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Macrophage-Induced Blood Vessels Guide Schwann Cell-Mediated Regeneration of Peripheral Nerves.

Cattin AL, Burden JJ, Van Emmenis L, Mackenzie FE, Hoving JJ, Garcia Calavia N, Guo Y, McLaughlin M, Rosenberg LH, Quereda V, Jamecna D, Napoli I, Parrinello S, Enver T, Ruhrberg C, Lloyd AC - Cell (2015)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: MRC Laboratory for Molecular Cell Biology, UCL, Gower Street, London WC1E 6BT, UK.

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Blood Vessels Permeate the Bridge prior to SC Migration(A) Graph shows the proportion of macrophages (Iba1+), fibroblasts (prolylhydroxylase+/ Iba1−), ECs (RECA-1+), and neutrophils (lipocallin-2+) within the bridge of transected rat sciatic nerves and in contralateral intact nerves (Uncut), Day 2, and Day 3 after transection (n = 4, graph shows mean value ± SEM).(B) Rat sciatic nerve longitudinal sections immunostained for ECs (RECA-1+, red) and SCs (S100+, green), Day 2 and Day 3 after transection. Nuclei were counterstained with Hoechst (blue). Scale bar, 100 μm.(C and D) Quantification of the vascularization of the bridge as shown in (B). (C) Graph shows the percentage of RECA-1 positive area at the indicated times (n = 6). (D) Graph shows the average number of blood vessels/mm2 of bridge at the indicated times (n = 6). Graphs show mean value ± SEM.(E) Longitudinal section of a mouse sciatic nerve immunostained for ECs (CD31+, red) and SCs (S100+, green), Day 5 after transection. Scale bar, 100 μm. For reconstruction of longitudinal sections shown in (B) and (E), multiple images from the same sample were acquired using the same microscope settings.See also Figure S1.
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fig1: Blood Vessels Permeate the Bridge prior to SC Migration(A) Graph shows the proportion of macrophages (Iba1+), fibroblasts (prolylhydroxylase+/ Iba1−), ECs (RECA-1+), and neutrophils (lipocallin-2+) within the bridge of transected rat sciatic nerves and in contralateral intact nerves (Uncut), Day 2, and Day 3 after transection (n = 4, graph shows mean value ± SEM).(B) Rat sciatic nerve longitudinal sections immunostained for ECs (RECA-1+, red) and SCs (S100+, green), Day 2 and Day 3 after transection. Nuclei were counterstained with Hoechst (blue). Scale bar, 100 μm.(C and D) Quantification of the vascularization of the bridge as shown in (B). (C) Graph shows the percentage of RECA-1 positive area at the indicated times (n = 6). (D) Graph shows the average number of blood vessels/mm2 of bridge at the indicated times (n = 6). Graphs show mean value ± SEM.(E) Longitudinal section of a mouse sciatic nerve immunostained for ECs (CD31+, red) and SCs (S100+, green), Day 5 after transection. Scale bar, 100 μm. For reconstruction of longitudinal sections shown in (B) and (E), multiple images from the same sample were acquired using the same microscope settings.See also Figure S1.

Mentions: In order to determine the mechanism by which SC cords are directed across the bridge, we first determined the cell composition of the bridge, prior to SC migration. In the vast majority of rats (>95%), a bridge between the distal and proximal nerve stumps was formed 2 days following transection (day 2). In agreement with previous observations (Avellino et al., 1995; Jurecka et al., 1975), we found that the bridge was mostly composed of macrophages (50%) and neutrophils (24%) with fibroblasts (13%) and endothelial cells (ECs) (5%) as minor components (Figures 1A and S1A). At day 3, however, we noted a significant increase in the number of ECs indicating that the bridge may have become vascularized (Figure 1A). Consistent with this, vascularization could be observed macroscopically (Figure S1B) and confocal analysis of the entire bridge region confirmed this to be the case; at day 2, the bridge contained very few blood vessels whereas by day 3, there was a dramatic influx of blood vessels, which permeated the entire bridge (Figure 1B, quantified in Figures 1C and 1D). Analysis of nerves in which the vascularization was at a slightly earlier stage showed that the blood vessels appeared to emanate from both proximal and distal stumps (Figure S1C) but importantly, the nerve was fully vascularized by the time the SC cords entered into the bridge from either stump (Figures 1B and S1D). In mice, the regeneration process is similar but takes place more slowly, but as observed in rats, we found that the bridge was fully vascularized prior to SC migration into the bridge (Figures 1E and S1D). Thus in both rats and mice, ECs cross the bridge prior to the migration of the SC cords.


Macrophage-Induced Blood Vessels Guide Schwann Cell-Mediated Regeneration of Peripheral Nerves.

Cattin AL, Burden JJ, Van Emmenis L, Mackenzie FE, Hoving JJ, Garcia Calavia N, Guo Y, McLaughlin M, Rosenberg LH, Quereda V, Jamecna D, Napoli I, Parrinello S, Enver T, Ruhrberg C, Lloyd AC - Cell (2015)

Blood Vessels Permeate the Bridge prior to SC Migration(A) Graph shows the proportion of macrophages (Iba1+), fibroblasts (prolylhydroxylase+/ Iba1−), ECs (RECA-1+), and neutrophils (lipocallin-2+) within the bridge of transected rat sciatic nerves and in contralateral intact nerves (Uncut), Day 2, and Day 3 after transection (n = 4, graph shows mean value ± SEM).(B) Rat sciatic nerve longitudinal sections immunostained for ECs (RECA-1+, red) and SCs (S100+, green), Day 2 and Day 3 after transection. Nuclei were counterstained with Hoechst (blue). Scale bar, 100 μm.(C and D) Quantification of the vascularization of the bridge as shown in (B). (C) Graph shows the percentage of RECA-1 positive area at the indicated times (n = 6). (D) Graph shows the average number of blood vessels/mm2 of bridge at the indicated times (n = 6). Graphs show mean value ± SEM.(E) Longitudinal section of a mouse sciatic nerve immunostained for ECs (CD31+, red) and SCs (S100+, green), Day 5 after transection. Scale bar, 100 μm. For reconstruction of longitudinal sections shown in (B) and (E), multiple images from the same sample were acquired using the same microscope settings.See also Figure S1.
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Related In: Results  -  Collection

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fig1: Blood Vessels Permeate the Bridge prior to SC Migration(A) Graph shows the proportion of macrophages (Iba1+), fibroblasts (prolylhydroxylase+/ Iba1−), ECs (RECA-1+), and neutrophils (lipocallin-2+) within the bridge of transected rat sciatic nerves and in contralateral intact nerves (Uncut), Day 2, and Day 3 after transection (n = 4, graph shows mean value ± SEM).(B) Rat sciatic nerve longitudinal sections immunostained for ECs (RECA-1+, red) and SCs (S100+, green), Day 2 and Day 3 after transection. Nuclei were counterstained with Hoechst (blue). Scale bar, 100 μm.(C and D) Quantification of the vascularization of the bridge as shown in (B). (C) Graph shows the percentage of RECA-1 positive area at the indicated times (n = 6). (D) Graph shows the average number of blood vessels/mm2 of bridge at the indicated times (n = 6). Graphs show mean value ± SEM.(E) Longitudinal section of a mouse sciatic nerve immunostained for ECs (CD31+, red) and SCs (S100+, green), Day 5 after transection. Scale bar, 100 μm. For reconstruction of longitudinal sections shown in (B) and (E), multiple images from the same sample were acquired using the same microscope settings.See also Figure S1.
Mentions: In order to determine the mechanism by which SC cords are directed across the bridge, we first determined the cell composition of the bridge, prior to SC migration. In the vast majority of rats (>95%), a bridge between the distal and proximal nerve stumps was formed 2 days following transection (day 2). In agreement with previous observations (Avellino et al., 1995; Jurecka et al., 1975), we found that the bridge was mostly composed of macrophages (50%) and neutrophils (24%) with fibroblasts (13%) and endothelial cells (ECs) (5%) as minor components (Figures 1A and S1A). At day 3, however, we noted a significant increase in the number of ECs indicating that the bridge may have become vascularized (Figure 1A). Consistent with this, vascularization could be observed macroscopically (Figure S1B) and confocal analysis of the entire bridge region confirmed this to be the case; at day 2, the bridge contained very few blood vessels whereas by day 3, there was a dramatic influx of blood vessels, which permeated the entire bridge (Figure 1B, quantified in Figures 1C and 1D). Analysis of nerves in which the vascularization was at a slightly earlier stage showed that the blood vessels appeared to emanate from both proximal and distal stumps (Figure S1C) but importantly, the nerve was fully vascularized by the time the SC cords entered into the bridge from either stump (Figures 1B and S1D). In mice, the regeneration process is similar but takes place more slowly, but as observed in rats, we found that the bridge was fully vascularized prior to SC migration into the bridge (Figures 1E and S1D). Thus in both rats and mice, ECs cross the bridge prior to the migration of the SC cords.

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: MRC Laboratory for Molecular Cell Biology, UCL, Gower Street, London WC1E 6BT, UK.

Show MeSH
Related in: MedlinePlus