Insulin-like growth factor 2 and short-range stimulatory loops in control of human placental growth.
Substructures of the first-trimester human placenta (within 3 months post-conception) display 'pseudo-malignant' properties. We show here, by in situ hybridization, that the insulin-like growth factor 2 (IGF-2) gene expression is particularly active in the cytotrophoblasts, which dominate these structures. Because the majority of placental IGF-2 mRNA is polysomal in extracts of first-trimester placenta, the spatial pattern of IGF-2 transcripts generally also defines the pattern of IGF-2 production. In primary trophoblast cultures, rendered quiescent by serum starvation. IGF-2 performs as a human embryonic growth factor by activating cell cycle entry/progression. Although both type 1 and 2 IGF receptor mRNAs can be found co-distributed with IGF-2 mRNA during placental development (supporting an autocrine role for IGF-2), these occasional patterns are confined to cytotrophoblasts with low proliferative potential. The reciprocity in ligand and receptor expression patterns are discussed in terms of rate-limiting steps in the involvement of IGF-2 in the proliferative phenotype of the early human placenta.
Ohlsson
R
R
Centre for Biotechnology, Karolinska Institute, Huddinge University Hospital, Sweden.
Holmgren
L
L
Glaser
A
A
Szpecht
A
A
Pfeifer-Ohlsson
S
S
D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D005260:Female; D005786:Gene Expression Regulation; D005796:Genes; D006706:Homeostasis; D006801:Humans; D007335:Insulin-Like Growth Factor II / Q000096:biosynthesis / Q000235:genetics* / Q000494:pharmacology; D009693:Nucleic Acid Hybridization; D010920:Placenta / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D011247:Pregnancy; D012333:RNA, Messenger / Q000235:genetics; D011956:Receptors, Cell Surface / Q000235:genetics; D017451:Receptors, Somatomedin; D013002:Somatomedins / Q000235:genetics*; D014158:Transcription, Genetic
D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D013002:Somatomedins; D007335:Insulin-Like Growth Factor II