Laminin distribution during corticospinal tract development and after spinal cord injury

The glycoprotein laminin is a prominent constituent of basal laminae and has been suggested to play an important role in axonal growth. We have tested this hypothesis, by examining the temporal and spatial distribution of laminin in the rat spinal cord, relative to elongating corticospinal tract (CST) axons, during normal development and after newborn and adult spinal lesions. The distribution of laminin was demonstrated in spinal cord sections from animals ranging in age from 14 days embryonic to adult using immunocytochemistry. Anti-laminin immunolabeling was seen around blood vessels and meninges in all the animals examined. However, within the grey and white matter its distribution was age-dependent. In the normal cord, immunostaining appeared in small amounts in early embryos, but was absent from all postnatal animals even at ages when the CST was growing down the cord. Following injury, intense immunostaining was associated with lesions in both newborn and adult operates at all postoperative periods examined. Within the matrix of the lesion laminin immunostaining was especially prominent. In the intact cord it was prominent only around blood vessels near the lesion site. Our results indicate that the distribution of laminin does not closely correlate with axonal growth of the CST either during normal development or after spinal injury.