Klaus von der Mark

Bio: Klaus von der Mark is an academic researcher from University of Erlangen-Nuremberg. The author has contributed to research in topics: Cartilage & Collagen, type I, alpha 1. The author has an hindex of 57, co-authored 154 publications receiving 13007 citations. Previous affiliations of Klaus von der Mark include University of Texas Health Science Center at Houston & Max Planck Society.

Nanosize and Vitality: TiO2 Nanotube Diameter Directs Cell Fate

Abstract: We generated, on titanium surfaces, self-assembled layers of vertically oriented TiO2 nanotubes with defined diameters between 15 and 100 nm and show that adhesion, spreading, growth, and differentiation of mesenchymal stem cells are critically dependent on the tube diameter. A spacing less than 30 nm with a maximum at 15 nm provided an effective length scale for accelerated integrin clustering/focal contact formation and strongly enhances cellular activities compared to smooth TiO2 surfaces. Cell adhesion and spreading were severely impaired on nanotube layers with a tube diameter larger than 50 nm, resulting in dramatically reduced cellular activity and a high extent of programmed cell death. Thus, on a TiO2 nanotube surface, a lateral spacing geometry with openings of 30−50 nm represents a critical borderline for cell fate.

Relationship between cell shape and type of collagen synthesised as chondrocytes lose their cartilage phenotype in culture

Abstract: WHEN chondrocytes from sternal or articular cartilage are kept in monolayer culture at low density, they eventually lose their cartilage phenotype1–4. Within four passages or approximately 1 month in culture they change from a polygonal or round to a flattened, amoeboid-like shape5–7, and instead of cartilage collagen (type II collagen8) they synthesise the genetically different type I collagen. It is not known whether there is a strict correlation between the occurrence of cell flattening and the change in collagen synthesis within individual cells. We have reported that preferentially flattened, fibroblast-like cells at the edge of cartilage colonies synthesise type I collagen, whereas round or polygonal chondrocytes generally synthesise type II collagen1–3. The change is nearly complete in a culture at a time when excessive flattening is observed4. Using an immunofluorescence double staining technique9,10, we have now found that there is no strict correlation between cell morphology and type of collagen synthesised.

TiO2 nanotube surfaces: 15 nm--an optimal length scale of surface topography for cell adhesion and differentiation.

Abstract: Studies of biomimetic surfaces in medicine and biomaterial fields have explored extensively how the micrometer-scale topography of a surface controls cell behavior, but only recently has the nanoscale environment received attention as a critical factor for cell behavior. Several investigations of cell interactions have been performed using surface protrusion topographies at the nanoscale; such topographies are typically based on polymer demixing, ordered gold cluster arrays, or islands of adhesive ligands at distinct length scales. Recent work has indicated that the fabrication of ordered TiO2 nanotube layers with controlled diameters can be achieved by anodization of titanium in adequate electrolytes. Such surfaces can almost ideally be used as nanoscale spacing models for size-dependent cellular response. This is particularly important as these studies are carried out on titanium surfaces—a material used for clinical titanium implantations for the purpose of bone, joint, or tooth replacements. Therefore, principles elucidated from this work can guide implant surface modifications toward an optimized surface geometry and profile to best fit and cell interactions for adequate bone growth.

TiO2 nanotubes: synthesis and applications.

Abstract: TiO(2) is one of the most studied compounds in materials science. Owing to some outstanding properties it is used for instance in photocatalysis, dye-sensitized solar cells, and biomedical devices. In 1999, first reports showed the feasibility to grow highly ordered arrays of TiO(2) nanotubes by a simple but optimized electrochemical anodization of a titanium metal sheet. This finding stimulated intense research activities that focused on growth, modification, properties, and applications of these one-dimensional nanostructures. This review attempts to cover all these aspects, including underlying principles and key functional features of TiO(2), in a comprehensive way and also indicates potential future directions of the field.

The adipocyte-secreted protein Acrp30 enhances hepatic insulin action

Abstract: Acrp30 is a circulating protein synthesized in adipose tissue. A single injection in mice of purified recombinant Acrp30 leads to a 2-3-fold elevation in circulating Acrp30 levels, which triggers a transient decrease in basal glucose levels. Similar treatment in ob/ob, NOD (non-obese diabetic) or streptozotocin-treated mice transiently abolishes hyperglycemia. This effect on glucose is not associated with an increase in insulin levels. Moreover, in isolated hepatocytes, Acrp30 increases the ability of sub-physiological levels of insulin to suppress glucose production. We thus propose that Acrp30 is a potent insulin enhancer linking adipose tissue and whole-body glucose metabolism.