Design of a migration assay for human gingival fibroblasts on biodegradable magnesium surfaces

A novel regenerative approach to Guided Bone Regeneration (GBR) in dental surgery is based on the development of biodegradable and volume stable barrier membranes made of metallic magnesium. Currently used volume stable barrier membranes are made of titanium-reinforced PTFE or titanium-reinforced collagen membranes, both, however, are accompanied by a high incidence of wound dehiscence resulting in membrane exposure, which leads to an increased infection risk. An exposed membrane could also occur directly after insertion due to insufficient soft tissue coverage of the membrane. In both cases, fast wound margin regeneration is required. As a first step of soft-tissue regeneration, gingival fibroblasts need to migrate over the barrier membrane and close the dehiscent wound. Based on this aim, this study investigated the migration behaviour of human gingival fibroblasts on a magnesium surface. Major experimental challenges such as formation of hydrogen bubbles due to initial magnesium corrosion and non-transparent material surfaces have been addressed to allow cell adhesion and to follow cell migration. The designed scratch-based cell migration assay involved vital fluorescent cell staining on a pre-corroded magnesium membrane to simulate invivo wound dehiscence. The assay has been used to compare cell migration on pre-corroded magnesium to titanium surfaces and tissue culture plastic as control substrates. First results of this assay showed that human gingival fibroblasts migrate slower on pre-corroded magnesium compared to plastic and titanium. However, the scratch was finally closed on all materials. Compared to titanium surfaces and tissue culture plastic, the surface roughness and the surface free energy (SFE) could not explain slower cell migration on magnesium surfaces. Immunohistological investigations of cellular structure revealed, that magnesium ions increased focal adhesion at concentration of additionally 75 mM MgCl₂ in cell culture medium. The use of our designed cell migration assay has shown that ionic medium alterations due to magnesium corrosion has a higher impact on the cell migration rate than surface alterations.

The design of a migration assay on non-transparent magnesium surfaces will add the option to study cell response to surface modifications, coatings and the corrosion process itself under life view conditions.