Blastocyst-Bearing Sows Display a Dominant Anti-Inflammatory Cytokine Profile Compared to Cyclic Sows at Day 6 of the Cycle

Abstract

In the context of porcine embryo transfer (ET) technology, understanding the tightly regulated local uterine immune environment is crucial to achieve an adequate interaction between the transferred embryos and the receiving endometrium. However, information is limited on the uterine immune status of cyclic-recipient sows when receiving embryos during ET. The present study postulated that the anti- and proinflammatory cytokine profile 6 days after the onset of estrus differs between endometria from uninseminated cyclic sows and blastocyst-bearing sows. On Day 6 of the cycle, endometrial explants were collected from sows inseminated or not inseminated during the postweaning estrus and cultured for 22 h. The culture medium was then analyzed for the contents of a total of 16 cytokines using Luminex MAP® technology. The results showed important differences in the endometrial production of most cytokines between the sow categories, with a predominant anti-inflammatory environment displayed by the blastocyst-bearing endometria. These findings suggest that sperm, seminal plasma (SP) and/or early embryos modify the uterine environment by inducing an immune-tolerant cytokine profile already visible at Day 6. Whether the SP or some of its active components may help to develop strategies to maximize the reproductive performance of recipients after ET needs further investigation.

Intrauterine Infusion of TGF-β1 Prior to Insemination, Alike Seminal Plasma, Influences Endometrial Cytokine Responses but Does Not Impact the Timing of the Progression of Pre-Implantation Pig Embryo Development

“…“Donors,” but not “recipients,” were subjected to two inducing stimuli (AI components and embryos). These stimuli are able to modify the endometrial immune response in gilts [ 54 ] and sows [ 58 ]. Moreover, the maternal immune system might detect the presence of pre-implantation embryos and react accordingly [ 59 , 60 , 61 ].…”

Seminal Plasma: Relevant for Fertility?

“…These spermadhesins, the PSPs in particular, attach sequentially to the sperm plasma membrane from the testis to the ejaculate [ 86 ], promoting sperm survival through membrane stabilization [ 87 ], and fertilization capability [ 87 , 88 ] by modulating capacitation and sperm-oviduct/oocyte interactions [ 85 , 86 , 89 , 90 , 91 ]. Moreover, they appear to regulate the timing of ovulation [ 92 ] and further showing immunostimulatory activities in vitro and in vivo, presumably in relation to specific cytokines [ 4 , 11 , 25 , 93 ]. Besides spermadhesins, a plethora (several hundred specific to Sus scrofa taxonomy) of other less abundant pig-specific SP proteins are present [ 32 , 34 ], yet only a few influence the reproductive processes.…”

“…In the human and pig, cytokines relate to sperm viability, semen function and hence fertility [ 41 , 70 , 95 , 110 ]. As well, cytokines—probably in concert with other SP proteins [ 11 , 111 ]—play a role in modulating the uterine immune-cytokine network [ 6 , 88 , 112 , 113 , 114 , 115 , 116 , 117 ], to facilitate the transitions in immune responses by the female mentioned earlier and what appears central for successful fertility [ 93 , 102 , 118 , 119 , 120 ]. In this context, it is also worth noting the function of the adipokines secreted by white adipose tissue.…”

“…Such a steady low efficiency has, together with experimental evidence of the effects of seminal plasma on the female, called for the application of SP during or after human embryo transfer [ 205 , 206 , 207 ]. Growing evidence has established SP playing major roles in embryo development and birth rates [ 102 ], and although the matter remains unsolved for humans, the experimental evidence from various animal models has quite nicely defined these effects on the female [ 12 , 93 , 120 ] ( Figure 5 ).…”

“…Do we have evidence that the SP per se is, by inducing the changes of gene expression in the internal genitalia of the female we have already pointed out, able to mark differences in fertility when added separately from spermatozoa? The answer seems to be yes, as rates in early embryo survival [ 88 , 93 , 102 , 120 , 173 , 208 ], implantation [ 101 , 102 , 115 ], placental development [ 116 ], farrowing, litter size and even offspring development and health [ 44 ] could be improved by additional inseminations with homologous/pools of SP.…”