DIFFERENZIAMENTO E CREAZIONE DI UN MICROAMBIENTE RIGENERATIVO NELLA LESIONE MIDOLLARE DA PARTE DEI PRECURSORI NEURALI POST MORTEM (PM-NPCS). ANALISI DI TIPO BIOCHIMICO, MORFOLOGICO, ED IN VIVO ATTRAVERSO LA RISONANZA MAGENTICA ED IL RECUPERO FUNZIONALE DEGLI ARTI POSTERIORI

Traumatic injuries in central nervous system lead to severe and permanent neurological deficit. Particularly, traumatic spinal cord injury often results in a devastating loss of neurological function below the injury site. Since the loss of CNS neurons may not be replaced by the proliferation of the surviving ones, intraspinal transplantation of exogenous neuronal cells or tissue has been accepted for a long time as a way to obtain a partial reconstruction of the lost cord tissue and to promote recovery of neurological function. Cell-based therapies in the injured spinal cord are intended to fill lesion cavities, which typically develop at an injury site, and to provide a cellular growth-conducive substrate for re-growing axons. Various cell types such as fibroblasts, olfactory ensheathing cells, Schwann cells and neural stem ⁄precursor cells have been used to regenerate or replace injured spinal cord parenchyma, and to elicit axonal regen- eration which is the primary goal of regenerative medicine and one of the prime motivations for the study of stem cells (NCSs). Unfortunately when NSCs are administrated in a spinal cord injury model they modulate the inflammatory response but do not differentiate into mature cells and are quickly engulfed by macrophages present at lesion site. Recently we isolated a new class of neural stem cell from the subventricular zone of mice forebrain named Post-Mortem Neural Precursor Cells (PM-NPCs), that are capable of surviving after a prolonged ischemic insult. PM-NPCs for their potentiality in terms of proliferation and differentiation capabilities, are a good tool for tissue replacement therapies. In this study we focused on transplantation of PM-NPCs in a murine model of spinal cord injury by endovenous injection within 2 hours after injury. After administration, cells migrate specifically to the site of injury, as demonstrated both by ex-vivo immunoistochemistry and in-vivo MRI after PM-NPCs labelling with Superparamagnetic Iron Oxide Particles (SPIOs). Interestingly, these cells survive in such an unfavorable enviroment wich is the injury site and differentiate predominantly into cholinergic neurons, reconstituting a rich axonal and dendritic network and promoting a marked axonal regeneration across the injury site of monoaminergic fibers within 30 days from their administration. Fluororuby injection in the dorsal funiculi rostral to the lesion site shows that some spared and/or regenereting corticospinal (CS) labelled fibres bypass the lesion site and are in the caudal portion of PM-NSCs mice treated spinal cord, where few or none CS labelled fibers are found in saline trated mice. Moreover, beavhioral assesment evaluated by means of Basso Mouse Scale (BMS), shows a significantly improve of hind limb function in PM-NPCs treated mice compared with animals treated with placebo. Eventually, the molecular analysis of the lesion site shows that PM-NPCs induce a remodulation of inflammatory response through the reduction of astrocytes activation and glial scar formation, and the reduction of immunitary cells infiltration (neutrophils and macrophages) leading to a better tissue preservation. Moreover, the expression of proinflammatory cytokines and release of neurotrophic factors are reguated by PM-NPCs treatement: some proinflammatory cytokines (IL-6, MIP-2 and TNF alpha) levels significantly decrease after 48 hours from spinal cord injury and PM-NPCs transplantation, while after 7 days we observe an increase of IL-6 and TNF alpha probably because at longer time those cytokines are necessary to support the regenerative process according to the literature. These data suggest that PM-NPCs may represent a good source for cellular therapy in neurodegenerative disorders, specially on spinal cord injury.