SKIN DERIVED SCHWANN CELL TRANSPLANT AND IL6 NEUTRALIZATION FOLLOWING NERVE INJURY

Schwann cells (SCs), the glial cells of the peripheral nervous system, are highly plastic and are thought to be the key players in successful regeneration following nerve injury. Recently, the use of SC therapy, including therapies using SCs derived from skin (SKPSCs), has shown much potential for improving clinical outcomes after nerve injury. One of the primary mechanisms by which SKPSCs appear to enhance recovery is via the secretion of factors (ie. cytokine) known to play vital roles in regulating inflammation following injury. In particular, interleukin-6 (IL6), a pleiotropic cytokine upregulated after nerve injury, is thought to play an important role in the macrophage recruitment and phenotype regulation important for successful regeneration. Still, others have demonstrated that IL6 can play deletrious roles in the nerve as well. The dichotomous nature of IL6 in the nerve is highly context specific, highly complex and yet to be fully understood. Since we have recently identified IL6 as being expressed by SKPSCs at levels 20x higher than most other cytokines, and this cytokine is notorious for being a potent regulator of the immune system, here, we set out to determine the complex role of IL6 following SKPSCs transplant in the injured nerve. To answer this question, we administered IL6 neutralizing antiody or an IgG control during the first week following sciatic nerve crush injury and immediate SKPSC tranplant. We found that SKPSC tranplants alone increased macrophage densities in the distal stump, however this effect remained unaffected by anti-IL6 or IgG treatment. We also tested for difference in functional recovery due to our treaments and found that peak CMAP amplitudes were greatest when SKPSCs therapy was augmented with anti-IL6 treatment, compared to control treatments. Our results suggest that IL6 ultimately has a comprimising effect on SKPSCs therapy, but this effect is not due to early regulation of macrophage densities

Implantable photonic neural probes for light-sheet fluorescence brain imaging

Significance: Light-sheet fluorescence microscopy is a powerful technique for high-speed volumetric functional imaging. However, in typical light-sheet microscopes, the illumination and collection optics impose significant constraints upon the imaging of non-transparent brain tissues. Here, we demonstrate that these constraints can be surmounted using a new class of implantable photonic neural probes. Aim: Mass manufacturable, silicon-based light-sheet photonic neural probes can generate planar patterned illumination at arbitrary depths in brain tissues without any additional micro-optic components. Approach: We develop implantable photonic neural probes that generate light sheets in tissue. The probes were fabricated in a photonics foundry on 200 mm diameter silicon wafers. The light sheets were characterized in fluorescein and in free space. The probe-enabled imaging approach was tested in fixed and in vitro mouse brain tissues. Imaging tests were also performed using fluorescent beads suspended in agarose. Results: The probes had 5 to 10 addressable sheets and average sheet thicknesses < 16 μm for propagation distances up to 300 μm in free space. Imaging areas were as large as ≈ 240 μm x 490 μm in brain tissue. Image contrast was enhanced relative to epifluorescence microscopy. Conclusions: The neural probes can lead to new variants of light-sheet fluorescence microscopy for deep brain imaging and experiments in freely-moving animals

Implantable photonic neural probes for light-sheet fluorescence brain imaging

Significance: Light-sheet fluorescence microscopy (LSFM) is a powerful technique for highspeed volumetric functional imaging. However, in typical light-sheet microscopes, the illumination and collection optics impose significant constraints upon the imaging of non-transparent brain tissues. We demonstrate that these constraints can be surmounted using a new class of implantable photonic neural probes. Aim: Mass manufacturable, silicon-based light-sheet photonic neural probes can generate planar patterned illumination at arbitrary depths in brain tissues without any additional micro-optic components. Approach: We develop implantable photonic neural probes that generate light sheets in tissue. The probes were fabricated in a photonics foundry on 200-mm-diameter silicon wafers. The light sheets were characterized in fluorescein and in free space. The probe-enabled imaging approach was tested in fixed, in vitro, and in vivo mouse brain tissues. Imaging tests were also performed using fluorescent beads suspended in agarose. Results: The probes had 5 to 10 addressable sheets and average sheet thicknesses <16 μm for propagation distances up to 300 μm in free space. Imaging areas were as large as ≈240 μm × 490 μm in brain tissue. Image contrast was enhanced relative to epifluorescence microscopy. Conclusions: The neural probes can lead to new variants of LSFM for deep brain imaging and experiments in freely moving animals