title: CD34+ cells derived from fetal liver contained a high proportion of immature megakaryocytic progenitor cells.
abstract: Endoreplication and maturation of the megakaryocyte (MK) may be retarded or delayed during ontogenesis. In this study, CD34+ cells were isolated from both human fetal liver and adult bone marrow and incubated with thrombopoietin (TPO). The cell number, morphological characteristics, platelet-associated antigen phenotype, maturation stage and DNA ploidy of CD41+ cells were examined from day 0 to day 12 in culture. 1) TPO stimulated the proliferation of fetal liver (FL)-derived CD34+ cells with a mean 73.14-fold increase of CD41+ cells after 12 d in culture. Adult BM-derived CD34+ cells increased only slightly, with a mean 8.18-fold increase of CD41+ cells. 2) Although the membrane phenotype of both FL CD34+-derived MKs and BM CD34+ -derived MKs analyzed with CD41a, CD42a, CD61 and CD34 were similar, all FL CD34+-derived MKs were in maturation stage I and II and in low ploidy (<4N) class. By comparison, BM CD34+ MKs possessed 15% MKs in maturation stage III and IV and with 23% MKs in high ploidy class ( > 4N). 3) Most of cultured FL-derived CD34+ cells did not have a well developed demarcation system (DM) and numerous alpha-granules after 12 d incubation. von Willebrand factor (vWF) appeared earlier on the cultured BM-derived CD34+ cells than on FL-derived CD34+ cells. 4) The expression of both cyclin E and cyclin B1 progressively increased in FL CD34+ cells induced by TPO during 12 d in culture. 5) The expression of cyclin D1 gradually decreased in FL CD34+ cells induced by TPO over 12 d incubation. 6) Immunocytochemical analysis showed that cyclin D3 was detected only in cytoplasm of cultured FL-derived CD34+ cells, whereas in both cytoplasm and nuclei of cultured BM-derived CD34+ cells. These data suggest that FL-derived CD34+ cells contain a high proportion of immature megakaryocytic progenitor cells. It further suggests that TPO can push these progenitor cells into proliferation by upregulating the expression of cyclins B1 and E, and drive a high proportion of cells into megakaryocytic lineage.
authors.affiliation: Department of Experimental Medicine, Northern Hospital, Shenyang, Liaoning, China.
authors.forename: D C
authors.initials: DC
authors.lastname: Ma
authors.forename: Y H
authors.initials: YH
authors.lastname: Sun
authors.forename: W
authors.initials: W
authors.lastname: Zuo
authors.forename: K Z
authors.initials: KZ
authors.lastname: Chang
authors.forename: J J
authors.initials: JJ
authors.lastname: Chu
authors.forename: Y G
authors.initials: YG
authors.lastname: Liu
mesh_terms: D000328:Adult; D018952:Antigens, CD34 / Q000032:analysis*; D016824:Antigens, Human Platelet / Q000096:biosynthesis; D001854:Bone Marrow Cells / Q000276:immunology; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D016213:Cyclins / Q000096:biosynthesis; D004247:DNA / Q000235:genetics; D005333:Fetus / Q000166:cytology*; D006801:Humans; D008099:Liver / Q000196:embryology*; D008533:Megakaryocytes / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D011003:Ploidies; D013234:Stem Cells / Q000276:immunology*; D013926:Thrombopoietin / Q000494:pharmacology; D014841:von Willebrand Factor / Q000096:biosynthesis
chemical_list: D018952:Antigens, CD34; D016824:Antigens, Human Platelet; D016213:Cyclins; D014841:von Willebrand Factor; D004247:DNA; D013926:Thrombopoietin