Analysis of Primitive CD34⁻and CD34⁺Hematopoietic Cells from Adults: Gain and Loss of CD34 Antigen by Undifferentiated Cells Are Closely Linked to Proliferative Status in Culture

Abstract

There is limited understanding of CD34− hematopoietic cells and the linkage between CD34 antigen expression and cell proliferation. In this study, early CD34− CD38− LIN− (CD34−) cells were purified from mobilized adult peripheral blood and carefully analyzed in vitro for growth and modulation of CD34. Mobilized CD34+CD38− LIN− (CD34+) cells were used for comparison. Expression of CD34, CD38, and LIN antigens was determined, and proliferative responses were assessed with PKH tracking dye, expression of Ki67 antigen, and uptake of pyronin Y. Suspension cultures of adult CD34− cells generated CD34+ cells and progenitors for >8 weeks. Stromal cultures demonstrated the presence of long‐term culture‐initiating cells within the CD34− fraction. While CD34− cells were slower to initiate growth than the CD34+ cells were, no significant difference in hematopoietic cell output was found. Upon cultivation of CD34− cells, CD34 antigen appeared within 48 hours but was restricted to those cells that had initiated growth. Surprisingly, CD34+ precursors lost CD34 expression in culture if they remained in G0 for more than 2 days. Those cells later regained expression of CD34 antigen upon initiation of growth. Comparison of cells that did or did not rapidly modulate CD34 antigen revealed no differences in long‐term growth potential. In conclusion, in vitro expression of CD34 by CD34− and CD34+ populations is tightly linked to cellular proliferation. In this culture system, expression of CD34 antigen by LIN− cells constitutes an early hallmark of growth. Measurement of CD34 expression by LIN− cells in expansion culture underestimates the total content of hematopoietic cells.

Not just a marker: CD34 on human hematopoietic stem/progenitor cells dominates vascular selectin binding along with CD44

“…As expected, we found more CD34 neg than CD34 pos cells (15% vs 1%, respectively), which is in accordance with previous studies 5,31 ( Figure 1A). Flow cytometric analysis comparing the Lin ) express a range of E-selLs from ;100 to 250 kDa, whereas the Lin neg CD38 neg CD34 pos cells express ligands at a molecular weight (MW) just over 100 kDa primarily ( Figure 1B middle panel).…”

“…1 However, studies have revealed that the CD34 neg fraction of normal human BM is capable of differentiating into CD34 pos subsets that possess a more activated phenotype. [4][5][6]15 However, the CD34 neg fraction suffers from a profound impairment in migration after IV transplantation compared with the CD34 pos fraction. 5,7,8,11,13,[49][50][51][52] Our flow cytometric and western blot data revealed a more pronounced E-selL activity on the CD34 pos subset of the Lin neg CD38 neg fraction than on the CD34 neg subset, suggesting that the enhanced migratory ability of CD34 pos cells is due to its possession of a specific set of functional E-selLs, required for proper migration and homing of HSPCs.…”

“…1 Although the role of CD34 as a marker of HSCs is under debate, 2,3 recent studies suggest the existence of a population of dormant human HSCs that are CD34 negative (CD34 neg ) but become positive (CD34 pos ) just prior to cell division. [4][5][6][7][8] Studying this negative population is challenging because a defined marker for its enrichment is still lacking and also because it demonstrates extremely poor homing and engraftment capabilities compared with its CD34 pos counterpart. [9][10][11] Studies of gene expression comparing lineage negative fractions of human peripheral blood HSPCs that either express the CD34 antigen or not imply that CD34 neg HSPC subsets are more kinetically and functionally dormant, whereas CD34 expression in CD34 pos HSPCs is related to cell cycle entry, metabolic activation, and HSPC mobilization and homing.…”

5-Androstenediol Promotes Survival of γ-Irradiated Human Hematopoietic Progenitors through Induction of Nuclear Factor-κB Activation and Granulocyte Colony-Stimulating Factor Expression

“…Death and apoptotic markers and cell lineage-specific surface phenotypes were determined using BD FACS Caliber flow cytometry (BD Biosciences, San Jose, CA). All antibodies and dyes including anti-CD34, anti-CD11b, Annexin-V, and 7-aminoactinomycin D (7AAD) or propidium iodide were purchased from BD Biosciences (Xiao et al, 2001;Dooley et al, 2004).…”

A large-scale genome-wide association study of Asian populations uncovers genetic factors influencing eight quantitative traits

“…The protein encoded by CD46 is a type I membrane glycoprotein that acts as a cofactor to protect complement activation on host cells 12 . C1orf132 encodes a hypothetical protein of unknown function, and the protein encoded by CD34 is implicated in early hematopoiesis and is thought to mediate the attachment of stem cells to the bone marrow extracellular matrix and/or stromal cells 13 . Thus, the functional connection to variation in pulse rate remains unclear at this stage.…”