Vibrio cholerae neuraminidase (VCN) treatment of donor bone marrow cells results in a reduction in the number of hematopoietic colonies (CFUs) formed in the spleens of lethally irradiated mice. Treatment of marrow cells with sodium periodate under mild conditions, known to preferentially oxidize sialic acid, also reduced CFUs while subsequent potassium borohydride reduction restored CFUs to 80% of control levels. Innoculum viability as measured by in vitro incorporation of tritiated precursors into proteins, nucleic acids, and oligosaccharides was unaffected by VCN treatment. The ability of bone marrow cells in culture to respond to the hormone erythropoietin, as measured by the incorporation of 59 Fe into cyclohexanone-extractable heme, was also not affected by neuraminidase, making a cytotoxic effect of the VCN preparation unlikely. Incubation of VCN-treated marrow with either P-galactosidase or trypsin had no effect on the VCN-induced reduction in CFUs. These results are consistent with the idea that membrane sialic acid plays a direct and specific role in the implantation and development of CFUs.
Key words: borohydride reduction, spleen colonies, neuraminidase (vibrio cholerae), periodate oxidation, N-acetyl-neuraminic acid, hematopoietic stem cell, erythropoietin
We have been interested in the characterization of the surface properties of the pluripotent hematopoietic stem cell, the precursor of all circulating blood cells. The discrete areas of proliferating hematopoietic tissue found in the spleens of lethally irradiated mice 7-10 days after injection of donor bone marrow (1) are clones derived from a s i n p cell (2,3), the colony-formingunit (CFUs), believed to represent the hematopoietic stem cell.
Although both bone marrow and spleen will support the proliferation and differentiation of CJWs (4), only a fraction of the total CFUs in the innoculum implant and proliferatel in the spleen (5-7). In addition, the spleen has been shown to be a predominantly erythropoietic microenvironment, while bone marrow supports mainly granulopoietic differentiation (4). The inductive events in hematopoietic differentiation are believed to be mediated