Differential expression of ABC transporters (MDR1, MRP1, BCRP) in developing human embryos.

Three ABC transporters (MDR1, MRP1, BCRP), belonging to the family of multidrug resistance (MDR) proteins, play a crucial role in the protection mechanisms during embryogenesis and mediate drug resistance in cancer cells. The distribution of these transporters in the series of human embryonal/fetal intestine, liver and kidneys of various stages of intrauterine development (IUD) by indirect two-step immunohistochemical method was investigated. The organ- and age-specific expression patterns of these transporters were depicted and compared with the expression in adult organs. The evaluation of intestine and liver samples demonstrate differences in expression pattern of ABC transporters during IUD. On the contrary, in kidneys the age-specific localization was not observed. However, the increasing positivity from the kidney surface towards deeper, more differentiated parts was found. Hopefully, our study may contribute to elucidation of the role of multidrug resistance (MDR) pathways during IUD in man.

The Role of PPARs in MDR - a lesson from embryonic development.

One of the most important features of embryonic cells is their resistence to xenobiotics, which provides a natural protection for embryos against these potentially harmful molecules. In this way, embryo cells resemble cancer cells and thus understanding the basis of this phenomenon may contribute to overcoming the multi-drug-resistance (MDR) of some tumours. Peroxisome proliferator-activated receptors (PPARs) are steroid nuclear receptors that regulate diverse biological processes such as lipid and carbohydrate metabolism, development, differentiation, apoptosis, neoplastic transformation, inflammation and regeneration of tissues. Recently it has been found that they may also regulate the expression of some MDR proteins. In this article we summarise the main known relationships between some MDR pumps and three isoforms of PPAR receptors (PPAR-alpha, PPAR-beta/delta, PPAR-gamma). We hypothesize that regulation of MDR proteins by PPAR ligands in embryos could lead to the improvement of cancer treatment.

Involvement of p53 and Bcl-2 family proteins in regulating programmed cell death and proliferation in human embryogenesis.

Homeostasis and development in vertebrates are regulated by cell proliferation, differentiation and death. Permeability of mitochondrial membranes, a decisive feature of apoptosis, is regulated by Bcl-2 family regulators. Protein p53 is able to reduce bcl-2 and promote bax expression. This study focused on the immunohistochemical detection of the expression levels of Bcl-2 family regulators (anti-apoptotic Bcl-2 and Bcl-XL, pro-apoptotic Bcl-Xs and Bax), p53, and PCNA as a marker of proliferation, together with the evaluation of the level of apoptosis in human embryos (anlage of limbs, axial skeleton, metanephros, and intestine). Expression of observed proteins was assessed by a three-step immunohistochemistry and evidenced by the double-staining technique. Apoptosis was detected by the TUNEL technique. This study provided circumstantial evidence of the exclusive role of Bcl-2 and Bcl-XL proteins in the inhibition of apoptosis - only rarely were the Bcl-2/ Bcl-XL positive cells stained by TUNEL. The role of pro-apoptotic members of Bcl-2 family remains ambiguous, as TUNEL positive cells are both Bax/Bcl-Xs positive and negative. This study provided substantial evidence that expression patterns of observed proteins are neither fully explainable by "rheostat" theory, nor are the findings obtained from animal model tissue or cell culture commonly applicable to human embryos.

Expression of BCL-2 in the developing kidney of human embryos and fetuses qualitative and quantitative study.

Twelve human embryos and fetuses aged of 7-30 weeks of intrauterinal life were examined to determine the expression of bcl-2 gene in the developing kidney. Tissue samples were routinely processed and three-step indirect immunohistochemical method was used for the detection of Bcl-2 protein. End-point cytophotometry was performed with computer-controlled microscope photometer with a scanning table and the mean relative absorbance of the final product of peroxidase reaction was determined and taken as a measure of Bcl-2 expression. The morphometric evaluation was carried out from the TV display using Weibel s universal hexagonal raster and we determined the relative volume of Bcl-2 positive structures in the various zones of the embryonal kidney. The aim of our research was mapping of the Bcl-2 occurrence in the developing kidney of human embryos and fetuses. The Bcl-2 protein is involved in the regulation of apoptosis and its effect is antiapoptotic. The highest Bcl-2 expression was proved in the cells of metanephrogenic blastema. The lower occurrence of Bcl-2 positive cells was demonstrated in proximal tubules analges+ and it was almost on the borderline of detection in branches of ureteral bud. In the fetal period the marked Bcl-2 expression was maintained in the epithelial cells of proximal tubules analges.

The role of the apoptosis and the genes regulating apoptosis in the early differentiation of human embryo.

Apoptosis (programmed cell death) is an important process participating in the formation of organs and tissues during embryogenesis. Our aim of the work is studying the role of the apoptosis during the human embryonic differentiation. We tend to give acquired findings into the correlation with expression of proteins Bcl-2 and Bax (products of genes regulating apoptosis). Detection of the apoptosis was carried out on 25 routinely processed human embryos by means of TUNEL technique. The level of expression of Bcl-2 and Bax was determined using standard three-step immunohistochemical procedure. Results were achieved by the comparison of apoptoic index and the level expression of Bcl-2 and Bax was semiquantitatively evaluated. The low value of apoptotic index was mostly accompanied by the high expression of Bcl-2 and the Bax expression was not proportionally related to the value of apoptic index.