FTIR microspectroscopic imaging as a new tool to distinguish chemical composition of mouse blastocyst

Synchrotron-Infrared (SR-IR) mapping and Focal plane array (FPA) imaging have been applied for discrimination of the three biochemical components of the mouse blastocyst. The mouse blastocyst consists of two clusters of cells known as the inner cell mass (ICM) formed within the blastocoel cavity and the thin layer of outer cells called the trophectoderm. Using Hierachical Cluster Analysis (HCA) and Principle Component Analysis (PCA), it can be shown that the composition and distribution of biochemical components within the blastocyst show differences in the protein secondary structure and the lipid content. It is worth noting that the secondary structure of the outer layer cells indicates more distinctive β-type secondary structure. The blastocoel cavity was observed to be predominantly α-helix. Significantly, the ICM region showed the predominant high absorption intensities of lipid content (CH₂, CH₃ symmetric and asymmetric stretching around 3000-2800 cm^-1). The results show agreement between both SR-IR mapping and FPA-IR imaging. We propose that the biochemical difference within the blastocyst, especially the high lipid content in the ICM region, could be involved in the process of lipid signaling during pre-implantation. The use of both techniques is shown to be significant approach for revealing the biochemical components within the blastocyst. Crown