INVESTIGADORES
MUÑOZ Estela Maris
congresos y reuniones científicas
Título:
The microglia regulate pineal gland shape and function
Autor/es:
M.P. IBAñEZ RODRíGUEZ; S. NOCTOR; E. MUÑOZ
Lugar:
Galveston, TX.
Reunión:
Congreso; GRC on Pineal Cell Biology; 2014
Institución organizadora:
Gordon Research Conferences
Resumen:
In rat, the pineal gland (PG) begins as an evagination of the diencephalic roof at
around E15 and becomes a solid organ at the end of the gestation period. In this study
we characterized the major cellular and morphological events that take place in the
developing PG from E15 to E21. Also, we studied the adult PG in normal conditions
(Sham) and after disrupting the PG sympathetic innervation via bilateral superior
cervical ganglionectomy (SCGx). In this case, PGs were collected at 3, 6, 9 and 13 days
after surgery. We examined the expression patterns of the transcription factor Pax6;
the astrocyte markers vimentin (vim), GFAP and S100â; the microglia markers Iba-1
and Isolectin IB4 which also labels blood vessels; the mitotic markers pSer10-histone H3
(pH3) and PCNA, and the neuron-specific class III â-tubulin (Tuj1). Pax6 was expressed
in pinealocyte precursors throughout PG development, with the highest nuclear levels
at early stages of embryogenesis. A few pH3-positive mitotic cells were present in the
apical region of the stratified neuroepithelium of the pineal anlage from E15 to E17,
but they were more abundant and randomly distributed in later stages. Interestingly,
these mitotic cells showed basal Pax6 levels. Vim was expressed in the embryonic PG
while GFAP and S100â were not detected. In the PG recess, Pax6/vim-positive cells
were radially disposed. In later stages, especially at E18 and E19, cells immunolabeled
for both Pax6 and vim were observed in rosette-like arrangements. At E20 and E21,
high levels of vim expression were confined to a few randomly distributed cells. Iba-1/
IB4-positive microglial cells, likely derived from choroid plexus and meninges,
colonized the PG from E15 onwards. They exhibited morphological features similar to
those of active cells, and often they were observed in close proximity of Pax6-
expressing precursors. To further understand the role of PG microglia, we performed
bilateral SCGx to challenge the local microglial cells. The presence of degenerating
nerve fibers activated PG microglia. Although these cells were observed in the entire
SCGx gland, they were more abundant in the pineal stalk and proximal region, and
they were located mainly close to IB4-positive blood vessels and in tight spatial
relationship with degenerating Tuj1-positive nerve fibers. In contrast to the embryonic
PG, GFAP and S100â were expressed in the adult PG in a region-dependent manner. A
heterogeneous population of astrocytes that expressed one or both markers was
observed in both Sham and SCGx conditions, being more abundant in denervated PGs.
In the adult PG, a few cells were positive for Pax6; these cells were located
perivascularly in close relationship with microglial cells, which in some cases acted as
cellular bridges between those potential precursor cells and astrocytes. Interestingly
the expression of Pax6 was slightly higher in the SCGx PGs. The cells positive for the
mitotic marker PCNA were more abundant in the denervated glands and they were
also immunoreactive for Iba-1. In brief, the PG evolves from Pax6/vim-positive
precursor cells capable of adopting different morphologies and arrangements
throughout development to give rise the main cell type, the pinealocyte, and a
subpopulation of interstitial cells that is also present in the adult PG. The
ganglionectomy activates the local microglia and maybe leads to the dedifferentiation
of the PG. We speculate that microglia modulate PG morphogenesis and have a role in
maintaining the adult phenotype by actively interacting with precursor cells,
astrocytes, nerve fibers and blood vessels.