Reagents and antibodies (Abs)
LPS from Escherichia coli O55:B5 and recombinant mouse CX3CL1 were purchased from LIST Biological Laboratories (Campbell, CA) and R&D Systems (Minneapolis, MN), respectively. …
Animal model:
LPS-induced PTL was conducted similarly as described previously [16]. In brief, two female mice were co-housed with a male one of the same genotype and checked for vaginal plugs as the evidence of mating at the next morning. The day of vaginal plug detection was designated as gd 0.5 of pregnancy, and the pregnant mice were removed from the male. All pregnant mice delivered their pups on gd 19 or 20. At gd 15.5, the pregnant mice were intraperitoneally administered with LPS (25 g in 200 l of PBS) or PBS 200 l, followed by the observation until delivery. The presence of intact or partial fetal tissue in the cage was noted as the evidence for delivery, and the delivery before gd 18.5 was judged as pre-term labor, and pups born before gd 18.5 could not survive >24 h after birth [30]. In our dose, 25 g was the highest dose of LPS that reproducibly induced PTL without significant morbidity or mortality in gravid C57BL/6 females, based on the established method [31, 32]. In some experiments, pregnant WT mice were i.p. injected with anti-CX3CL1 Ab (200 g/mouse) or control IgG at 3 h after LPS injection, and were observed until delivery. The percentage of preterm labor was calculated as follows: percentage (%) = 100 x (number of LPS-treated mice that delivered until gd 18.5/number of LPS-treated pregnant mice). All animal experiments were approved by the Committee on Animal Care and Use at Wakayama Medical University.
Blood and tissue sampling:
At gd 5.5, 10.5, 15.5, 18.5, or 6 h after LPS or PBS injection, mice were anesthetized by the intraperitoneal injection of Avertin (tribromoethanol, 20 g/g), and whole blood samples were taken, followed by centrifugation (3,000 x g for 15 min) to collect serum. In each pregnant mouse, uterus was removed, and viable fetuses were dissected from the amniotic sac and umbilical cord, to weigh the obtained fetuses and placentas. Gestational tissues including uterus (from between implantation sites), placenta and amnion were stored at -80C until processing for the subsequent analyses.