Uterine lavage or aspirate: which view of the intrauterine environment?

Fluid within the uterine cavity provides the microenvironment for preimplantation blastocyst development and early implantation. Analysis of uterine fluid sampled by aspiration or lavage provides a view of this microenvironment but the similarity or otherwise of the sample components is not known. This study compared proteins in aspirates versus lavage samples taken sequentially from the same women, using surface-enhanced laser desorption/ionization-time of flight-mass spectrometry (SELDI-TOF-MS), multiplex cytokine assays, and an activity assay for proprotein convertase 6. Both lavage and aspiration enabled analysis of uterine fluid components, but they provided substantially different protein profiles. Although there were many similarities in overall protein profiles and most specific proteins examined were detected in both fluids, these were neither qualitatively nor quantitatively comparable within each participant. A likely explanation is that lavage samples the entire uterine cavity including washing the endometrial surface (glycocalyx), whereas aspiration sampling is very local.

Analysis of fertility-related soluble mediators in human uterine fluid identifies VEGF as a key regulator of embryo implantation.

Embryo implantation requires synchronized dialogue between the receptive endometrium and activated blastocyst via locally produced soluble mediators. During the midsecretory (MS) phase of the menstrual cycle, increased glandular secretion into the uterine lumen contains important mediators that modulate the endometrium and support the conceptus during implantation. This study aimed first to identify the growth factor and cytokine profile of human uterine fluid from fertile women during the midproliferative (MP; nonreceptive) and MS (receptive) phases of the cycle, and from women with unexplained infertility during the MS phase. The second aim was to determine important functions of endometrial secretions for embryo implantation. Analysis of uterine fluid using quantitative Luminex assays revealed the presence of over 30 cytokines and growth factors, of which eight [platelet-derived growth factor-AA, TNF-B, soluble IL-2 receptor-A, Fms-like tyrosine kinase 3 ligand, soluble CD40 ligand, IL-7, interferon-A2, and chemokine (C-X-C motif) ligand 1-3] were previously unknown in human uterine fluid. Comparison of the fertile MP, MS, and infertile MS cohorts revealed vascular endothelial growth factor (VEGF) levels are significantly reduced in uterine fluid during the MS phase in women with unexplained infertility compared with fertile women. Functional studies demonstrated that culturing mouse embryos with either MS-phase uterine fluid from fertile women or recombinant human VEGF significantly enhanced blastocyst outgrowth. Furthermore, treatment of human endometrial epithelial cells with uterine fluid or recombinant human VEGF-A significantly increased endometrial epithelial cell adhesion. Taken together, our data support the concept that endometrial secretions, including VEGF, play important roles during implantation. Identifying the soluble mediators in human uterine fluid and their actions during implantation provides insight into interactions essential for establishing pregnancy, fertility markers, and infertility treatment options.