Adhesion factors and cytokines in the cyclic canine endometrium
Rita Payan Carreira, Dep Clinical Sciences, SLU, Uppsala, Sweden, and CECAV, University of
Trás-os-Montes e Alto Douro, Vila Real, Portugal
Cyclic remodeling occurs in the canine endometrium as in other species due to changes in the
endometrial receptors for sex steroids. These receptors regulate numerous molecules acting
locally to determine patterns of cell proliferation, differentiation, apoptosis and thus tissue
remodeling. Among these substances, the expression of transforming growth factor-beta (TGFβ) isoforms and tumour necrosis factor (TNF) have been found to be cyclic in the rodent and
human endometrium.
TGF-β have been proposed to be associated with embryo implantation. We have evaluated the
pattern of expression of the TGF-β protein isoforms in the canine endometrium during the
estrous cycle. Scoring intensity (weak, moderate or strong) was obtained for the different parts
of the epithelium (surface epithelium, SE; superficial glandular epithelium, SGE; deep glandular
epithelium, DGE) and the stroma. Stronger immunolabelling was found in the stroma than in
the epithelium for TGFβ1, but not for TGFβ2 or TGFβ3, independently of the stage of the cycle.
For TGFβ1, decreased intensity scores were observed at early diestrus, in particular in the
epithelium. In contrast, higher intensity scores for TGFβ3 at the DGE were found in
progesterone-associated stages, but not for the SGE and SE. For TGFβ2, the strongest scores
were detected in the DGE, whilst SE and SGE showed very similar intensities. For this isoform, a
decrease in the intensity scores was detected at estrus and early diestrus in the stroma, SE and
SGE.
TNF has strong pro-inflammatory and immune-stimulatory actions and is involved in the
control of cell differentiation, proliferation and migration. We studied the temporal
immunolocalisation of TNF in the canine endometrium during the oestrous cycle and at
embryo invasion. TNF immunolabelling was found in both stromal fibroblasts and eåpithelial
components in all stages. Stromal immunostaining was consistently stronger than epithelial
staining. A tendency for a decrease in the surface epithelium score was found in early
dioestrus. The overall TNF immunoreactivity was higher in early pregnancy samples compared
to diestrus stages.
In conclusion, this work describes cyclic changes in TNF and the TGFβ isoforms in the dog
endometrium. The expression is of TGF-β is weaker during early diestrus, a period that
corresponds to the dog implantation period. The higher expression of TNF in early pregnancy
also suggests a role during implantation.