Abstract
The fascinating prospect to direct tissue regeneration by magnetic activation has been recently explored. In this study we investigate the possibility to boost bone regeneration in an experimental defect in rabbit femoral condyle by combining static magnetic fields and magnetic biomaterials. NdFeB permanent magnets are implanted close to biomimetic collagen/hydroxyapatite resorbable scaffolds magnetized according to two different protocols . Permanent magnet only or non-magnetic scaffolds are used as controls. Bone tissue regeneration is evaluated at 12weeks from surgery from a histological, histomorphometric and biomechanical point of view. The reorganization of the magnetized collagen fibers under the effect of the static magnetic field generated by the permanent magnet produces a highly-peculiar bone pattern, with highly-interconnected trabeculae orthogonally oriented with respect to the magnetic field lines. In contrast, only partial defect healing is achieved within the control groups. We ascribe the peculiar bone regeneration to the transfer of micro-environmental information, mediated by collagen fibrils magnetized by magnetic nanoparticles, under the effect of the static magnetic field. These results open new perspectives on the possibility to improve implant fixation and control the morphology and maturity of regenerated bone providing "in site" forces by synergically combining static magnetic fields and biomaterials.
Highlights
Throughout life bone is continuously subjected to a range of mechanical forces that influence both its external geometry and internal architecture.[1]
The reorganization of the magnetized collagen fibers under the effect of the static magnetic field generated by the permanent magnet produces a highly-peculiar bone pattern, with highlyinterconnected trabeculae orthogonally oriented with respect to the magnetic field lines
Mechanical forces, transmitted to the cytoskeleton by membrane receptors such as integrins, are envisaged to activate a number of intracellular signaling pathways including changes in intracellular calcium levels and MAP kinase activity that replicate the effect of mechanical loading and regulate osteocyte and osteoblast function eventually leading to the development and normal function of bone tissue.[22,23,24,25,26,27,28]
Summary
Throughout life bone is continuously subjected to a range of mechanical forces that influence both its external geometry and internal architecture.[1]. Mechanical forces, transmitted to the cytoskeleton by membrane receptors such as integrins, are envisaged to activate a number of intracellular signaling pathways including changes in intracellular calcium levels and MAP kinase activity that replicate the effect of mechanical loading and regulate osteocyte and osteoblast function eventually leading to the development and normal function of bone tissue.[22,23,24,25,26,27,28] Recently we proposed a novel approach to stimulation of bone growth by exploiting the synergic effect of static magnetic fields and magnetized biomimetic materials.[29,30,31] Initial studies demonstrated that a biomimetic and biodegradable scaffold magnetized with magnetic iron oxide nanoparticles implanted in contact with a titanium coated permanent magnet in an experimental bone defect in a rabbit condyle was able to dynamically re-organize its internal structure over a four week follow-up period, strongly influencing newlyformed bone tissue volume.[32]
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