Figure 4.

(a) BDA tracing of the corticospinal tract in a scaffold-alone animal. BDA was injected into the sensorimotor cortex contralateral to the spinal cord injury at or beyond 70 days p.i. such that BDA-positive fibers would be visible at the site of, or caudal to, the spinal cord lesion if corticospinal tract fibers were present and passing through the injury site. Arrows indicate where the tracer passes into the lesioned side of the cord. Note the tortuous path of the fibers (arrows; see text). The rostral end is to the right, and the lesion cavity is on the bottom. (b) Positive BDA tracing caudal to the injury in the same cord as in a. (c) GAP-43, a marker for regenerating axons, is positive in the same cord as seen in a and b just rostral to the injury. Likewise, scaffold plus cells cords exhibit BDA tracing with the same tortuousity immediately (d) rostral to as well as (e) caudal to the injury, and (f) a large number of GAP-43-positive axons just rostral to the injury. The cells-alone (g) and lesion-control cords (h) exhibit BDA staining rostral to the injury but not caudal, and there are minimal fibers positive for GAP-43 (i, cells alone; j, lesion control; scale bars in a–b, d–e, and g–h, 10 μm; in c, f, and i–j, 20 μm).