The sodium-iodide symporter expression in placental tissue at different gestational age: an immunohistochemical study.
BACKGROUND
Iodide (I(-)) is crucial for foetal thyroid function. Foetal iodide results from maternal circulating iodide and from deiodination of iodothyronines within the placenta. The Na(+)/I(-) symporter (NIS) localized in placental cells appears to be involved in iodide exchange. Low NIS expression has been reported in trophoblast cells from the first trimester and pregnancy at term.


OBJECTIVE
The aim of this study was to examine NIS expression by immunohistochemistry in the major components of human ovular tissue and placenta.


METHODS
Formalin-fixed and paraffin-embedded specimens of placental tissue from the first trimester and at term were analysed. NIS expression was quantified as percentage of NIS-positive cells/total cells. NIS expression was also evaluated by real-time polymerase chain reaction (RT-PCR) in five first-trimester and five at-term placental specimens.


RESULTS
In the first-trimester specimens heterogeneous NIS immunoreactivity was found in cyto-syncytiotrophoblast cells, with a range of NIS-positive cells from 5% to 80% (mean +/- SD 21.85 +/- 23.95), in mesenchymal and endothelial cells from 1% to 40% (14.5 +/- 11.16), in decidual cells from 5% to 40% (10.38 +/- 11.98) and in endometrial glands from 3% to 40% (21.86 +/- 13.93). In specimens from placenta at term, NIS-positive cyto-syncytiotrophoblast cells were between 5% and 40% (mean 17.85 +/- 18.15), mesenchymal and endothelial cells between 1% and 40% (13.67 +/- 12.16), decidual tissue between 5% and 30% (16.43 +/- 9.08), and endometrial glands between 3% and 40% (16.67 +/- 15.27). No significant differences in NIS expression were observed between the first trimester and placenta at term. A similar level of mRNA expression for the NIS gene was obtained by RT-PCR both in ovular material of the first trimester and in placenta at term.


CONCLUSIONS
We found NIS to be expressed in various placental and ovular components and its expression to remain constant during pregnancy.
Di Cosmo
C
C
Department of Endocrinology and Metabolism, University of Pisa, Pisa, Italy.
Fanelli
G
G
Tonacchera
M
M
Ferrarini
E
E
Dimida
A
A
Agretti
P
P
De Marco
G
G
Vitti
P
P
Pinchera
A
A
Bevilacqua
G
G
Naccarato
A G
AG
Viacava
P
P
D003656:Decidua / Q000737:chemistry; D004717:Endometrium / Q000737:chemistry; D042783:Endothelial Cells / Q000737:chemistry; D005260:Female; D015870:Gene Expression; D005865:Gestational Age; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D008648:Mesoderm / Q000737:chemistry; D010920:Placenta / Q000737:chemistry*; D011247:Pregnancy; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D027981:Symporters / Q000032:analysis* / Q000235:genetics; D013961:Thyroid Gland / Q000737:chemistry; D014327:Trophoblasts / Q000737:chemistry; D000099209:Sodium-Iodide Symporters
D012333:RNA, Messenger; D027981:Symporters; D000099209:Sodium-Iodide Symporters