Primitive hematopoietic cells in murine bone marrow express the CD34 antigen

Area of Science:

• Hematology
• Immunology
• Stem Cell Biology

Background:

• CD34 antigen is a well-established marker for enriching human hematopoietic stem cells (HSCs) with repopulating potential.
• Previous studies have not fully detailed CD34 expression on primitive murine hematopoietic cells, despite homology with human CD34.

Purpose of the Study:

• To investigate the expression of CD34 on primitive murine hematopoietic cells using a novel monoclonal antibody, RAM34.
• To functionally characterize CD34-positive (CD34+) and CD34-negative (CD34-) murine bone marrow (BM) cells.

Main Methods:

• Utilized a novel monoclonal antibody (RAM34) against murine CD34 to fractionate BM cells.
• Assayed fractionated cells in vitro and in vivo for functional properties, including stem cell activity and differentiation potential.
• Employed single-parameter cell sorting based on CD34 expression.

Main Results:

• A significant portion (4-17%) of murine BM cells expressed CD34 at intermediate to high levels, with improved resolution compared to previous antibodies.
• Sixty percent of CD34+ BM cells lacked mature lineage markers.
• Highly enriched HSC populations (Sca-1+Thy-1(lo)Lin-/lo) showed intermediate CD34 expression, with the remainder being CD34-.
• CD34+ fraction was markedly enriched for in vitro colony-forming cells, spleen colony-forming units (CFU-S), B and T lymphocyte progenitors, and long-term repopulating stem cells.
• CD34- BM cells showed depleted stem cell activities and limited short-term B-cell production.

Conclusions:

• A substantial proportion of murine HSCs and multilineage progenitor cells express detectable CD34 levels.
• The RAM34 antibody is an effective tool for subsetting primitive murine hematopoietic cells.
• Findings facilitate direct comparisons between CD34+ murine and human stem and progenitor cell biology.