Karen Bieback - Academia.edu (original) (raw)

Papers by Karen Bieback

Klinische Pädiatrie, 2012

Regenerative therapy based on stem cells is applied as standard therapy in pediatric oncology. Fu... more Regenerative therapy based on stem cells is applied as standard therapy in pediatric oncology. Furthermore, they are frequently used to treat immunodefi ciency disorders of infants. For severe neonatal diseases, e. g. hypoxic-ischemic encephalopathy in term neonates or bronchopulmonary dysplasia in preterm infants, animal models have been established. According to some fi rst preclinical results stem cell administration appears as a promising tool to improve the clinical outcome in high-risk infants. Provided the benefi t of regenerative therapies can further be evaluated in appropriate preclinical neonate models, carefully controlled clinical trials to assess the signifi cance of regenerative therapies, such as autologous stem cell administration, are indicated.

Stem Cells and Development, 2015

Recently, mesenchymal stromal cell-derived extracellular vesicles (MSC-EVs) have been suggested a... more Recently, mesenchymal stromal cell-derived extracellular vesicles (MSC-EVs) have been suggested as an alternative to MSCs for the treatment of various inflammatory disorders. However, while a first case report observed beneficial therapeutic effects of repeated MSC-EV infusions in a patient with therapy-refractory graftversus-host disease, in vitro findings revealed that MSC-EVs were significantly less immunosuppressive than their parental cells. In this study, we compared the immunosuppressive potency of MSCs derived from bone marrow (BM-MSCs) and adipose tissue (AT-MSCs), with their secreted EVs in a standardized lymphocyte proliferation assay (LPA). Both BM-MSCs and AT-MSCs exhibited a remarkable inhibition of lymphocyte proliferation (LP) (88.1% -1.5% and 75.5% -1.5%, respectively), while isolated EVs derived from them failed to suppress LP at dose levels up to 100 mg/mL. Thus, our data further substantiate previous reports suggesting that cell-cell contact plays an important role on the immunosuppressive potential mediated by MSCs. Hence, MSC-EVs are still a matter of debate and might not be a reasonable substitute for MSCs with regard to the immunosuppressive function. Collectively, these contrasting findings may also reflect the importance of relevant translational aspects when designing new studies. Standardization of MSC culture conditions before EV collection as well as isolation and characterization methods with regard to EV purity are urged. Moreover, before clinical use, dose-finding studies evaluating MSC-EV preparations in suitable preclinical models are warranted.

Standardization of Good Manufacturing Practice-compliant production of bone marrow-derived human mesenchymal stromal cells for immunotherapeutic applications

Cytotherapy, 2015

Human mesenchymal stem or stromal cells (MSCs) represent a potential resource not only for regene... more Human mesenchymal stem or stromal cells (MSCs) represent a potential resource not only for regenerative medicine but also for immunomodulatory cell therapies. The application of different MSC culture protocols has significantly hampered the comparability of experimental and clinical data from different laboratories and has posed a major obstacle for multicenter clinical trials. Manufacturing of cell products for clinical application in the European Community must be conducted in compliance with Good Manufacturing Practice and requires a manufacturing license. In Germany, the Paul-Ehrlich-Institut as the Federal Authority for Vaccines and Biomedicines is critically involved in the approval process. This report summarizes a consensus meeting between researchers, clinicians and regulatory experts on standard quality requirements for MSC production. The strategy for quality control testing depends on the product's cell composition, the manufacturing process and the indication and ta...

Interactive CardioVascular and Thoracic Surgery, 2013

Objectives: CD133pos cells are currently evaluated for use in cardiac cell therapy. We hypothesiz... more Objectives: CD133pos cells are currently evaluated for use in cardiac cell therapy. We hypothesized that they exert their beneficial effects in a paracrine manner and investigated this in a cell culture ischaemia model. Furthermore, we checked whether purified CD133pos cells perform better than non-fractionated mononuclear cells (MNC). Methods: CD133pos cells were isolated from bone marrow MNC and conditioned medium was prepared from CD133pos and non-fractionated MNC. HL-1 cardiomyocytes were subjected to simulated ischaemia in the respective conditioned media or in control medium. After treatment, total remaining cells, apoptotic cells and nuclear shrinking were quantified using an automated imaging system. Furthermore, metabolic activity and phosphorylation of kinases Akt, Erk1/2, GSK3b and transcription factor Stat3 were investigated. Results: After simulated ischaemia, the rate of detached dead cells was lowest in CD133pos conditioned medium (26 ± 6%) and highest in control medium (36 ± 6%). In CD133pos conditioned medium, the fraction of nonapoptotic cells was most enhanced and nuclear shrinking as a consequence of apoptosis was reduced. Cell viability was also highest in CD133pos conditioned medium (109.4 ± 8.8% in relation to control). In both conditioned media, phosphorylation of Akt, Erk1/2, and GSK3b was lower than in control medium. Stat3 phosphorylation was sustained on the level of control. Conclusions: Factors released from purified CD133pos bone marrow cells exhibit more pronounced protective effects on HL-1 cardiomyocytes under simulated ischaemia than from non-fractionated MNC. These effects are not associated with the phosphorylation of cell survival promoting kinases Akt, Erk1/2, GSK3b and transcription factor Stat3. Although the molecular mechanism of cardioprotection by CD133pos cells requires further investigation, our results reinforce the advantage of enriching CD133pos cells for cardiac cell therapy.

Neuroscience Letters, 2008

PloS one, 2011

The possible different therapeutic efficacy of human mesenchymal stem cells (hMSC) derived from u... more The possible different therapeutic efficacy of human mesenchymal stem cells (hMSC) derived from umbilical cord blood (CB), adipose tissue (AT) or bone marrow (BM) for the treatment of myocardial infarction (MI) remains unexplored. This study was to assess the regenerative potential of hMSC from different origins and to evaluate the role of CD105 in cardiac regeneration. Male SCID mice underwent LAD-ligation and received the respective cell type (400.000/per animal) intramyocardially. Six weeks post infarction, cardiac catheterization showed significant preservation of left ventricular functions in BM and CD105(+)-CB treated groups compared to CB and nontreated MI group (MI-C). Cell survival analyzed by quantitative real time PCR for human GAPDH and capillary density measured by immunostaining showed consistent results. Furthermore, cardiac remodeling can be significantly attenuated by BM-hMSC compared to MI-C. Under hypoxic conditions in vitro, remarkably increased extracellular aci...

Mechanisms of paracrine cardioprotection by cord blood mesenchymal stromal cells

European Journal of Cardio-Thoracic Surgery, 2014

Among the mechanisms by which somatic stem cells may improve left ventricular function in ischaem... more Among the mechanisms by which somatic stem cells may improve left ventricular function in ischaemic heart disease are pro-survival stimuli mediated by secreted factors. This phenomenon is frequently referred to, but remains poorly understood. We therefore investigated the non-regenerative cardioprotective effects of cord blood mesenchymal stromal cells (CBMSCs) in vitro and sought to identify relevant intracellular signalling pathways. Conditioned medium from CBMSCs and fibroblasts was prepared, and secreted factors were analysed by Luminex(®) immunobead assay. Murine cardiomyocyte-derived HL-1 cells were subjected to simulated ischaemia by glucose and serum deprivation and hypoxia in CBMSC-conditioned or cell-free control medium or in medium conditioned by foreskin fibroblasts. The proportions of vital, apoptotic and necrotic cells (poly-caspase activity, annexin V and ethidium homodimer-III staining) were quantified using a high-content imaging system. Metabolic activity and proliferation rate were determined via 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium and 5-bromo-2-deoxyuridine assays. Phosphorylation of Akt, extracellular-signal-regulated kinase (ERK)1/2, signal transducer and activator of transcription 3 (STAT3) and glycogen synthase kinase 3β was determined by western blot, and experiments were repeated in the presence of specific small-molecule inhibitors (Wortmannin, UO126 and Stattic). CBMSC medium reduced the proportion of dead HL-1 cardiomyocytes from 39 ± 3 to 28 ± 1% (P < 0.05) and the rate of late apoptotic cells to 68 ± 2% of that in control medium (P < 0.001). Metabolic activity was increased by 12 ± 1% compared with control (P < 0.05), while in fibroblast medium it was not (5 ± 2%, P = 1). This was associated with increased phosphorylation of Akt (2-fold, P < 0.05), ERK1/2 (3-fold, P < 0.01) and STAT3 (12-fold, P < 0.001). Combined blocking of the phosphatidylinositol-4,5-bisphosphate 3-kinase/Akt and mitogen-activated protein kinase/ERK signalling abolished the protective CBMSC effect, while blocking the pathways individually had no effect. Inhibition of STAT3 phosphorylation drastically lowered HL-1 cell viability in control medium, but not in medium conditioned by CBMSCs. The factors released by CBMSCs protect cardiomyocyte-like HL-1 cells from simulated ischaemia more than those released from fibroblasts. While CBMSC-triggered Akt and ERK1/2 activation provides protection in a compensatory manner, STAT3 is crucial for cardiomyocyte survival in ischaemia, but is not a key mediator of cytoprotective stem cell actions.

Progress in characterization, preparation and clinical applications of non-hematopoietic stem cells, 29–30 September 2006, Tübingen, Germany

Cytotherapy, 2007

Basic research and clinical applications of non-hematopoietic stem cells, 4–5 April 2008, Tübingen, Germany

Cytotherapy, 2009

From 4 to 5 April 2008, international experts met for the second time in Tubingen, Germany, to pr... more From 4 to 5 April 2008, international experts met for the second time in Tubingen, Germany, to present and discuss the latest proceedings in research on non-hematopoietic stem cells (NHSC). This report presents issues of basic research including characterization, isolation, good manufacturing practice (GMP)-like production and imaging as well as clinical applications focusing on the regenerative and immunomodulatory capacities of NHSC.

BMC Medicine, 2013

Background: Mesenchymal stromal cells (MSCs) are attractive for cell-based therapies ranging from... more Background: Mesenchymal stromal cells (MSCs) are attractive for cell-based therapies ranging from regenerative medicine and tissue engineering to immunomodulation. However, clinical efficacy is variable and it is unclear how the phenotypes defining bone marrow (BM)-derived MSCs as well as donor characteristics affect their functional properties.

Therapeutischer Nutzen mesenchymaler Stammzellen bei zerebrovaskulären Erkrankungen

Aktuelle Neurologie, 2008

Journal of tissue engineering and regenerative medicine, Jan 15, 2015

The use of fetal bovine serum (FBS) as a culture medium supplement in cell therapy and clinical t... more The use of fetal bovine serum (FBS) as a culture medium supplement in cell therapy and clinical tissue engineering is challenged by immunological concerns and the risk of disease transmission. Here we tested whether human, thrombin-activated, pooled, platelet-rich plasma (tPRP) can be substituted for FBS in the engineering of osteogenic and vasculogenic grafts, using cells from the stromal vascular fraction (SVF) of human adipose tissue. SVF cells were cultured under perfusion flow into porous hydroxyapatite scaffolds for 5 days, with the medium supplemented with either 10% tPRP or 10% FBS and implanted in an ectopic mouse model. Following in vitro culture, as compared to FBS, the use of tPRP did not modify the fraction of clonogenic cells or the different cell phenotypes, but increased by 1.9-fold the total number of cells. After 8 weeks in vivo, bone tissue was formed more reproducibly and in higher amounts (3.7-fold increase) in constructs cultured with tPRP. Staining for human-s...

Klinische Pädiatrie, 2012

Regenerative therapy based on stem cells is applied as standard therapy in pediatric oncology. Fu... more Regenerative therapy based on stem cells is applied as standard therapy in pediatric oncology. Furthermore, they are frequently used to treat immunodefi ciency disorders of infants. For severe neonatal diseases, e. g. hypoxic-ischemic encephalopathy in term neonates or bronchopulmonary dysplasia in preterm infants, animal models have been established. According to some fi rst preclinical results stem cell administration appears as a promising tool to improve the clinical outcome in high-risk infants. Provided the benefi t of regenerative therapies can further be evaluated in appropriate preclinical neonate models, carefully controlled clinical trials to assess the signifi cance of regenerative therapies, such as autologous stem cell administration, are indicated.

Stem Cells and Development, 2015

Recently, mesenchymal stromal cell-derived extracellular vesicles (MSC-EVs) have been suggested a... more Recently, mesenchymal stromal cell-derived extracellular vesicles (MSC-EVs) have been suggested as an alternative to MSCs for the treatment of various inflammatory disorders. However, while a first case report observed beneficial therapeutic effects of repeated MSC-EV infusions in a patient with therapy-refractory graftversus-host disease, in vitro findings revealed that MSC-EVs were significantly less immunosuppressive than their parental cells. In this study, we compared the immunosuppressive potency of MSCs derived from bone marrow (BM-MSCs) and adipose tissue (AT-MSCs), with their secreted EVs in a standardized lymphocyte proliferation assay (LPA). Both BM-MSCs and AT-MSCs exhibited a remarkable inhibition of lymphocyte proliferation (LP) (88.1% -1.5% and 75.5% -1.5%, respectively), while isolated EVs derived from them failed to suppress LP at dose levels up to 100 mg/mL. Thus, our data further substantiate previous reports suggesting that cell-cell contact plays an important role on the immunosuppressive potential mediated by MSCs. Hence, MSC-EVs are still a matter of debate and might not be a reasonable substitute for MSCs with regard to the immunosuppressive function. Collectively, these contrasting findings may also reflect the importance of relevant translational aspects when designing new studies. Standardization of MSC culture conditions before EV collection as well as isolation and characterization methods with regard to EV purity are urged. Moreover, before clinical use, dose-finding studies evaluating MSC-EV preparations in suitable preclinical models are warranted.

Standardization of Good Manufacturing Practice-compliant production of bone marrow-derived human mesenchymal stromal cells for immunotherapeutic applications

Cytotherapy, 2015

Human mesenchymal stem or stromal cells (MSCs) represent a potential resource not only for regene... more Human mesenchymal stem or stromal cells (MSCs) represent a potential resource not only for regenerative medicine but also for immunomodulatory cell therapies. The application of different MSC culture protocols has significantly hampered the comparability of experimental and clinical data from different laboratories and has posed a major obstacle for multicenter clinical trials. Manufacturing of cell products for clinical application in the European Community must be conducted in compliance with Good Manufacturing Practice and requires a manufacturing license. In Germany, the Paul-Ehrlich-Institut as the Federal Authority for Vaccines and Biomedicines is critically involved in the approval process. This report summarizes a consensus meeting between researchers, clinicians and regulatory experts on standard quality requirements for MSC production. The strategy for quality control testing depends on the product's cell composition, the manufacturing process and the indication and ta...

Interactive CardioVascular and Thoracic Surgery, 2013

Objectives: CD133pos cells are currently evaluated for use in cardiac cell therapy. We hypothesiz... more Objectives: CD133pos cells are currently evaluated for use in cardiac cell therapy. We hypothesized that they exert their beneficial effects in a paracrine manner and investigated this in a cell culture ischaemia model. Furthermore, we checked whether purified CD133pos cells perform better than non-fractionated mononuclear cells (MNC). Methods: CD133pos cells were isolated from bone marrow MNC and conditioned medium was prepared from CD133pos and non-fractionated MNC. HL-1 cardiomyocytes were subjected to simulated ischaemia in the respective conditioned media or in control medium. After treatment, total remaining cells, apoptotic cells and nuclear shrinking were quantified using an automated imaging system. Furthermore, metabolic activity and phosphorylation of kinases Akt, Erk1/2, GSK3b and transcription factor Stat3 were investigated. Results: After simulated ischaemia, the rate of detached dead cells was lowest in CD133pos conditioned medium (26 ± 6%) and highest in control medium (36 ± 6%). In CD133pos conditioned medium, the fraction of nonapoptotic cells was most enhanced and nuclear shrinking as a consequence of apoptosis was reduced. Cell viability was also highest in CD133pos conditioned medium (109.4 ± 8.8% in relation to control). In both conditioned media, phosphorylation of Akt, Erk1/2, and GSK3b was lower than in control medium. Stat3 phosphorylation was sustained on the level of control. Conclusions: Factors released from purified CD133pos bone marrow cells exhibit more pronounced protective effects on HL-1 cardiomyocytes under simulated ischaemia than from non-fractionated MNC. These effects are not associated with the phosphorylation of cell survival promoting kinases Akt, Erk1/2, GSK3b and transcription factor Stat3. Although the molecular mechanism of cardioprotection by CD133pos cells requires further investigation, our results reinforce the advantage of enriching CD133pos cells for cardiac cell therapy.

Neuroscience Letters, 2008

PloS one, 2011

The possible different therapeutic efficacy of human mesenchymal stem cells (hMSC) derived from u... more The possible different therapeutic efficacy of human mesenchymal stem cells (hMSC) derived from umbilical cord blood (CB), adipose tissue (AT) or bone marrow (BM) for the treatment of myocardial infarction (MI) remains unexplored. This study was to assess the regenerative potential of hMSC from different origins and to evaluate the role of CD105 in cardiac regeneration. Male SCID mice underwent LAD-ligation and received the respective cell type (400.000/per animal) intramyocardially. Six weeks post infarction, cardiac catheterization showed significant preservation of left ventricular functions in BM and CD105(+)-CB treated groups compared to CB and nontreated MI group (MI-C). Cell survival analyzed by quantitative real time PCR for human GAPDH and capillary density measured by immunostaining showed consistent results. Furthermore, cardiac remodeling can be significantly attenuated by BM-hMSC compared to MI-C. Under hypoxic conditions in vitro, remarkably increased extracellular aci...

Mechanisms of paracrine cardioprotection by cord blood mesenchymal stromal cells

European Journal of Cardio-Thoracic Surgery, 2014

Among the mechanisms by which somatic stem cells may improve left ventricular function in ischaem... more Among the mechanisms by which somatic stem cells may improve left ventricular function in ischaemic heart disease are pro-survival stimuli mediated by secreted factors. This phenomenon is frequently referred to, but remains poorly understood. We therefore investigated the non-regenerative cardioprotective effects of cord blood mesenchymal stromal cells (CBMSCs) in vitro and sought to identify relevant intracellular signalling pathways. Conditioned medium from CBMSCs and fibroblasts was prepared, and secreted factors were analysed by Luminex(®) immunobead assay. Murine cardiomyocyte-derived HL-1 cells were subjected to simulated ischaemia by glucose and serum deprivation and hypoxia in CBMSC-conditioned or cell-free control medium or in medium conditioned by foreskin fibroblasts. The proportions of vital, apoptotic and necrotic cells (poly-caspase activity, annexin V and ethidium homodimer-III staining) were quantified using a high-content imaging system. Metabolic activity and proliferation rate were determined via 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium and 5-bromo-2-deoxyuridine assays. Phosphorylation of Akt, extracellular-signal-regulated kinase (ERK)1/2, signal transducer and activator of transcription 3 (STAT3) and glycogen synthase kinase 3β was determined by western blot, and experiments were repeated in the presence of specific small-molecule inhibitors (Wortmannin, UO126 and Stattic). CBMSC medium reduced the proportion of dead HL-1 cardiomyocytes from 39 ± 3 to 28 ± 1% (P < 0.05) and the rate of late apoptotic cells to 68 ± 2% of that in control medium (P < 0.001). Metabolic activity was increased by 12 ± 1% compared with control (P < 0.05), while in fibroblast medium it was not (5 ± 2%, P = 1). This was associated with increased phosphorylation of Akt (2-fold, P < 0.05), ERK1/2 (3-fold, P < 0.01) and STAT3 (12-fold, P < 0.001). Combined blocking of the phosphatidylinositol-4,5-bisphosphate 3-kinase/Akt and mitogen-activated protein kinase/ERK signalling abolished the protective CBMSC effect, while blocking the pathways individually had no effect. Inhibition of STAT3 phosphorylation drastically lowered HL-1 cell viability in control medium, but not in medium conditioned by CBMSCs. The factors released by CBMSCs protect cardiomyocyte-like HL-1 cells from simulated ischaemia more than those released from fibroblasts. While CBMSC-triggered Akt and ERK1/2 activation provides protection in a compensatory manner, STAT3 is crucial for cardiomyocyte survival in ischaemia, but is not a key mediator of cytoprotective stem cell actions.

Progress in characterization, preparation and clinical applications of non-hematopoietic stem cells, 29–30 September 2006, Tübingen, Germany

Cytotherapy, 2007

Basic research and clinical applications of non-hematopoietic stem cells, 4–5 April 2008, Tübingen, Germany

Cytotherapy, 2009

From 4 to 5 April 2008, international experts met for the second time in Tubingen, Germany, to pr... more From 4 to 5 April 2008, international experts met for the second time in Tubingen, Germany, to present and discuss the latest proceedings in research on non-hematopoietic stem cells (NHSC). This report presents issues of basic research including characterization, isolation, good manufacturing practice (GMP)-like production and imaging as well as clinical applications focusing on the regenerative and immunomodulatory capacities of NHSC.

BMC Medicine, 2013

Background: Mesenchymal stromal cells (MSCs) are attractive for cell-based therapies ranging from... more Background: Mesenchymal stromal cells (MSCs) are attractive for cell-based therapies ranging from regenerative medicine and tissue engineering to immunomodulation. However, clinical efficacy is variable and it is unclear how the phenotypes defining bone marrow (BM)-derived MSCs as well as donor characteristics affect their functional properties.

Therapeutischer Nutzen mesenchymaler Stammzellen bei zerebrovaskulären Erkrankungen

Aktuelle Neurologie, 2008

Journal of tissue engineering and regenerative medicine, Jan 15, 2015

The use of fetal bovine serum (FBS) as a culture medium supplement in cell therapy and clinical t... more The use of fetal bovine serum (FBS) as a culture medium supplement in cell therapy and clinical tissue engineering is challenged by immunological concerns and the risk of disease transmission. Here we tested whether human, thrombin-activated, pooled, platelet-rich plasma (tPRP) can be substituted for FBS in the engineering of osteogenic and vasculogenic grafts, using cells from the stromal vascular fraction (SVF) of human adipose tissue. SVF cells were cultured under perfusion flow into porous hydroxyapatite scaffolds for 5 days, with the medium supplemented with either 10% tPRP or 10% FBS and implanted in an ectopic mouse model. Following in vitro culture, as compared to FBS, the use of tPRP did not modify the fraction of clonogenic cells or the different cell phenotypes, but increased by 1.9-fold the total number of cells. After 8 weeks in vivo, bone tissue was formed more reproducibly and in higher amounts (3.7-fold increase) in constructs cultured with tPRP. Staining for human-s...