title: Proliferation and differentiation of porcine inner cell mass and epiblast in vitro.
abstract: The proliferation rate and differentiation state were investigated in porcine inner cell masses (ICMs) and epiblasts in vitro. ICMs isolated from early blastocysts (Day 7 of pregnancy) and epiblasts isolated from preelongated blastocysts (Day 11 of pregnancy) were cultured for up to 5 days in the presence of human leukemia inhibitory factor (hLIF) (1000 U/ml). The proliferation rate was evaluated by determination of the percentage of cells in S-phase. The differentiation state was determined by studying the expression of the stage-specific embryonic antigen-1 (SSEA-1), a marker for undifferentiated murine embryonic stem (ES) cells, and the expression of laminin and cytokeratins 8/18, markers of ES cell differentiation. The staining pattern showed that freshly collected Day 11 epiblasts appeared undifferentiated but rapidly lost this characteristic in vitro. A decrease in the proliferation rate was also observed during culture. This decrease was reduced in the presence of high concentrations of hLIF (optimal concentrations: 5000 U/ml). Conversely, treatment of Day 11 epiblast cells with retinoic acid, an agent known to induce differentiation in murine ES cells, caused a dramatic decrease in the proliferation rate in vitro. In contrast to Day 11 epiblasts, Day 7 ICMs expressed SSEA-1 in vitro and showed a higher proliferation rate (p < 0.01). However, their proliferation rate also decreased during culture and following trypsinization. These results indicate that the undifferentiated characteristics of Day 7 ICMs are more likely to be maintained in vitro than are those of Day 11 epiblasts, which are rapidly committed into early differentiation.
authors.affiliation: INRA, URA-CNRS 1291, Nouzilly, France. florence.wianny@ens-lyon.fr
authors.forename: F
authors.initials: F
authors.lastname: Wianny
authors.forename: C
authors.initials: C
authors.lastname: Perreau
authors.forename: M T
authors.initials: MT
authors.lastname: Hochereau de Reviers
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000166:cytology* / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D002478:Cells, Cultured; D005260:Female; D005347:Fibroblasts / Q000502:physiology; D006131:Growth Inhibitors / Q000378:metabolism; D007150:Immunohistochemistry; D015850:Interleukin-6; D007700:Kinetics; D053605:Leukemia Inhibitory Factor; D016256:Lewis X Antigen / Q000096:biosynthesis; D008222:Lymphokines / Q000378:metabolism; D051379:Mice; D011247:Pregnancy; D013234:Stem Cells / Q000378:metabolism; D013552:Swine; D014212:Tretinoin / Q000378:metabolism
chemical_list: D006131:Growth Inhibitors; D015850:Interleukin-6; C507837:LIF protein, human; D053605:Leukemia Inhibitory Factor; D016256:Lewis X Antigen; C507838:Lif protein, mouse; D008222:Lymphokines; D014212:Tretinoin