Collagen IV deposits do not prevent regrowing axons from penetrating the lesion site in spinal cord injury

Scarring is suggested to impede axon regrowth across the lesion site in the injured adult mammalian central nervous system. Collagen Type IV, as a major component of the scar formed after injury, is an impediment for successful axonal regeneration and a decrease in its amount is a prerequisite for regrowing axons to cross the lesion in the postcommissural fornix in the injured adult rat (Stichel et al. [1999] Neurosci. 93:321–333). The aim of the present study was to analyze the relationship between collagen IV deposits and regrowing axons at various times after dorsal hemi‐section of the adult rat spinal cord. Immunohistochemical double staining revealed that penetrating neurofilament‐positive axons and collagen IV deposits were co‐localized in the lesion site in the initial stages of axonal sprouting (between 7 and 14 days post‐operatively) and were still present 1 and 2 months post‐operatively. Interestingly, collagen IV‐immunoreactive areas located around cystic cavities formed at the site of injury 1 month post‐operatively, were devoid of axons. In conclusion, our observations indicate that collagen IV deposits after spinal cord injury do not prevent neurofilament‐positive regrowing axons from penetrating the lesion site. J. Neurosci. Res. 62:686–691, 2000. © 2000 Wiley‐Liss, Inc.