This study describes the expression of insulin-like growth factor-I (IGF-I) and IGF-I receptor (IGF-IR) genes in the mouse uterus during the peri-implantation period (Days 1-6 of pregnancy), as well as effects of estradiol (E) and progesterone (P) on cell-specific IGF-I gene expression in the uterus of the ovariectomized adult mouse. Northern blot analysis showed that IGF-I mRNA levels were low but readily detectable in the uterus on Day 1 of pregnancy and steadily increased, reaching high levels just before (Day 4) and after initiation of implantation (Days 5 and 6). In general, IGF-IR transcripts were present in low abundance in uterine RNA throughout the peri-implantation period. However, six sizes of uterine IGF-IR transcripts were detected, and the relative abundance of two of these transcripts varied significantly during the peri-implantation period. Cell-specific expression of the IGF-I gene was examined by in situ hybridization to mRNA and immunohistochemical detection of protein. The results indicated that the synthesis of IGF-I on Days 1 and 2 was most predominant in glandular and luminal epithelial cells. However, on Days 3 and 4, stromal cells, and on Days 5 and 6, decidual cells appeared to be the predominant sites of synthesis of this growth factor. Uterine IGF-I gene expression was stimulated by ovarian steroids. Northern blot analysis showed that IGF-I transcripts were rare in the ovariectomized adult mouse uterus, but an injection of P and/or E caused a rapid accumulation of these transcripts. Analysis of the cell-specific expression of uterine IGF-I showed that E induced IGF-I gene expression primarily in epithelial cells, whereas P did so in the stroma. Superimposition of E on the P-primed uterus further stimulated IGF-I expression in the stroma. The results of these studies are consistent with an autocrine/paracrine function of uterine IGF-I, and indicate that ovarian steroids regulate the cell-specific and temporal patterns of expression of this gene in the peri-implantation mouse uterus.

Immunohistochemistry and in situ and Northern blot hybridization were employed to determine temporal and spatial expression of transforming growth factor-beta 1 (TGF beta 1) in the mouse uterus during the periimplantation period. The polyclonal antisera anti-LC-(1-30) and anti-CC-(1-30), raised against two different preparations of a peptide corresponding to the amino-terminal 30 amino acids of TGF beta 1, were used for histochemical analyses because of their distinct staining patterns. Anti-LC shows intracellular staining, while staining by anti-CC is primarily extracellular. The colocalization of intracellular staining by anti-LC with in situ hybridization of TGF beta 1 mRNA in the luminal and glandular epithelia on days 1-4 of pregnancy (day 1 = vaginal plug) indicates that the epithelial cells are the primary sites of TGF beta 1 synthesis during the preimplantation period. On the other hand, staining of the extracellular matrix of the stroma by anti-CC during this period suggests an active accumulation of TGF-beta 1 that is synthesized in and secreted from the epithelia. While intracellular staining and accumulation of TGF-beta 1 mRNA in the epithelia were clearly evident on days 1-4, the extracellular staining showed temporal fluctuations. The clear extracellular staining of the stroma that was observed on day 1 was absent on day 2; moderate staining was again visualized in the stroma on day 3 and was markedly increased on day 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Embryonic stem (ES) cells are pluripotent cells with the capacity to generate any type of cell. Here we describe the isolation of ES-like cells from canine blastocysts. Canine embryos were collected from beagle bitches at day 11-16 of first estrus. A total of 80 normal embryos were obtained from 15 dogs. Of the embryos, 13 were at the morulae stage, 39 at the blastocyst stage, and 28 at the hatched blastocyst stage. The inside of morulae or inner cell masses (ICMs) of blastocysts were isolated mechanically, and cultured onto mouse embryonic fibroblasts (MEF) as feeder layers. Primary cell colonies were formed in 0% (0/13) of morulae, 25.6% (10/39) of blastocysts, and 67.9% (19/28) of hatched blastocysts. These colonies were separated either by enzymatic dissociation or by mechanical disaggregation. Dissociation with collagenase resulted in immediate differentiation, but with mechanical disaggregation these cells remained undifferentiated, and two ES-like cell lines (cES1, cES2) continued to grow in culture after eight passages. These cells had typical stem cell-like morphology and expressed specific markers such as alkaline phosphatase activity, stage specific embryonic antigen-1 and Oct-4. These cells formed embryoid bodies (EBs) in a suspension culture; extended culture of EBs resulted in the formation of cystic EBs. When the simple EBs were cultured on tissue culture plates, they differentiated into several types of cells including neuron-like, epithelium-like, fibroblast-like, melanocyte-like, and myocardium-like cells. These observations indicate that we successfully isolated and characterized canine ES-like cells.