Heparan sulfates that upregulate regeneration of post-traumatic sciatic nerves of adult guinea pigs

Abstract

We reported that supplementation of soluble heparan sulfate (HS) to the fluid regenerative neural environment could restore functional, axonal reconnection of the severed nerve with the target muscle (Eur J Neurosci 11: 1914-26, 1999). The HS supplements used were from guinea-pig sciatic nerve and bovine kidney. Both showed similar efficacy in facilitating resumption of conduction velocity and re-myelination. We then asked if the composition of HS used as supplements differed from those recoverable from post-crush nerve homogenates. Unsaturated disaccharides resulting from digestions of the glycosaminoglycan (GAG) extracts with a mixture of heparitinases I-III were therefore analyzed by anion-exchange HPLC. The HS supplements comprised non-sulfated [ΔHexA-GlcNAc], monosulfated [ΔHexA-GlcNSO3, ΔHexA(2S)-GlcNAc, ΔHexA-GlcNAc(6S)] and disulfated [ΔHexA-GlcNSO3(6S)] forms, among which the non-sulfated form was predominant. Both supernatant and pellet fractions of injured nerves similarly indicated predominance of ΔHexA-GlcNAc but these were far lower in amount than those introduced as supplement. Whereas the pellet fractions of crushed nerves indicated ΔHexA-GlcNSO3(6S) that peaked at 14 days post-injury, no 6-sulfated HS disaccharides were detectable in the supernatant fractions. The results suggest the importance of non-sulfated forms in stabilizing matrix organization and transient enrichment of 6-sulfated forms of HS in fine-tuning the environment for growth factor-mediated cellular processes. Our HS supplements were therefore timely in providing the required S-domains of HS for tissue reorganization and axonal regrowth (Supported by RGC grant HKU7249/97M).