Interleukin 1 Signaling Is Regulated by Leukemia Inhibitory Factor (LIF) and Is Aberrant in Lif−/− Mouse Uterus1

Abstract

This study addresses the regulation of the interleukin 1 (IL1) system in the murine uterine luminal epithelium (LE) and stroma by leukemia inhibitory factor (LIF). Using RT-PCR we compared expression of Il1a, Il1b, Il1rn, Il1r1, and Il1r2 during the pre- and peri-implantation periods of pregnancy in wild-type (WT) and LIF-null LE and stroma. In WT LE, Il1a transcripts were down-regulated on Day 4 of pregnancy (D4), with renewed expression by the evening of D4 (D4 pm). In Lif(-/-) LE there was a gradual decrease in expression on D2, and expression became undetectable by D6. Il1b and Il1r1 expression were similar in WT and null mice, but Il1rn expression was almost completely lost during the peri-implantation period in Lif(-/-) LE. In the stroma, Il1a was sharply down-regulated on D4 and reappeared on D4 pm but was only expressed from D3 to D5 in the null mice. Stromal Il1r1 and Il1r2 were also misregulated. Il1rn showed constitutive expression in null stroma in contrast to the loss of expression on D4 in the WT mouse. In Lif-deficient mice, immunostaining indicated a reduction of endometrial IL1A at the time of implantation and of IL1B in stroma. LE-stromal coculture revealed that LIF stimulated the apical secretion of both IL1A and PTGES2 by LE cells without affecting basal secretion of IL1A and with only a small effect on basal PTGES2 secretion. We conclude that Il1a and Il1rn in LE and Il1a, Il1rn, and Il1r1 in stroma are regulated by LIF, which stimulates apical secretion of IL1A by LE.

Determining the LIF-sensitive period for implantation using a LIF-receptor antagonist

“…The disappearance of IL1A may therefore contribute to the restricted enhancement and spread of a PTGS2 response, which is initiated on queue. These results support our recent in vitro data showing that LIF stimulates IL1A and PGE 2 secretion in a co-culture system (Fouladi-Nashta et al 2008) and that LIF signalling may both directly and indirectly regulate IL1A and IL1B expression in the peri-implantation uterus. IL1A (and IL1B) expression is not implantation site specific (Fouladi-Nashta et al 2008) and therefore the absence of IL1A is unlikely to be due to lack of/or aberrant embryonic signals.…”

“…We have shown that members of the IL1 system are dysregulated during the implantation period in the uteri of Lif null mice compared to wild-type mice (Fouladi-Nashta et al 2008). Examination of IL1A and IL1B protein in hLIF-05 treated and control uteri on day 5 of pregnancy revealed no differences in expression, Determining the LIF-sensitive period suggesting that abrogation of LIF signalling in the LE does not directly regulate IL1A or IL1B expression at this level.…”

“…Often, the genetic alteration prevents the survival of null mice to adulthood and thus studies on reproductive physiology are hampered, reviewed in Salamonsen et al (2001). Previous work has centred upon identifying possible targets of LIF during early pregnancy from comparisons between wild-type and Lif deficient mice (Fouladi-Nashta et al 2004, 2005, 2008, Sherwin et al 2004. However, this neither permits the study of the temporal and spatial influence of LIF, particularly during pregnancy nor does it address the possibility that the phenotype may partly arise from the gene deletion construct causing -cis or -trans effects on adjacent genes.…”

“…Experiments have shown that functional inactivation of LIFR by hLIF-05 is required for the arrest of murine rod differentiation in vitro (Neophytou et al 1997) and previous work in our laboratory has shown that LIF induced effects can be antagonised by hLIF-05 in cultured murine uterine stromal cells (Fouladi-Nashta et al 2004, 2008. However, this antagonist has not been used previously in vivo.…”

“…IL1-associated molecules are temporally regulated during the implantation period in wild-type mice and this regulation is aberrant in the uteri of Lif null mice (Fouladi-Nashta et al 2008). To determine if hLIF-05 inhibition causes misregulation of IL1 during early pregnancy, immunohistochemical analysis of IL1A and IL1B was performed in control and LIF-inhibited uteri on days 5 and 6 of pregnancy.…”