Abstract
BackgroundIt is well established that spontaneous conceptus loss in swine is associated with an imbalance of both angiogenic and immunological factors. Leptin (LEP), a metabolic hormone, has also been implicated in the promotion of angiogenesis. In this study, LEP and its long form receptor (OB-Rb) were evaluated during porcine pregnancy to assess their basal level of expression and their potential role in conceptus development.MethodsExpression and secretion of LEP and OB-Rb were quantified in the endometrium of non-pregnant (n = 5), and in the endometrium and chorioallantoic membrane (CAM) of pregnant sows (parity 2 to 5) at gestational days (gd) 20 (n = 8) and 50 (n = 8). Data were analyzed by a 3-way ANOVA testing the effects of conceptus health, tissue type and gestational day.ResultsLeptin and OB-Rb transcripts were significantly higher (P < 0.05) in pregnant than in non-pregnant sows. Significantly greater LEP (P < 0.001) was detected in the endometrial tissue at gd20 compared with gd50. At the protein level, the lowest LEP expression (P < 0.01) was detected in the CAM at gd50, while OB-Rb protein was significantly lower (P < 0.01) at gd50 in the CAM than in the endometrium collected from gd20 and gd50 conceptus attachment sites. Immunofluorescence staining confirmed the expression of these proteins at both gestational days and in both tissue types.ConclusionsChanges in the expression patterns of LEP and OB-Rb between gd20 and gd50 suggest a role for the LEP/OB-R complex at the early stages of porcine pregnancy, possibly affecting the attachment process. Further mechanistic studies are warranted to understand the specific role of leptin in porcine pregnancy.
Highlights
It is well established that spontaneous conceptus loss in swine is associated with an imbalance of both angiogenic and immunological factors
LEP expression Leptin transcripts were found to significantly increase (P = 0.015) in early pregnancy endometrium compared to the non-pregnant tissues
The greatest LEP expression was detected in endometrial samples collected from conceptus attachment sites at gd20 when compared with endometrial samples at gd50 as well as chorioallantoic membrane (CAM) samples collected at gd20 and gd50 (Figure 1), regardless of conceptus health
Summary
It is well established that spontaneous conceptus loss in swine is associated with an imbalance of both angiogenic and immunological factors. Previous studies from our laboratory have demonstrated that conceptus losses are associated with an imbalance of mRNA transcripts for multiple angiogenic and inflammatory cytokines [10,11,12] as well as factors that can regulate mRNA stability such as the tristetraprolin family members (Khalaj et al, unpublished data). The reduction in vascularization has been shown to be associated with a decreased production of vascular endothelial growth factor (VEGF) transcripts [6,10]. These findings suggest a correlation between abnormal angiogenesis at the maternal-fetal interface and fetal loss
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