Uterine Fluid Proteins for Minimally Invasive Assessment of Endometrial Receptivity

Abstract

Context Clinically used endometrial (EM) receptivity assays are based on transcriptomic patterning of biopsies at midsecretory endometrium (MSE) to identify the possible displacement or disruption of window of implantation (WOI) in patients with recurrent implantation failure (RIF). However, biopsies are invasive and cannot be performed in the same cycle with in vitro fertilization embryo transfer, while uterine fluid (UF) analysis is considered minimally invasive and can immediately precede embryo transfer. Objective To determine whether UF proteome can be used for WOI monitoring and whether it would highlight the etiology of RIF. Patients Paired early secretory endometrial (ESE) and MSE UF samples from six fertile control women for discovery, and an additional 11 paired ESE/MSE samples from controls and 29 MSE samples from RIF patients for validation. Results Using discovery mass spectrometry (MS) proteomics we detected 3158 proteins from secretory phase UF of which 367 undergo significant (q < 0.05) proteomic changes while transitioning from ESE to MSE. Forty-five proteins were further validated with targeted MS, and 21 were found to display similar levels between control ESE and RIF MSE, indicating displacement of the WOI. A panel of PGR, NNMT, SLC26A2 and LCN2 demonstrated specificity and sensitivity of 91.7% for distinguishing MSE from ESE samples. The same panel distinguished control MSE samples from RIF MSE with a 91.7% specificity and 96.6% sensitivity. Conclusion UF proteins can be used for estimating uterine receptivity with minimal invasiveness. Women with RIF appear to have altered MSE UF profiles that may contribute to their low IVF success rate.

Extracellular vesicles in embryo implantation and disorders of the endometrium

“…These observations imply that the secretion of EVs would be hampered in the endometria of infertile women. Recently, the uterine fluid proteome of women with RIF and controls has been compared and several differentially abundant proteins were identified, some of which are associated with EVs 34 . Endometrial EVs modulated fertility is also evident from studies in dairy cows with divergent fertility.…”

Sperm Proteome after Interaction with Reproductive Fluids in Porcine: From the Ejaculation to the Fertilization Site

“…Focusing on 25 exclusive sperm-interacting proteins from UF, to the best of the authors’ knowledge, few of these have been previously identified in boar and might play a role during fertilization. Regarding apolipoprotein-E, it was found in blood [ 46 ] and expressed in human endometrium during the proliferative phase [ 47 , 48 , 49 ]. Within the uterus, this protein is involved in cholesterol uptake, immune response, and preparing the endometrium for embryo implantation [ 50 ].…”

“…Another protein, belonging to the family of heat shock proteins, the heat shock 70-kDa protein 1-like, was detected in spermatozoa incubated with UF. This protein participates in several physiological processes (i.e., cell cycle, cell proliferation, and differentiation) and has been identified in UF from different species, such as human [ 47 , 58 ], equine [ 55 ], ovine [ 32 ], mouse [ 59 ], bovine, and porcine [ 60 ]. In particular, the binding of this protein to porcine and bovine spermatozoa during their journey from the uterus towards the oviduct avoids early capacitation and aids in the maintenance of sperm viability [ 59 , 61 , 62 ].…”

“…It is known that the loss of cholesterol is a key factor regulating sperm motility, hyperactivation, and capacitation, due to the association between apolipoprotein A-1 and high-density lipoprotein, triggering the acrosome reaction [ 105 , 106 ]. Subsequently, apolipoprotein A-1 was identified in the UF during the secretory phase in human [ 47 ], horse [ 55 ], and more abundant in the estrus than the luteal phase in sheep [ 32 ]. In sows, this protein has also been identified in the endometrium transcriptome at day 14 of the estrus cycle [ 48 ].…”

“…This protein, known to be expressed in spermatozoa, could also be present in SP or UF exosomes. In fact, it has been identified in human SP extracellular vesicles [ 111 ] and in UF from humans, horses, and sheep [ 32 , 47 , 55 ]. A recent analysis of the transcriptome in porcine endometrial and oviductal tissue showed the presence of calmodulin at day 18 of the estrus cycle (corresponding to the late follicular phase) [ 49 ], supporting the results of the current study.…”