Heat Shock Differentially Compromises Embryonic Development and Gene Expression in a Mouse Embryoid Body Model System

This study established an in vitro model to investigate peri- and post-implantation embryo development under heat shock conditions. In Experiment 1, we compared the gene expression profiles of the three germ layers in in vivo mouse embryos with those of mEBs derived from mouse embryonic stem cells. mEBs (Days 1-5) closely resembled developing E5.5-E6.5 embryos, expressing key germ layer markers: <i>nestin</i> (ectoderm), <i>flk-1</i> (mesoderm), and <i>ttr</i> (endoderm). In Experiment 2, mEBs were randomly allocated to one of the following treatments: a control group (37 °C) or a heat shock group (39 °C or 41 °C) for 12 h or 24 h. Timing of germ layer marker expression, including <i>ttr</i>, was delayed by 1-2 days in the heat-shocked groups compared with the control group. Morphological analysis of mEBs revealed that the peripheral cell layer exhibited signs of disassembly or degeneration and became increasingly apoptotic under heat shock conditions. Additionally, these mEBs showed increased expression of heat shock proteins 70 and 72 in response to elevated temperatures and prolonged heat shock durations. Mouse EBs closely mimic in vivo-developing embryos in their germ layer marker expression profiles. In vitro heat shock delays germ layer marker gene expression and induces heat shock protein 72 expression in mEBs.