Extracting Prostate from Mouse Urogenital System: A Technique to Separate Prostate Gland from Other Urinary and Genital System Organs in Male Mouse

All procedures involving animals have been reviewed by the local institutional animal care committee and the JoVE veterinary review board.

1. The Urogenital System (UGS) Dissection

NOTE: The schematic is presented in Figure 1.

1. Euthanize a 3-month-old male C57BL/6 mouse using the CO₂ inhalational euthanasia method or another approved technique.
   NOTE: Mice between the ages of 3 and 12 months can be used successfully for the experiment. Older mice (> 6 months) will most likely have more fat around the UGS, which will need to be cleared. Identification and separation of the lobes is often difficult in mice younger than 3 months. Other strains can be used for the experiment as well.
2. Place the mouse on its back and secure the legs using pins so that the ventral side of the animal is exposed.
3. Spray 70% ethanol on the mouse’s abdomen and wipe it clean.
   NOTE: Shaving the abdomen hair before dissection is not required.
4. Lift the skin from the abdomen, along with the muscle layer, with a pair of medium blunt forceps and make an inverted Y-shaped incision on the abdomen using scissors.
   1. First, make a straight incision with a pair of sharp scissors from just above the penis to the sternum (Figure 2a).
   2. Cut from the base of the incision towards each toe, up to the thighs (Figure 2b). Fold back the skin on both sides and at the bottom to view the entire abdominal area (Figure 2c-e).
      NOTE: The cut size varies depending on the mouse’s age and size. The size of the initial straight incision may range from 1.5 to 4 cm, depending on the size of the mouse.
5. Move over the other organs to expose the UGS. Lift and move the brown-yellow intestines (Figure 2f). Pick up the abdominal fat pads (the opaque white spongy tissue) with forceps and move them to the sides (Figure 2g).
   NOTE: The UGS comprises the seminal vesicles, urethra, prostate, ductus deferens (vas deferens), and urinary bladder. It can be identified by the characteristic pair of opaque white semicircular arches (which are the seminal vesicles), with the fluid-filled bladder sac attached to the base. The translucent tissue located right under the seminal vesicles is the prostate.
6. Locate the UGS, firmly hold the urinary bladder with blunt forceps, and lift the entire UGS upwards from the mouse abdomen.
   NOTE: If the bladder is full, drain it first with a small syringe to provide a better grip with the forceps and reduce the risk of rupturing the bladder.
7. Continuing to pull up on the bladder, slide a pair of scissors underneath the bladder and prostate all the way to the spine, and make a cut. Cut through any remaining connections to the abdominal cavity (Figure 2h and 2i). Be careful not to cut too close to the UGS to avoid accidental cutting through any prostate tissue.
   NOTE: While making the cut under the UGS, the scissors should be inserted all the way to the back of the mouse, so that the cut snaps the vertebral column as well. This method results in severing nearly all of the connections between the UGS and the abdominal cavity in one snip, reducing the time needed to extract the tissue from the mouse.
8. Remove the UGS and place it in 2-6 mL (enough to cover the tissue) of phosphate-buffered saline (PBS) or Dulbecco's modified Eagle medium (DMEM, high glucose) in a 6 cm Petri dish (Figure 2j and 2k) and move it to a dissection microscope (10X magnification).
   NOTE: Change the dissecting media as required in the remaining steps.

Figure 1:  Schematic flowchart demonstrating dissection of the mouse urogenital system and isolation of the prostate. Flow chart for the protocol steps described in sections 1

Figure 2: Dissection of the mouse UGS. Step-by-step images from the dissection of the UGS from a 3-month-old mouse: (a and b) making the incisions, (c-e) pulling back the skin to expose the abdominal area, (f) shifting the intestines, (g) moving the abdominal fat pads, (h and i) extracting the UGS from the abdominal cavity, (j) the extracted UGS, (k) the extracted UGS with the different organs and tissues marked as follows: SV (yellow) = seminal vesicles; P (red) = prostate; F (purple) = fat; V (light blue) = vas deferens; and B (green) = bladder.