Biomedical subjects

Norbert M Meenen

Publications and source records attributed to Norbert M Meenen.

5 recordsLinked to original sources

PubMed2005

Cultivation of three-dimensional cartilage-carrier-constructs under reduced oxygen tension.

Three-dimensional cartilage-carrier-constructs were produced according to a standard protocol from chondrocytes of an adult mini-pig. Experiments with different oxygen concentrations (21, 10 and 5%, v/v O(2)) were performed and the constructs were compared qualitatively and quantitatively. The appearance of the cartilage obtained under reduced oxygen tension seemed to be closer to native cartilage with respect to shape of the cells, distribution of the cells within the matrix, smoothness of the surface, etc. The thickness of the cartilage formed by free swelling was always in the same range as for native cartilage (approximately 1mm). Qualitatively the most stable attachment of the cartilage on top of the carrier was found for 10% O(2) (v/v). Especially at 5% O(2) (v/v) the attachment between cartilage and carrier was not sufficient. The constructs generated at lower oxygen tensions had a significantly higher amount of glycosaminoglycan per DNA, but still significantly less when compared to native cartilage. Furthermore, the cultivated cartilage contained a large amount of collagen type II. The experiments proved the applied concept for generation of cartilage-carrier-constructs and the usefulness of cultivation under reduced oxygen tension.

Animals↗

PubMed2005

Bioreactor cultivation of three-dimensional cartilage-carrier-constructs.

A flow-chamber bioreactor was designed for generation of three-dimensional cartilage-carrier-constructs. A specific attribute of the flow-chamber is a very thin medium layer for improved oxygen supply and a counter current flow of medium and gas. Three-dimensional cartilage-carrier-constructs were produced according to a standard protocol from chondrocytes of an adult mini-pig. The final step of this protocol was performed either in the bioreactor or in 12-well plates. The bioreactor experiments showed a significantly higher matrix thickness but a lower ratio of glycosaminoglycan to DNA. For both culture methods the constructs contained a high amount of collagen II. Appearance of the cartilage obtained in the bioreactor seemed to be closer to native cartilage with respect to distribution of the cells within the matrix, smoothness of the surface etc. All results considered the flow-chamber bioreactor is a very useful tool for generation of three dimensional cartilage-carrier constructs.

Bioreactors↗

PubMed2005

Bioreactor design for tissue engineering.

Bioreactor systems play an important role in tissue engineering, as they enable reproducible and controlled changes in specific environmental factors. They can provide technical means to perform controlled studies aimed at understanding specific biological, chemical or physical effects. Furthermore, bioreactors allow for a safe and reproducible production of tissue constructs. For later clinical applications, the bioreactor system should be an advantageous method in terms of low contamination risk, ease of handling and scalability. To date the goals and expectations of bioreactor development have been fulfilled only to some extent, as bioreactor design in tissue engineering is very complex and still at an early stage of development. In this review we summarize important aspects for bioreactor design and provide an overview on existing concepts. The generation of three dimensional cartilage-carrier constructs is described to demonstrate how the properties of engineered tissues can be improved significantly by combining biological and engineering knowledge. In the future, a very intimate collaboration between engineers and biologists will lead to an increased fundamental understanding of complex issues that can have an impact on tissue formation in bioreactors.

Animals↗

PubMed2002

RGD-peptides for tissue engineering of articular cartilage.

One keypoint in the development of a biohybrid implant for articular cartilage defects is the specific binding of cartilage cells to a supporting structure. Mimicking the physiological adhesion process of chondrocytes to the extracellular matrix is expected to improve cell adhesion of in vitro cultured chondrocytes. Our approach involves coating of synthetic scaffolds with tailor-made, cyclic RGD-peptides, which bind to specific integrin receptors on the cell surface. In this study we investigated the expression pattern of integrins on the cell surface of chondrocytes and their capability to specifically bind to RGD-peptide coated materials in the course of monolayer cultivation. Human chondrocytes expressed integrins during a cultivation period of 20 weeks. Receptors proved to be functionally active as human and pig chondrocytes attached to RGD-coated surfaces. A competition assay with soluble RGD-peptide revealed binding specificity to the RGD-entity. Chondrocyte morphology changed with increasing amounts of cyclic RGD-peptides on the surface.

Amino Acid Sequence↗

PubMed2001

Surgery of skeletal metastases.

During a period of 5 years, 74 female and 27 male patients with an average age of 63.3 years underwent a total of 117 operations for the management of impending ( n=41) or already existing ( n=76) pathologic fractures due to osseous metastases. The average stay in hospital was 17.8 days, and the average postoperative survival 15.8 months. The patients whose limbs were stabilized as a preventive measure were discharged 1.5 days earlier and survived surgery 5.9 months longer than the patients with pathologic fractures. The large percentage of female patients is due to the predominant role of mammary cancer (50%) and the comparatively long survival of patients after a primary diagnosis of this type of carcinoma. The other diagnoses involved were (in order of frequency): bronchial carcinoma (11%), hypernephroma (8%) and non-Hodgkin's lymphoma (8%). The metastases were mainly located at the proximal end or shaft of the femur (59.8%) and in the humerus (18.8%) so that in the majority of cases it was possible to implant weight-bearing prostheses or at least achieve enough stability to allow non-weight-bearing physiotherapy and thus early remobilization. The rate of systemic complications (excluding fatalities) was 14.5%. Local complications in the operated area occurred in 24.8% of cases. As a result, revision surgery was necessary in 10 cases (8.5%), and the fatality rate in hospital (6 weeks) was 7.9%. In view of the advanced stage of the disease in most of the patients, some of them with polypathia, we see these results as a basis for the generous indication for preventive stabilization of osseous metastases. Except in some cases, the primary intention of this therapy is not to cure the disease or prolong life but to improve the quality of life remaining for these patients while keeping their stay in hospital as short as possible and the rate of complications at an acceptable level.

Adult↗