We previously reported that nidogen is an extracellular matrix protein regulating Schwann cell proliferation and migration. Since Schwann cells play a critical role in peripheral nerve regeneration, nidogen may play a role in it via regulation of Schwann cells. Here, we demonstrate direct evidence that nidogen induces elongation of regenerative axon growth of adult sensory neurons, and that the effect is Schwann cell dependent. Continuous infusion of recombinant ectodomain of tumor endothelial marker 7, which specifically blocks nidogen function in Schwann cells, suppressed regenerative neurite growth in a sciatic nerve axotomy model. Taken together, it is likely that nidogen is required for proper regeneration of peripheral nerves after injury.
Animals ; Axotomy ; Cell Movement ; Cell Proliferation ; Male ; Membrane Glycoproteins/*physiology ; Membrane Proteins/pharmacology ; *Nerve Regeneration ; Nerve Tissue Proteins/pharmacology ; Neurites/drug effects/*physiology/ultrastructure ; Rats ; Rats, Sprague-Dawley ; Recombinant Proteins/pharmacology ; Schwann Cells/cytology/*physiology ; Sensory Receptor Cells/*physiology

OBJECTIVETo study the effects of androgen on the expression of phosphacan and NG2 proteoglycan (NG2) and neurite regeneration in neonatal rats with hypoxic-ischemic brain damage (HIBD) and the potential mechanism underlying the protective effect of androgen against HIBD.

METHODSOne hundred and twenty neonatal Sprague-Dawley rats were randomly divided into three groups: sham-operated, HIBD and androgen treatment. HIBD was induced by the ligation of left common carotid artery and hypoxia exposure. The androgen treatment group rats were injected with testosterone propionate (25 mg/kg) immediately after HIBD. Phosphacan and NG2 expression in the cortex and the hippocampus was detected with the immunohistochemical method 24 and 72 hrs and 7 and 10 days after hypoxia-ischemia (HI). The ultrastructure and neurite regeneration of neurons in the cortex and the hippocampus were observed under a transmission electron microscope.

RESULTSThe neurite regeneration was obvious in the sham-operated group, but seldom in the HIBD group. The androgen treatment group showed increased neurite regeneration compared with the HIBD group. There were fewer phosphacan and NG2 positive cells in the cortex and the hippocampus in the sham-operated group. Phosphacan and NG2 expression in the cortex and the hippocampus was observed at 24 hrs, increased at 72 hrs, and peaked at 7 days after HI in the HIBD group and remained at a higher expression 10 days after HI than in the sham-operated group. The levels of phosphacan and NG2 expression in the cortex and the hippocampus in the androgen treatment group were significantly reduced compared with those in the HIBD group 24 and 72 hrs and 7 and 10 days after HI (P<0.01).

CONCLUSIONSPhosphacan and NG2 may be important inhibitory factors for neurite regeneration following HIBD in neonatal rats. The neuroprotection of androgen against neonatal HIBD is produced possibly through an inhibition of phosphacan and NG2 expression.

Animals ; Animals, Newborn ; Antigens ; analysis ; Brain Chemistry ; drug effects ; Female ; Hypoxia-Ischemia, Brain ; physiopathology ; Immunohistochemistry ; Male ; Microscopy, Electron, Transmission ; Nerve Regeneration ; drug effects ; Neurites ; physiology ; ultrastructure ; Proteoglycans ; analysis ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Receptor-Like Protein Tyrosine Phosphatases, Class 5 ; analysis ; Testosterone Propionate ; pharmacology