Post‐natal Development of Perineuronal Nets in the Retrosplenial Cortex of Albino Rat

Abstract

The brain extracellular matrix (ECM) has attracted growing interest due to its highly regulated spatiotemporal expression during development and maturation of central nervous system. The present study deals with the post‐natal appearance and transformation into adult distribution patterns of the ECM components related to proteoglycans (PGs) and glycoproteins (GPs) in the retrosplenial cortex (RSC) of albino rats at birth (P0), 1 week (P1), P2, P3, P4, P5, P6, P7 and P8. The differentiating PGs and GPs components of the ECM were shown to make their appearance as early as 1–2 weeks post‐natally. At this developmental stage, these components of the ECM appeared in association with some neurons and glia cells or diffusely localized at the neutrophill. Interestingly, Golgi complexes of labelled neurons were usually stained with lectin VVA or WFA, and this labelling dramatically disappeared on reaching P4. During P2–3, the pericoated neuronal cells underwent a progressive increment in number, and presented an inside‐out pattern of migration and differentiation (toward the V‐II cortical layers). On reaching P4, most of the coated neurons appeared distributed into the cortical layer IV and II. At a later stage (P5–8), the overall density and intensity of labelled neurons progressively increased and apparently reached the adult stage of development. They also displayed the usual differential labelling characteristics, after using the cationic iron colloid/lectin staining, for the first time at this juncture. The present findings indicated that the perineuronal ECM components are significantly correlated with age and suggest a possible developmental or biological significance including promotion of migration, as well as functional maturation of the retrosplenial neurons.

Quantitative Histochemical Study on the Postnatal Development of Perineuronal Nets in the Retrosplenial Cortex of Albino Rats

“…The distribution of PNs as stained with WFA and VVA, as well as with SBA coincides with previous descriptions performed by using the same lectins, reported in rat (Härtig et al, 1992;Sayed et al, 2002Sayed et al, , 2004Mubarak et al, 2004Mubarak et al, , 2008 and in other species such as mice (Brückner et al, 2000(Brückner et al, , 2003, guinea pig (Ojima et al, 1998), shorttailed opossum (Brückner et al, 1998) or in humans (Bertolotto et al, 1991). In this investigation, the RSC of rats presents several netassociated neuronal subsets, as previously described in many areas of CNS including the cerebral cortex, the hippocampus, the thalamus, the cerebellum, the brain stem and the spinal cord (Celio and Blümcke, 1994).…”

“…Taken together with the previous studies, it is concluded that the basic morphological features of PNs in the RSC was largely identical, although certain heterogeneity is already revealed at the cytochemical and molecular level (Köppe et al, 1997a, b;Sayed et al, 2002Sayed et al, , 2004Mubarak et al, 2008). Notably, distinct differences have been revealed among PNs with respect to the density and intensity of PGs and/or GPs molecules accumulating in the microenvironment of corresponding neuronal cells.…”

“…The present investigation deals with the postnatal development and quantification of PNs, as well as their course of differentiation and maturation in the RSC, which has not been morphometrically documented in rats (Sayed et al, 2002(Sayed et al, , 2004. The expression of developing PGs and GPs components of PNs in the RSC was revealed as early as 1-2 weeks after birth, which follows an inside-out gradient, and attains the adult pattern at Pw6-8.…”

“…Notably, distinct differences have been revealed among PNs with respect to the density and intensity of PGs and/or GPs molecules accumulating in the microenvironment of corresponding neuronal cells. According to their molecular composition, the developing PNs could be differentially identified, for the first time at the 5th postnatal week, into PGs coats, GPs coats as well as coat complexes that formed of PGs networks intermingling with GPs molecules (Sayed et al, 2002(Sayed et al, , 2004. In line with Köppe et al, (1997a) the differential accumulation of the ECM molecules, in the perineuronal spaces, is a continuous rather than a transient process, which is considered to be a key factor for the molecular determination of neuronal micromilieu (Sayed et al, 2004).…”