Hematopoietic stem cells (HSCs) can differentiate into all cells of the blood system and are essential for maintaining the blood system. Hematopoietic stem cells are a type of pluripotent stem cell with the ability to self renew and generate intermediate cells of various blood cell systems through hierarchical processes, thereby regenerating the body's blood cells.
To study stem cell niches, researchers must be able to determine the ability of cell populations to generate adult cell systems under controlled conditions. The typical strategy used in the experiment is to transplant bone marrow rich in HSCs into the blood system of recipient mice, and the blood system of recipient mice is artificially cleared after sub lethal dose irradiation. In these mice, adult blood cells, as well as stem cells and precursor cells, will all die after 2 weeks of irradiation. Transplanted cells can differentiate into new blood systems, thereby rescuing mice.

HSC can achieve further division based on its short-term (ST HSC), * (LT-HSC), and mid-term (IT HSC) reconstruction abilities [1,2]. In most reports, researchers determine LT-HSC by measuring its ability to generate circulating monocytes, granulocytes, and lymphocytes at different time points between 16-44 weeks after transplantation. The sub competitive analysis of transplanted cells should be completed 4-6 weeks after transplantation. In transplantation studies, wild-type inbred C57/BL6 mice are commonly used, provided that these mice carry the Ptprcb leukocyte marker (CD45.2/Ly5.2) allele. The Sloan Kettering Institute has cultivated a strain of mice called C57BL/6-Ly5.1 by backcrossing SJL mice with wild-type C57/BL6 mice. These mice carry the Ptprcb leukocyte marker (CD45.1/Ly5.1) allele. By using commonly used anti-CD45.1 and CD45.2 antibodies, researchers can easily identify host and transplant cells, and determine the role of HSCs in competitive experiments. In this article, we briefly describe a simple experiment that involves measuring the levels of Cd45.2 donor and CD45.1 host white blood cells in the peripheral blood of irradiated mice after transplantation.

(Author: John F. Woolley, PhD 1, 2 Leonardo Salmona, PhD 1, 2)
Unit: 1 Department of Pharmacology and Toxicology, University of Toronto, Canada 2 Toronto University Health Network Princess Margaret Cancer Center, Canada