Macrophage-Induced Blood Vessels Guide Schwann Cell-Mediated Regeneration of Peripheral Nerves.
Here we show that blood vessels direct the migrating cords of Schwann cells.Importantly, disrupting the organization of the newly formed blood vessels in vivo, either by inhibiting the angiogenic signal or by re-orienting them, compromises Schwann cell directionality resulting in defective nerve repair.This study provides important insights into how the choreography of multiple cell-types is required for the regeneration of an adult tissue.
Affiliation: MRC Laboratory for Molecular Cell Biology, UCL, Gower Street, London WC1E 6BT, UK.
- Blood Vessels/metabolism*
- Peripheral Nerves/physiology*
- Schwann Cells/metabolism*
- Cell Hypoxia
- Endothelial Cells/metabolism
- Neovascularization, Physiologic
- Rats, Sprague-Dawley
- Vascular Endothelial Growth Factor A/genetics
© Copyright Policy
- CC BY
fig3: Migrating SCs Interact with the Vasculature of the Bridge(A) Representative confocal image of a longitudinal section of a rat sciatic nerve bridge, Day 3 after transection, immunostained to detect axons (neurofilament (NF), red), SCs (S100+, green), and ECs (RECA-1+, blue) and shows cords of SCs and associated regrowing axons interacting with the vasculature as they emerge from the proximal stump and enter the bridge. Scale bar, 50 μm.(B) Rat sciatic nerve longitudinal sections immunostained to detect SCs (S100+, green) and ECs (RECA-1+, red), Day 4 after transection. Scale bar, 100 μm. White rectangle indicates the region used to build the 3D model shown in (E). For reconstruction of longitudinal sections shown in (A) and (B), multiple images from the same sample were acquired using the same microscope settings.(C) Frequency distribution graph showing the distance of the nuclei of SCs (S100+), non SCs (S100-/RECA-), or macrophages (Iba1+) to the closest blood vessel, Day 4 after transection (n = 4, graph shows mean value ± SEM).(D) 3D-projection of a rat nerve bridge showing a S100-positive SC (green) interacting with a newly formed EdU-positive (red) blood vessel (RECA-1+, white). Scale bar, 20 μm. See also Movie S1.(E) Snapshots of a 3D-image obtained by the surface rendering of a z-stack projection of confocal images of the rat nerve bridge, immunostained to detect SCs (S100+, green) and ECs (RECA-1+, red). A SC can be seen to interact with two different blood vessels through cytoplasmic protrusions. Scale bar, 20 μm. Arrowheads indicate points of contact between a SC and blood vessels.(F) Representative confocal image of a longitudinal section of a sciatic nerve bridge from PLP-EGFP mice, Day 5 after transection, immunostained to detect ECs (CD31+, red). Scale bar, 50 μm.(G) Snapshots from Movie S2 showing blebs and protrusions mediating the contacts between SCs and ECs within the bridge.(H) Snapshots from Movie S1 of a 3D model obtained by surface rendering of a z stack projection of a longitudinal section of a bridge region from the sciatic nerve of PLP-EGFP mice, Day 5 after transection. The sections were immunostained to detect ECs (CD-31+, blue) and axons (NF+, red). Scale bar, 20 μm.See also Figure S3.
Confocal microscopy analysis of the SCs entering into the bridge demonstrated a close association of the migrating SC cords and the polarized blood vessels (Figure 3A). Moreover, at later time points when the SCs had migrated further into the bridge, these interactions were maintained (Figure 3B). Analysis of matrix components of the bridge showed that fibronectin filled the space between the cells throughout the bridge and that strands of elastin also permeated the bridge region. In contrast, laminin and collagen I and IV could be detected only around the blood vessels (Figure S3A). To quantify the degree and specificity of the interactions between the SCs and the blood vessels, we measured the shortest distance between the nuclei of SCs at the leading edge and their closest blood vessel and compared it to the distance of other cell types present in the bridge. We found that the majority of SCs were extremely close (<10 μm) to blood vessels with the population showing a strong distribution toward the blood vessels, whereas the other cell types had a more random distribution within the bridge (Figure 3C). Moreover, the degree of interaction between SCs and blood vessels was probably underestimated, as we frequently observed SCs interacting with blood vessels via long protrusions while the nuclei were further away.