COEXPRESSION OF GFAP AND VIMENTIN IN ASTROCYTES PROLIFERATING IN RESPONSE TO INJURY IN THE MOUSE CEREBRAL HEMISPHERE - A COMBINED AUTORADIOGRAPHIC AND DOUBLE IMMUNOCYTOCHEMICAL STUDY
K. Janeczko, COEXPRESSION OF GFAP AND VIMENTIN IN ASTROCYTES PROLIFERATING IN RESPONSE TO INJURY IN THE MOUSE CEREBRAL HEMISPHERE - A COMBINED AUTORADIOGRAPHIC AND DOUBLE IMMUNOCYTOCHEMICAL STUDY, International journal of developmental neuroscience, 11(2), 1993, pp. 139-147
Changes in the distribution of proliferating astrocytes expressing gli
al fibrillary acidic protein (GFAP) and/or vimentin were examined in t
he injured cerebral hemisphere in adult mice. The injury was followed
by [H-3]thymidine injections at different time intervals. The brain se
ctions were doubly immunostained for GFAP and vimentin and subjected t
o autoradiography. In that way three cell types were distinguished imm
unocytochemically: (1) astrocytes co-expressing glial fibrillary acidi
c protein (GFAP) and vimentin, (2) astrocytes expressing only GFAP and
(3) astrocyte-like cells expressing vimentin. Thereafter, numbers of
immunopositive and autoradiographically labelled cells and their locat
ions within the region of injury were recorded at each stage of the ex
periment. Two hours as well as 1 day after the injury proliferation of
GFAP-positive astrocytes and of those co-expressing GFAP and vimentin
could only be seen as statistically insignificant phenomena. On day 2
the reactive proliferation of each immunocytochemically defined cell
type was already maximal, then gradually decreased and its last signs
were recorded on day 8. On day 2, among all the proliferating GFAP-pos
itive astrocytes, 67.2% were also vimentin-positive. Later, the propor
tion declined to 50.7% and 38.5% on days 4 and 8, respectively. The la
belled astrocyte-like vimentin-positive cells were located closest to
the lesion margins. In comparison, the astrocytes co-expressing GFAP a
nd vimentin and those expressing exclusively GFAP, occupied regions pr
ogressively farther from the lesion site. At the initial stages of the
response to injury, vimentin expression in cells starting their react
ive proliferation did not precede the expression of GFAP. This was con
sidered as an argument against a hypothesis that reactive astrocyte di
vision induces a two-stage increase in the cytoskeletal protein level
in which synthesis of vimentin precedes that of GFAP.