PreImplantation Factor (PIF) correlates with early mammalian embryo development-bovine and murine models

Christopher W Stamatkin,Eytan R Barnea,Roumen G Roussev,Victor Absalon-Medina,Sivakumar Ramu,Robert O Gilbert,Chelsi Goodman,Mike Stout,Robert A Godke,Carolyn B Coulam

doi:10.1186/1477-7827-9-63

Abstract

BackgroundPreImplantation Factor (PIF), a novel peptide secreted by viable embryos is essential for pregnancy: PIF modulates local immunity, promotes decidual pro-adhesion molecules and enhances trophoblast invasion. To determine the role of PIF in post-fertilization embryo development, we measured the peptide's concentration in the culture medium and tested endogenous PIF's potential trophic effects and direct interaction with the embryo.MethodsDetermine PIF levels in culture medium of multiple mouse and single bovine embryos cultured up to the blastocyst stage using PIF-ELISA. Examine the inhibitory effects of anti-PIF-monoclonal antibody (mAb) added to medium on cultured mouse embryos development. Test FITC-PIF uptake by cultured bovine blastocysts using fluorescent microscopy.ResultsPIF levels in mouse embryo culture medium significantly increased from the morula to the blastocyst stage (ANOVA, P = 0.01). In contrast, atretic embryos medium was similar to the medium only control. Detectable - though low - PIF levels were secreted already by 2-cell stage mouse embryos. In single bovine IVF-derived embryos, PIF levels in medium at day 3 of culture were higher than non-cleaving embryos (control) (P = 0.01) and at day 7 were higher than day 3 (P = 0.03). In non-cleaving embryos culture medium was similar to medium alone (control). Anti-PIF-mAb added to mouse embryo cultures lowered blastocyst formation rate 3-fold in a dose-dependent manner (2-way contingency table, multiple groups, X2; P = 0.01) as compared with non-specific mouse mAb, and medium alone, control. FITC-PIF was taken-up by cultured bovine blastocysts, but not by scrambled FITC-PIF (control).ConclusionsPIF is an early embryo viability marker that has a direct supportive role on embryo development in culture. PIF-ELISA use to assess IVF embryo quality prior to transfer is warranted. Overall, our data supports PIF's endogenous self sustaining role in embryo development and the utility of PIF- ELISA to detect viable embryos in a non-invasive manner.

Highlights

PreImplantation Factor (PIF), a novel peptide secreted by viable embryos is essential for pregnancy: PIF modulates local immunity, promotes decidual pro-adhesion molecules and enhances trophoblast invasion
PIF is secreted by viable embryos The dynamics of PIF secretion by cultured mouse embryos was assessed
We showed that PIF was detected in the medium of morula stage embryos cultured in groups and PIF levels further increased in the blastocyst stage in serially cultured embryos (ANOVA, P = 0.05 and P = 0.01), respectively as compared with controls. (Figure 2)

Summary

Introduction

PreImplantation Factor (PIF), a novel peptide secreted by viable embryos is essential for pregnancy: PIF modulates local immunity, promotes decidual pro-adhesion molecules and enhances trophoblast invasion. Since the immune milieu of pregnancy is unique - not replicated in any other circumstances - specific embryoderived signals have a crucial role leading to maternal recognition of pregnancy [4]. To orchestrate such critical ‘cross-talk’, a viable embryo must be present, which may be accepted by the mother, whereas, a non-viable conceptus will fail to develop or later be rejected since maternal acceptance does not occur. The search to identify embryo-specific markers which reflect viability of cultured embryos by assessing the medium or by performing an embryo biopsy (beyond morphological evaluation) has been ongoing. Far no marker has entered into routine clinical use in humans or other mammals undergoing IVF procedures [5,6]

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