Jörg C Gerlach

University of Pittsburgh, Pittsburgh, Pennsylvania, United States

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Publications (81)221.76 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The development of functional engineered tissue constructs depends on high cell densities and appropriate vascularization. In this study we implemented a four-compartment three-dimensional (3D) perfusion bioreactor culture model for studying the effects of medium perfusion on endothelial, hepatic and hematopoietic cell populations of primary human fetal liver in an in-vivo like environment. Human fetal liver cells were cultured in bioreactors configured to provide either perfusion or diffusion conditions. Metabolic activity of the cultures was monitored daily by measuring glucose consumption and lactate production. Cell viability during culture was analyzed by lactate dehydrogenase activity. Hepatic functionality was determined by the release of albumin and alpha-fetoprotein (AFP) in culture medium samples. After 4 days of culture cells were analyzed for the expression of a variety of endothelial, hepatic and hematopoietic genes, as well as the surface marker expression of CD31 and CD34 in flow cytometry. We found that medium perfusion increased expression of endothelial genes such as CD31, vWF, CD140b, CD309 and CD144 while decreasing expression of the erythrocyte specific hematopoietic gene CD235a. Hepatic differentiation was promoted under perfusion conditions as demonstrated by lower AFP and higher albumin secretion compared to cultures not exposed to medium perfusion. Additionally, cultures exposed to medium perfusion gave higher rates of glucose consumption and lactate production, indicating increased metabolic activity. In conclusion, high-density bioreactors configured to provide constant medium perfusion significantly induced hepatic and endothelial cell differentiation and provided improved conditions for the culture of human fetal liver cells compared to cultures without perfusion.
    Tissue Engineering Part C Methods 01/2015; · 4.64 Impact Factor
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    ABSTRACT: Investigation A novel active wound dressing (AWD) concept based on a microporous hollow fiber membrane network was investigated in an animal model. It provides a local solution-perfused environment for regenerative cell nutrition, wound irrigation, debris removal, electrolyte balancing, pH regulation, and topical antibiosis. The device is capable of supplying soluble factors, as tested experimentally for the recombinant human growth and differentiation factor-5 (rhGDF-5). Methods Following in vitro studies for rhGDF-5 using primary human keratinocytes and dermal fibroblasts, we employed a porcine partial thickness wound model with five distinct wounds on each back of n = 8 pigs. Four wound groups were perfused differently over 9 days and compared with a negative control wound without perfusion: (1) 1% trehalose solution, pH 5.5; (2) rhGDF-5 (150 ng/ml) in 1% trehalose solution, pH 5.5; (3) nutrition solution; and (4) rhGDF-5 (150 ng/ml) in nutrition solution with 1% trehalose, pH 5.5. Results Promoted wound healing was observed within group 1 and more pronounced within group 2. Groups 3 and 4, with nutrition solution, showed significant adverse effects on wound healing (p < 0.05). Conclusions The investigated AWD concept appears to be an interesting therapeutic tool to study further wound healing support. Additionally, topical application of rhGDF-5 could be promising.
    Burns 10/2014; · 1.84 Impact Factor
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    ABSTRACT: The construction and long-term maintenance of three-dimensional in vitro bone marrow models is of great interest but still quite challenging. Here we describe the use of a multi-compartment hollow-fiber membrane based three-dimensional perfusion bioreactor for long-term culture of whole human bone marrow mononuclear cells. We also investigated bioreactors with incorporated open-porous foamed hydroxyapatite scaffolds, mimicking the in vivo bone matrix. Cells in bioreactors with and without scaffolds were cultured to six weeks and compared to Petri-dish controls. Cells were analysed for gene expression, surface markers by flow cytometry, metabolic activity, hematopoietic potential, viability, and attachment by immunocytochemistry. Cells in bioreactors were metabolic active during long-term culture. The percentages of hematopoietic stem cell and mature endothelial cell fractions were maintained in bioreactors. The expression of most of the analyzed genes stabilized and increased after long-term culture of six weeks. Compared to Petri-dish culture controls, bioreactor perfusion culture improved in both the short and long term, the colony formation unit capacity of hematopoietic progenitors. Cells attached to the ample surface area provided by hydroxyapatite scaffolds. The implementation of a hydroxyapatite scaffold did not influence colony formation capacity, percentages of cell type specific fractions, gene expression, cell viability or metabolic turnover when compared to control cells cultured in bioreactors without scaffolds. In conclusion, three-dimensional perfusion bioreactor culture enables long-term maintenance of primary human bone marrow cells, with hydroxyapatite scaffolds providing an in vivo-like scaffold for three-dimensional culture. Biotechnol. Bioeng. © 2014 Wiley Periodicals, Inc.
    Biotechnology and Bioengineering 10/2014; · 4.16 Impact Factor
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    ABSTRACT: AimThe transcription factor CCAAT/enhancer binding protein alpha (C/EBPα) has been shown to play an important role in liver development, cell proliferation and differentiation. It is, however, largely unknown, if C/EBPα regulates cell differentiation and proliferation differently in the diverse cell types of the human liver. We investigated the role of C/EBPα in primary human fetal liver cells and liver cell sub-populations in vitro using a three-dimensional perfusion bioreactor as an advanced in vivo-like human organ culture model.Methods Human fetal liver cells were investigated in vitro. C/EBPα gene expression was knocked down using siRNA or over-expressed by plasmid transfection. Cell type specific gene expression was studied, cell populations and their proliferation were investigated, and metabolic parameters were analyzed.ResultsWhen C/EBPα gene expression was knocked down, we observed a significantly reduced expression of typical endothelial, hematopoietic and mesenchymal genes such as CD31, vWF, CD90, CD45 and α-smooth muscle actin in fetal cells. Theintracellular expression of hepatic proteins and genes for liver specific serum proteins α–fetoprotein and albumin were reduced, their protein secretion was increased. Fetal endothelial cell numbers were reduced and hepatoblast numbers were increased. C/EBPα over-expression in fetal cells resulted in increased endothelial numbers, but did not affect mesenchymal cell types or hepatoblasts.Conclusions We demonstrated that the effects of C/EBPα are specific for the different human fetal liver cell types, using an advanced three-dimensional perfusion bioreactor as a humanin vivo-like model.
    Hepatology Research 09/2014; · 2.07 Impact Factor
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    ABSTRACT: Primary human hepatocytes represent an important cell source for in vitro investigation of hepatic drug metabolism and disposition. In this study, a multi-compartment capillary membrane-based bioreactor technology for three-dimensional (3D) perfusion culture was further developed and miniaturized to a volume of less than 0.5 ml to reduce demand for cells. The miniaturized bioreactor was composed of two capillary layers, each made of alternately arranged oxygen and medium capillaries serving as a 3D culture for the cells. Metabolic activity and stability of primary human hepatocytes was studied in this bioreactor in the presence of 2.5% fetal calf serum (FCS) under serum-free conditions over a culture period of 10 days. The miniaturized bioreactor showed functions comparable to previously reported data for larger variants. Glucose and lactate metabolism, urea production, albumin synthesis and release of intracellular enzymes (AST, ALT, GLDH) showed no significant differences between serum-free and serum-supplemented bioreactors. Activities of human-relevant cytochrome P450 (CYP) isoenzymes (CYP1A2, CYP3A4/5, CYP2C9, CYP2D6, CYP2B6) analyzed by determination of product formation rates from selective probe substrates were also comparable in both groups. Gene expression analysis showed moderately higher expression in the majority of CYP enzymes, transport proteins and enzymes of Phase II metabolism in the serum-free bioreactors compared to those maintained with FCS. In conclusion, the miniaturized bioreactor maintained stable function over the investigated period and thus provides a suitable system for pharmacological studies on primary human hepatocytes under defined serum-free conditions. Copyright © 2012 John Wiley & Sons, Ltd.
    Journal of Tissue Engineering and Regenerative Medicine 11/2012; · 4.43 Impact Factor
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    ABSTRACT: The presence of mesenchymal stem cells (MSCs) has been described in various organs. Pericytes possess a multilineage differentiation potential and have been suggested to be one of the developmental sources for MSCs. In human liver, pericytes have not been defined. Here, we describe the identification, purification, and characterization of pericytes in human adult and fetal liver. Flow cytometry sorting revealed that human adult and fetal liver contains 0.56%±0.81% and 0.45%±0.39% of CD146(+)CD45(-)CD56(-)CD34(-) pericytes, respectively. Of these, 41% (adult) and 30% (fetal) were alkaline phosphatase-positive (ALP(+)). In situ, pericytes were localized around periportal blood vessels and were positive for NG2 and vimentin. Purified pericytes could be cultured extensively and had low population doubling times. Immunofluorescence of cultures demonstrated that cells were positive for pericyte and mesenchymal cell markers CD146, NG2, CD90, CD140b, and vimentin, and negative for endothelial, hematopoietic, stellate, muscle, or liver epithelial cell markers von Willebrand factor, CD31, CD34, CD45, CD144, CD326, CK19, albumin, α-fetoprotein, CYP3A7, glial fibrillary acid protein, MYF5, and Pax7 by gene expression; myogenin and alpha-smooth muscle actin expression were variable. Fluorescence-activated cell sorting analysis of cultures confirmed surface expression of CD146, CD73, CD90, CD10, CD13, CD44, CD105, and ALP and absence of human leukocyte antigen-DR. In vitro differentiation assays demonstrated that cells possessed robust osteogenic and myogenic, but low adipogenic and low chondrogenic differentiation potentials. In functional in vitro assays, cells had typical mesenchymal strong migratory and invasive activity. In conclusion, human adult and fetal livers harbor pericytes that are similar to those found in other organs and are distinct from hepatic stellate cells.
    Stem cells and development 08/2012; · 4.15 Impact Factor
  • Advances in Applied Ceramics 08/2012; 111(5-6):262-268. · 0.69 Impact Factor
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    ABSTRACT: Cell banked epidermal skin progenitor cells have the potential to provide an "off-the-freezer" product. Such cells may provide a skin donor area-independent cell-spray grafting therapy for the treatment of burns. We first characterized fetal skin samples of gestational ages ranging from 6 to 21 weeks. As the results suggest that the phenotypic differentiation occurs after 10 weeks, which may complicate follow-up in vitro studies, we developed and compared different cell isolation techniques for human fetal skin-derived epithelial cells from tissue ages 6 to 9 weeks. We initially screened seven methods of characterization, concluding that two methods warranted further investigation: incubating the epidermal tissue in Petri-dishes with culture medium for spontaneous cell outgrowth, and wiping the epidermal tissue onto a dry Petri-dish culture surface followed by adding culture medium. Non-controllable culture contamination with dermal cells was the reason for excluding the other five methods. The results suggest that epidermal cells can be isolated from tissue exhibiting a single homogeneous layer of CK15(+) basal keratinocytes up to week 9. At later gestational ages, the ongoing skin differentiation results in a multi-layer basal structure and progenitors associated with the hair bulb would have to be considered. Spraying the resulting cells with a clinical spray device was successfully demonstrated in an in vitro model. CONCLUSION: Gestational age 6-9 weeks epidermal human fetal skin cells from the basal layer can be reproducibly isolated and transferred into culture for studies on the development of skin cell transplantation therapies.
    Burns: journal of the International Society for Burn Injuries 06/2012; · 1.95 Impact Factor
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    ABSTRACT: Based on a hollow fiber perfusion technology with internal oxygenation, a miniaturized bioreactor with a volume of 0.5 mL for in vitro studies was recently developed. Here, the suitability of this novel culture system for pharmacological studies was investigated, focusing on the model drug diclofenac. Primary human liver cells were cultivated in bioreactors and in conventional monolayer cultures in parallel over 10 days. From day 3 on, diclofenac was continuously applied at a therapeutic concentration (6.4 µM) for analysis of its metabolism. In addition, the activity and gene expression of the cytochrome P450 (CYP) isoforms CYP1A2, CYP2B6, CYP2C9, CYP2D6, and CYP3A4 were assessed. Diclofenac was metabolized in bioreactor cultures with an initial conversion rate of 230 ± 57 pmol/h/10(6) cells followed by a period of stable conversion of about 100 pmol/h/10(6) cells. All CYP activities tested were maintained until day 10 of bioreactor culture. The expression of corresponding mRNAs correlated well with the degree of preservation. Immunohistochemical characterization showed the formation of neo-tissue with expression of CYP2C9 and CYP3A4 and the drug transporters breast cancer resistance protein (BCRP) and multidrug resistance protein 2 (MRP2) in the bioreactor. In contrast, monolayer cultures showed a rapid decline of diclofenac conversion and cells had largely lost activity and mRNA expression of the assessed CYP isoforms at the end of the culture period. In conclusion, diclofenac metabolism, CYP activities and gene expression levels were considerably more stable in bioreactor cultures, making the novel bioreactor a useful tool for pharmacological or toxicological investigations requiring a highly physiological in vitro representation of the liver. Biotechnol. Bioeng. © 2012 Wiley Periodicals, Inc.
    Biotechnology and Bioengineering 06/2012; · 4.16 Impact Factor
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    ABSTRACT: Properly regulated inflammation facilitates recognition and reaction to injury or infection, but inadequate or overly robust inflammation can lead to disease. Sepsis is an inflammatory disease that accounts for nearly 10% of total U.S. deaths, costing more than $17 billion. Acute inflammation in sepsis may evolve too rapidly to be modulated appropriately, and we suggest that therapies should focus not on abolishing inflammation, but rather on attenuating the positive feedback cycle of inflammation/damage/inflammation. In Gram-negative sepsis, bacterial endotoxin causes inflammation and is driven and regulated by the cytokine tumor necrosis factor-α (TNF-α), which is, in turn, negatively regulated via its endogenous inhibitor, soluble TNF-α receptor (sTNFR). We generated stably gene-modified variants of human HepG2 hepatocytes, using lentiviral constructs coding for mouse sTNFR driven by the constitutive cytomegalovirus promoter, and seeded them in a scaled-down, experimental liver bioreactor. When connected to anesthetized, cannulated rats subjected to endotoxin infusion and maintained solely by the animals' circulation, this biohybrid device elevated circulating sTNFR, reduced the levels of TNF-α and other key inflammatory mediators, alleviated hypotension, and reduced circulating markers of organ damage. This novel class of biohybrid devices may bemodified for patient- and disease-specific application, and, thus, may represent a disruptive strategy that offers the potential for rational inflammation reprogramming.
    Disruptive science and technology. 05/2012; 1(1).
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    ABSTRACT: Although hepatic cell transplantation (CT) holds the promise of bridging patients with end-stage chronic liver failure to whole liver transplantation, suitable cell populations are under debate. In addition to hepatic cells, mesenchymal stem cells (MSCs) and hematopoietic stem cells (HSCs) are being considered as alternative cell sources for initial clinical cell work. Fetal liver (FL) tissue contains potential progenitors for all these cell lineages. Based on the collagenase incubation of tissue fragments, traditional isolation techniques yield only a fraction of the number of available cells. We report a 5-step method in which a portal vein in situ perfusion technique is used for tissue from the late second trimester. This method results in the high viabilities known for adult liver vascular perfusion, addresses the low cell yields of conventional digestion methods, and reduces the exposure of the tissue to collagenase 4-fold. We used donated tissue from gestational weeks 18 to 22, which yielded 1.8 ± 0.7 × 10(9) cells with an average viability of 78%. Because HSC transplantation and MSC transplantation are of interest for the treatment of hepatic failure, we phenotypically confirmed that in addition to hepatic progenitors, the resulting cell preparation contained cells expressing typical MSC and HSC markers. The percentage of FL cells expressing proliferation markers was 45 times greater than the percentage of adult hepatocytes expressing these markers and was comparable to the percentage of immortalized HepG2 liver hepatocellular carcinoma cells; this indicated the strong proliferative capacity of fetal cells. We report a case of human FL CT with the described liver cell population for clinical end-stage chronic liver failure. The patient's Model for End-Stage Liver Disease (MELD) score improved from 15 to 10 within the first 18 months of observation. In conclusion, this human FL cell isolation protocol may be of interest for further clinical translation work on the development of liver cell-based therapies.
    Liver Transplantation 02/2012; 18(2):226-37. · 3.79 Impact Factor
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    ABSTRACT: Medical treatment of burns and chronic wounds remains a challenge. We discussed a therapy concept that combines skin cell spray transplantation with a novel wound dressing based on artificial hollow fiber membrane capillaries. In skin cell-based therapy development, autologous skin progenitor cells are isolated from a healthy skin area and sprayed onto the wound. A medical device was introduced that uses perfused capillaries, known from clinical plasma separation, as a temporarily applied extracorporeal wound capillary bed. The functions of the dressing are comparable with those of dialysis; the capillaries, however, are applied externally onto the wound. Perfusion with a clinical peripheral nutrition and buffer solution can provide wound irrigation, wound debris removal, cell nutrition, pH regulation, and electrolyte balance while potentially serving to address delivery of regenerative factors and antibiosis. An innovative active skin wound dressing that provides cell support and stimulates regeneration by wound irrigation is discussed.
    Artificial Organs 11/2011; 36(4):446-9. · 1.87 Impact Factor
  • Placenta 10/2011; 32. · 3.29 Impact Factor
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    ABSTRACT: Continuous production of red blood cells (RBCs) in an automated closed culture system using hematopoietic stem cell (HSC) progenitor cell populations is of interest for clinical application because of the high demand for blood transfusions. Previously, we introduced a four-compartment bioreactor that consisted of two bundles of hollow fiber microfiltration membranes for transport of culture medium (forming two medium compartments), interwoven with one bundle of hollow fiber membranes for transport of oxygen (O(2)), carbon dioxide (CO(2)), and other gases (forming one gas compartment). Small-scale prototypes were developed of the three-dimensional (3D) perfusion cell culture systems, which enable convection-based mass transfer and integral oxygenation in the cell compartment. CD34(+) HSC were isolated from human cord blood units using a magnetic separation procedure. Cells were inoculated into 2- or 8-mL scaled-down versions of the previously designed 800-mL cell compartment devices and perfused with erythrocyte proliferation and differentiation medium. First, using the small-scale 2-mL analytical scale bioreactor, with an initial seeding density of 800,000 cells/mL, we demonstrated approximately 100-fold cell expansion and differentiation after 7 days of culture. An 8-mL laboratory-scale bioreactor was then used to show pseudocontinuous production by intermediately harvesting cells. Subsequently, we were able to use a model to demonstrate semicontinuous production with up to 14,288-fold expansion using seeding densities of 800,000 cells/mL. The down-scaled culture technology allows for expansion of CD34(+) cells and stimulating these progenitors towards RBC lineage, expressing approximately 40% CD235(+) and enucleation. The 3D perfusion technology provides an innovative tool for studies on RBC production, which is scalable.
    Tissue Engineering Part C Methods 09/2011; 18(2):133-42. · 4.64 Impact Factor
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    ABSTRACT: To further differentiate adipose-derived stem cells (ASCs) into mature adipocytes and create three-dimensional (3D) adipose tissue in vitro, we applied multicompartment hollow fiber-based bioreactor technology with decentral mass exchange for more physiological substrate gradients and integral oxygenation. We hypothesize that a dynamic 3D perfusion in such a bioreactor will result in longer-term culture of human adipocytes in vitro, thus providing metabolically active tissue serving as a diagnostic model for screening drugs to treat diabetes. ASCs were isolated from discarded human abdominal subcutaneous adipose tissue and then inoculated into dynamic 3D culture bioreactors to undergo adipogenic differentiation. Insulin-stimulated glucose uptake from the medium was assessed with and without TNF-alpha. 3D adipose tissue was generated in the 3D-bioreactors. Immunohistochemical staining indicated that 3D-bioreactor culture displayed multiple mature adipocyte markers with more unilocular morphologies as compared with two-dimensional (2D) cultures. Results of real-time polymerase chain reaction showed 3D-bioreactor treatment had more efficient differentiation in fatty acid-binding protein 4 expression. Repeated insulin stimulation resulted in increased glucose uptake, with a return to baseline between testing. Importantly, TNF-alpha inhibited glucose uptake, an indication of the metabolic activity of the tissue. 3D bioreactors allow more mature adipocyte differentiation of ASCs compared with traditional 2D culture and generate adipose tissue in vitro for up to 2 months. Reproducible metabolic activity of the adipose tissue in the bioreactor was demonstrated, which is potentially useful for drug discovery. We present here, to the best of our knowledge for the first time, the development of a coherent 3D high density fat-like tissue consisting of unilocular structure from primary adipose stem cells in vitro.
    Tissue Engineering Part C Methods 09/2011; 18(1):54-61. · 4.64 Impact Factor
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    ABSTRACT: For the development and implementation of primary human cell- and stem cell-based applications in regenerative medicine, large amounts of cells with well-defined characteristics are needed. Such cell quantities can be obtained with the use of hollow fiber-based bioreactors. While the use of such bioreactors generally requires a perfusion circuit, the configuration and complexity of such circuits is still in debate. We evaluated various circuit configurations to investigate potential perfusate volume shifts in the arterial and venous sides of the perfusion circuit, as well as in the feed and waste lines. Volume shifts with changes in flow conditions were measured with graduated bubble traps in the circuit, and perfusion pressures were measured at three points in the circuits. The results of this study demonstrate that the bioreactor perfusion circuit configuration has an effect on system pressures and volume shifts in the circuit. During operation, spikes in post-bioreactor pressures caused detrimental, potentially dangerous volume shifts in the feed and waste lines for configurations that lacked feed pumps and/or waste line check valves. Our results indicate that a more complex tubing circuit adds to safety of operation and avoids technical challenges associated with the use of large-scale hollow fiber bioreactors (e.g., for extracorporeal liver support or erythrocyte production from hematopoietic stem cells), including volume shifts and the need for a large reservoir. Finally, to ensure safe use of bioreactors, measuring pre-, intra-, and post-bioreactor pressures, and pump operation control is also advisable, which suggests the use of specifically developed bioreactor perfusion devices.
    The International journal of artificial organs 05/2011; 34(5):410-21. · 1.45 Impact Factor
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    ABSTRACT: Drug-induced liver injury is a common reason for drug attrition in late clinical phases, and even for post-launch withdrawals. As a consequence, there is a broad consensus in the pharmaceutical industry, and within regulatory authorities, that a significant improvement of the current in vitro test methodologies for accurate assessment and prediction of such adverse effects is needed. For this purpose, appropriate in vivo-like hepatic in vitro models are necessary, in addition to novel sources of human hepatocytes. In this report, we describe recent and ongoing research toward the use of human embryonic stem cell (hESC)-derived hepatic cells, in conjunction with new and improved test methods, for evaluating drug metabolism and hepatotoxicity. Recent progress on the directed differentiation of human embryonic stem cells to the functional hepatic phenotype is reported, as well as the development and adaptation of bioreactors and toxicity assay technologies for the testing of hepatic cells. The aim of achieving a testing platform for metabolism and hepatotoxicity assessment, based on hESC-derived hepatic cells, has advanced markedly in the last 2-3 years. However, great challenges still remain, before such new test systems could be routinely used by the industry. In particular, we give an overview of results from the Vitrocellomics project (EU Framework 6) and discuss these in relation to the current state-of-the-art and the remaining difficulties, with suggestions on how to proceed before such in vitro systems can be implemented in industrial discovery and development settings and in regulatory acceptance.
    Alternatives to laboratory animals: ATLA 05/2011; 39(2):147-71. · 1.32 Impact Factor
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    ABSTRACT: Although significant progress has been made in the field of orthotopic liver transplantation, cell-based therapies seem to be a promising alternative to whole-organ transplantation. The reasons are manifold but organ shortage is the main cause for this approach. However, many problems such as the question which cell type should be used or which application site is best for transplantation have been raised. In addition, some clinicians have had success by cultivating liver cells in bioreactors for temporary life support. Besides answering the question which cell type, which injection site or even which culture form should be used for liver support recent international harmonization of legal requirements is needed to be addressed by clinicians, scientists and companies dealing with cellular therapies. We here briefly summarize the possible cell types used to partially or temporarily correct liver diseases, the most recent development of bioreactor technology and important regulatory issues.
    Journal of Materials Science Materials in Medicine 04/2011; 22(5):1087-99. · 2.14 Impact Factor
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    ABSTRACT: Reliable and stable in vitro cellular systems maintaining specific liver functions important for drug metabolism and disposition are urgently needed in preclinical drug discovery and development research. The cell line HepaRG exhibits promising properties such as expression and function of drug-metabolizing enzymes and transporter proteins, which resemble those found in freshly isolated human hepatocytes. In this study, HepaRG cells were cultured up to 68 days in a three-dimensional multicompartment capillary membrane bioreactor, which enables high-density cell culture under dynamic conditions. The activity of drug-metabolizing cytochrome P450 (P450) enzymes was investigated by a cocktail of substrates for CYP1A1/2 (phenacetin), CYP2C9 (diclofenac), CYP2B6 (bupropion), and CYP3A4 (midazolam). The model P450 substrates, which were introduced to the bioreactor system mimicking in vivo bolus doses, showed stable metabolism over the entire experimental period of several weeks with the exception of bupropion hydroxylase, which increased over time. Ketoconazole treatment decreased the CYP3A4 activity by 69%, and rifampicin induced the CYP3A4- and CYP2B6-dependent activity 6-fold, which predicts well the magnitude of changes observed in vivo. Moreover, polarity of transporter expression and formation of tissue-like structures including bile canaliculi were demonstrated by immune histochemistry. The long-lasting bioreactor system using HepaRG cells thus provides a promising and stable liver-like in vitro model for continuous investigations of the hepatic kinetics of drugs and of drug-drug interactions, which well predict the situation in vivo in humans.
    Drug metabolism and disposition: the biological fate of chemicals 03/2011; 39(7):1131-8. · 3.74 Impact Factor
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    ABSTRACT: There is a therapeutic gap for patients with deep partial thickness wounds (Grade IIb) of moderate size that were initially not treated with split- or mesh grafting to avoid overgrafting, but developed delayed wound healing around two weeks after injury--at which time grafting is typically not indicated anymore. Delayed wound healing is often associated with esthetically unsatisfactory results and sometimes functional problems. An innovative cell isolation method for cell spray transplantation at the point of care, which eliminates cell culture prior to treatment, was implemented for this population of burn patients in our center. Autologous skin cell spray transplantation was initiated by taking healthy skin. The dermal/epidermal layers were separated using enzymatic digestion with 40 min dispase application, followed by 15 min trypsin application for basal kerationcyte isolation, 7 min cell washing by centrifugation, followed by transferring the cells for spraying into Ringer lactate solution. The procedure was performed on site in a single session immediately following the biopsy. After sharp wound debridement, cells were immediately transplanted by deposition with a cell sprayer for even distribution of the cell suspension. Eight patients were treated (mean age 30.3 years, mean burn total body surface area 14%, mean Abbreviated Burn Severity Index (5 points). The mean time to complete re-epithelialization was 12.6 days. All patients exhibited wound healing with improved esthetic and functional quality. Our initial experience for the use of non-cultured cells using a two-enzyme approach with cell washing suggests shortened time for wound closure, suggesting that the method may potentially avoid longer-term complications.
    The International journal of artificial organs 03/2011; 34(3):271-9. · 1.45 Impact Factor

Publication Stats

909 Citations
221.76 Total Impact Points


  • 2004–2014
    • University of Pittsburgh
      • • Department of Surgery
      • • Bioengineering
      • • McGowan Institute for Regenerative Medicine
      Pittsburgh, Pennsylvania, United States
  • 2002–2012
    • Charité Universitätsmedizin Berlin
      • • Surgery
      • • Department of General, Visceral and Transplantation Surgery
      Berlín, Berlin, Germany
  • 2008–2011
    • Linköping University
      Linköping, Östergötland, Sweden
  • 2010
    • Pennington Biomedical Research Center
      Baton Rouge, Louisiana, United States
  • 2009
    • Università della Calabria
      • Department of Chemical Engineering and Materials
      Rende, Calabria, Italy
  • 2003
    • Humboldt State University
      Arcata, California, United States
  • 2002–2003
    • Humboldt-Universität zu Berlin
      • Department of Biology
      Berlín, Berlin, Germany
  • 1994–1996
    • Freie Universität Berlin
      • Institute of Chemistry and Biochemistry
      Berlín, Berlin, Germany