Protective effect of low molecular weight polyethylene glycol on the repair of experimentally damaged neural membranes in rat’s spinal cord

Abstract

Objectives: Membrane disruption is one of the main factors that cause axonal damage and functional deficits manifested in spinal cord injury (SCI). In this study, we used polyethylene glycol (PEG) to induce immediate membrane sealing and to promote functional recovery after SCI.Methods: The effects of PEG (200–2000 Da) on the damaged membrane were monitored by means of spinal cord evoked potentials (SCEPs) in an SCI model in rats. In a parallel study, membranes of neural cells were mechanically damaged in culture by ultrasound waves (20 kHz) and the repairing effects of PEGs were examined afterwards at the single cell level.Results: Analysis of SCEPs showed that the smaller the PEG, the higher was the ultimate recovery of SCEP (i.e. 200 Da caused 49·5% and 2000 Da up to 16·3%). The rate of recovery was maximum with a polynomial trend, when the damaged spinal cord was treated with PEG200 for 25 minutes.The analysis of survival rate of mechanically damaged cells in culture, measured by MTT assay, showed that again smaller PEGs, caused higher membrane sealing rate; 77·8±3·5 for PEG400 (20% w/w) vs 32·1±6·9 for PEG2000 (20% w/w). The large ones (PEG1000 and 2000) that presented minor repair at low concentration, showed no significant sealing effects at high concentrations (>50%).Conclusion: Our studies showed that the application of low molecular weight PEGs, (<50% w/w) can be considered as one of the effective early treatments for SCI.