Reinout Stoop | TNO - Academia.edu (original) (raw)

Papers by Reinout Stoop

Biomaterials, 2015

Cells and tissues are intrinsically adapted to molecular gradients and use them to maintain or ch... more Cells and tissues are intrinsically adapted to molecular gradients and use them to maintain or change their activity. The effect of such gradients is particularly important for cell populations that have an intrinsic capacity to differentiate into multiple cell lineages, such as bone marrow derived mesenchymal stromal cells (MSCs). Our results showed that nutrient gradients prompt the spatiotemporal organization of MSCs in 3D culture. Cells adapted to their 3D environment without significant cell death or cell differentiation. Kinetics data and whole-genome gene expression analysis suggest that a low proliferation activity phenotype predominates in stromal cells cultured in 3D, likely due to increasing nutrient limitation. These differences implied that despite similar surface areas available for cell attachment, higher cell concentrations in 3D reduced MSCs proliferation, while activating hypoxia related-pathways. To further understand the in vivo effects of both proliferation and cell concentrations, we increased cell concentrations in small (1.8 ml) implantable wells. We found that MSCs accumulation and conditioning by nutrient competition in small volumes leads to an ideal threshold of cell-concentration for the induction of blood vessel formation, possibly signaled by the hypoxia-related stanniocalcin-1 gene. Biomaterials j o u r n a l h o m e p a g e : w w w .e l se v i e r. co m/ lo ca t e / b i o m a t e ri a l s http://dx.

PLoS ONE, 2014

The recently developed histological scoring system for non-alcoholic fatty liver disease (NAFLD) ... more The recently developed histological scoring system for non-alcoholic fatty liver disease (NAFLD) by the NASH Clinical Research Network (NASH-CRN) has been widely used in clinical settings, but is increasingly employed in preclinical research as well. However, it has not been systematically analyzed whether the human scoring system can directly be converted to preclinical rodent models. To analyze this, we systematically compared human NAFLD liver pathology, using human liver biopsies, with liver pathology of several NAFLD mouse models. Based upon the features pertaining to mouse NAFLD, we aimed at establishing a modified generic scoring system that is applicable to broad spectrum of rodent models. The histopathology of NAFLD was analyzed in several different mouse models of NAFLD to define generic criteria for histological assessment (preclinical scoring system). For validation of this scoring system, 36 slides of mouse livers, covering the whole spectrum of NAFLD, were blindly analyzed by ten observers. Additionally, the livers were blindly scored by one observer during two separate assessments longer than 3 months apart. The criteria macrovesicular steatosis, microvesicular steatosis, hepatocellular hypertrophy, inflammation and fibrosis were generally applicable to rodent NAFLD. The inter-observer reproducibility (evaluated using the Intraclass Correlation Coefficient) between the ten observers was high for the analysis of macrovesicular steatosis and microvesicular steatosis (ICC = 0.784 and 0.776, all p<0.001, respectively) and moderate for the analysis of hypertrophy and inflammation (ICC = 0.685 and 0.650, all p<0.001, respectively). The intra-observer reproducibility between the different observations of one observer was high for the analysis of macrovesicular steatosis, microvesicular steatosis and hypertrophy (ICC = 0.871, 0.871 and 0.896, all p<0.001, respectively) and very high for the analysis of inflammation (ICC = 0.931, p<0.001). We established a simple NAFLD scoring system with high reproducibility that is applicable for different rodent models and for all stages of NAFLD etiology.

Osteoarthritis and Cartilage, 2013

Fibrosis is a major contributor to joint stiffness in osteoarthritis (OA). We investigated severa... more Fibrosis is a major contributor to joint stiffness in osteoarthritis (OA). We investigated several factors associated with the persistence of transforming growth factor beta (TGF-β)-induced fibrosis and whether these factors also play a role in OA-related fibrosis. Mice were injected intra-articularly (i.a.) with an adenovirus encoding either TGF-β or connective tissue growth factor (CTGF). In addition, we induced OA by i.a. injection of bacterial collagenase into the right knee joint of C57BL/6 mice. mRNA was isolated from the synovium for Q-PCR analysis of the gene expression of various extracellular matrix (ECM) components, ECM degraders, growth factors and collagen cross-linking-related enzymes. Sections of murine knee joints injected with Ad-TGF-β or Ad-CTGF or from experimental OA were stained for lysyl hydroxylase 2 (LH2). The number of pyridinoline cross-links per triple helix collagen in synovium biopsies was determined with high-performance liquid chromatography (HPLC). Expression of collagen alpha-1(I) chain precursor (Col1a1), tissue inhibitor of metalloproteinases 1 (TIMP1) and especially procollagen-lysine, 2-oxoglutarate 5-dioxygenase 2b (Plod2b) were highly upregulated by TGF-β but not by CTGF. Elevated expression of Plod2b mRNA was associated with high lysyl hydroxylase 2 (LH2) protein staining after TGF-β overexpression and in experimental OA. Furthermore, in experimental OA the number of hydroxypyridinoline cross-links was significant increased compared to control knee joints. Our data show that elevated LH2b expression is associated with the persistent nature of TGF-β-induced fibrosis. Also in experimental OA, LH2b expression as well as the number of hydroxypyridinoline cross-link were significantly upregulated. We propose that LH2b, and the subsequent increase in pyridinoline cross-links, is responsible for the persistent fibrosis in experimental OA.

Osteoarthritis and Cartilage, 2011

Purpose: There are not clear evidences about the migration of mesenchymal stem cells from a syste... more Purpose: There are not clear evidences about the migration of mesenchymal stem cells from a systemic circulation to another niche as an injury place in the organism. The current study treats to answer this question. Methods: Mesenchymal stem cells (MSCs) have been injected via intravenous and directly into the monkey joint, these MSCs were previously characterized by flow cytometry revealing that were positive for CD90 and CD44 and negatives for CD34 and CD45 indicating that presence of MSCs markers. CD105 enriched sub-population of MSCs was labelled with oxacarbocyanine -DiO (green) when they were injected via intravenous (IV), with octadecyl (C18) indocarbocyanine -DiI (red) when they were injected directly into the knee, intra-articular (IA) and another group of MSCs were modified to express constitutively the green fluorescence protein (GFP) to follow their evolutions through the animals injected by different ways and their localization. The animal models used were adult monkeys Macaca Fascicularis which had been injured into the left knee to create an Osteoarthritis (OA) animal model and the right knee was used as control. First step: one group of three animals was injected with 1×10 6 GFP-MSCs/KG of animal in the vein twice and these animals were sacrificed only one week after the second injection because the purpose of this experiment was following the GFP-MSCs into the organism. Second steep: one group of two animals was injected twice in the vein with 1×10 6 CD105 + -MSCs labelled with DiO only and another two animals were injected directly in the knee twice with 1×10 6 CD105 + -MSCs labelled with DiI at the same time these animals were injected twice in the vein with 1×10 6 CD105 + -MSCs labelled with DiO. The injections were realized into the animals with an interval of one week between them. The animals were sacrificed one month after treatment. Results: Immunohistochemistry analysis of the tissues from the animals revealed that and GFP-MSCs and CD105 + -MSCs migrated towards the injured knee joint. Neither labelled cells nor teratomes were found in other vital organs into the animals. The CD105 + -MSCs labelled with DiI (red) and with DiO (green) were only located in the injured knee (0.01% from the total injected) and they were not found in the normal one. Furthermore CD105 + -MSCs labelled with DiI (red) and with DIO (green) were found in crossed ligaments and knee muscle (vastus medialis), synovial membrane, both meniscus and cartilage of patello femoral groove all of them only in the injured joint and not in the normal one. An exhaustive immunofluorescence analysis of DiO labelled cells founded in the injured knee revealed that they were negatives for CD68, which is a macrophage antibody marker, and 4% of CD105 + -MSCs labelled with DiO (green) were positives for SDF-1, which is a marker of osteoclastogenesis and produces liberation of IL-6, in the patello femoral groove and crossed ligaments of injured joint and not in the normal one. Conclusions: These results seem indicate that: 1. The MSCs injected in a peripherical vein go to injured tissue, in this case injury knee. 2. The MSCs injected directly in an injured place keep in the same place. 3. The MSCs could be recruitment by SDF-1.

Tissue Engineering Part A, 2010

Human multipotent mesenchymal stromal cells (hMSCs) are multipotent cells that, in the presence o... more Human multipotent mesenchymal stromal cells (hMSCs) are multipotent cells that, in the presence of appropriate stimuli, can differentiate into different lineages such as the osteogenic, chondrogenic, and adipogenic lineages. In the presence of ascorbic acid, MSCs secrete an extracellular matrix mainly composed of collagen type I. Here we assessed the potential role of endogenous collagen synthesis in hMSC differentiation and stem cell maintenance. We observed a sharp reduction in proliferation rate of hMSCs in the absence of ascorbic acid, concomitant with a reduction in osteogenesis in vitro and bone formation in vivo. In line with a positive role for collagen type I in osteogenesis, gene expression profiling of hMSCs cultured in the absence of ascorbic acid demonstrated increased expression of genes involved in adipogenesis and chondrogenesis and a reduction in expression of osteogenic genes. We also observed that matrix remodeling and anti-osteoclastogenic signals were high in the presence of ascorbic acid. The presence of collagen type I during the expansion phase of hMSCs did not affect their osteogenic and adipogenic differentiation potential. In conclusion, the collagenous matrix supports both proliferation and differentiation of osteogenic hMSCs but, on the other hand, presents signals stimulating matrix remodeling and inhibiting osteoclastogenesis.

Tissue Engineering Part A, 2012

Cardiovascular tissue engineering has shown considerable progress, but in vitro tissue conditioni... more Cardiovascular tissue engineering has shown considerable progress, but in vitro tissue conditioning to stimulate the development of a functional extracellular matrix still needs improvement. We investigated the environmental factor oxygen concentration for its potential to increase the amount of collagen and collagen cross-links, and therefore improve tissue quality. Cardiovascular tissue engineered (TE) constructs, made of rapidly degrading PGA/P4HB scaffold seeded with human vascular-derived cells, were cultured at 7%, 4%, 2%, 0.5% O(2) for 4 weeks and compared to control cultures at 21% O(2). Tissue properties were evaluated by measuring the extracellular matrix production and mechanical behavior. The culture environment was monitored closely and the oxygen gradient throughout the constructs was simulated with a theoretical model. TE constructs cultured at 21%, 7% and 4% O(2) showed dense and homogeneous tissue formation with comparable strength, stiffness, collagen and collagen cross-link content. At 2% O(2), collagen content and stiffness decreased, whereas at 0.5% O(2), hardly any tissue was formed. Overall, tissue properties deteriorated at the lowest oxygen concentrations, opposing our hypothesis that was based on previous culture at low oxygen concentrations. Further research will focus on establishing the balance between applied oxygen conditions (concentration and exposure time) and optimal tissue outcome.

Stem Cells, 2007

Osteoarthritis (OA) is a multifactorial disease strongly correlated with history of joint trauma,... more Osteoarthritis (OA) is a multifactorial disease strongly correlated with history of joint trauma, joint dysplasia, and advanced age. Mesenchymal stem cells (MSCs) are promising cells for biological cartilage regeneration. Conflicting data have been published concerning the availability of MSCs from the iliac crest, depending on age and overall physical fitness. Here, we analyzed whether the availability and chondrogenic differentiation capacity of MSCs isolated from the femoral shaft as an alternative source is age-or OA etiology-dependent. MSCs were isolated from the bone marrow (BM) of 98 patients, categorized into three OA-etiology groups (age-related, joint trauma, joint dysplasia) at the time of total hip replacement. All BM samples were characterized for cell yield, proliferation capacity, and phenotype. Chondrogenic differentiation was studied using micromass culture and analyzed by histology, immunohistochemistry, and quantitative reverse transcriptasepolymerase chain reaction. Significant volumes of viable BM (up to 25 ml) could be harvested from the femoral shaft without observing donor-site morbidity, typically containing >10 7 mononuclear cells per milliliter. No correlation of age or OA etiology with the number of mononuclear cells in BM, MSC yield, or cell size was found. Proliferative capacity and cellular spectrum of the harvested cells were independent of age and cause of OA. From all tested donors, MSCs could be differentiated into the chondrogenic lineage. We conclude that, irrespective of age and OA etiology, sufficient numbers of MSCs can be isolated and that these cells possess an adequate chondrogenic differentiation potential. Therefore, a therapeutic application of MSCs for cartilage regeneration of OA lesions seems feasible. STEM CELLS 2007;25:3244 -3251 Disclosure of potential conflicts of interest is found at the end of this article.

Osteoarthritis and Cartilage, 2012

Osteoarthritis and Cartilage, 2006

Osteoarthritis and Cartilage, 2004

Objective: For autologous chondrocyte transplantation (ACT) chondrocytes are expanded in vitro. D... more Objective: For autologous chondrocyte transplantation (ACT) chondrocytes are expanded in vitro. During expansion these cells may dedifferentiate. This change in phenotype is characterized by a raised expression of type I collagen and a decrease in type II collagen expression. Since high expression of type II collagen is of central importance for the properties of hyaline cartilage, we investigated if the growth factor bone morphogenetic protein-2 (BMP-2) may modulate the chondrogenic phenotype in monolayer cell cultures and in threedimensional culture systems.

Biomaterials, 2015

Cells and tissues are intrinsically adapted to molecular gradients and use them to maintain or ch... more Cells and tissues are intrinsically adapted to molecular gradients and use them to maintain or change their activity. The effect of such gradients is particularly important for cell populations that have an intrinsic capacity to differentiate into multiple cell lineages, such as bone marrow derived mesenchymal stromal cells (MSCs). Our results showed that nutrient gradients prompt the spatiotemporal organization of MSCs in 3D culture. Cells adapted to their 3D environment without significant cell death or cell differentiation. Kinetics data and whole-genome gene expression analysis suggest that a low proliferation activity phenotype predominates in stromal cells cultured in 3D, likely due to increasing nutrient limitation. These differences implied that despite similar surface areas available for cell attachment, higher cell concentrations in 3D reduced MSCs proliferation, while activating hypoxia related-pathways. To further understand the in vivo effects of both proliferation and cell concentrations, we increased cell concentrations in small (1.8 ml) implantable wells. We found that MSCs accumulation and conditioning by nutrient competition in small volumes leads to an ideal threshold of cell-concentration for the induction of blood vessel formation, possibly signaled by the hypoxia-related stanniocalcin-1 gene. Biomaterials j o u r n a l h o m e p a g e : w w w .e l se v i e r. co m/ lo ca t e / b i o m a t e ri a l s http://dx.

PLoS ONE, 2014

The recently developed histological scoring system for non-alcoholic fatty liver disease (NAFLD) ... more The recently developed histological scoring system for non-alcoholic fatty liver disease (NAFLD) by the NASH Clinical Research Network (NASH-CRN) has been widely used in clinical settings, but is increasingly employed in preclinical research as well. However, it has not been systematically analyzed whether the human scoring system can directly be converted to preclinical rodent models. To analyze this, we systematically compared human NAFLD liver pathology, using human liver biopsies, with liver pathology of several NAFLD mouse models. Based upon the features pertaining to mouse NAFLD, we aimed at establishing a modified generic scoring system that is applicable to broad spectrum of rodent models. The histopathology of NAFLD was analyzed in several different mouse models of NAFLD to define generic criteria for histological assessment (preclinical scoring system). For validation of this scoring system, 36 slides of mouse livers, covering the whole spectrum of NAFLD, were blindly analyzed by ten observers. Additionally, the livers were blindly scored by one observer during two separate assessments longer than 3 months apart. The criteria macrovesicular steatosis, microvesicular steatosis, hepatocellular hypertrophy, inflammation and fibrosis were generally applicable to rodent NAFLD. The inter-observer reproducibility (evaluated using the Intraclass Correlation Coefficient) between the ten observers was high for the analysis of macrovesicular steatosis and microvesicular steatosis (ICC = 0.784 and 0.776, all p<0.001, respectively) and moderate for the analysis of hypertrophy and inflammation (ICC = 0.685 and 0.650, all p<0.001, respectively). The intra-observer reproducibility between the different observations of one observer was high for the analysis of macrovesicular steatosis, microvesicular steatosis and hypertrophy (ICC = 0.871, 0.871 and 0.896, all p<0.001, respectively) and very high for the analysis of inflammation (ICC = 0.931, p<0.001). We established a simple NAFLD scoring system with high reproducibility that is applicable for different rodent models and for all stages of NAFLD etiology.

Osteoarthritis and Cartilage, 2013

Fibrosis is a major contributor to joint stiffness in osteoarthritis (OA). We investigated severa... more Fibrosis is a major contributor to joint stiffness in osteoarthritis (OA). We investigated several factors associated with the persistence of transforming growth factor beta (TGF-β)-induced fibrosis and whether these factors also play a role in OA-related fibrosis. Mice were injected intra-articularly (i.a.) with an adenovirus encoding either TGF-β or connective tissue growth factor (CTGF). In addition, we induced OA by i.a. injection of bacterial collagenase into the right knee joint of C57BL/6 mice. mRNA was isolated from the synovium for Q-PCR analysis of the gene expression of various extracellular matrix (ECM) components, ECM degraders, growth factors and collagen cross-linking-related enzymes. Sections of murine knee joints injected with Ad-TGF-β or Ad-CTGF or from experimental OA were stained for lysyl hydroxylase 2 (LH2). The number of pyridinoline cross-links per triple helix collagen in synovium biopsies was determined with high-performance liquid chromatography (HPLC). Expression of collagen alpha-1(I) chain precursor (Col1a1), tissue inhibitor of metalloproteinases 1 (TIMP1) and especially procollagen-lysine, 2-oxoglutarate 5-dioxygenase 2b (Plod2b) were highly upregulated by TGF-β but not by CTGF. Elevated expression of Plod2b mRNA was associated with high lysyl hydroxylase 2 (LH2) protein staining after TGF-β overexpression and in experimental OA. Furthermore, in experimental OA the number of hydroxypyridinoline cross-links was significant increased compared to control knee joints. Our data show that elevated LH2b expression is associated with the persistent nature of TGF-β-induced fibrosis. Also in experimental OA, LH2b expression as well as the number of hydroxypyridinoline cross-link were significantly upregulated. We propose that LH2b, and the subsequent increase in pyridinoline cross-links, is responsible for the persistent fibrosis in experimental OA.

Osteoarthritis and Cartilage, 2011

Purpose: There are not clear evidences about the migration of mesenchymal stem cells from a syste... more Purpose: There are not clear evidences about the migration of mesenchymal stem cells from a systemic circulation to another niche as an injury place in the organism. The current study treats to answer this question. Methods: Mesenchymal stem cells (MSCs) have been injected via intravenous and directly into the monkey joint, these MSCs were previously characterized by flow cytometry revealing that were positive for CD90 and CD44 and negatives for CD34 and CD45 indicating that presence of MSCs markers. CD105 enriched sub-population of MSCs was labelled with oxacarbocyanine -DiO (green) when they were injected via intravenous (IV), with octadecyl (C18) indocarbocyanine -DiI (red) when they were injected directly into the knee, intra-articular (IA) and another group of MSCs were modified to express constitutively the green fluorescence protein (GFP) to follow their evolutions through the animals injected by different ways and their localization. The animal models used were adult monkeys Macaca Fascicularis which had been injured into the left knee to create an Osteoarthritis (OA) animal model and the right knee was used as control. First step: one group of three animals was injected with 1×10 6 GFP-MSCs/KG of animal in the vein twice and these animals were sacrificed only one week after the second injection because the purpose of this experiment was following the GFP-MSCs into the organism. Second steep: one group of two animals was injected twice in the vein with 1×10 6 CD105 + -MSCs labelled with DiO only and another two animals were injected directly in the knee twice with 1×10 6 CD105 + -MSCs labelled with DiI at the same time these animals were injected twice in the vein with 1×10 6 CD105 + -MSCs labelled with DiO. The injections were realized into the animals with an interval of one week between them. The animals were sacrificed one month after treatment. Results: Immunohistochemistry analysis of the tissues from the animals revealed that and GFP-MSCs and CD105 + -MSCs migrated towards the injured knee joint. Neither labelled cells nor teratomes were found in other vital organs into the animals. The CD105 + -MSCs labelled with DiI (red) and with DiO (green) were only located in the injured knee (0.01% from the total injected) and they were not found in the normal one. Furthermore CD105 + -MSCs labelled with DiI (red) and with DIO (green) were found in crossed ligaments and knee muscle (vastus medialis), synovial membrane, both meniscus and cartilage of patello femoral groove all of them only in the injured joint and not in the normal one. An exhaustive immunofluorescence analysis of DiO labelled cells founded in the injured knee revealed that they were negatives for CD68, which is a macrophage antibody marker, and 4% of CD105 + -MSCs labelled with DiO (green) were positives for SDF-1, which is a marker of osteoclastogenesis and produces liberation of IL-6, in the patello femoral groove and crossed ligaments of injured joint and not in the normal one. Conclusions: These results seem indicate that: 1. The MSCs injected in a peripherical vein go to injured tissue, in this case injury knee. 2. The MSCs injected directly in an injured place keep in the same place. 3. The MSCs could be recruitment by SDF-1.

Tissue Engineering Part A, 2010

Human multipotent mesenchymal stromal cells (hMSCs) are multipotent cells that, in the presence o... more Human multipotent mesenchymal stromal cells (hMSCs) are multipotent cells that, in the presence of appropriate stimuli, can differentiate into different lineages such as the osteogenic, chondrogenic, and adipogenic lineages. In the presence of ascorbic acid, MSCs secrete an extracellular matrix mainly composed of collagen type I. Here we assessed the potential role of endogenous collagen synthesis in hMSC differentiation and stem cell maintenance. We observed a sharp reduction in proliferation rate of hMSCs in the absence of ascorbic acid, concomitant with a reduction in osteogenesis in vitro and bone formation in vivo. In line with a positive role for collagen type I in osteogenesis, gene expression profiling of hMSCs cultured in the absence of ascorbic acid demonstrated increased expression of genes involved in adipogenesis and chondrogenesis and a reduction in expression of osteogenic genes. We also observed that matrix remodeling and anti-osteoclastogenic signals were high in the presence of ascorbic acid. The presence of collagen type I during the expansion phase of hMSCs did not affect their osteogenic and adipogenic differentiation potential. In conclusion, the collagenous matrix supports both proliferation and differentiation of osteogenic hMSCs but, on the other hand, presents signals stimulating matrix remodeling and inhibiting osteoclastogenesis.

Tissue Engineering Part A, 2012

Cardiovascular tissue engineering has shown considerable progress, but in vitro tissue conditioni... more Cardiovascular tissue engineering has shown considerable progress, but in vitro tissue conditioning to stimulate the development of a functional extracellular matrix still needs improvement. We investigated the environmental factor oxygen concentration for its potential to increase the amount of collagen and collagen cross-links, and therefore improve tissue quality. Cardiovascular tissue engineered (TE) constructs, made of rapidly degrading PGA/P4HB scaffold seeded with human vascular-derived cells, were cultured at 7%, 4%, 2%, 0.5% O(2) for 4 weeks and compared to control cultures at 21% O(2). Tissue properties were evaluated by measuring the extracellular matrix production and mechanical behavior. The culture environment was monitored closely and the oxygen gradient throughout the constructs was simulated with a theoretical model. TE constructs cultured at 21%, 7% and 4% O(2) showed dense and homogeneous tissue formation with comparable strength, stiffness, collagen and collagen cross-link content. At 2% O(2), collagen content and stiffness decreased, whereas at 0.5% O(2), hardly any tissue was formed. Overall, tissue properties deteriorated at the lowest oxygen concentrations, opposing our hypothesis that was based on previous culture at low oxygen concentrations. Further research will focus on establishing the balance between applied oxygen conditions (concentration and exposure time) and optimal tissue outcome.

Stem Cells, 2007

Osteoarthritis (OA) is a multifactorial disease strongly correlated with history of joint trauma,... more Osteoarthritis (OA) is a multifactorial disease strongly correlated with history of joint trauma, joint dysplasia, and advanced age. Mesenchymal stem cells (MSCs) are promising cells for biological cartilage regeneration. Conflicting data have been published concerning the availability of MSCs from the iliac crest, depending on age and overall physical fitness. Here, we analyzed whether the availability and chondrogenic differentiation capacity of MSCs isolated from the femoral shaft as an alternative source is age-or OA etiology-dependent. MSCs were isolated from the bone marrow (BM) of 98 patients, categorized into three OA-etiology groups (age-related, joint trauma, joint dysplasia) at the time of total hip replacement. All BM samples were characterized for cell yield, proliferation capacity, and phenotype. Chondrogenic differentiation was studied using micromass culture and analyzed by histology, immunohistochemistry, and quantitative reverse transcriptasepolymerase chain reaction. Significant volumes of viable BM (up to 25 ml) could be harvested from the femoral shaft without observing donor-site morbidity, typically containing >10 7 mononuclear cells per milliliter. No correlation of age or OA etiology with the number of mononuclear cells in BM, MSC yield, or cell size was found. Proliferative capacity and cellular spectrum of the harvested cells were independent of age and cause of OA. From all tested donors, MSCs could be differentiated into the chondrogenic lineage. We conclude that, irrespective of age and OA etiology, sufficient numbers of MSCs can be isolated and that these cells possess an adequate chondrogenic differentiation potential. Therefore, a therapeutic application of MSCs for cartilage regeneration of OA lesions seems feasible. STEM CELLS 2007;25:3244 -3251 Disclosure of potential conflicts of interest is found at the end of this article.

Osteoarthritis and Cartilage, 2012

Osteoarthritis and Cartilage, 2006

Osteoarthritis and Cartilage, 2004

Objective: For autologous chondrocyte transplantation (ACT) chondrocytes are expanded in vitro. D... more Objective: For autologous chondrocyte transplantation (ACT) chondrocytes are expanded in vitro. During expansion these cells may dedifferentiate. This change in phenotype is characterized by a raised expression of type I collagen and a decrease in type II collagen expression. Since high expression of type II collagen is of central importance for the properties of hyaline cartilage, we investigated if the growth factor bone morphogenetic protein-2 (BMP-2) may modulate the chondrogenic phenotype in monolayer cell cultures and in threedimensional culture systems.