Volume of liquid below the epithelium of an F9 cell as a signal for differentiation into visceral endoderm.
When retinoic acid-primed F9 cells are allowed to aggregate, they form embryoid bodies with an outer layer of (&agr;)-fetoprotein-producing visceral endoderm cells and an internal cavity. I show that maturation of the visceral endoderm is dependent on the size of F9 aggregates. Size fractionation of aggregates of retinoic acid-primed F9 cells on Percoll density gradients revealed that only aggregates with diameters larger than 180 microm developed into embryoid bodies with an endoderm layer secreting (&agr;)-fetoprotein. Size dependent alpha-fetoprotein-secretion was also observed when retinoic acid-primed F9 cells were cultured on porous microcarrier beads larger than 185 microm. Retinoic acid-primed F9 cells on flat microporous membranes did not differentiate and secrete alpha-fetoprotein unless exposed to a limited volume of medium at their basolateral surface. This suggested that maturation of the visceral endoderm is signaled by the volume of liquid phase below the epithelium. I postulate that the epithelial layer of an F9 aggregate encloses liquid and forms a barrier to diffusion of some critical factor(s). The concentration of such a factor may reach a threshold due to enlargement of the liquid phase during growth of the F9 aggregate and thereby signal maturation of the outer layer of cells into visceral endoderm.
Miki
K
K
Nagoya University Bioscience Center, Chikusa, Nagoya 464-8601, Japan. miki@niehs.nih.gov
D000818:Animals; D018236:Carcinoma, Embryonal / Q000473:pathology; D002449:Cell Aggregation; D002454:Cell Differentiation / Q000187:drug effects; D004707:Endoderm / Q000166:cytology*; D004847:Epithelial Cells / Q000166:cytology; D051379:Mice; D015398:Signal Transduction; D013234:Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D014212:Tretinoin / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D000509:alpha-Fetoproteins / Q000096:biosynthesis / Q000378:metabolism
D000509:alpha-Fetoproteins; D014212:Tretinoin