**3.2. Comparative two-dimensional protein profile analysis of placenta tissues obtained from spontaneous unexplained preterm labor with intact membrane and its corresponding control**

To further investigate the proteomic alterations in the sPTL-IM, the spot intensities in placenta samples (maternal and fetal sides) from sPTL-IM and sTL-IM were compared using ImageMaster 2D platinum software program.

A normalized amount of protein extracted from placenta tissues of sPTL-IM and sTL-IM was fixed on 13-cm pH 3–10 IPG strips. Second dimension separation was performed on 10% widerange PAGE, as described under "Materials and Methods" section. Silver-stained 2D gels representing sPTL-IM and sTL-IM (fetal and maternal sides) are shown in **Figure 1A** and **B**, respectively. A comparison of the fetal side of the placenta tissues obtained from both the sPTL-IM and sTL-IM proteomes revealed highly similar protein profiles (**Figure 1AI** and **BI**) despite important differences being observed in the relative levels of several proteins as illustrated by the closer view of differentially expressed protein profiles (**Figure 1C**). These results were in parallel for the maternal side of the placenta tissues (**Figure 1AII**, **BII**, and **C**).

Student's *t*-test analysis revealed 12 differentially expressed proteins that are significant (two spots with greater staining and 10 spots with decreased staining; dotted circles in **Figure 1** indicate upregulated proteins, whereas solid circles indicate downregulated proteins, AI and BI, *P* < 0.05) in the fetal side of sPTL-IM with 100% reproducibility across the sample set. Whereas on the maternal side, only two gel spots with decreased staining showed at least 2.0 fold changes (solid circle in **Figure 1AII** and **BII**, *P* < 0.05) for the same comparison.
