Tissue engineering of composite grafts: Cocultivation of human oral keratinocytes and human osteoblast-like cells on laminin-coated polycarbonate membranes and equine collagen membranes under different culture conditions

An Overview of the Use of Equine Collagen as Emerging Material for Biomedical Applications

Type I collagen has always aroused great interest in the field of life-science and bioengineering, thanks to its favorable structural properties and bioactivity. For this reason, in the last five decades it has been widely studied and employed as biomaterial for the manufacture of implantable medical devices. Commonly used sources of collagen are represented by bovine and swine but their applications are limited because of the zoonosis transmission risks, the immune response and the religious constrains. Thus, type-I collagen isolated from horse tendon has recently gained increasing interest as an attractive alternative, so that, although bovine and porcine derived collagens still remain the most common ones, more and more companies started to bring to market a various range of equine collagen-based products. In this context, this work aims to overview the properties of equine collagen making it particularly appealing in medicine, cosmetics and pharmaceuticals, as well as its main biomedical applications and the currently approved equine collagen-based medical devices, focusing on experimental studies and clinical trials of the last 15 years. To the best of our knowledge, this is the first review focusing on the use of equine collagen, as well as on equine collagen-based marketed products for healthcare.

Bridging the gap between traditional cell cultures and bioreactors applied in regenerative medicine: practical experiences with the MINUSHEET perfusion culture system

To meet specific requirements of developing tissues urgently needed in tissue engineering, biomaterial research and drug toxicity testing, a versatile perfusion culture system was developed. First an individual biomaterial is selected and then mounted in a MINUSHEET(®) tissue carrier. After sterilization the assembly is transferred by fine forceps to a 24 well culture plate for seeding cells or mounting tissue on it. To support spatial (3D) development a carrier can be placed in various types of perfusion culture containers. In the basic version a constant flow of culture medium provides contained tissue with always fresh nutrition and respiratory gas. For example, epithelia can be transferred to a gradient container, where they are exposed to different fluids at the luminal and basal side. To observe development of tissue under the microscope, in a different type of container a transparent lid and base are integrated. Finally, stem/progenitor cells are incubated in a container filled by an artificial interstitium to support spatial development. In the past years the described system was applied in numerous own and external investigations. To present an actual overview of resulting experimental data, the present paper was written.

Supportive development of functional tissues for biomedical research using the MINUSHEET® perfusion system

Functional tissues generated under in vitro conditions are urgently needed in biomedical research. However, the engineering of tissues is rather difficult, since their development is influenced by numerous parameters. In consequence, a versatile culture system was developed to respond the unmet needs.

Optimal adhesion for cells in this system is reached by the selection of individual biomaterials. To protect cells during handling and culture, the biomaterial is mounted onto a MINUSHEET® tissue carrier. While adherence of cells takes place in the static environment of a 24 well culture plate, generation of tissues is accomplished in one of several available perfusion culture containers. In the basic version a continuous flow of always fresh culture medium is provided to the developing tissue. In a gradient perfusion culture container epithelia are exposed to different fluids at the luminal and basal sides. Another special container with a transparent lid and base enables microscopic visualization of ongoing tissue development. A further container exhibits a flexible silicone lid to apply force onto the developing tissue thereby mimicking mechanical load that is required for developing connective and muscular tissue. Finally, stem/progenitor cells are kept at the interface of an artificial polyester interstitium within a perfusion culture container offering for example an optimal environment for the spatial development of renal tubules.

The system presented here was evaluated by various research groups. As a result a variety of publications including most interesting applications were published. In the present paper these data were reviewed and analyzed. All of the results point out that the cell biological profile of engineered tissues can be strongly improved, when the introduced perfusion culture technique is applied in combination with specific biomaterials supporting primary adhesion of cells.

Air-liquid interface cultures enhance the oxygen supply and trigger the structural and functional differentiation of intestinal porcine epithelial cells (IPEC)

The specific function of the epithelium as critical barrier between the intestinal lumen and the organism’s internal microenvironment is reflected by permanent maintenance of intercellular junctions and cellular polarity. The intestinal epithelial cells are responsible for absorption of nutritional components, facing mechanical stress and a changing oxygen supplementation via blood stream. Oxygen itself can regulate the barrier and the absorptive function of the epithelium. Therefore, we compared the dish cell culture, the transwell-like membrane culture and the oxygen enriched air–liquid interface (ALI) culture. We demonstrated strong influence of the different culture conditions on morphology and function of intestinal porcine epithelial cell lines in vitro. ALI culture resulted in a significant increase in cell number, epithelial cell layer thickness and expression as well as apical localisation of the microvilli-associated protein villin. Remarkable similarities regarding the morphological parameters were observed between ALI cultures and intestinal epithelial cells in vivo. Furthermore, the functional analysis of protein uptake and degradation by the epithelial cells demonstrated the necessity of sufficient oxygen supply as achieved in ALI cultures. Our study is the first report providing marked evidence that optimised oxygen supply using ALI cultures directly affects the morphological differentiation and functional properties of intestinal epithelial cells in vitro.