COLONY-STIMULATING FACTOR-I IN CONCEPTUS AND UTERINE TISSUES IN PIGS

Colony-stimulating factor-1 (CSF-1), a growth factor for cells of mono cyte/macrophage lineages, is produced by uterine and placental tissues in humans and mice and may stimulate placental growth and development . The present study characterized CSF-1 mRNA and protein expressed by porcine uterine, conceptus, allantochorion, and fetal tissues at vario us stages of pregnancy. A human CSF-1 cDNA and an anti-human CSF-1 mon oclonal antibody were utilized to examine CSF-1 mRNA and protein. Nort hern blot analyses detected mRNA transcripts of 3.6-5.1 kb in pig tiss ues. A 4.0-kb transcript was common to all tissues examined. Endometri al CSF-1 mRNA increased (p < 0.05) as pregnancy proceeded, with highes t levels at term, and was temporally associated with concentrations of estrogen (E) in plasma. Placental expression of the CSF-1 gene increa sed (p < 0.05) throughout gestation with the major increase occurring between Days 20 and 30, after which time high levels of mRNA were main tained to term. The changes in placental CSF-1 mRNA were temporally as sociated with periods of rapid placental and fetal growth. High levels of CSF-1 mRNA were also detected in skeletal muscle, kidney, and inte stine of fetuses. Immunoreactive CSF-1 was detected in all of the tiss ues examined. Partial cloning of the porcine CSF-1 gene indicated grea ter than 98% identity with the human CSF-1 gene. CSF-1 gene expression in endometrium was not affected by exogenous E or progesterone treatm ent in ovariectomized gilts. These results suggest that CSF-1 may infl uence placental and fetal growth, and its differential expression in f etal tissues indicates that CSF-1 may also affect embryonic differenti ation and growth of those tissues.