摘要
Implants made of magnesium(Mg)are increasingly employed in patients to achieve osteosynthesis while degrading in situ.Since Mg implants and Mg^(2+)have been suggested to possess anti-inflammatory properties,the clinically observed soft tissue inflammation around Mg implants is enigmatic.Here,using a rat soft tissue model and a 1-28 d observation period,we determined the temporo-spatial cell distribution and behavior in relation to sequential changes of pure Mg implant surface properties and Mg^(2+)release.Compared to nondegradable titanium(Ti)implants,Mg degradation exacerbated initial inflammation.Release of Mg degradation products at the tissue-implant interface,culminating at 3 d,actively initiated chemotaxis and upregulated mRNA and protein immunomodulatory markers,particularly inducible nitric oxide synthase and toll-like receptor-4 up to 6 d,yet without a cytotoxic effect.Increased vascularization was demonstrated morphologically,preceded by high expression of vascular endothelial growth factor.The transition to appropriate tissue repair coincided with implant surface enrichment of Ca and P and reduced peri-implant Mg^(2+)concentration.Mg implants revealed a thinner fibrous encapsulation compared with Ti.The detailed understanding of the relationship between Mg material properties and the spatial and time-resolved cellular processes provides a basis for the interpretation of clinical observations and future tailoring of Mg implants.
