RESUMEN
The expression and function of podoplanin (PDPN) in the normal human placenta has been debated in placental evaluation. This study emphasizes the importance of a multimodal approach of PDPN expression in normal human placentas. A complete examination is performed using immunohistochemistry, RNAscope and automated Digital Image examination (DIA) interpretation. QuPath DIA-based analysis automatically generated the stromal and histological scores of PDPN expression for immunohistochemistry and RNAscope stains. The umbilical cord's isolated fibroblasts and luminal structures expressed PDPN protein and PDPN_mRNA. RNAscope detected PDPN_mRNA upregulation in syncytial placental knots trophoblastic cells, but immunohistochemistry did not certify this at the protein level. The study found a significant correlation between the IHC and RNAscope H-Score (p = 0.033) and Allred Score (p = 0.05). A successful multimodal strategy for PDPN assessment in human placentas confirmed PDPN expression heterogeneity in the full-term human normal placenta and umbilical cord at the protein and mRNA level. In placental syncytial knots trophoblastic cells, PDPN showed mRNA overexpression, suggesting a potential role in placenta maturation.
RESUMEN
Background Human embryo vasculogenesis (blood vessel development starting from endothelial precursors) includes the ability of mesenchymal cells and pluripotent stem cells to differentiate into endothelial cells. Quantification of endothelial progenitor cells is difficult to assess during the early steps of human embryo development due to several factors, especially due to the paucity of human embryo tissue which is usually discarded after early-stage pregnancy abortive methods. CD133 (Promimin-1) is a general marker of progenitor cells, but combined with other endothelial markers such as CD34, it may identify endothelial progenitor cells during embryonic development. CD34 immunohistochemistry was previously performed by our team to identify human embryo capillaries and comparatively assess microvessel density between different human embryonic tissues. TIE2 is an angiopoietin receptor strongly involved in the newly formed blood vessel maturation due to its expression in some mesenchymal precursors for future pericytes. CD34 assesses the presence of endothelial cells but its single use does not evaluate the endothelial progenitor state as CD133 may do nor vessel maturation as TIE2 may do. Data about the dynamics of CD133/TIE2 expression in the early stages of human embryo development are scarce. Hence, in this study, we aimed to comparatively assess the dynamic of CD133+ endothelial precursors and TIE2 expression on five and seven-week-old human embryonic tissues with a special emphasis on their expression on embryonic vascular beds. Methodology CD133 and TIE2 immunohistochemistry was performed on five and seven-week-old human embryonic tissues followed by their quantification using the Qu Path digital image analysis (DIA) automated method. Results CD133 and TIE2 showed divergent patterns of expression during the initial phases of human embryonic development, specifically in the vascular endothelium of tiny capillaries. The expression of CD133 in endothelial cells lining the perfused lumen gradually decreased from five to seven-week-old embryos. It remained expressed with greater intensity in cells located at the tip of the vascular bud that emerged into pre-existing capillaries. TIE2 was much more specific than CD133, being restricted to the level of the vascular endothelium; therefore, it was easier to quantify using digital image analysis. The endothelium of the embryonic aorta was an exception to the divergent expression, as CD133 and TIE2 were consistently co-expressed in the seven-week-old embryo. The Qu Path DIA assessment increased the accuracy of CD133 and TIE2 evaluation, being the first time they were quantified by using automated software and not manually. Conclusions High heterogeneity of CD133 and TIE2 was observed between five and seven-week-old embryonic tissues as well as between different embryonic regions from the same gestational age. The unique finding of CD133/TIE2 co-expression persistence inside aortic endothelium needs further studies to elucidate the role of this co-expression.