Emperipolesis of erythroblasts within Kupffer cells during hepatic hemopoiesis in human fetus

Abstract

The state in which cells can inhabit other cells without damage is known as emperipolesis. Emperipolesis has been found in various physiological and pathological conditions. We performed a study of emperipolesis of erythroblasts within Kupffer cells in the human fetal liver. We found that Kupffer cells, identified by CD68 immunolabeling, contained 4-8 erythroblasts in a hypertrophic cytoplasm on light microscopy. Emperipoletic erythroblasts were present in various maturation stages from proerythroblast to reticulocyte. By electron microscopy, we found that erythroblasts occupied membrane-bound vacuoles that were separated from each other by thin partitions of Kupffer cell cytoplasm. Neither emperipoletic erythroblasts nor their Kupffer cell hosts showed evidence of damage. Emperipoletic cells in mitosis were found, which suggests the capacity for the proliferation of erythroblasts within Kupffer cells. Some Kupffer cells were seen to contain both emperipoletic cells and phagosomes, without evidence of interaction. Erythroblasts and other hemopoietic cells were also found to be closely associated with the sinusoidal surface of Kupffer cells. However, intercellular junctions, if present, were inconspicuous. On occasion, Kupffer cells engorged with erythroblasts nearly occluded the sinusoidal lumen. Our results demonstrate that emperipolesis of erythroblasts within Kupffer cells occurs in human fetal hepatic hemopoiesis. We suggest that emperipolesis may be one of the mechanisms that support the maturation of erythroblasts in the fetal liver.

Stress reticulocytes lose transferrin receptors by an extrinsic process involving spleen and macrophages

“…Macrophages are among the most likely candidate cell types mediating the loss of reticulocyte TfRs in the spleen . Therefore, hematocrits, RBC numbers, and flow cytometry results for TO staining and surface TfR expression of circulating RBCs were examined in mice treated with liposomal clodronate and control mice treated with plain liposomes on day 4 of recovery from anemia induced by three consecutive daily phlebotomies (Fig.…”

“…Ultrastructural studies have demonstrated that macrophages are likely mediators of extrinsic membrane remodeling before and after reticulocyte release from the hematopoietic organs. In normal human fetal erythropoiesis, hepatic sinusoidal macrophages surround newly formed reticulocytes in a process, emperipolesis, which precedes reticulocyte entry into hepatic venous sinuses . In normal rat bone marrow, reticulocytes have intimate contact with central macrophages of erythroblastic islands before entering marrow venous sinusoids .…”

Progress of Research in Cell‐in‐Cell Phenomena

“…Emperipolesis has been reported to occur under various physiological and pathological conditions (Poppema,1978; Reid et al,1979; Kang et al,1987; Lee et al,1999). It describes the movements of viable cells after they were internalized (“inside round‐about wandering”) and is often used as a general term to refer to the process of cells entering, moving within and exiting other cells.…”

Hematopoietic Microenvironment in the Fetal Liver: Roles of Different Cell Populations

“…Their functions in the maintenance of hematopoiesis consist in phagocytosis of the nuclei extruded from late-stage erythroblasts [17,18] and secretion of erythropoietin [19]. The presence of dividing and maturing erythroblasts in the vacuoles of Kupffer cells, which has been observed in the fetal liver [18], may also indicate the role of these cells in the regulation of erythropoiesis.…”