Implanted biomaterials often fail because they elicit a foreign body response (FBR) and concomitant fibrotic encapsulation. To design clinically relevant interference approaches, it is crucial to first examine the FBR mechanisms. Here, we report the development and validation of infrared-excited nonlinear microscopy to resolve the three-dimensional (3D) organization and fate of 3D-electrospun scaffolds implanted deep into the skin of mice, and the following step-wise FBR process. We observed that immigrating myeloid cells (predominantly macrophages of the M1 type) engaged and became immobilized along the scaffold/tissue interface, before forming multinucleated giant cells. Both macrophages and giant cells locally produced vascular endothelial growth factor (VEGF), which initiated and maintained an immature neovessel network, followed by formation of a dense collagen capsule 2–4 weeks post-implantation. Elimination of the macrophage/giant-cell compartment by clodronate and/or neutralization of VEGF by VEGF Trap significantly diminished giant-cell accumulation, neovascularization and fibrosis. Our findings identify macrophages and giant cells as incendiaries of the fibrotic encapsulation of engrafted biomaterials via VEGF release and neovascularization, and therefore as targets for therapy.
Objectives: Cortical demyelination is common in multiple sclerosis (MS) and can be extensive. Cortical lesions contribute to disability independently from white matter lesions and may form via a distinct mechanism. However, current magnetic resonance imaging (MRI) methods at 3 tesla (3T) are insensitive to cortical, and especially subpial cortical, lesions. Subpial lesions are wellseen on T 2 * weighted imaging at 7 tesla (7T), but T 2 * weighted methods on 3T scanners are limited by poor lesion-to-cortex and cerebrospinal fluid (CSF)-to-lesion contrast. We aimed to develop and evaluate a CSF-suppressed, T 2 *-weighted sequence optimized for subpial cortical lesion visualization. Materials and methods:We developed a new MRI sequence, Inversion Recovery Susceptibility Weighted Imaging with Enhanced T 2 -Weighting (IR-SWIET, 0.8mm x 0.8mm in plane, 0.64mm slice thickness with whole brain coverage, acquisition time ~5 min). We compared cortical lesion visualization independently on IR-SWIET (median signal from four acquisitions),
Background: Dramatic improvements in visualization of cortical (especially subpial) multiple sclerosis (MS) lesions allow assessment of impact on clinical course. Objective: Characterize cortical lesions by 7 tesla (T) T2*-/T1-weighted magnetic resonance imaging (MRI); determine relationship with other MS pathology and contribution to disability. Methods: Sixty-four adults with MS (45 relapsing–remitting/19 progressive) underwent 3 T brain/spine MRI, 7 T brain MRI, and clinical testing. Results: Cortical lesions were found in 94% (progressive: median 56/range 2–203; relapsing–remitting: 15/0–168; p = 0.004). Lesion distribution across 50 cortical regions was nonuniform ( p = 0.006), with highest lesion burden in supplementary motor cortex and highest prevalence in superior frontal gyrus. Leukocortical and white matter lesion volumes were strongly correlated ( r = 0.58, p < 0.0001), while subpial and white matter lesion volumes were moderately correlated ( r = 0.30, p = 0.002). Leukocortical ( p = 0.02) but not subpial lesions ( p = 0.40) were correlated with paramagnetic rim lesions; both were correlated with spinal cord lesions ( p = 0.01). Cortical lesion volumes (total and subtypes) were correlated with expanded disability status scale, 25-foot timed walk, nine-hole peg test, and symbol digit modality test scores. Conclusion: Cortical lesions are highly prevalent and are associated with disability and progressive disease. Subpial lesion burden is not strongly correlated with white matter lesions, suggesting differences in inflammation and repair mechanisms.
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