Self-assembled nanomaterial, chondroitinase ABC and CNTF combination treatment provides a permissive environment for optic-tract regeneration in hamster

Abstract

A tissue gap caused by deep transections of the optic tract (OT) in the midbrain can completely block the reinnervation of the superior colliculus (SC) by the retina. We find that a self-assembling peptide (SAP) nanofiber scaffold used in combination with ciliary neurotrophic factor (CNTF) and Chondroitinase ABC (Chon. ABC) can synergistically facilitate the reconstruction of a tissue substrate that supports regeneration across the tissue disruption. Brain wounds were inflicted in anesthetized adult Syrian hamsters. The scalp and skull were opened surgically and the OT at the brachium of the SC was completely severed with a deep knife wound, extending 1-2 mm below the surface from the midline to a point beyond the lateral margin of SC. Three groups of young adult hamsters (8 wk) were prepared. In group one (SAP/CNTF), following the transection of the brachium of SC the animals were treated with 20μl of 1% SAP RAD16-I injected into the site of injury. In group two (Chon.ABC/CNTF), 20 μl of 2.5units/ml Chon.ABC was injected into the lesion site. In group three (SAP/Chon.ABC/CNFT), both SAP and Chon.ABC were injected. These experimental animals received 5 intravitreal injections of 1μg CNTF in 1μl PBS once every five days. Four days prior to sacrifice CTB-FITC was injected intravitreally to anterogradely label the regenerating axons. Histological results revealed that there was no reinnervation of SC 4 weeks after surgery in the SAP/CNTF and Chon.ABC/CNTF groups of animals. However, CTB-FITC was found in the SC of the animals treated with SAP/Chon.ABC/CNTF implying that the regenerated axons had reinnervated the target. In behavioral studies the adult hamsters, after 4 wk post surgery, showed a functional return of vision only in the third group, treated with SAP/Chon.ABC/CNTF. Thus, the SAP/Chon.ABC/CNTF combination treatment is shown to offer an effective new means of creating a permissive environment for axonal growth, allowing regrowth of axons into the SC.