K. Lips et al., RESTRICTED APPEARANCE OF TENASCIN AND CHONDROITIN SULFATE PROTEOGLYCANS AFTER TRANSECTION AND SPROUTING OF ADULT-RAT POSTCOMMISSURAL FORNIX, Journal of neurocytology, 24(6), 1995, pp. 449-464
Transected fibres of the adult rat postcommissural fornix sprout over
short distances but fail to traverse the lesion site and terminate in
close vicinity to the wound. As a step in defining the molecular envir
onment responsible for regeneration failure at the lesion site, we hav
e used immunocytochemistry to analyse the spatio-temporal expression p
attern of two putative growth-inhibitory extracellular matrix componen
ts, tenascin and chondroitin sulphate proteoglycans and their topograp
hical relationship to the sprouting axons. Both tenascin and chondroit
in sulphate proteoglycan labelling appeared after fornix transection a
nd were confined to the immediate vicinity of the lesion site. While t
enascin-labelling was associated with astrocytes and microglia/macroph
ages, which accumulate around the wound. Tenascin-like immunoreactivit
y disappeared between 17 days and 4 weeks, but chondroitin sulphate pr
oteoglycan staining persisted at least up to 14 months after transecti
on. Regrowing fornix fibres invaded and elongated within the chondroit
in sulphate proteoglycan-immunopositive region up to the lesion site,
where they terminated. This zone of axonal. growth inhibition was neit
her characterized by an increase of chondroitin sulphate proteoglycan
immunoreactivity nor by the presence of tenascin-immunopositive struct
ures. The spatio-temporal distribution patterns of tenascin and chondr
oitin sulphate proteoglycan and the permeability of the chondroitin su
lphate proteoglycan-immunopositive region for sprouting axons do not s
upport the hypothesis that chondroitin sulphate proteoglycan alone and
/or tenascin inhibit the advance of sprouting fornix fibres.