The Preparation of Primary Hematopoietic Cell Cultures From Murine Bone Marrow for Electroporation

This procedure begins with the harvest of mouse, femurs and tibia. After removal of the hip, knee, and ankle joints, the marrow is isolated via injection of RPMI medium into the open end of the bone. After obtaining a single cell suspension, bone marrow cells are differentiated into mast cells, loaded into 96 well electroporation plates, and then transfected.

Using the gene pulse or MX cell electroporation system. Using square wave pulse protocols, transfection efficiencies of about 30%can be obtained. The first step of the procedure is to harvest bone marrow from the femur and tibia eye of a six to 12 week old mouse.

To begin euthanize the mouse by CO2 inhalation, harvest femur and tibia eye from the hind legs of each mouse. Then with the razor blade, cut each end of the femur to remove the hip and knee joints and to expose the marrow in a similar manner. Cut each end of the tibia eye to remove the knee and ankle adjacent regions and to expose the marrow.

Next, take a syringe with a 26 and a half gauge needle and drop RPMI supplemented with 10%FBS, penicillin, streptomycin, beamer, capita ethanol, and L-glutamine. Using tweezers, hold the bone over a Petri dish containing RPMI media. Insert the syringe needle into one end of the bone and depress the plunger to flush out the bone marrow.

The syringe needle can be moved up and down inside the bone to flush out residual marrow. Repeat the procedure for all the bones and then proceed with establishing the cultures To establish the bone marrow cultures pipe. Bet the flushed bone marrow up and down several times to break up the tissue into a cell suspension.

Then place a 70 micron filter on top of a 50 milliliter conical tube and add the cell suspension to the filter. Next, rinse the Petri dish one time with RPMI. Then add the rinse to the 70 micron filter using the rubber end of a one milliliter syringe plunger grind the bone marrow pieces remaining on top of the 70 micron filter.

Wash the filter one time with RPMI after washing the filter. Centrifuge the cell suspension at 1200 RPM for five minutes. Wash the cell pellet by Resus suspending in PBS.

Count the cells using a hemo cytometer. We typically obtain approximately 90 million cells from one mouse's bones, two femur plus two tibia. After counting the cells, centrifuge them again at 1200 RPM for five minutes.

Resuspend the cells in a small amount of RPMI and aliquot them in a tissue culture flasks, containing enough RPMI so that the final concentration is 1 million cells per milliliter. Then add cytokines to promote the development of your cell type of interest. In this case, the cytokine interleukin three is added to promote the development of basophils and mast cells to acquire basophils incubate for 10 days for mast cells incubate for five weeks when generating mast cells.

The media and IL three should be changed once a week. Here is a look at how bone marrow cells should appear just after plating. This image demonstrates the differentiation of bone marrow cells into basophils and mast cells 10 days after the addition of interleukin three.

Once the desired cell type is obtained, proceed with the electroporation step. To begin the electroporation step, determine the number of cells in the culture. Flask cells are typically electroporated at a density of 10 million per milliliter.

So transfer the required cell number to conical tubes and centrifuge the tubes at 1200 RPM for five minutes. After centrifuge, aspirate the media, wash the cells with one XPBS and centrifuge again at 1200 RPM for five minutes. Then aspirate the PBS and add BioRad gene pulsar electroporation buffer to make a cell suspension of 10 million cells per milliliter.

After resus suspending the cells, add the desired plasmid DNA at a final concentration of 10 to 20 micrograms per milliliter. Gently mix the cell solution aqua 150 microliters of the cell suspension into wells of your choice on a 96 well electroporation plate. Next, put the electroporation plate in the MXL plate chamber and close the lid prior to transfection of bone marrow cells and electroporation.

Protocol must be programmed into the MXL unless using a preset or stored protocol through optimization experiments, we have discovered that the highest transfection efficiencies of bone marrow cells occur using square wave pulse protocols. We will vary the electroporation conditions on the plate to deliver square wave pulses at 2000 micro phs in a thousand ohms. Once the protocol has been set and loaded onto the device, press pulse to ate the cells after electroporation is complete, transfer the cells to a tissue culture plate.

We typically transfer each 150 microliter electroporation sample to a well at a 48 well tissue culture plate containing 300 microliters RPMI with 10 nanograms per milliliter. Interleukin three cells are incubated overnight at 37 degrees Celsius, then assayed 24 hours later for expression and suppression. This is a fluorescent microscopy image of the cells.

After successful electroporation using 20 micrograms per milliliter GFP plasmid, using the MX cell electroporation system, transfection efficiencies of about 30%can be obtained. The system allows you to vary conditions to maximize your transfection efficiency while maintaining cell viability. The MX cell system is especially useful for primary mammalian cells such as these mouse hematopoietic cells.

We've just shown you how to isolate bone marrow cells from mice and transfect differentiated mast cells using the MX cell electroporation system. So that's it. Thanks for watching and good luck with your experiments.