Abstract
BackgroundMagnesium alloys as biodegradable implant materials received much interest in recent years. It is known that products of implant degradation can induce several types of immune response. Hence, the aim of this study was to examine the morphological changes of efferent lymph nodes after implantation of different resorbable magnesium alloys (MgCa0.8, LAE442) in comparison to commercially available resorbable (PLA) and non-resorbable (titanium) implant materials as well as control groups without implant material.MethodsThe different implant materials were inserted intramedullary into the rabbit tibia. After postoperative observation periods of three and six months, popliteal lymph nodes were examined histologically and immunhistologically and compared to lymph nodes of sham operated animals and animals without surgery. Haematoxylin and eosin staining was performed for cell differentiation. Mouse anti-CD79α and rat anti-CD3 monoclonal primary antibodies were used for B- and T-lymphocyte detection, mouse anti-CD68 primary antibodies for macrophage detection. Evaluation of all sections was performed applying a semi quantitative score.ResultsThe histological evaluation demonstrated low and moderate levels of morphological changes for both magnesium alloys (LAE442 and MgCa0.8). Higher than moderate values were reached for titanium in sinus histiocytosis and histiocytic apoptosis (3 months) and for PLA in histiocytic apoptosis (3 and 6 months). The immune response to all investigated implants had a non-specific character and predominantly was a foreign-body reaction. LAE442 provoked the lowest changes which might be due to a lower degradation rate in comparison to MgCa0.8. Therewith it is a promising candidate for implants with low immunogenic potential.ConclusionBoth examined magnesium alloys did not cause significantly increased morphological changes in efferent lymph nodes in comparison to the widely used implant materials titanium and PLA. LAE442 induced even lower immunological reactions. Therewith MgCa0.8 and especially LAE442 are appropriate candidates for biomedical use.
Highlights
Magnesium alloys as biodegradable implant materials received much interest in recent years
Both examined magnesium alloys did not cause significantly increased morphological changes in efferent lymph nodes in comparison to the widely used implant materials titanium and PLA
The control groups with surgery but without implant showed the presence of sinus histiocytosis, follicular hyperplasia and heterophilic infiltration with low score values overall and demonstrated decrease of all investigated characteristic values from three to six months
Summary
Magnesium alloys as biodegradable implant materials received much interest in recent years. Even in spite of chemical inertness of metals like titanium, corrosion processes in contact with biological systems (aging of prosthesis) are described [23,24], accompanied by release of ions, which are not sensitizers on their own, but can induce the immune system by generating complexes with native proteins [10,11,12,13,14,25,26,27]. These metal-protein complexes are supposed to be candidate antigens (i.e. allergens) for developing delayed hypersensitivity [11]. DTH based on interactions between antigen-presenting cells, which process and present antigen, and CD4+ T-cells, which initiate this type of immune response by the release of cytokines and by macrophage activation [9]
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