Sn. Lennard et al., TRANSFORMING GROWTH-FACTOR BETA(1) EXPRESSION IN THE ENDOMETRIUM OF THE MARE DURING PLACENTATION, Molecular reproduction and development, 42(2), 1995, pp. 131-140
In situ hybridization, Northern blotting, and immunohistochemical tech
niques were used to study the expression of transforming growth factor
beta 1 (TGF beta(1)) in the endometrium of the mare during the first
150 days of pregnancy (term = 330-340 days). In situ hybridization usi
ng an oligonucleotide (45mer) probe, based on a homologous region with
in all known mammalian TGF beta(1) DNA sequences, demonstrated TGF bet
a(1) mRNA accumulation in the glandular and lumenal epithelial cells o
f the endometrium from day 33 onwards which corresponds to the time of
implantation (day 33-45). Expression in the endometrium remained at a
high level to the end of the sampling period (day 150). There was als
o marked expression of TGF beta(1) in the mononuclear cells accumulate
d around the periphery of the specialized trophoblast cells of the end
ometrial cup within the endometrium and in the mononuclear cells accum
ulated in the endometrial stroma of mares carrying failing donkey-in-h
orse pregnancies created by embryo transfer. The sense (control) oligo
nucleotide probe exhibited no hybridization to any tissue at any stage
. Northern blot analysis demonstrated that the oligonucleotide probe a
nd a porcine TGF beta(1) cDNA clone hybridized to a single 2.5 kb tran
script in horse endometrial and lymphocyte RNA, thus validating the ol
igonucleotide probe for detection of horse TGF beta(1) mRNA. Furthermo
re, both probes demonstrated an increased signal in the pregnant endom
etrium from day 33 onwards, thereby confirming the in situ hybridizati
on results. Immunostaining with a specific anti-bovine TGF beta(1) ser
um also showed increasing TGF beta(1) accumulation in endometrial epit
helia during pregnancy, and localization of the protein in endometrial
stroma and in the trophoblast layer of the placenta after day 60 of p
regnancy. These results show that TGF beta(1) expression increases in
the maternal endometrium of the mare at the time of implantation and t
hat it may play a role in regulating endometrial and/or trophoblast gr
owth and differentiation during placentation in this species. It may a
lso influence fetal development (via placental transfer) at a later st
age of gestation. (C) 1995 Wiley-Liss, Inc.