PMID- 34517414 OWN - NLM STAT- MEDLINE DCOM- 20211101 LR - 20220302 IS - 1460-2350 (Electronic) IS - 0268-1161 (Print) IS - 0268-1161 (Linking) VI - 36 IP - 10 DP - 2021 Sep 18 TI - The expression and activity of Toll-like receptors in the preimplantation human embryo suggest a new role for innate immunity. PG - 2661-2675 LID - 10.1093/humrep/deab188 [doi] AB - STUDY QUESTION: Is the innate immunity system active in early human embryo development? SUMMARY ANSWER: The pattern recognition receptors and innate immunity Toll-like receptor (TLR) genes are widely expressed in preimplantation human embryos and the pathway appears to be active in response to TLR ligands. WHAT IS KNOWN ALREADY: Early human embryos are highly sensitive to their local environment, however relatively little is known about how embryos detect and respond to specific environmental cues. While the maternal immune response is known to be key to the establishment of pregnancy at implantation, the ability of human embryos to detect and signal the presence of pathogens is unknown. STUDY DESIGN, SIZE, DURATION: Expression of TLR family and related genes in human embryos was assessed by analysis of published transcriptome data (n = 40). Day 5 (D-5) human embryos (n = 25) were cultured in the presence of known TLR ligands and gene expression and cytokine production measured compared to controls. PARTICIPANTS/MATERIALS, SETTING, METHODS: Human embryos surplus to treatment requirements were donated with informed consent from several ART centres. Embryos were cultured to Day 6 (D-6) in the presence of the TLR3 and TLR5 ligands Poly (I: C) and flagellin, with gene expression measured by quantitative PCR and cytokine release into medium measured using cytometric bead arrays. MAIN RESULTS AND THE ROLE OF CHANCE: TLR and related genes, including downstream signalling molecules, were expressed variably at all human embryo developmental stages. Results showed the strongest expression in the blastocyst for TLRs 9 and 5, and throughout development for TLRs 9, 5, 2, 6 and 7. Stimulation of Day 5 blastocysts with TLR3 and TLR5 ligands Poly (I: C) and flagellin produced changes in mRNA expression levels of TLR genes, including the hyaluronan-mediated motility receptor (HMMR), TLR5, TLR7, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kappaB) and monocyte chemoattractant Protein-1 (MCP-1) (P < 0.05, P < 0.001 compared to unstimulated controls), and release into culture medium of cytokines and chemokines, notably IL8 (P = 0.00005 and 0.01277 for flagellin and Poly (I: C), respectively). LIMITATIONS, REASONS FOR CAUTION: This was a descriptive and experimental study which suggests that the TLR system is active in human embryos and capable of function, but does not confirm any particular role. Although we identified embryonic transcripts for a range of TLR genes, the expression patterns were not always consistent across published studies and expression levels of some genes were low, leaving open the possibility that these were expressed from the maternal rather than embryonic genome. WIDER IMPLICATIONS OF THE FINDINGS: This is the first report of the expression and activity of a number of components of the innate immunity TLR system in human embryos. Understanding the role of TLRs during preimplantation human development may be important to reveal immunological mechanisms and potential clinical markers of embryo quality and pregnancy initiation during natural conception and in ART. STUDY FUNDING/COMPETING INTEREST(S): This work was funded by the Ministry of Higher Education, The State of Libya, the UK Medical Research Council, and the NIHR Local Comprehensive Research Network and NIHR Manchester Clinical Research Facility and the European Union's Horizon 2020 Research and Innovation Programmes under the Marie Sklodowska-Curie Grant Agreement No. 812660 (DohART-NET). In accordance with H2020 rules, no new human embryos were sacrificed for research activities performed from the EU funding, which concerned only in silico analyses of recorded time-lapse and transcriptomics datasets. None of the authors has any conflict of interest to declare. TRIAL REGISTRATION NUMBER: n/a. CI - (c) The Author(s) 2021. Published by Oxford University Press on behalf of European Society of Human Reproduction and Embryology. FAU - Aboussahoud, Wedad S AU - Aboussahoud WS AD - Division of Developmental Biology and Medicine, Maternal and Fetal Health Research Centre, School of Medical Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, Manchester, UK. AD - Maternal and Fetal Health Research Centre, St. Mary's Hospital, Manchester University NHS Foundation Trust, Manchester Academic Health Sciences Centre, Manchester, UK. FAU - Smith, Helen AU - Smith H AD - Division of Developmental Biology and Medicine, Maternal and Fetal Health Research Centre, School of Medical Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, Manchester, UK. AD - Division of Cell Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, Manchester, UK. FAU - Stevens, Adam AU - Stevens A AD - Division of Developmental Biology and Medicine, Maternal and Fetal Health Research Centre, School of Medical Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, Manchester, UK. AD - Maternal and Fetal Health Research Centre, St. Mary's Hospital, Manchester University NHS Foundation Trust, Manchester Academic Health Sciences Centre, Manchester, UK. FAU - Wangsaputra, Ivan AU - Wangsaputra I AD - Division of Developmental Biology and Medicine, Maternal and Fetal Health Research Centre, School of Medical Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, Manchester, UK. AD - Maternal and Fetal Health Research Centre, St. Mary's Hospital, Manchester University NHS Foundation Trust, Manchester Academic Health Sciences Centre, Manchester, UK. FAU - Hunter, Helen R AU - Hunter HR AD - Department of Reproductive Medicine, Old St. Mary's Hospital, Manchester University NHS Foundation Trust, Manchester Academic Health Sciences Centre, Manchester, UK. FAU - Kimber, Susan J AU - Kimber SJ AD - Division of Cell Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, Manchester, UK. FAU - Seif, Mourad W AU - Seif MW AD - Division of Developmental Biology and Medicine, Maternal and Fetal Health Research Centre, School of Medical Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, Manchester, UK. AD - Department of Reproductive Medicine, Old St. Mary's Hospital, Manchester University NHS Foundation Trust, Manchester Academic Health Sciences Centre, Manchester, UK. FAU - Brison, Daniel R AU - Brison DR AUID- ORCID: 0000-0002-4307-1293 AD - Department of Reproductive Medicine, Old St. Mary's Hospital, Manchester University NHS Foundation Trust, Manchester Academic Health Sciences Centre, Manchester, UK. LA - eng GR - G0801057/MRC_/Medical Research Council/United Kingdom GR - MR/L004992/1/MRC_/Medical Research Council/United Kingdom GR - DH_/Department of Health/United Kingdom PT - Journal Article PT - Research Support, Non-U.S. Gov't PL - England TA - Hum Reprod JT - Human reproduction (Oxford, England) JID - 8701199 RN - 0 (Toll-Like Receptors) SB - IM MH - *Blastocyst MH - *Embryo Implantation MH - Female MH - Humans MH - Immunity, Innate MH - Pregnancy MH - Toll-Like Receptors/genetics MH - Transcriptome PMC - PMC8450873 OTO - NOTNLM OT - ART OT - Toll-like receptor OT - cytokines OT - human embryo OT - infection OT - innate immunity OT - preimplantation EDAT- 2021/09/14 06:00 MHDA- 2021/11/03 06:00 PMCR- 2021/09/13 CRDT- 2021/09/13 21:08 PHST- 2021/03/22 00:00 [received] PHST- 2021/07/02 00:00 [revised] PHST- 2021/09/14 06:00 [pubmed] PHST- 2021/11/03 06:00 [medline] PHST- 2021/09/13 21:08 [entrez] PHST- 2021/09/13 00:00 [pmc-release] AID - 6369596 [pii] AID - deab188 [pii] AID - 10.1093/humrep/deab188 [doi] PST - ppublish SO - Hum Reprod. 2021 Sep 18;36(10):2661-2675. doi: 10.1093/humrep/deab188.