The hematopoietic stem and progenitor population supplies the organism with a large range of mature cells, including cells from the myeloid lineage (neutrophils, eosinophils, basophils, and monocytes). The process that drives the production of myeloid cells from hematopoietic stem cells is known as myelopoiesis, and adequate production of mature myeloid cells in response to changing demands is a prerequisite for proper coping of the organism with stress conditions, such as infections and blood loss. Insufficient production of mature myeloid cells may lead to inability to eliminate pathogens, reduced blood coagulation, and other life-threatening conditions1,2. In addition, alterations in myeloid lineage development may also be associated with hematological malignancies, such as acute myeloid leukemia (AML)3. Alterations in myelopoiesis may occur due to various reasons, such as defects in cell surface receptors4, altered expressions of transcription factors5, impaired signaling pathways6, mutations resulting in formation/activation of oncogenes7, or inactivation of tumor suppressor genes8.
Various methods have been developed to study myeloid development, and assess the effect of specific genetic alterations in this process. Common approaches used to study myelopoiesis involve primary cells and transgenic mice. Though these models allow acquisition of biologically relevant data, they have certain limitations. The use of primary cells encounters a limited number of cells and a restricted period of culture, narrowing the possibilities to alter gene expression and subsequent biological or biochemical analysis. Transgenic mice are costly and require a reasonable degree of biological justification. In addition, working with in vivo models adds a degree of complexity into understanding the role of a gene of interest in a given process. Therefore, alternative approaches to circumvent these limitations are needed. Cell lines have indisputable advantages: (1) they possess unlimited proliferation capacity that allows generating enough material for biochemical and biological studies, (2) they are susceptible to genetic manipulations (knockdown, knockout, overexpression), (3) the cost is relatively low, and (4) they allow a degree of biological simplification required in certain experimental approaches.
The parental IL-3 (Interleukin-3) dependent 32D cell line was established in 1983 by Greenberger and colleagues by infection of bone marrow cells from C3H/HeJ mice with Friend murine leukemia virus9. Several 32D clones were described in literature: cl-239, cl-310, and cl-1011. The 32D cl-3 cells were shown to proliferate in IL-3 and undergo neutrophilic differentiation upon treatment with granulocyte-colony stimulation factor (G-CSF)10. On the contrary, 32D cl-10 cells, while being IL-3 dependent, originally were not differentiating in response to G-CSF treatment. In 1995 the group of Dr. Ivo Touw retrovirally transduced 32D cl-10 cells with wild type and mutant forms of G-CSF receptor (G-CSF-R), in order to identify functionally important regions of this receptor11. This study resulted in generation of the 32D/G-CSF-R cells, which are similarly dependent on IL-3, but within 6 to 10 days after replacement of IL-3 with G-CSF, cells stop to proliferate and irreversibly differentiate into mature neutrophils. These properties make 32D cl-3 and 32D/G-CSF-R cells simplified models of murine neutrophilic differentiation that can be modulated by two well-defined growth and differentiation factors - IL-3 and G-CSF. During the last decades multiple groups have used 32D/G-CSF-R cells to study the role of particular genes in proliferation and differentiation of myeloid cells in culture12,13,14,15,16, and to study G-CSF signaling17,18. Importantly, the results obtained using this cell line correlated with data obtained with primary cells and transgenic mice16,19,20,21. Consequently, we believe that 32D/G-CSF-R cells, being a widely used and well-established model, represent a valuable system to study myeloid differentiation which can be used in parallel with other approaches addressing this question.
Here, detailed protocols describing handling of the 32D/G-CSF-R cell line, which cover expansion, differentiation, and assessment of proliferation and differentiation of these cells is presented. Detailed information for genetic modification of 32D/G-CSF-R cells, either by retroviral or lentiviral transduction, as well as protocols for virus titration are provided. In addition, several representative results that demonstrate potential applications of 32D/G-CSF-R cells are provided.