The placenta as a haematopoietic organ

Abstract

The recent description of the placenta as a tissue rich in haematopoietic stem and progenitor cells has not only opened up a whole new line of investigation into how haematopoiesis is regulated in this unique mammalian tissue, but has also resulted in the revisiting of longstanding and yet unanswered questions about the significance of having multiple haematopoietic organs during development. Due to its remarkable capacity for haematopoietic stem/progenitor cell expansion, the study of placental haematopoiesis is also of obvious clinical interest. In the following pages, we summarise what is currently known about the haematopoietic regulatory processes in the murine placenta and describe our most recent data demonstrating that the human placenta, like its murine counterpart, is also a source of haematopoietic stem and progenitor cells throughout development.

The Leukemia Inhibitory Factor Receptor Gene Is a Direct Target of RUNX1

“…1B) suggests that this promoter is also potentially regulated by RUNX1. RUNX1 plays a critical role in hematopoiesis and its expression has been documented in all tissues which support definitive hematopoiesis, including the placenta [Bee et al, 2009;Ottersbach and Dzierzak, 2010]. In keeping with this, RUNX1 expression was detected in the placental cell lines JAR and JEG-3 by qRT-PCR, although at lower levels than in the Kasumi-1 myeloid cell line (Fig.…”

Transient CD15-positive endothelial phenotype in the human placenta correlates with physiological and pathological fetoplacental immaturity

“…In recent years, there has been increasing evidence of a hematopoietic potential of the placenta and its participation in the development of embryonic and fetal hematopoiesis, associated with the accumulation in the stromal CD45+ hematopoietic stem and progenitor cells [9][10][11][26][27][28][29]. We suggest that CD15+ endothelium marks a transitory vascular niche of ''extraembryonic'' placental hematopoiesis and mirrors functional immaturity of the fetal myeloid hematopoiesis.…”

Hematopoietic Stem Cells

“…The murine placenta contains a large population of HSCs during midgestation within the vascular labyrinth region [129,141,142]. Tracking developing HSCs via their expression of Runx1-lacZ and CD41 revealed that they emerge in large vessels in the placenta and appear as early there as they do in the AGM region and before any HSCs had colonized the liver or were circulating in the blood.…”

“…Other vascular regions of the conceptus, such as the umbilical and vitelline arteries and the vascular labyrinth region of placenta, also harbor the earliest HSCs (reviewed in references [97,141]) although their role in the generation of these stem cells is less clear. Earlier studies on quail-chick chimeras showed that the avian allantois is a source of definitive hematopoietic cells [144].…”