Chemoarchitecture of glial fibrillary acidic protein (GFAP) and glutamine synthetase in the rat optic nerve: An immunohistochemical study

Abstract

Summary: An immunohistochemical analysis of the chemoarchitecture of glial fibrillary acidic protein (GFAP) and glutamine synthetase (GS) was conducted in the rat optic nerve. The optic nerve has been divided into 3 regions: the intraretinal, unmyelinated, and myelinated regions. However, it currently remains unclear whether the chemoarchitecture of GFAP and GS is homogeneously organized, especially in the myelinated region. The intraretinal region was divided into intraretinal regions 1 (i1) and 2 (i2). GFAP immunoreactivity was very strong in the i2 and unmyelinated regions, and strong in the i1 region. GS immunoreactivity was moderate in the i1 and i2 regions, and weak in the unmyelinated region. The myelinated region was separated into myelinated regions 1 (m1) and 2 (m2). In the m1 region, GFAP immunoreactivity was strong and GS immunoreactivity was moderate; however, GFAP immunoreactivity was moderate and GS immunoreactivity was weak in the m2 region. Thus, the chemoarchitecture was heterogeneously organized in the myelinated region, with the i1, i2 and m1 regions being the main GS distribution sites. Moreover, most GS-immunoreactive glial cells were oligodendrocytes in the myelinated region. Since GS is a key enzyme in glutamate metabolism, these results may facilitate future investigations for a clearer understanding of glutamate metabolism.

Caracterización de los oligodendrocitos en la vía visual del pez cebra en desarrollo y en procesos regenerativos

“…When we characterized the oligodendrocyte population in the visual system, we found, like in previous works (Parrilla, 2010), that they expressed the typical astrocytic marker GS. The expression of GS in oligodendrocytes has been largely described, also in the ON (Domercq et al, 1999;Jennings y Carroll, 2010;Kawano, 2015;Parrilla, 2010), as well as the arrange in rows and groups (Ankerhold y Stuermer, 1999;Parrilla, 2010;Parrilla et al, 2016). Our results, in addition to our glul gene expression analyses, show that GS may be implied in the ON regeneration.…”

“…La presencia de la GS en los oligodendrocitos ha sido ampliamente descrita en mamíferos, tanto en estudios in vitro (Baas et al, 1998;Fressinaud et al, 1991) como en secciones de tejido (Anlauf y Derouiche, 2013;Bernstein et al, 2014;D'Amelio et al, 1990;Miyake y Kitamura, 1992;Rai et al, 2013;Tansey et al, 1991), incluso en el NO de mamíferos (Domercq et al, 1999;Jennings et al, 2002;Kawano, 2015). También ha sido descrita su expresión en las células de Schwann en el SNP (Miller et al, 2002;Saitoh y Araki, 2010), donde la expresión y degradación proteasomal de la GS determinan su diferenciación (Saitoh y Araki, 2010).…”

“…Sin embargo, a pesar de los numerosos estudios que existen sobre los oligodendrocitos en el sistema visual de peces adultos (Ankerhold y Stuermer, 1999;Münzel et al, 2012Münzel et al, , 2014Nona, 1995;Nona et al, 1992Nona et al, , 2000Parrilla et al, 2016;Pinzon-Olejua et al, 2017;Schweitzer et al, 2003), no encontramos ninguno que se haya centrado en la caracterización inmunohistoquímica completa y rigurosa de los oligodendrocitos de la CNO, una estructura que nuestro grupo de investigación ha demostrado que es clave en los procesos de regeneración del sistema visual (Lillo et al, 1998Parrilla, 2010). Por otra parte, disponemos de numerosos estudios que muestran la expresión de la GS en los oligodendrocitos de mamíferos (Anlauf y Derouiche, 2013;Baas et al, 1998;Bernstein et al, 2014;Domercq et al, 1999;Fressinaud et al, 1991;Jennings et al, 2002;Kawano, 2015) o en las células de Schwann (Miller et al, 2002; Saitoh y Araki, 2010), donde incluso la expresión de la GS determina la diferenciación de estas células (Saitoh y Araki, 2010). A pesar de esto, no existen estudios publicados sobre peces en los que se demuestre su presencia en los oligodendrocitos, aunque en trabajos previos en nuestro laboratorio ya habíamos evidenciado la presencia de la GS en el NO del carpín (Parrilla et al, 2009).…”

“…The expression of GS in oligodendrocytes has been largely reported, not only in cultured cells but also in the mammalian ON (Anlauf y Derouiche, 2013;Baas et al, 1998;Bernstein et al, 2014;D'Amelio et al, 1990;Domercq et al, 1999;Fressinaud et al, 1991;Jennings et al, 2002;Kawano, 2015;Miyake y Kitamura, 1992;Rai et al, 2013;Tansey et al, 1991). In the PNS, it is expressed in Schwann cells, and its degradation regulates their differentiation (Saitoh y Araki, 2010).…”

Retinal and optic nerve degeneration in liver X receptor β knockout mice

“…GS catalyzes the condensation of glutamate and ammonia to form glutamine (39). GS immunoreactivity in oligodendrocytes has been previously demonstrated in the optic nerve and optic chiasm (40,41). GS is involved in the function of oligodendrocytes in rat brain, optic nerve, and retina (42).…”