Meningeal and endothelial cells are associated with wisping axons. (A-D) Axons were labeled with the axon tracer (B, C) or 3A10 (D) and are shown in magenta, von Willeband factor (vWF) is green (A-C) and nuclei are blue. (A) Cross-section through intact spinal cord. (B) Longitudinal section through the SCI of a wisping stage regenerate labeled with anti-FN (white, shown separately in (B')) and anti-vWF (green, shown separately in (B")). Arrowheads, cells double-labeled with FN and vWF. (C) Cross-section through axons wisping into the injury site of a wisping stage regenerate. Schematic longitudinal section of the spinal cord in the upper right corner shows where the section is in relationship to the injury site. (D) Single confocal plane of a longitudinal thick section of a wisping/spiking stage regenerate. Arrowhead, meninges (m). (E-I) Longitudinal section through a wisping stage regenerate imaged with electron microscopy. (E) Region containing axons wisping ahead of the TV. Asterisks, phagocytic cells. (F) Enlargement of meningeal cells in box F of (E). (G) Enlargement of meningeal-like cell in box G of (E) that is associated with dura mater ECM (ecm). Arrowhead, closed loop formed by meningeal-like cell processes; arrow, process resembling dura mater cell process. (H) Enlargement of meningeal-like cell in box H of (E), rotated 90°. This cell's processes (arrowheads) wrap around a bundle of axons (ax) cut in cross-section. (I) Enlargement of box I in (H) showing that this cell's processes (arrowheads) are also associated with ECM (ecm). D, dorsal; V, ventral; R, rostral; C, caudal. Scale bars: 200 μm (A-D); 50 μm (E); 10 μm (F-H); 1 μm (I).