Summary

Clasificación de células activadas por fluorescencia para la purificación de células dendríticas plasmocitoide de la médula ósea de ratones

Published: November 04, 2016
doi:

Summary

Se presenta un protocolo mediante el uso de células activadas por fluorescencia para aislar las células dendríticas plasmacitoides (PDC) con alta pureza a partir de la médula ósea de ratones propensos al lupus para los estudios funcionales de PDC.

Abstract

Fluorescence-activated cell sorting (FACS) is a technique to purify specific cell populations based on phenotypes detected by flow cytometry. This method enables researchers to better understand the characteristics of a single cell population without the influence of other cells. Compared to other methods of cell enrichment, such as magnetic-activated cell sorting (MCS), FACS is more flexible and accurate for cell separation due to the ability of phenotype detection by flow cytometry. In addition, FACS is usually capable of separating multiple cell populations simultaneously, which improves the efficiency and diversity of experiments. Although FACS has some limitations, it has been broadly used to purify cells for functional studies in both in vitro and in vivo settings. Here we report a protocol using fluorescence-activated cell sorting to isolate a very rare population of immune cells, plasmacytoid dendritic cells (pDC), with high purity from the bone marrow of lupus-prone mice for in vitro functional studies of pDC.

Introduction

Efficient separation of a cell population of choice from other cells enables studies of the population that may not be possible otherwise. Fluorescence-activated cell sorting (FACS) is a method to enrich an interesting cell population with high purity. 1,2 Different cell types usually express unique molecules, or a unique combination of several molecules, on the plasma membrane that can distinguish one cell population from another. Upon binding of these cell surface molecules by specific fluorescence-conjugated antibodies, a detecting machine called flow cytometer/sorter is able to excite and detect the light signals of different fluorescent dyes that represent different molecule markers on the cells at the single cell level. The combined information consisting of either the presence of a light signal (representing positive expression of the corresponding surface molecule) or the absence of a light signal (representing negative expression of a molecule) defines the phenotype of the cell. After passing through the detector, cells with the same phenotype of interest are diverted towards a designated collecting tube based on electrical charge.

FACS is broadly applied in various studies as long as the population to be enriched is labeled with fluorescence.3-7 It has been used to separate immunoglobulin (Ig)A-coated bacteria from non-IgA coated bacteria in the gut microbiota 8 and sort genetically engineered cell populations expressing fluorescent proteins. 9 Importantly, it has the capacity to separate more than one population simultaneously, which not only saves time and reagents but also allows for more sophisticated study designs. 10 However, FACS also has its limitations. If a population of interest is very rare (less than 1%), the sorting efficiency may be reduced, causing significant cell loss. In addition, some antibody binding may activate intracellular signal transduction that induces functional changes of the sorted cell population. 11 Therefore, the phenotype used for sorting should be selected carefully.

Other methods exist besides FACS that are also based on cell surface markers for the enrichment of specific cell populations, such as magnetic-activated cell sorting (MCS). 12 Similar to FACS, magnetic beads-conjugated antibodies can target specific cell surface molecules. Upon antibody-antigen interaction, magnetic beads-coated cells can be separated from non-coated cells after passing through a magnetic field. However, only a limited number of molecules can be targeted in MCS, as magnetic beads are, unlike various fluorescent colors in FACS, undistinguishable. It is thus difficult for MCS to define a cell phenotype with a complicated combination of surface markers. 13,14 In addition, MCS is also able to cause unintended activation of target cells.

In our studies of a mouse model of systemic lupus erythematosus (SLE), 15 we intended to purify plasmacytoid dendritic cells (pDC) to investigate their functional changes with disease progression. We first used MCS to enrich pDC from the bone marrow by targeting PDCA-1, a molecule highly and uniquely expressed on murine pDC at steady state. 16 However, the cell purity was unexpectedly low, likely due to the upregulation of PDCA-1 on other cell populations in an inflammatory environment such as SLE.16 Ultimately, we have used FACS with a combination of four surface markers (CD11c, CD11b, B220 and PDCA-1) to separate high-purity pDC as CD11c+CD11b-B220+PDCA-1+ population. Murine pDC has another specific surface marker Siglec-H. We decided not to use Siglec-H, as antibody binding of this molecule represses the function of pDC to produce IFNα. 11

Protocol

NOTA: MRL / Mp-Fas lpr (MRL / lpr) ratones propensos al lupus fueron criados y mantenidos en una instalación libre de patógenos específicos según los requisitos de Cuidado de Animales institucional y el empleo Comisión (IACUC) en Número de Virginia Tech (Animal Aseguramiento de Bienestar: A3208-01). Este estudio se llevó a cabo en estricta conformidad con las recomendaciones de la Guía para el Cuidado y Uso de Animales de Laboratorio de los Institutos Nacionales de Salud. Todos los experimentos con animales se realizaron …

Representative Results

El objetivo de enriquecer la médula ósea PDC con alta pureza, y sin la influencia de otros tipos de células, de MRL / lpr ratones propensos al lupus tanto de la edad joven y viejo para estudiar los cambios funcionales del PDC en cuanto a su capacidad de producir IFN. La primera estrategia de purificación usado fue MCS, que, como muestra la Figura 1, condujo a solamente 7,75% de pureza después de la enriquecimiento. En comparación con los MCS, FACS enriquecido PDC c…

Discussion

The protocol described in this manuscript is for high purity enrichment of live pDC that retain the ability to produce IFNα. The applications of this protocol include, but are not limited to, purification of pDC and/or any other mononuclear cells from the bone marrow of MRL/lpr and any other mouse strains for studies of cellular and molecular functions. Several critical steps in this protocol are to ensure high viability and purity of the sorted pDC. The first key step is the release of bone marrow from bones. To mi…

Disclosures

The authors have nothing to disclose.

Acknowledgements

We thank Flow Cytometry Laboratory at Virginia-Maryland College of Veterinary Medicine for the use of flow cytometry core facility. This work was supported by XML’s startup funds. XL is a Stamps Fellow in the Biomedical and Veterinary Sciences graduate program.

Materials

RPMI 1640 gibco by life technologies 11875-093
Fetal bovine serum HyClone SH30396.03
Sodium pyruvate gibco by life technologies 11360-070
MEM non-essential amino acids gibco by life technologies 11140-050
HEPES gibco by life technologies 15630-080
2-mercaptoethanol gibco by life technologies 21985-023
L-glutamine  gibco by life technologies 25030-164
Penicillin-Streptomycin gibco by life technologies 15140-122
1x Hank’s Balanced Salt Solution  gibco by life technologies 14175-079
MACS BSA Stock Solution Miltenyi Biotec 130-091-376
MgCl2 SIGMA M8266
DNase I SIGMA D4527
Red blood cell (RBC) lysis buffer  eBioscience 00-4300-54
Density gradient medium GE Healthcare 17-1440-02 Ficoll-Paque Plus 
anti-mouse CD19-PE BD Pharmingen 553786
anti-mouse CD11c-PE eBioscience 12-0114-82
anti-mouse CD11b-APC-CY7 BD Pharmingen 557657
anti-mouse PDCA-1-FITC eBioscience 11-3172-81
anti-mouse B220-V500  BD Pharmingen 561226
DAPI invitrogen D3571
Plasmacytoid Dendritic Cell Isolation Kit II, mouse Miltenyi Biotec 130-092-786
BD FACSAria I flow cytometer  BD Biosciences 643178
BD FACS Diva version 6 BD Biosciences

References

  1. Bonner, W. A., Hulett, H. R., Sweet, R. G., Herzenberg, L. A. Fluorescence activated cell sorting. Rev Sci Instrum. 43 (3), 404-409 (1972).
  2. Herzenberg, L. A., et al. The history and future of the fluorescence activated cell sorter and flow cytometry: a view from Stanford. Clin Chem. 48 (10), 1819-1827 (2002).
  3. Brown, M., Wittwer, C. Flow cytometry: principles and clinical applications in hematology. Clin Chem. 46 (8 Pt 2), 1221-1229 (2000).
  4. Laerum, O. D., Farsund, T. Clinical application of flow cytometry: a review. Cytometry. 2 (1), 1-13 (1981).
  5. Alvarez-Barrientos, A., Arroyo, J., Canton, R., Nombela, C., Sanchez-Perez, M. Applications of flow cytometry to clinical microbiology. Clin Microbiol Rev. 13 (2), 167-195 (2000).
  6. Mattanovich, D., Borth, N. Applications of cell sorting in biotechnology. Microb Cell Fact. 5 (12), (2006).
  7. Aldahlawi, A. M., Elshal, M. F., Damiaiti, L. A., Damanhori, L. H., Bahlas, S. M. Analysis of CD95 and CCR7 expression on circulating CD4(+) lymphocytes revealed disparate immunoregulatory potentials in systemic lupus erythematosus. Saudi J Biol Sci. 23 (1), 101-107 (2016).
  8. Cullender, T. C., et al. Innate and adaptive immunity interact to quench microbiome flagellar motility in the gut. Cell Host Microbe. 14 (5), 571-581 (2013).
  9. Fernandez, A. G., et al. High-throughput fluorescence-based isolation of live C. elegans larvae. Nat Protoc. 7 (8), 1502-1510 (2012).
  10. Cai, M., et al. DC-SIGN expression on podocytes and its role in inflammatory immune response of lupus nephritis. Clin Exp Immunol. 183 (3), 317-325 (2016).
  11. Blasius, A., et al. A cell-surface molecule selectively expressed on murine natural interferon-producing cells that blocks secretion of interferon-alpha. Blood. 103 (11), 4201-4206 (2004).
  12. Welzel, G., Seitz, D., Schuster, S. Magnetic-activated cell sorting (MCS) can be used as a large-scale method for establishing zebrafish neuronal cell cultures. Sci Rep. 5, 7959 (2015).
  13. Valli, H., et al. Fluorescence- and magnetic-activated cell sorting strategies to isolate and enrich human spermatogonial stem cells. Fertil Steril. 102 (2), 566-580 (2014).
  14. Yamashiro, S., et al. Phenotypic and functional change of cytokine-activated neutrophils: inflammatory neutrophils are heterogeneous and enhance adaptive immune responses. J Leukoc Biol. 69 (5), 698-704 (2001).
  15. Apostolidis, S. A., Lieberman, L. A., Kis-Toth, K., Crispin, J. C., Tsokos, G. C. The dysregulation of cytokine networks in systemic lupus erythematosus. J Interferon Cytokine Res. 31 (10), 769-779 (2011).
  16. Asselin-Paturel, C., Brizard, G., Pin, J. J., Briere, F., Trinchieri, G. Mouse strain differences in plasmacytoid dendritic cell frequency and function revealed by a novel monoclonal antibody. J Immunol. 171 (12), 6466-6477 (2003).
  17. Liao, R., et al. Tacrolimus Protects Podocytes from Injury in Lupus Nephritis Partly by Stabilizing the Cytoskeleton and Inhibiting Podocyte Apoptosis. PLoS One. 10 (7), e0132724 (2015).

Play Video

Cite This Article
Liao, X., Makris, M., Luo, X. M. Fluorescence-activated Cell Sorting for Purification of Plasmacytoid Dendritic Cells from the Mouse Bone Marrow. J. Vis. Exp. (117), e54641, doi:10.3791/54641 (2016).

View Video