RESUMO
After traumatic injury, adult central nervous system (CNS) axons fail to regenerate. We have previously shown that one major impediment for axon regeneration is the basement membrane (BM) forming at the lesion center, by means of a wound healing collagenous scar, after lesioning the postcommisural fornix of the adult rat [Eur. J. Neurosci. 11 (1999) 632] [6]. This BM consists of a supramolecular network of collagen type IV, laminin (LN), nidogen, and associated proteoglycans [Crit. Rev. Biochem. Mol. Biol. 27 (1992) 93] [5]. Following axotomy, axons of the proximal stump of the transected postcommissural fornix fail to cross the lesion site. This regenerative failure is spatially and temporally highly correlated with the appearance of BM in the lesion site [Restor. Neurol. Neurosci. 15 (1999) 1] [7]. However, if the deposition of BM is prevented, the injured axons: (i) regenerate in their former pathway, (ii) are conductive across and behind the lesion site, and (iii) form chemical synapses in their target area, the mammillary body [Eur. J. Neurosci. 11 (1999) 632]. The developing BM is surrounded by neuropil and can easily be stained immunohistochemically using anti-collagen IV antibodies on fresh frozen sections (10 microm). To examine a clinically more relevant model of traumatic CNS injuries we developed a transection model of the thoracic dorsal corticospinal tract (CST) in the rat spinal cord. In contrast to fornix lesion this transection is performed in close proximity to the meninges. This involves the BM being completely washed out if fresh frozen tissue is used on slides. If the animals are sacrificed by perfusion with aldehydes the collagen IV and the LN antigen are masked by the fixative. To restore the correct immunohistochemical staining pattern (BM, blood vessels) a special protocol including an enzyme digestion is necessary. If thick sections are stained free floating, the tissue is destroyed due to the enzyme treatment. Here we present a method to prevent loss of the lesion-induced BM and to perform the correct immunohistochemical stainings of BM proteins in the traumatically injured spinal cord.
