Objective: To investigate the expression and the significance of toll-like receptor 3 (TLR-3) in placenta, tumor necrosis factor-alpha(TNF-alpha) in maternal and cord blood of idiopathic fetal growth restriction (IFGR), and their correlation with the pathogenesis of symmetric and asymmetric IFGR.
Methods: From April 2008 to April 2009, 42 primiparae of singleton pregnancy and their IFGR babies, who delivered at term through cesarean section, in the Third Affiliated Hospital of Zhengzhou University were enrolled. All subjectects were divided into symmetric IFGR group (n = 20) and asymmetric IFGR group (n = 22). Another 42 non-IFGR pairs were randomly selected as the control group. The polink-2 plus polymerized horseradish peroxidase (HRP) immunohistochemical method and the enzyme linked immunosorbent assay (ELISA) were applied to detect TLR-3 and TNF-alpha levels.
Results: (1) The expression of TLR-3 protein were observed in all maternal placenta of the three groups. TLR-3 essentially expressed in syncytiotrophoblasts and hofbouer cells in the symmetric IFGR and control group, but expressed mostly in hofbouer cells and less in syncytiotrophoblasts in the asymmetric IFGR group. (2) The expression of TLR-3 in the syncytiotrophoblasts of the symmetric and asymmetric IFGR group was significantly lower than in the control group (111 +/- 14 and 118 +/- 11 vs. 156 +/- 9, P < 0.01). The number of TLR-3 positive in Hofbourer cell in the symmetric IFGR group was lower than the control group (8.9 +/- 2.8 vs 17.5 +/- 2.8, P < 0.01), but the number in the asymmetric IFGR group was higher (23.8 +/- 3.7) compared with the control group (P < 0.01). (3) The TNF-alpha levels in the maternal and cord blood of the symmetric and the asymmetric group were higher than that of the control group [maternal: (90 +/- 10) microg/L and (86 +/- 11) microg/L vs. (73 +/- 9) microg/L; cord blood: (92 +/- 12) microg/L and (96 +/- 8) microg/L vs. (79 +/- 9) microg/L; P < 0.01]. (4) Neither symmetric nor the asymmetric IFGR group showed any correlations between the maternal and cord blood levels of TNF-alpha (P > 0.05). (5) Significant correlation was found between the TNF-alpha level of the cord blood and TLR-3 expression in the placenta in both the symmetric and asymmetric IFGR group (P < 0.05), but no relationship was found between the maternal blood TNF-alpha level and TLR-3 expression in the placenta (P > 0.05).
Conclusions: The variantions of TLR-3 expression in placenta and the increased expression of TNF-alpha in cord blood are associated with the genesis IFGR. The reduced expression of TLR-3 may related to symmetric IFGR, while the increased TLR-3 level in hofbouer cells may lead to asymmetric IFGR.