Conceptus interferon gamma is essential for establishment of pregnancy in the pig

Abstract

Establishment and maintenance of pregnancy in the pig is a complex process that relies on conceptus regulation of the maternal proinflammatory response to endometrial attachment. Following elongation, pig conceptuses secrete interferon gamma (IFNG) during attachment to the endometrial luminal epithelium. The objective here was to determine if conceptus production of IFNG is important for early development and establishment of pregnancy. CRISPR/Cas9 gene editing and somatic cell nuclear transfer technologies were used to create an IFNG loss-of-function study in pigs. Wild-type (IFNG+/+) and null (IFNG−/−) fibroblast cells were used to create embryos through somatic cell nuclear transfer. IFNG expression was not detected in IFNG−/− conceptuses on either day 15 or day 17 of pregnancy. Ablation of conceptus IFNG production resulted in the reduction of stromal CD3+ and mast cells which localized to the site of conceptus attachment on day 15. The uteri of recipients with IFNG−/− conceptuses were inflamed, hyperemic and there was an abundance of erythrocytes in the uterine lumen associated with the degenerating conceptuses. The endometrial stromal extracellular matrix was altered in the IFNG−/− embryo pregnancies and there was an increased endometrial mRNA levels for collagen XVII (COL17A1), matrilin 1 (MATN1), secreted phosphoprotein 1 (SPP1) and cysteine-rich secretory protein 3 (CRISP3), which are involved with repair and remodeling of the extracellular matrix. These results indicate conceptus IFNG production is essential in modulating the endometrial proinflammatory response for conceptus attachment and survival in pigs.

Improvements in pig agriculture through gene editing

“…Pigs were the first livestock species that were successfully created to make the first disease resistant animals (Whitworth et al 2016 , 2018 ). This was flowed by creating pigs via precision breeding to improve production traits (Telugu et al 2017 ), to lessen the impact on the environment (Forsberg et al 2013 ), improve digestion (Guan et al 2017 ) as well as to understand reproductive performance (Johns et al 2021 ).…”

“…However, all recipient gilts aborted between Day 25 and 30 of gestation. In addition, the CRISPR/Cas9 knock out of conceptus interferon gamma production causes a hyperinflammatory response within the uterus which resulted in conceptus fragmentation (Johns et al 2021 ). The approaches have been successfully used to understand conceptus interaction(s) with the maternal uterus, expanding our knowledge on embryo development, establishment of pregnancy and survival.…”

“…These CD163 knock out pigs were fully resistant to the virus that causes porcine respiratory and reproductive syndrome (PRRS) (Whitworth et al 2016 ). In addition to creating pigs with disease resistance traits, gene editing can be used to improve production traits (Telugu et al 2017 ), to lessen the impact on the environment (Forsberg et al 2013 ), improve digestion (Guan et al 2017 ) as well as to understand reproductive performance (Johns et al 2021 ) Pigs are also used as models for evaluating somatic cell genome editing, as well as for gene therapy (Korpela et al 2021 ; Liu et al 2021 ). Gene editing is explored across the livestock industry to improve animal welfare and increasing efficiency.…”

Revisiting the Transcriptome Landscape of Pig Embryo Implantation Site at Single-Cell Resolution

“…Interestingly, PTGS2 null conceptus was able to live beyond 30 days of gestation, suggesting that conceptus PGE2 is not essential for early pregnancy ( Pfeiffer et al, 2020 ), probably because of a compensatory mechanism involving PGE2 auto-amplification loop in the endometrium in response to conceptus E 2 ( Waclawik et al, 2009 ). On the contrast, conceptus IFNG production is essential for endometrial proinflammatory response and conceptus attachment ( Johns et al, 2021 ). The interaction between trophoblast cells and uterine epithelial cells represents the key mechanism of embryo implantation.…”

Context is key: Maternal immune responses to pig allogeneic embryos

“…In this regard, conceptus‐derived factors are responsible for maintaining an adequate immune balance. IFNG is shown to regulate a large number of endometrial genes involved in immune tolerance during the process of conceptus attachment to the luminal epithelium and placental development (Johns et al, 2021; Yoo et al, 2020). Conceptus IFNG is considered responsible for inducing the expression of swine leukocyte antigen‐ DQA (SLA‐DQA), a major histocompatibility complex (MHC) class II gene, in pig endometrium at the time of conceptus implantation; likely regulating immune response at the maternal‐fetal interface to support the maintenance of pregnancy (Kim et al, 2012).…”