Inhibitory effect of hyaluronidase-4 in a rat spinal cord hemisection model

Objective: In this study, the effects of anti-hyaluronidase-4 (Hyal-4) antibody on the histological changes of Hyal-4 and the corresponding chondroitin sulfate proteoglycan (CSPG) expression in the rat spinal cord hemisection model were examined. Methods: After creating a rat spinal cord hemisection injury, experiments were conducted by administering anti-Hyal-4 antibody or control immunoglobulin G by intraspinal injection as a single dose, or intrathecal administration, using osmotic pumps, as multiple doses. Frozen sections of the injured spinal cord were made after a single-dose administration on days 1 and 4 and 1 week or at 1, 2, 3, and 4 weeks after the start of pump-aided injections. Immunofluorescence studies were then conducted using CS56 for CSPGs and anti-glial fibrillary acidic protein antibody for reactive astrocytes. Results: No difference was observed between the test and control groups in the single-dose administration of the antibody. In pump-aided administration, CSPGs in the control group decreased at 4 weeks, but those in the anti-Hyal-4 antibody administered group did not. Conclusion: Persistent suppression of Hyal-4 allowed CSPGs to remain and also increase in the rat spinal cord hemisection model, confirming Hyal-4 as an endogenous digestive enzyme of CSPGs.