Self-assembling nano material for brain-lesion repair and functional return of vision: in vivo experiments on developing and adult brain

Abstract

A tissue gap caused by deep transections of the optic tract (OT) in the midbrain can completely block the re-innervation of the superior colliculus (SC) by the retina, even when done at young ages when the axons have regenerative potential. We find that a self-assembling nano material (SANM) nanofiber scaffold can facilitate the reconstruction of a tissue substrate that supports regeneration across the tissue disruption. Brain wounds were inflicted in anesthetized postnatal P2 and adult Syrian hamsters. Animals with early lesions survived 4, 6, 8, and 10 weeks. At surgery, animals were treated by injection, into the brain wound, of 10 ul of 1% SANM. Control animals with the same lesion included 3 with isotonic saline injection (10 ul), and 27 earlier cases with knife cuts and no injection, surviving 6-9 days. Histological results revealed that only in the animals treated with SANM, the tissue appears to have reconnected across the lesion at all survival times (c2=34.8, df (1), p<<0.001). In a group of adult animals (8 wk) the optic tract was transected at the brachium of the superior colliculus. When 100 µl of SANM was injected into the OT lesion the tissue reconnected in all cases. For controls we injected 100 µl of saline. Axons grew across the lesion site in the SANM treated cases. In behavioral studies the adult hamsters show a functional return of vision in the SANM treated cases beginning at 6 weeks post surgery. The tissue bridges supported partial re-innervation of the caudal SC by the severed retinofugal axons. Thus, the SANM is shown to offer a new means of ameliorating the tissue disruptions caused by traumatic injury to the CNS, allowing regrowth of axons that have regenerative potential.