Among the major issues of hematology is the lack of donor-derived hematopoietic progenitor cells (HPCs) transplanted for treatment of hematologic diseases and congenital hematopoiesis disorders. Thus, a search of new additional sources of HPCs is needed. It has been shown that human placenta plays an important role in embryonic hematopoiesis [3, 9] . At the same time, the immune phenotype of placental HPCs and their multipotency have not been completely studied as yet. Investigation of

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... HPCs and comparison of their properties with the properties of fetal and adult HPCs are important for assessment of their possible clinical application. The purpose of this study has been to compare the phenotypes of HPCs from placenta, umbilical cord blood and fetal liver. Placenta was received after full-term delivery (physiological or by caesarean section) in 39-41 weeks of pregnancy from 23-36 year old women according to their informed consent. Cord blood was obtained by standard methods of umbilical blood sampling. All samples were tested for the aerobic and anaerobic microorganisms and a fungal infection. ABSTRACT The study of placental hematopoietic progenitor cells (HPCs) and comparison of their properties with other fetal and adult HPCs is necessary for assessing of their possible clinical application. It has been shown that HPCs from placenta are heterogeneous by phenotype: placental tissue contains three populations with different level of CD34 expression such as CD34 +++ CD45 low/-, CD34 ++ CD45 low/and CD34 +/low CD45 low/-. Similar to fetal liver placenta contains both, population of CD34 ++ CD45 low/and CD34 + CD45 low/cells, suggesting hematopoiesis in placental tissue. CD34 ++ CD45 low/population also expressed CD133, almost negative for lineage markers, and had lymphocyte-like morphology conforming the presence of primitive HPCs in this population. Additionally, we found later progenitors with phenotype CD34 +/low CD45 + in placental tissue as the majority of these cells expressed hematopoietic lineage markers. Population with phenotype CD34 +++ CD45 low was observed in the placenta that may evidence for their generation in the placental tissue or migration from the other sites of hematopoiesis and changing phenotype under placental microenvironment.