Glial cell types, lineages, and response to injury in rat and fish: Implications for regeneration

Abstract

Axons of the mammalian central nervous system do not regenerate spontaneously after axonal injury, unlike the central nervous system axons of fish and amphibians and the peripheral nervous system of mammals, which possess a good regenerative ability (Grafstein: The Retina: A Model for Cell Biology Studies, Part II, 1986; Kiernan: Biol Rev 54:155-197, 1979; Murray: J Comp Neurol 168:175-196, 1976; Ramón y Cajal: Degeneration and Regeneration of the Nervous System, 1928; Reier and Webster: J Neurocytol 3:591-618, 1974; Sperry: Physiol Zool 23:351-361, 1948). It was previously believed that intrinsic differences between the central nervous system neurons of mammals and fish account for their differences in regenerative ability. The past decade, however, has seen an accumulation of evidence, indicating that mammalian central nervous system neurons are able to regenerate injured axons, at least to some extent. This was first demonstrated by Aguayo and colleagues (David and Aguayo: Science 214:931-933, 1981; Kierstead et al: Science 246:255-257, 1989), who showed that injured mammalian central nervous system axons can grow for a considerable distance into an autograft of a peripheral nerve. It was also demonstrated that injured rabbit optic axons can regenerate into their own environment (i.e., into the distal part of the injured optic nerve), if the injured nerve is treated so as to make it conducive for growth (Lavie et al: J Comp Neurol 298:293-314, 1990; Eitan et al: Science 264:1764-1768, 1994).(ABSTRACT TRUNCATED AT 250 WORDS)

Involvement of wound-associated factors in rat brain astrocyte migratory response to axonal injury: in vitro simulation.

“…Axons of the central nervous system (CNS) 1 of mammals do not normally regenerate after injury, unlike those of phylogenetically lower vertebrate, such as fish and amphibians, or the peripheral nerves of mammals (for reviews see [1][2][3]. Because injured mammalian CNS axons can, under certain conditions, grow for considerable distances (for reviews see [1][2][3], it is generally believed today that the ability or inability of nerves to regenerate their injured axons depends on the cellular milieu surrounding the axons and its response to axonal injury.…”

“…Because injured mammalian CNS axons can, under certain conditions, grow for considerable distances (for reviews see [1][2][3], it is generally believed today that the ability or inability of nerves to regenerate their injured axons depends on the cellular milieu surrounding the axons and its response to axonal injury.…”

“…Several studies have demonstrated the involvement of regeneration-related cross-talk between the immune and the nervous system. This cross-talk is apparently deficient in the CNS due to impairment of macrophage invasion (4; for reviews see [1][2][3]. This impairment has been recently shown to be due to a CNS-resident macrophage inhibitory factor (5).…”

“…Astrocytes have been viewed as the cells which, following injury, form a scar that either acts as a mechanical barrier for growth or as a barrier due to a deficiency in growth supportive elements and/or presence of growth inhibitory elements (for reviews see [1][2][3].…”

Les molécules qui dirigent la migration des astrocytes

“…L'orientation et la migration des astrocytes, qui contribuent à déterminer la position de la cicatrice gliale, jouent donc un rôle essentiel dans les capacités de récupé-ration du système nerveux après une lésion accidentelle ou pathologique. Chez les mammifères, contrairement aux vertébrés inférieurs, la migration des astrocytes est très limitée, ce qui pourrait expliquer les capacités de régéné-ration relativement restreintes de leur système nerveux [4]. Les réponses astrocytaires semblent être réglées par des facteurs de croissance et des cytokines inflammatoires qui sont libérés par les cellules lésées (astrocytes, neurones …), par les cellules microgliales ou par les leucocytes infiltrés.…”