Human embryonic stem cells (hESCs) are unique cells in that they can be maintained in vitro as pluripotent cells and can be induced to differentiate into many cell types by manipulating culture conditions. Therefore, hESCs have the potential of providing an unlimited supply of cells for cell-based therapy as well as providing a resource to study basic human developmental biology. Subsequently, much attention has been focused on directing hESC differentiation along specific developmental lineages [1-4].
Currently, the most utilized method to test for the undifferentiated state of hESCs is to analyze the expression of the proteins OCT4, NANOG, Alkaline phosphatase, SSEA3, SSEA4, TRA-1-60, and TRA-1-81 [5]. The transcription factor, OCT4 is essential for the formation and maintenance of pluripotent embryonic stem cells (6,7). High levels of OCT4 expression is seen in undifferentiated hESCs and is downregulated upon differentiation (8), thus making OCT4 an important marker to study hESCs. The stage specific embryonic antigens or SSEAs (SSEA1, 3 and 4) are also good markers of undifferentiated hESCs (9). The antibodies for SSEAs recognize epitopes on related glycosphingolipids or GSLs (10). The SSEA4 antibody recognizes the terminal sialic acid on GSL-7 (10). Upon differentiation, SSEA4 expression levels decrease and SSEA1 expression increases on human embryonic stem cells over time when treated with Retinoic acid (11).
The FlowCellect™ Human Embryonic Stem Cell Characterization kit uses an antibody-based detection method, utilizing fluorescently conjugated antibodies to detect hOCT4, SSEA4 and SSEA1. The FlowCellect™ Human Embryonic Stem Cell Characterization kit is designed specifically for flow cytometers with a single blue (488 nm) laser light source. The FlowCellect™ Human Embryonic Stem Cell Characterization kit is not intended for use in microscopy applications including ICC, IHC and HTS, western blot or any other fluorometric analysis platforms.
The kit is optimized for use on the Guava EasyCyte™ Plus cytometer that requires cell concentrations to be less than 500 cells per microliter. The kit does not include culture media or other materials that should be readily available in a common laboratory setting that routinely performs experiments of the type described here.