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A New Role for the Human Placenta as a Hematopoietic Site Throughout GestationInstitute for Regeneration Medicine, Human Embryonic Stem Cell Program, Department of Cell and Tissue Biology, Blood Systems Research Institute, San Francisco, California, Alicia.Barcena{at}ucsf.edu
Department of Laboratory Medicine University of California at San Francisco, San Francisco, California, Blood Systems Research Institute, San Francisco, California
Institute for Regeneration Medicine, Human Embryonic Stem Cell Program, Department of Cell and Tissue Biology
Institute for Regeneration Medicine, Human Embryonic Stem Cell Program, Department of Cell and Tissue Biology We investigated whether the human placenta contributes to embryonic and fetal hematopoietic development. Two cell populations—CD34++CD45low and CD34 +CD45low—were found in chorionic villi. CD34++ CD45low cells display many markers that are characteristic of multipotent primitive hematopoietic progenitors and hematopoietic stem cells. Clonogenic in vitro assays showed that CD34++CD45 low cells contained colony-forming units-culture with myeloid and erythroid potential and differentiated into CD56+ natural killer cells and CD19+ B cells in culture. CD34+CD45low cells were mostly enriched in erythroid- and myeloid-committed progenitors. While the number of CD34++CD45low cells increased throughout gestation in parallel with placental mass. However, their density (cells per gram of tissue) reached its peak at 5 to 8 weeks, decreasing more than 7-fold from the ninth week onward. In addition to multipotent progenitors, the placenta contained intermediate progenitors, indicative of active hematopoiesis. Together, these data suggest that the human placenta is potentially an important hematopoietic organ, opening the possibility of banking placental hematopoietic stem cells along with cord blood for transplantation.
Key Words: Human placenta embryonic and fetal hematopoiesis multipotent hematopoietic progenitor.
Reproductive Sciences, Vol. 16, No. 2,
178-187 (2009) |
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