Expression of netrin‐1, slit‐1 and slit‐3 but not of slit‐2 after cerebellar and spinal cord lesions

Abstract

To determine whether members of the Netrin-1 and Slit families and their receptors are expressed after central nervous system (CNS) injury, we performed in situ hybridization for netrin-1, slit-1, 2 and 3, and their receptors (dcc, unc5h-1, 2 and 3, robo-1, 2 and 3) 8 days, 2-3 months and 12-18 months after traumatic lesions of rat cerebellum. The expression pattern of these molecules was unchanged in axotomized Purkinje cells, whereas unc5h3 expression was upregulated in deafferented granule cells. Cells expressing slit-2 or dcc were never detected at the lesion site. By contrast, cells expressing netrin-1, slit-1 and slit-3, unc5h-1, 2 and 3, and robo-1, 2 and 3 (rig-1) could be detected at the cerebellar lesion site as soon as 8 days after injury. Expression of unc5h-2, robo-1, robo-2, slit-1 and slit-3 at the lesion site was maintained until 3 months, and up to 12-18 months for unc5h-1 and 3 and robo-3. Likewise, in the mouse spinal cord, netrin-1, slit-1 and slit-3 were also expressed at the lesion site 8 days after injury. Most of the cells expressing these mRNAs were located at the centre of the lesions, suggesting that they are macrophages/activated microglial cells (macrophagic cells) or meningeal fibroblastic cells. The macrophagic nature of most Netrin-1-positive cells and the macrophagic or fibroblastic nature of Robo-1-positive cells were corroborated by double staining. Thus, Netrin-1, Slits and their receptors may contribute to the regenerative failure of axons in the adult CNS by inhibiting axon outgrowth or by participating in the formation of the CNS scar.

An in vitro spinal cord injury model to screen neuroregenerative materials

“…Further, the observed infiltration of microglial cells into lesion sites indicates that acute inflammatory responses can be mimicked within the lesion sites in vitro. Their activation in SCI can be a significant barrier to the development of efficacious interventions as there is evidence implicating them as inhibitors of axonal regeneration via expression of inhibitory guidance molecules such as Netrin-1 and repulsive guidance molecules [60,61]. Microglial attachment to nanofibers provides an in vitro readout 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 for the optimization and testing of biocompatible materials and coatings that evoke minimal inflammatory responses.…”

Molecular/genetic manipulation of extrinsic axon guidance factors for CNS repair and regeneration

“…Axotomy of intramedullary motoneurons results in persistent up-regulation of semaphorin3A mRNA and protein (Lindholm et al 2004) and, after spinal cord lesions, semaphorin4D expression is transiently up-regulated in oligodendrocytes, but not astrocytes, microglia, or oligodendrocytes precursors (Moreau-Fauvarque et al 2003). Furthermore, netrin-1, slit-1, and 3, and their receptors; unc5h-1, 2 and 3, robo-1, 2 and 3, are expressed following injury to the cerebellum and spinal cord (Wehrle et al 2005). Such changes in expression often correlate with a lack of regeneration.…”

Spinal Interneuron Axons Spontaneously Regenerate after Spinal Cord Injury in the Adult Feline

“…Guidance proteins from the midline include netrin-1 (Serafini et al, 1996), slits (Brose et al, 1999;Kidd et al, 1999), and Sonic hedgehog (Shh) (Charron et al, 2003). All of these guidance proteins are upregulated at or near the injury site after SCI (Chen et al, 2005;Wehrle et al, 2005). Together, it is tempting to speculate that lesions restricted to the midline lead to the release of guidance molecules from within the lesion site, thus mimicking the mediolateral distribution of these molecules during development.…”