finding of a gallbladder carcinoma was observed and two patients needed an additional laparoscopic trocar. The rate of postoperative complications was 4.9% with a mean length of stay of 2.4 days. No significant differences were observed when comparing results between robotic novices and robotic experts. Patients with higher BMI trended towards longer surgical console and overall operative time, but resulted in similar rates of conversions and complications when compared to normal weight patients. Robotic Single-Site cholecystectomy can be performed safely and effectively with low rates of complications and conversions in patients with differing BMI and by surgeons with varying levels of experience.
    Journal of hepato-biliary-pancreatic sciences. 10/2013;
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    ABSTRACT: Mesenchymal stem cells or multipotent mesenchymal stromal cells (MSCs) have been extensively investigated in small animal models to treat both acute and chronic liver injuries. Mechanisms of action are not clearly elucidated but may include their ability to differentiate into hepatocyte-like cells, to reduce inflammation, and to enhance tissue repair at the site of injury. This approach is controversial and evidence in large animals is missing. Side effects of MSC infusion such as the contribution to a fibrotic process have been reported in experimental settings. Nevertheless, MSCs moved quickly from bench to bedside and over 280 clinical trials are registered, of which 28 focus on the treatment of liver diseases. If no severe side-effects were observed so far, long-term benefits remain uncertain. More preclinical data regarding mechanisms of action, long term safety and efficacy are warranted before initiating large scale clinical application. The proposal of this review is to visit the current state of knowledge regarding mechanisms behind the therapeutic effects of MSCs in the treatment of experimental liver diseases, to address questions about efficacy and risk, and to discuss recent clinical advances involving MSC-based therapies.
    Stem Cell Research 08/2013; 11(3):1348-1364. · 4.47 Impact Factor
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    ABSTRACT: Two types of hydrogel microspheres have been developed. Fast ionotropic gelation of sodium alginate (Na-alg) in the presence of calcium ions was combined with slow covalent cross-linking of poly(ethylene glycol) (PEG) derivatives. For the first type, the fast obtainable Ca-alg hydrogel served as spherical matrix for the simultaneously occurring covalent cross-linking of multi-arm PEG derivative. A two-component interpenetrating network was formed in one step upon extruding the mixture of the two polymers into the gelation bath. For the second type, heterobifunctional PEG was grafted onto Na-alg prior to gelation. Upon extrusion of the polymer solution into the gelation bath, fast Ca-alg formation ensured the spherical shape and was accompanied by cross-linker-free covalent cross-linking of the PEG side chains. Thus, one-component hydrogel microspheres resulted. We present the physical properties of the hydrogel microspheres and demonstrate the feasibility of cell microencapsulation for both types of polymer networks.
    Macromolecular Symposia 07/2013; 329(1).
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    ABSTRACT: Experiments injecting pluripotent cells into blastocyst embryos open exciting possibilities for the generation of self‐specific organs in xenogeneic animals.
    American Journal of Transplantation 06/2013; 13(6):1377. · 6.19 Impact Factor
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    ABSTRACT: In humans, circulating CD4(+)CD25(high) T cells contain mainly regulatory T cells (Treg; FoxP3(+)IL-7Rα(low)), but a small subset is represented by activated effector T cells (Tact; FoxP3(-)IL-7Rα(high)). The balance between Tact and Treg may be important after transplantation. The aim of this study was first to analyze and correlate CD4(+)CD25(high) Tact and Treg with the clinical status of kidney transplant recipients and second to study prospectively the effect of two immunosuppressive regimens on Tact/Treg during the first year after transplantation. CD4(+)CD25(high) Tact and Treg were analyzed by flow cytometry, either retrospectively in 90 patients greater than 1 year after kidney transplantation (cross-sectional analysis) or prospectively in 35 patients receiving two immunosuppressive regimens after kidney transplantation (prospective analysis). A higher proportion of Tact and a lower proportion of Treg were found in the majority of kidney recipients. In chronic humoral rejection, a strikingly higher proportion of Tact was present. A subgroup of stable recipients receiving calcineurin inhibitor-free immunosuppression (mycophenolate mofetil, azathioprine, or sirolimus) had Tact values that were similar to healthy individuals. In the prospective analysis, the proportion of Tact significantly increased in both immunosuppression groups during the first year after transplantation. These data highlight distinct patterns in the proportion of circulating Tact depending on the clinical status of kidney recipients. Moreover, the prospective analysis demonstrated an increase in the proportion of Tact, regardless of the immunosuppressive regimen. The measurement of Tact, in addition to Treg, may become a useful immune monitoring tool after kidney transplantation.
    Clinical Journal of the American Society of Nephrology 08/2011; 6(8):2025-33. · 5.07 Impact Factor
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    ABSTRACT: Streptozotocin (STZ) is the most widely used diabetogenic agent in animal models of islet transplantation. However, the immunomodifying effects of STZ and the ensuing hyperglycemia on lymphocyte subsets, particularly on T regulatory cells (Tregs), remain poorly understood. This study evaluated how STZ-induced diabetes affects adaptive immunity and the consequences thereof on allograft rejection in murine models of islet and skin transplantation. The respective toxicity of STZ and hyperglycemia on lymphocyte subsets was tested in vitro. The effect of hyperglycemia was assessed independently of STZ in vivo by the removal of transplanted syngeneic islets, using an insulin pump, and with rat insulin promoter diphtheria toxin receptor transgenic mice. Early lymphopenia in both blood and spleen was demonstrated after STZ administration. Direct toxicity of STZ on lymphocytes, particularly on CD8(+) cells and B cells, was shown in vitro. Hyperglycemia also correlated with blood and spleen lymphopenia in vivo but was not lymphotoxic in vitro. Independently of hyperglycemia, STZ led to a relative increase of Tregs in vivo, with the latter retaining their suppressive capacity in vitro. The higher frequency of Tregs was associated with Treg proliferation in the blood, but not in the spleen, and higher blood levels of transforming growth factor-β. Finally, STZ administration delayed islet and skin allograft rejection compared with naive mice. These data highlight the direct and indirect immunosuppressive effects of STZ and acute hyperglycemia, respectively. Thus, these results have important implications for the future development of tolerance-based protocols and their translation from the laboratory to the clinic.
    Diabetes 07/2011; 60(9):2331-40. · 7.90 Impact Factor
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    ABSTRACT: No guidelines exist concerning treatment of asymptomatic bacteriuria in renal transplant recipients (RTR). Because of scarce clinical symptoms and fear of complications, such episodes are frequently treated based on subjective criteria without clear clinical benefit, with the risk of selecting resistant pathogens. We retrospectively analysed the outcome of 334 asymptomatic Escherichia coli (E. coli) and Enterococcus faecalis (E. faecalis) bacteriuria that occurred in 77 RTR later than 1 month post-transplantation. We distinguished: Type I, high-grade bacteriuria with pyuria; Type II, high-grade bacteriuria without pyuria; Type III, low-grade bacteriuria with pyuria and Type IV, low-grade bacteriuria without pyuria. None of the 334 episodes was followed by acute rejection or chronic pyelonephritis. One hundred and one (30%) episodes were treated [32 (62%) Type I, 38 (45%) Type II, 13 (36%) Type III and 18 (11%) Type IV]. Evolution to symptomatic urinary tract infection (UTI) was similar between treated and untreated episodes (0/101 versus 4/233, P = 0.32). The four UTI resolved favourably without further complication upon treatment. Persistent asymptomatic bacteriuria occurred in 45 (46%) treated episodes (2 Type I, 27 Type II, 8 Type III and 9 Type IV), with selection of resistant pathogen in 35 cases (78%). Spontaneous bacterial clearance occurred in 138 (59%) untreated episodes (15 Type I, 23 Type II, 9 Type III and 91 Type IV). Negative control cultures tended to be more frequent in treated Type I (P = 0.09) and in untreated Type II episodes (P = 0.08). Restricting antibiotic treatments for asymptomatic low-grade bacteriuria and high-grade bacteriuria in the absence of pyuria, occurring later than 1 month posttransplantation, might be safe in RTR.
    Nephrology Dialysis Transplantation 05/2011; 26(12):4109-14. · 3.37 Impact Factor
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    ABSTRACT: The major challenge in transplantation medicine remains long-term allograft acceptance, with preserved allograft function under minimal chronic immunosuppression. To safely achieve the goal of sustained donor-specific T and B cell non-responsiveness, research efforts are now focusing on therapies based on cell subsets with regulatory properties. In particular the transfusion of human regulatory T cells (Treg) is currently being evaluated in phase I/II clinical trials for the treatment of graft versus host disease following hematopoietic stem cell transplantation, and is also under consideration for solid organ transplantation. The purpose of this review is to recapitulate current knowledge on naturally occurring as well as induced human Treg, with emphasis on their specific phenotype, suppressive function and how these cells can be manipulated in vitro and/or in vivo for therapeutic purposes in transplantation medicine. We highlight the potential but also possible limitations of Treg-based strategies to promote long-term allograft survival. It is evident that the bench-to-beside translation of these protocols still requires further understanding of Treg biology. Nevertheless, current data already suggest that Treg therapy alone will not be sufficient and needs to be combined with other immunomodulatory approaches in order to induce allograft tolerance.
    Self/Nonself - Immune Recognition and Signaling 01/2011; 2(1):26-34.
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    ABSTRACT: Embryonic stem cells (ESC) can differentiate into all cell lineages, and ESC-like cells were shown to induce hematopoietic chimerism and tolerance in allogeneic models. The aim of our study was to test the capacity of mouse ESC (mESC) to engraft in rats in a xenotransplantation setting. Forty-six rats were transplanted intravenously with 1 million mESC, without immunosuppression (group 1, n = 23) or with cyclosporine (group 2, n = 23). Three months after mESC transplantation, skin grafts were performed from allogeneic, xenogeneic identical to mESC, or xenogeneic third party donors. At day 27 post-transplant, we detected circulating mouse cells in the blood of 4/23 and 5/23 animals of group 1 and group 2, respectively. Chimerism was confirmed by PCR. We also identified long-term surviving murine cells within livers of chimeric animals. Skin grafts showed no difference in survival between allogeneic and xenogeneic donors. Transplantation of xenogeneic mouse ESC induced short-term chimerism in the blood and persistent tissue chimerism in the liver of recipient rats, but did not induce tolerance to skin grafts. Improved immunosuppressive protocols should be tested to prolong chimerism and allow tolerance.
    Xenotransplantation 10/2010; 17(5):362-9. · 2.57 Impact Factor
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    ABSTRACT: Positron Emission Tomography (PET) using (18)F-fluorodeoxyglucose (FDG) associated with computed tomography (CT) is increasingly used for the detection and the staging of pancreatic cancer, but data regarding its clinical added value in pre-surgical planning is still lacking. The aim of this study is to investigate the performance of FDG PET associated with contrast-enhanced CT in detection of pancreatic cancer. We prospectively evaluated FDG PET/CT studies obtained in patients with suspicion of operable pancreatic cancer between May 2006 and January 2008. Staging was conducted according to a standardized protocol, and findings were confirmed in all patients by surgical resection or biopsy examination. Forty-five patients with a median age of 69 (range 22-82) were included in this study. Thirty-six had malignant tumors and nine had benign lesions (20%). The sensitivity of enhanced versus unenhanced PET/CT in the detection of pancreatic cancer was 96% versus 72% (P=0.076), the specificity 66.6% versus 33.3% (P=0.52), the positive predictive value 92.3% versus 80% (P=0.3), the negative predictive value 80% versus 25% (P=0.2), and the accuracy 90.3% versus 64% (P=0.085). Our preliminary data obtained in a limited number of patients shows that contrast-enhanced FDG PET/CT offers good sensitivity in the detection and assessment of pancreatic cancer, but at the price of a relatively low specificity. Enhanced PET/CT seems to be superior to unenhanced PET/CT. Further larger prospective studies are needed to establish its value for pre-surgical diagnosis and staging in pancreatic cancer.
    Journal of Gastroenterology and Hepatology 10/2010; 26(4):657-62. · 3.33 Impact Factor
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    ABSTRACT: Xenotransplantation carries inherent risks of infectious disease transmission to the recipient and even to society at large, and it should only be carried out with strict regulation and oversight. In collaboration with the International Xenotransplantation Association, the University Hospital Geneva, and the World Health Organization, an international inventory has been established (www.humanxenotransplant.org) aiming to collect basic data on all types of currently ongoing or recently performed xenotransplantation procedures in humans. We collected information from publications in scientific journals, presentations at international congresses, the internet, and declarations of International Xenotransplantation Association members on xenotransplantation procedures in humans performed during the past 15 years. We identified a total of 29 human applications of xenotransplantation, including 7 that were currently ongoing. Procedures involved transplantation of xenogeneic cells, i.e., islets of Langerhans, kidney cells, chromaffin cells, embryonic stem cells, fetal and adult cells from various organs or extracorporeal perfusion using hepatocytes, liver, spleen, or kidney. The treatments were performed in 12 different countries, 9 of them having no national regulation on xenotransplantation. Several clinical applications of cell xenotransplantation are ongoing around the world, often without any clear governmental regulation. This information should be used to inform national health authorities, healthcare staff, and the public, with the objective of encouraging good practices, with internationally harmonized guidelines and regulation of xenotransplantation.
    Transplantation 09/2010; 90(6):597-603. · 3.78 Impact Factor
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    ABSTRACT: Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine produced by many cells and tissues including pancreatic beta-cells, liver, skeletal muscle, and adipocytes. This study investigates the potential role of MIF in carbohydrate homeostasis in a physiological setting outside of severe inflammation, utilizing Mif knockout (MIF-/-) mice. Compared with wild-type (WT) mice, MIF-/- mice had a lower body weight, from birth until 4 months of age, but subsequently gained weight faster, resulting in a higher body weight at 12 months of age. The lower weight in young mice was related to a higher energy expenditure, and the higher weight in older mice was related to an increased food intake and a higher fat mass. Fasting blood insulin level was higher in MIF-/- mice compared with WT mice at any age. After i.p. glucose injection, the elevation of blood insulin level was higher in MIF-/- mice compared with WT mice, at 2 months of age, but was lower in 12-month-old MIF-/- mice. As a result, the glucose clearance during intraperitoneal glucose tolerance tests was higher in MIF-/- mice compared with WT mice until 4 months of age, and was lower in 12-month-old MIF-/- mice. Insulin resistance was estimated (euglycemic-hyperinsulinemic clamp tests), and the phosphorylation activity of AKT was similar in MIF-/- mice and WT mice. In conclusion, this mouse model provides evidence for the role of MIF in the control of glucose homeostasis.
    Journal of Endocrinology 09/2010; 206(3):297-306. · 4.06 Impact Factor
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    ABSTRACT: Anti-CD154 (MR1) monoclonal antibody (mAb) and rapamycin (RAPA) treatment both improve survival of rat-to-mouse islet xenograft. The present study investigated the effect of combined RAPA/MR1 treatment on rat-to-mouse islet xenograft survival and analyzed the role of CD4(+)CD25(+)Foxp3(+) T regulatory cells (Treg) in the induction and maintenance of the ensuing tolerance. C57BL/6 mice were treated with MR1/RAPA and received additional monoclonal anti-IL2 mAb or anti CD25 mAb either early (0-28 d) or late (100-128 d) post-transplantation. Treg were characterised in the blood, spleen, draining lymph nodes and within the graft of tolerant and rejecting mice by flow cytometry and immunohistochemistry. Fourteen days of RAPA/MR1 combination therapy allowed indefinite islet graft survival in >80% of the mice. Additional administration of anti-IL-2 mAb or depleting anti-CD25 mAb at the time of transplantation resulted in rejection (100% and 89% respectively), whereas administration at 100 days post transplantation lead to lower rejection rates (25% and 40% respectively). Tolerant mice showed an increase of Treg within the graft and in draining lymph nodes early post transplantation, whereas 100 days post transplantation no significant increase of Treg was observed. Rejecting mice showed a transient increase of Treg in the xenograft and secondary lymphoid organs, which disappeared within 7 days after rejection. These results suggest a critical role for Treg in the induction phase of tolerance early after islet xenotransplantation. These encouraging data support the need of developing further Treg therapy for overcoming the species barrier in xenotransplantation.
    PLoS ONE 01/2010; 5(4):e10352. · 3.53 Impact Factor
  • Transplantation 01/2010; 90. · 3.78 Impact Factor

Publication Stats

2k Citations
342.91 Total Impact Points

Institutions

  • 1993–2010
    • University of Geneva
      • • Department of Surgery
      • • Division of Visceral Surgery
      • • Department of Pharmacology
      Genève, GE, Switzerland
  • 1997–2009
    • Hôpitaux Universitaires de Genève
      • • Service de radiologie
      • • Département de chirurgie
      Genève, Geneva, Switzerland
  • 1999–2003
    • Massachusetts General Hospital
      • Transplantation Biology Research Center
      Boston, MA, United States
  • 1998–2003
    • Harvard Medical School
      • Department of Surgery
      Boston, Massachusetts, United States