Fluororuby as a marker for detection of acute axonal injury in rat spinal cord

• Published in: Brain research 2001-10, Vol.915 (1), p.118-123
• Main Authors: Lu, Jike, Ashwell, Ken W.S, Hayek, Ray, Waite, Phil
• Format: Article
• Language: English
• Subjects: Acute Disease; Animals; Axonal injury; Axonal Transport - drug effects; Axonal Transport - physiology; Axons - drug effects; Axons - pathology; Biological and medical sciences; Biomarkers; Degeneration; Development. Senescence. Regeneration. Transplantation; Dextrans; Female; Fluorescent Dyes; Fluororuby; Fundamental and applied biological sciences. Psychology; Marker; Molecular Probes; Rats; Rats, Sprague-Dawley; Rhodamines; Spinal cord; Spinal Cord - drug effects; Spinal Cord - pathology; Spinal Cord - physiopathology; Spinal Cord Injuries - pathology; Spinal Cord Injuries - physiopathology; Time Factors; Tracer; Vertebrates: nervous system and sense organs; Wallerian Degeneration - pathology; Wallerian Degeneration - physiopathology
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/S0006-8993(01)02940-7

Axonal damage is a common pathological consequence of spinal cord injury. Previous studies have detected axonal injury with silver stains for degeneration or immunohistochemistry for alterations in components such as β-amyloid precursor protein, neurofilament or ubiquitin. Fluororuby has recently been introduced as a neuronal tracer in studies of spinal cord injury and regeneration. Our study was carried out to determine whether Fluororuby can be used to identify injured axons and monitor the time course of axonal damage. Adult rats underwent needle puncture injury to the white matter in the midline and lateral spinal cord at T11. At the same time, 0.05 μl of Fluororuby was injected into the cord at the same sites. After survival times ranging from 6 h to 3 weeks, spinal cords were cut into longitudinal frozen sections and examined with confocal microscopy. Fluororuby was found to label key features of axonal injury including axonal swelling, retraction balls and disrupted axons. Damaged axons close to the injury site were consistently labeled within 6 h, with indications of swollen and disconnected axons spreading further from the site during the first week. Fewer injured axons were labeled after 1 week survival, but the marker revealed longer distances of degenerating axons both distal and rostral to the injury site. Our findings indicate that Fluororuby is a quick, sensitive, reliable and technically simple fluorescent marker for early stages of acute axonal injury and degeneration.