Extramedullary hematopoiesis in the adult mouse liver is associated with specific hepatic sinusoidal endothelial cells

Abstract

The liver is an important hematopoietic organ during fetal In previous work, two anatomically distinct-liver sinusoid life. After birth, liver hematopoiesis ceases; however, the abilendothelial cells (LEC): LEC-1 and LEC-2, have been deity of the liver to support hematopoiesis can be reestablished scribed. We also reported that extramedullary hepatic hemaunder certain conditions. [1][2][3] In an in vivo experimental model topoiesis occurs only in close contact with LEC-1, suggesting of extramedullary hematopoiesis, we have reported the forthat these cells may provide the microenvironment necessary mation of hematopoietic colonies within the hepatic sinufor the maintenance and growth of hematopoietic cells. In the soids. 4,5 These results indicate that critical hematopoietic mipresent work, we studied the capacity of LEC-1 and LEC-2 croenvironment (HM) components are probably expressed to maintain in vitro hematopoiesis. LEC-1 and LEC-2 were within the liver sinusoids. We have also reported that the isolated and cloned from livers of adult mice. Bone marrow sinusoidal walls of the liver are composed of two kinds of cells (BM) enriched with primitive hematopoietic progenitors liver endothelial cells (LEC), type-1 and type-2 (LEC-1 and were isolated from day-2, post-5-FU-treated mice (5-FUBMC).LEC-2, respectively). 6,7 LEC-1 supported the maintenance and differentiation of he-The formation of hematopoietic foci during liver extramatopoietic progenitors for more than 6 weeks in vitro. In medullary hematopoiesis occurs only in the periportal docontrast, LEC-2 cells poorly supported the proliferation of mains of the liver, in close contact with LEC-1; 4,6,7 that locahematopoietic cells for only two weeks of the co-culture. LECtion suggests the possibility that these LECs may provide 1 and 5-FUBMC cocultures showed cobblestone-area formavarious factors necessary for the maintenance and growth of tion and the presence of hematopoietic progenitors that are the circulating hematopoietic stem cells. This evidence also able to form colonies (CFC) in the adhering fraction after six suggests that in vivo there is a differential capacity to support weeks of coculture. LEC-1 co-cultures treated with a cocktail hematopoiesis by LEC-1 and LEC-2 which are located in the of cytokines (stem cell factor, interleukin [IL] 1 a, IL-3, and hepatic sinusoids. The HM is a complex system composed, Epo) showed that megakaryocyte (CFU-Mk) and erythrocyte mainly, of stromal cells, such as endothelial cells, fibroblasts, progenitors (BFU-e) were present during the entire period of adipocytes, osteoclasts, and monocytes which secrete cytothe culture. Granulocyte-macrophage progenitors (CFU-GM) kines, produce extracellular matrix, and mediate direct celluwere present only during the first three weeks of the culture. lar contact that regulates in vivo and in vitro hematopoieThese results suggest that LEC-1, but not LEC-2, provide an sis. [8][9][10]

Role of SDF-1 (CXCL12) in regulating hematopoietic stem and progenitor cells traffic into the liver during extramedullary hematopoiesis induced by G-CSF, AMD3100 and PHZ

“…Interestingly, liver EMH induced by both G-CSF and AMD3100 was characterized by the presence of HSPCs in close contact with LSEC. On the other hand, it is known that liver EMH occur under stress hematopoiesis induced by PHZ [20]. Here, we show an increased number of circulating CFU-C and a high number of HSPCs into the liver sinusoids after 72 h of PHZ.…”

“…The isolation, cloning, and characterization of LSEC have been previously reported [20]. They express the EC markers flk-1, Von Willebrand factor (vWF), CD34, and VCAM-1 [20].…”

“…They express the EC markers flk-1, Von Willebrand factor (vWF), CD34, and VCAM-1 [20]. LSEC were maintained in iscove's Modified Dulbecco's Media (IMDM; Gibco, Grand Island, NY-USA) 10% fetal bovine serum (FBS; Sigma) and used for experiments after the cells reached 70% confluence.…”

“…injection of 5-FU at 150 mg/kg of body weight [20]. After 48 h, the animals were sacrificed by cervical dislocation, and the femurs were removed aseptically and flushed with 0.5 mL of phosphate-buffered saline (PBS) to obtain the BM cells, described here as 5-FU BM cells.…”

“…Although during the adult life hematopoiesis occurs primarily in the bone marrow; under certain pathological and experimental conditions it may occurs in other extramedullary organs, such as the liver [19][20][21]. There is evidence showing that mobilizing agents, such as G-CSF, induce not only mobilization of HSPCs from BM to the blood, but also migration of these cells to other extramedullary organs, such as the liver [22].…”