Transforming growth factor beta (TGFB) signaling is activated during porcine implantation: proposed role for latency-associated peptide interactions with integrins at the conceptus–maternal interface

Abstract

The process of implantation is mediated by a complex network of signaling and adhesive factors. In the pig, latent and active transforming growth factor beta (TGFB), TGFB receptors (TGFBR), and integrins (ITGs) are present during the peri-implantation period. TGFB signals via TGFBR and activates downstream effector SMAD proteins 2 and 3 (p-SMAD2/3). Latency-associated peptide (LAP), part of the latent TGFB complex, is known to bind to ITG heterodimers and activate TGFB. We hypothesize that active TGFBs and TGFBRs along with LAP and ITGs functionally interact at the conceptus-maternal interface to mediate events essential for conceptus development and attachment in pigs. Uteri and conceptuses from days 10, 12, 16, 20, and 24 pregnant gilts were immunostained for TGFB, LAP, and ITG subunits (ITGAV, ITGB1, ITGB3, ITGB5, ITGB6, and ITGB8). Activation of TGFBRs was evaluated by the presence of phosphorylated downstream effector SMAD2/3. Binding of LAP to ITGs was also evaluated using porcine trophectoderm cells. Abundant active TGFB was detected at the apical surfaces of epithelia at the conceptus-maternal interface, and p-SMAD2/3 was detected at both conceptus attachment and nonattachment sites during implantation. Separate aggregates of LAP, ITGB1, ITGB5, and later ITGB3 were detected at the porcine conceptus-maternal interface, and binding of LAP to ITGs on apical surfaces was demonstrated. Results suggest that functional LAP-ITG adhesion complexes support conceptus attachment and promote TGFB activation leading to TGFB interaction with TGFBR supporting events of porcine implantation.

Transcriptional profiling by RNA-Seq of peri-attachment porcine embryos generated by a variety of assisted reproductive technologies

“…81). TGF-␤ signaling has recently been implicated in mediating the interaction of porcine conceptuses with the uterine endometrium at both early and late stages of embryonic attachment (47). Interestingly, though, in our data, the suppression of TGF-␤ signaling in IVF embryos was observed primarily in the ED samples, and not the TE samples.…”

Implantation and Establishment of Pregnancy in the Pig

“…In addition, when LAP is infused into the uteri of pregnant pigs, conceptuses failed to implant, suggesting that infused LAP competed with the endogenous LLC for binding to integrins expressed on trophectoderm (Massuto et al 2009b ). In support of this idea, aggregates of LAP, β1, β3, and β5, have been detected at the porcine conceptus trophectoderm-uterine LE interface, suggesting functional adhesion complexes that support conceptus attachment during porcine implantation (Massuto et al 2009a ). Both fi bronectin and vitronectin have been detected at sites of conceptus attachment in the pig (Bowen et al 1996 ), and the glycosylation variant of fi bronectin, oncofetal fi bronectin (oFN), is constitutively expressed by porcine conceptus trophectoderm as well as uterine LE throughout gestation (Tuo and Bazer 1996 ).…”

“…The inter-α-trypsin inhibitor heavy chain-like (IαIH4) protein contains a von Willebrand type A domain, a recognition site for the αvβ3 integrin receptor (Geisert et al 1998 ). The latencyassociated peptide (LAP) of transforming growth factor beta (TGFB) binds to αvβ1, αvβ3, and αvβ5 (Massuto et al 2009a ). Fibronectin is capable of binding α4β1, α5β1, and αvβ3 (Bowen et al 1996 ).…”

Analysis of integrins and vascular endothelial growth factor isoforms mRNA expression in the canine uterus during perimplantation period

“…This observation suggests that intergrins are also involved in angiogenesis, what may explain their expression in the uterus during the stage of early pregnancy. There are several notes indicating the role of the integrins expression during pregnancy and embryo implantation in several mammalian species (Johnson et al 2001, Roberts et al 2009, Massuto et al 2010. However, there are no available published data concerning these mechanisms during dog pregnancy.…”