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Endometrial mucins and human embryo implantation. / Sean Gereint Griffiths
Swansea University Author: Sean Gereint Griffiths
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Failure of the embryo to implant into the uterine lining results in infertility and is also the rate limiting step in FVF. The tethered, glycoprotein MUC1 is a protective cell surface receptor that has been associated with infertility. Evidence suggests MUC1 and other endometrial mucins regulate emb...
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Failure of the embryo to implant into the uterine lining results in infertility and is also the rate limiting step in FVF. The tethered, glycoprotein MUC1 is a protective cell surface receptor that has been associated with infertility. Evidence suggests MUC1 and other endometrial mucins regulate embryo implantation. Endometrial epithelia must be shielded from infection whilst permitting the recognition and implantation of the embryo. The protein backbone of MUC1 is thought to act as a scaffold for L-selectin ligands and may be integral to the initial tethering of the embryo during early implantation. Objectives The remit of this thesis was to model the expression of MUC1 and other mucins in the human endometrium using endometrial cell lines and to use atomic force microscopy to understand the role played by these proteins in shaping the non-specific and embryo specific adhesive characteristics of endometrial monolayers. If possible the proposed L-selectin implantation mechanism was to be identified and functionally characterised. Methodology This project successfully married the traditional molecular tools of quantitative PCR and immunocytochemistry with novel application of INCELL analyzer high content screening protein analysis, peak force quantitative nano-mechanical mapping atomic force microscopy and single molecule force spectroscopy atomic force microscopy to characterise the specific and non-specific surface adhesion on live endometrial monolayers. Results Firstly, immunocytochemistry and qRTPCR revealed that basal MUC1 expression was significantly higher in Hec-1-B relative to Hec-IA, Ishikawa and Hec50. Secondly, INCELL analysis qualified a distinct heterogeneous expression of MUC1 across the endometrial monolayer and delineated altered patterning following treatment with estradiol and progestins. Thirdly, we have shown a direct and proportional correlation between MUC1 expression and adhesion in live Hec-IA and Hec-IB cell monolayers. Fourthly, this work has confirmed and characterised binding of recombinant L-selectin to the endometrial epithelial cell surface. Fifthly, it is shown that L-selectin surface binding decreases following a reduction in MUC1 surface presentation. Conclusions The results implicate MUC1 as a key component of endometrial adhesion and an initial mediator of implantation with a functional patterned expression suggesting areas of altered receptivity exist across endometrial monolayers. Abnormal MUC1 expression has been shown in endometrial pathologies and unexplained infertility. The current investigation suggests MUC1 protein may assist embryo attachment by retarding it sufficiently through mechanical impedance to allow specific L-selectin binding further securing the embryo. A non-receptive endometrium may contribute towards the infertile phenotype despite repeated IVF treatments, thus novel examination of potential embryo adhesion molecules such as MUC1 may aid understanding of endometrial characteristics which prevent embryo implantation and contribute towards IVF failure.
Faculty of Medicine, Health and Life Sciences