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Biomedical subjects

P Behrens

Publications and source records attributed to P Behrens.

At least 19 recordsLinked to original sources
PubMed2006

In vivo matrix-guided human mesenchymal stem cells.

Microfracture of subchondral bone results in intrinsic repair of cartilage defects. Stem or progenitor cells from bone marrow have been proposed to be involved in this regenerative process. Here, we demonstrate for the first time that mesenchymal stem (MS) cells can in fact be recovered from matrix material saturated with cells from bone marrow after microfracture. This also introduces a new technique for MS cell isolation during arthroscopic treatment. MS cells were phenotyped using specific cell surface antibodies. Differentiation of the MS cells into the adipogenic, chondrogenic and osteogenic lineage could be demonstrated by cultivation of MS cells as a monolayer, as micromass bodies or mesenchymal microspheres. This study demonstrates that MS cells can be attracted to a cartilage defect by guidance of a collagenous matrix after perforating subchondral bone. Protocols for application of MS cells in restoration of cartilage tissue include an initial invasive biopsy to obtain the MS cells and time-wasting in vitro proliferation and possibly differentiation of the cells before implantation. The new technique already includes attraction of MS cells to sites of cartilage defects and therefore may overcome the necessity of in vitro proliferation and differentiation of MS cells prior to transplantation.

Bone Marrow Cells↗
PubMed2006

Localized nodular pigmented villonodular synovitis of the upper ankle joint--diagnosis and treatment.

This paper introduces a case of local pigmented villonodular synovits (PVNS) of the upper ankle joint in a 37-year old patient. PVNS is a neoplasia of the synovial membrane. Two different entities of PVNS are known: generalized diffuse and local nodular. They differ in their degree of destruction and growth configuration, which is crucial for prognosis and operative treatment. The most common location of the local nodular form is the knee joint, followed by the finger joints. Occurrence in the ankle joint is not common but should be considered if clinical findings are present. MRI is the method of choice for diagnosis and assessment of the bone situation. Treatment consists of radical excision of the neoplasia. Radiosynoviorthesis is recommended as a post-operative treatment to increase the probability of a total removal of persisting PVNS cells. The rate of recurrence seems to be between 8 and 46%.

Adult↗
PubMed2005

Migration pattern, morphology and viability of cells suspended in or sealed with fibrin glue: a histomorphologic study.

INTRODUCTION: We studied the migration pattern, morphology and viability of cells suspended in five different fibrin glues. Besides this, the behaviour of chondrocytes seeded on porous matrices comprising different collagen types sealed with fibrin glue was investigated. MATERIAL AND METHODS: In an experiment A, cell suspension (0.5x10(6) cells) was incubated with different fibrin glues. Experiment B was set up to evaluate chondrocytes migration either through a collagen I/III (Chondro-Gide, Geistlich Biomaterials, Switzerland) or collagen II matrix sealed with different fibrin glues in a perfusion chamber system. Analysis were performed by lightmicroscopy (Mayer's hematoxylin-eosin; Masson-Goldner; TUNEL test) and by transmission and scanning electron microscopy. All fibrin glues were measured for TGF-beta 1 and 2 with a specific ELISA. RESULTS: After incubation of cell suspension in autologous fibrin glue, the morphology of cells is chondrocyte-like. Spindly, process-bearing cells were seen in commercial fibrin glue. Cells suspended in commercial fibrin glue revealed a significant higher percentage of TUNEL positive cells compared to fibrin tissue adhesives mixed with autologous serum (p=0.006). The TGF-beta 1 and 2 concentration was significantly higher in partial autologous fibrin sealant (PAF) compared to their commercial counterparts (p=0.001). Cells seeded on the collagen I/III matrix retained their chondrocytic morphology, while in the type II collagen matrix the chondrocytes displayed a fibroblastic phenotype. The ratio of TUNEL positive cells for the collagen I/III matrix was significantly surpassed by the values, when a collagen II matrix was used (p=0.008). No ingrowth of cells was seen in any of the experimental conditions. CONCLUSION: Partial autologous fibrin glue and collagen I/III matrices are favourable in respect to migration pattern, morphology and viability, but definitive conclusions can only be drawn after in vivo studies. This will be addressed in future animal studies.

Aprotinin↗
PubMed2004

Investigating the effects of bone cement, cyanoacrylate glue and marine mussel adhesive protein from Mytilus edulis on human osteoblasts and fibroblasts in vitro.

Bone cement is a widely used standard fixation substance in Orthopaedic Surgery. Cyanoacrylate glue is available for wound closure to supplement suturing. The mussel adhesive protein extracted from Mytilus edulis (Cell-Tak, BD Biosciences, Heidelberg, Germany) is an experimental fixation device used for in vitro purposes of cell adhesion. The aim of this study is to introduce a cell culture model investigating the effects of commonly applied and experimental glues on human fibroblasts and osteoblasts in vitro. Cells cultured without additives served as a control group. Microscopic examination was performed to evaluate the morphologic changes. An apoptosis test (Apo-Tag, Chemicon International, Temecula, CA, U. S. A.) was applied to determine the rate of natural cell death at the end of the study. It could be demonstrated that morphological changes in bone cement are different in fibroblasts and osteoblasts. Osteoblasts seem to grow on bone cement and develop an orderly formation. Fibroblasts grow in a confluent monolayer around bone cement but do not adhere to the cement itself. This is a desirable effect since most Orthopaedic applications aim at osteointegration as opposed to fibrous tissue overgrowth. Apoptosis attributed to bone cement is comparable to the respective natural rate of apoptosis. Cyanoacrylate glue and the mussel adhesive protein lead to an almost complete apoptosis in the investigated cells. Their routine application should be avoided. The developed cell culture model seems appropriate for performing further investigations.

Animals↗
PubMed2004

Tumour suppression induced by the macrophage activating lipopeptide MALP-2 in an ultrasound guided pancreatic carcinoma mouse model.

BACKGROUND AND AIM: Carcinoma of the exocrine pancreas has a particularly poor prognosis. Therefore, novel therapeutic strategies such as immunotherapy are required. Here we investigated the immunomodulatory capacity of macrophage activating lipopeptide 2 (MALP-2), which binds to toll-like receptors 2 and 6 and induces activation of nuclear factor kappaB in monocytes. This causes the release of early stage leucocyte attracting chemokines and proinflammatory cytokines. METHODS: MALP-2 was tested in a new orthotopic ultrasound guided pancreatic cancer mouse model. This model is close to the biological situation and avoids the stress and immunostimulation caused by laparotomy. Cells from the syngeneic, highly aggressive, and metastatic cell line Panc 02 were administered orthotopically, by ultrasound guidance, to C57bl/6 mice. MALP-2 was administered intratumorally or intraperitoneally and tumour growth, immune status, and leucocyte infiltration at the tumour site were determined. RESULTS: We showed a tumour suppressive effect induced by a single injection of MALP-2. Median survival increased from 21 to 30 days (p<0.002). Combining chemotherapy (gemcitabine) with MALP-2 treatment caused further prolonged survival (median survival 27 days with chemotherapy alone v 37 days for combined treatment; p<0.0002). The life prolonging effect was paralleled by a significant increase in cytotoxic T cells, restoration of beta2 integrin expression on lymphocytes, and high expression of CD45RB on T helper cells. Immunohistochemical stains showed strong cytotoxic T lymphocyte and natural killer cell infiltration. CONCLUSIONS: In conclusion, in a model of orthotopic pancreatic cancer in mice, we induced a tumour suppressive effect by treatment with a synthetic lipopeptide. Treatment with MALP-2 could be an option for immunotherapy in pancreatic cancer.

Adenocarcinoma↗
PubMed2003

Spontaneous hemarthrosis of the knee associated with clopidogrel and aspirin treatment.

We report a case of a 76-year-old-man who developed spontaneous hemarthrosis of his right knee following clopidogrel-aspirin treatment. Clopidogrel is an ADP receptor antagonist and in combination with aspirin widely used in patients with atherosclerotic vascular disease to reduce the incidence of ischemic events. To date, no case of spontaneous hemarthrosis following clopidogrel-aspirin therapy has been reported. Prompt aspiration after discontinuing the ADP receptor antagonist-aspirin combination therapy can assist early diagnosis and may prevent further damage to the joint. In conclusion, spontaneous hemarthrosis is a possible complication following clopidogrel-aspirin therapy and is recommended to be evaluated when appropriate clinical symptoms (e.g., intraarticular effusion) present.

Aged↗
PubMed2003

CSE1L/CAS: its role in proliferation and apoptosis.

CAS/CSE1L is the human homologue of the yeast gene CSE1. It was first cloned while searching for genes that rendered breast cancer cells resistant towards toxin induced apoptosis. Since depletion of CSE1 leads to cell-cycle arrest, CAS is thought to be involved in proliferation. CAS functions in the mitotic spindle checkpoint. CAS is located on chromosome 20q13, a locus often amplified in cancers of various origin, e.g. colonic or breast cancer. Since genetic instability is a hallmark of cancer, amplification or over expression of the CAS gene might interfere with or override its role in the mitotic spindle checkpoint. CAS is also implicated in the nuclear to cytoplasmic reshuffling of importin alpha, which itself is necessary for the nuclear transport of several proliferation activating proteins, transcription factors, oncogene and tumor suppressor gene products such as p53 and BRCA1. Inhibition of MEK1 mediated phosphorylation has been shown to enhance paclitaxel (Taxol) induced apoptosis in breast, ovarian, and lung tumor cell lines in-vitro. Since CAS is also phosphorylated (activated) by MEK1, and since the anti-cancer drug Taxol alters the microtubule assembly and activates pro-apoptotic signaling pathways, altering the activity/phosphorylation status of CAS via MEK1 inhibition may present a potential strategy in experimental cancer therapy.

Active Transport, Cell Nucleus↗
PubMed2003

Urothelial mesh--a new technique of cell culture on biomaterials.

INTRODUCTION: Urogenital malformations, trauma or tumours may demand surgical reconstruction in children. Cell culture is an important technology in biomaterial research and tissue engineering. Tissue-engineering of urothelial organs is of interest in children, because the number of complications and re-operations may be reduced. Actually, monolayer cultures of urothelium are used for tissue engineering and biocompatibility testing. A culture system that more closely mimics the physiologic environment of the urothelium would be of interest. The aim of this study was to determine the biological and mechanical characteristics of urothelial mesh cultured in vitro. METHODS: Meshes containing urothelium, lamina propria, and submucosal tissue were generated using a skin mesh graft cutter. Meshes were cultured in 6-well plates, on collagen I/III, polydioxanone/polylactic acid and silicone matrices. Cell morphology was examined by inversion microscopy, histology, and scanning electron microscopy. It was compared to urothelium cultured by methods reported in the literature. To define the basic mechanical properties, meshes were extended longitudinally by a servohydraulic testing machine and strain diagrams generated. RESULTS: Urothelium was reproducibly cultured from meshes. Cell growth could be induced onto fibrillary collagen, polydioxanone-polylactic acid matrices and shaped polyurethane surfaces. Cells formed confluent layers of flat cells, resembling native urothelium. The meshes have unique mechanical properties, allowing for stable fixation, surgical handling and mechanical stimulation. CONCLUSIONS: Meshes can be used for cell culture on biomaterials. They maintain epithelial-stromal integrity and mechanic stability. The small size of tissue bridges allows in vitro culture for long periods with many potential advantages for tissue engineering and biologic research. Applications are possible both in vitro and in vivo.

Biocompatible Materials↗
PubMed2003

Pyridinoline cross-links as markers for primary and secondary bone tumors.

BACKGROUND: Determination of hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) in urine is a promising method to determine bone resorption. This method is independent of gender, diet and kidney function (creatinine clearance > 25 mL/min). METHODS: The diagnostic efficacy of HP and LP was assessed in the urine of adult patients suffering from primary malignant bone tumors (n = 24), bone metastases (n = 38) and soft tissue sarcoma with additional osseous involvement (n = 13). The values were compared with those obtained from 543 healthy controls (aged 15 to 65 years). RESULTS: Results clearly exhibited a highly significant increase in HP values (57.75 nmol/mmol creatinine) in adult tumor patients (aged 15 to 65 years) in all three subgroups in comparison with the control group values (22.23 nmol/mmol creatinine) (p = 0.001). Although the LP fraction is more specific for bone than HP, the values of LP from all subgroups of the adult tumor patients were less distinctly but still significantly increased (p = 0.008). Regarding the HP:LP ratio, tumor patients exhibited a markedly increased average molar HP:LP ratio (12.0:1) in comparison to controls (6.6:1). CONCLUSION: Determination of HP and LP in urine appears to offer clinical utility for the detection of primary and secondary bone neoplasms. Prospective, longitudinal studies will be necessary to evaluate whether the HP:LP ratio is indicative of a relapse of the tumor and consecutively may be adopted in the follow-up of patients with neoplasms.

Adolescent↗
PubMed2002

Bone substitutes as carriers for transforming growth factor-beta(1) (TGF-beta(1)).

We studied the suitability of three different hydroxyapatite materials (Endobone, Bio-Oss and Algipore) as carriers for the bone growth promoting factor TGF-beta(1). The hydroxyapatite materials either were incubated for 24 h or directly loaded with hrTGF-beta(1) (Diagnostic Products Corporation, DPC) at a concentration of 10 ng hrTGF-beta(1)/mg. For the release experiment the hydroxyapatite materials covered with hrTGF-beta(1) were either suspended in pure phosphate buffered saline (PBS) or human serum albumin (HSA). The concentration of hrTGF-beta(1) was measured every 6 h the first day and then daily at the 2nd, 7th, 14th and 28th day. With Bio-Oss and Endobone the release of growth factor in HSA showed a two-phase kinetics. TGF-beta(1) reached a maximum concentration within the first 24 h and decreased almost linearly until day 28. With Algipore the concentration of growth factor reached a maximum after 12 h and showed a rapid decline until day 2. From day 2 the TGF-beta(1) concentrations remained low. Significantly, more TGF-beta(1) was released into HSA than into PBS. Our study suggests that the hydroxyapatite materials are suitable as TGF-beta(1) carriers.

Biocompatible Materials↗
PubMed2002

A cell-seeded biocomposite for cartilage repair.

Chondrocytes in monolayer cultures lose their phenotype and capability to express type-II collagen, they dedifferentiate into a fibroblastic cell type. Using three-dimensional culture systems a redifferentiation of these cells may occur. In the present study we investigated the morphology and biosynthetic activity of human articular chondrocytes seeded on porous matrices of type I/III collagen (Chondrogide, Geistlich Biomaterials, Wolhusen, Switzerland). Microscopical examinations showed that chondrocytes adhere firmly to a collagen-I/III-membrane exhibiting their characteristic spherical cell shape. Cell numbers after enzymatic digestion of the membrane showed a 93% recovery of seeded cells. Immunohistological examination revealed positive staining for type-II collagen in some areas. The generated biocomposite withstands mechanical stress, keeps its size and design and does not shrink in culture. It is therefore easy to handle, can be sutured, glued or fixed with pins. This study shows, that in vitro production of autologous cartilage-like tissue could be established using a bilayer collagen type I/III fleece. This biocomposite carries active chondrocytes and is currently being evaluated in vivo in a sheep model as well as in a clinical trial for the repair of localized cartilage defects in the knee.

Arthroplasty, Replacement, Hip↗
PubMed2002

[Characteristic mechanical properties of balloon-expandable peripheral stent systems].

PURPOSE: To measure in vitro geometric-mechanical characteristics of balloon-expandable peripheral stent systems for determining suitability for specific vascular regions. MATERIALS AND METHODS: Balloon-expandable stents including their delivery systems manufactured by Guidant (OTW Megalink trade mark ), Inflow Dynamics (Antares), Medtronic (AVE Bridge trade mark ), Biotronik (Peiron trade mark ) and Cordis (Corinthian IQ trade mark ) were selected for this study. When expanded, all stents had a nominal diameter of 8 mm. The length was 38 - 40 mm. Stent profile, trackability, length change on expansion, stiffness, elastic recoil, and radio-opacity in the crimped and expanded state of these stent systems were determined with specially developed test methods. RESULTS: The Corinthian IQ trade mark, Megalink trade mark and Peiron trade mark required the smallest force to pass through the vascular model. While the Bridge trade mark system had the largest profile with a diameter of 2.430 mm, all other stent systems had a significantly smaller diameter ranging from 1.970 mm for the Peiron trade mark to 2.078 mm for the Corinthian IQ trade mark. In the distal region of the stent delivery system, the Megalink trade mark was the most flexible and the Bridge trade mark system the stiffest. Elastic recoil for all stents was in the range of 2.5 % to 3.5 %, with the exception of the Bridge trade mark stent, which had an elastic recoil of 4.79 %. The Corinthian IQ trade mark stent had noticeably the highest radial stiffness. In the expanded condition, the Peiron trade mark was the most flexible while the Corinthian IQ trade mark and the Antares trade mark were found to be the stiffest. Length change (shrinkage on expansion) ranged from 0.54 to 6.57%, with the exception of the Corinthian IQ, which shrunk > 7mm (18.5%) on expansion. All stent systems in the crimped and expanded state were readily visible radiographically. CONCLUSION: Specific data of significant parameters are available to aid in the selection of balloon expandable stents systems to be deployed in complex vascular regions. All examined stent systems showed adequate mechanical properties, but clinically relevant differences were found in stent trackability, bending stiffness and shrinkage on expansion.

Angioplasty, Balloon↗
PubMed2002

Trackability, crossability, and pushability of coronary stent systems--an experimental approach.

Trackability, crossability and pushability are essential properties determining the handling characteristics and deliverability of stent systems. We present objective test methods to assess these parameters quantitatively in an in vitro model. The model consisted of a 6F guiding catheter, a guide wire (0.014") and a coronary vessel model (HD-PE tubing, I.D. 2.5 mm), all immersed in 37 degrees C water. Two attached sensors measured the reactive forces occurring at the proximal catheter shaft and the distal catheter and stent segments during model passage. For crossability assessment, the setup was completed by a stenosis model, mimicking two types of eccentric circular stenoses. A comparative study provided distinctive differences in trackability, stenosis crossability, and pushability. Analyzing the proximal and distal force measurements, these differences were quantified and the qualification of a particular stent system to be successfully delivered to a model target stenosis could be rated.

Angioplasty, Balloon, Coronary↗
PubMed2001

Cationic host-guest polymerization of N-vinylcarbazole and vinyl ethers in MCM-41, MCM-48, and nanoporous glasses.

The synthesis of poly(vinyl ether)s or polyvinylcarbazole under the conditions of constricted geometry can be achieved by means of cationic host-guest polymerisation of the corresponding monomers in the pores of MCM-41 (pore diameter 3.6 nm), MCM-48 (pore diameter 2.4 nm) and in nanoporous glasses (Gelsil with a pore diameter of 5 nm) with bis(4-methoxyphenyl)methyl chloride (BMCC) or triphenylmethyl chloride as the internal surface initiator. The reaction products are new polymer/ MCM-41, polymer/MCM-48 etc., host-guest hybrid materials. The molecular mass of the enclosed polymer and the degree of loading of the host compounds can be adjusted within certain limits. The molecular dynamics were investigated by using broad-band dielectric spectroscopy. Under the conditions of constricted geometry, molecular fluctuation is observed as well as a secondary beta-relaxation, which is hardly affected (in comparison with the free melt) and which corresponds to the relaxation between structural substates (dynamic glass transition). This process is several orders of magnitude faster in its relaxation rate than in the free melt and thus follows a confinement effect. This is already well known in lower molecular weight systems with constricted geometry.

Journal Article↗
PubMed2001

The Ets-1 transcription factor is up-regulated together with MMP 1 and MMP 9 in the stroma of pre-invasive breast cancer.

The first steps of stroma generation are of pivotal importance for carcinogenesis because at this stage are initiated both angiogenesis, the prerequisite for continuous tumour growth, and the proliferation of stromal fibroblasts. These developments contribute to the onset of tumour invasion by secreting several matrix-degrading proteases. Both angiogenesis and the production of proteases are tightly controlled at several levels; of significant importance is transcription. The Ets-1 transcription factor transactivates several genes encoding matrix-degrading proteases and is thought to be involved in both tumour vascularization and invasion. This study therefore investigated, by in situ hybridization and immunohistochemistry, the expression of Ets-1 and of two of its target genes, encoding matrix metalloproteinase (MMP) 1 and MMP 9, in order to demonstrate a topographical in vivo correlation between the expression of these three genes during breast cancer formation. All three genes were first expressed within both endothelial cells and stromal fibroblasts during the onset of stroma generation around intraductal and intralobular in situ carcinomas and they were significantly up-regulated in the stroma of invasive ductal and lobular cancers. The results of this study further support the suggested in vivo role of Ets-1 for both angiogenesis and tumour invasion, via matrix-degrading proteases which are already expressed during the early stages of breast carcinogenesis.

Breast Neoplasms↗
PubMed2001

Effects of hyaluronic acid on the morphology and proliferation of human chondrocytes in primary cell culture.

Hyaline articular cartilage is a specialised connective tissue with weight bearing and adsorbing functions. Injury or loss of which often leads to impaired joint function and severe pain. Since the self-renewing abilities of hyaline articular cartilage are limited, there is major interest in the development of bioengineered cartilaginous implants. A cell-matrix-biocomposite composed of a collagen I/III scaffold seeded with autologous chondrocytes is currently being used in clinical trials; however, in order to optimise culture conditions, we cultured human condrocytes and seeded them on type I/III collagen membranes and on Thermanox plastic coverslips with media containing 0 to 500 microg/ml Hyaluronic Acid. After 4 days, the cells were either fixed or BrdU incorporation procedures begun. HE staining clearly demonstrated that cells grown in HA form three dimensional clusters and produce secretory vesicles as opposed to the monolayer control cells with noticeably fewer secretory vesicles. BrdU incorporation revealed a noticeable increase in cell proliferation in cells grown in 100 microg/ml; however, no comparable increase in 500 micorg/ml but rather a slight depression in proliferation. Immunohistochemistry for collagen II and aggrecan revealed an obvious increase in deposition of these two substances with increased HA administration as compared to the control; however, again, the higher concentration of HA, 500 microg/ml, did not result in a further increase in production. These results suggest that HA at 100 microg/ml not only influences chondrocytes to differentiate and produce more Collagen II and aggrecan, but also increases proliferation. We, therefore, propose that the addition of HA at low to middle dosages in condrocyte culturing might help improve condrocyte redifferentation and thus, the bioengineered cartilage.

Cartilage, Articular↗