The recurrence of primary and secondary liver malignoma after partial liver resection remains a common, yet unsolved, problem. The exact mechanisms of tumor formation in the remaining parts of the liver are not understood so far. The following mouse model studied the proliferation of secondary liver malignoma after partial liver resection.
In mice, a liver resection of about 70%is normally compensated by liver hypertrophy of the remaining parts of the liver within two to three weeks. The endocrine factors, which play a role in the liver's regeneration, may also induce the growth of liver malignoma. This video introduces a method which can be used to investigate the relationship between liver hypertrophy after resection and tumor growth.
The experiment tried to prove that a partial liver resection accelerates the growth of liver malignoma. The shown illustration outlines the murine liver anatomy. To achieve a liver volume reduction of 65 to 70%resection of the median and left lateral lobe is necessary.
To induce a liver tumor, a predefined volume of cancerous cells is injected into the inferior right lobe. A Plexiglas box is used for anesthetic induction. The mouse is then positioned and the abdomen disinfected.
To provide adequate analgesia, five milligrams per kilogram body weight of Carprofen are administered. The skin incision is made along the median line of the abdomen, from the area above the xiphoid down to the lower abdomen. The xiphoid is carefully dissected from the surrounding tissue, and the abdominal fascia opened, along the linea alba.
A stay suture then fixes the now exposed xiphoid bone to a retainer above the animal's head, in order to expose the different liver parts. The retractor is introduced to spread the abdominal wall apart, and gain better access to the abdominal organs. A saline soaked cotton swab is used to shift the median lobe downward.
The now exposed falciform ligament is dissected. Median lobe and left lateral lobe are shifted upward against the diaphragm, in order to dissect the thin membrane between the left lateral lobe and the caudate lobe. A size 4.0 ligature is placed at the base of the left lateral lobe, which is subsequently returned to its original position using only the saline soaked cotton swab.
It is now tied up using multiple knots. A gradual change of the lobe's superficial color to a more cyanotic tone is a sign of adequately interrupted blood supply. After trimming the ligature threads, the left lateral lobe is resected by cutting along the slightly diagonal line along its base.
Now a new ligature is put in place at the median lobe's base. The lobe is likewise repositioned by applying gentle pressure from above with a cotton swab. The median lobe is similarly tied up with multiple knots.
With the previously described color change, again indicating effective disruption of blood flow. The ligature threads are trimmed, and the lobe is removed. Because the inferior vena cava runs through the dorsal portion of the lobe, it is prone to damage by the ligature, which may lead to liver necrosis.
This part of the lobe must therefore remain in situ. The inferior right lobe is demonstrated by moving the intestinal loops to the left. A 13 gauge syringe containing the tumor cell suspension is carefully introduced into the lobe until the syringe's tip is approximately in the lobe's center part.
Inject the tumor cells by slowly applying gentle pressure to the plunger over a period of about 30 to 45 seconds. Afterwards, the penetrated area must be compressed for at least three minutes to control bleeding. Retractor and stay suture are removed, and a single button suture is performed to close the fascia.
It is highly recommended to use two lines of sutures, as some animals may try to remove the sutures and reopen the laparotomy after the procedure. The skin is therefore separately adapted with single button knots. To provide adequate recovery and analgesia, the mouse is placed into a warm environment and the animal's drinking water is mixed with 500 milligrams per kilogram body weight of Metamizole.
In the experiment, 30 animals were divided into three groups. All groups were injected with tumor cells. Group A was treated only with a laparotomy.
Animals in groups B and C underwent liver resection of 30 and 70%of the original liver volume, respectively. It was then found that a liver resection of 70%correlated significantly positive with a greater tumor volume and tumor weight. Immunohistochemistry also showed a greater proliferation rate of tumor cells in animals from the liver resection groups, when comparing them with tumor cells from the laparotomy group.
This correlation confirms clinical observations, although further examinations are required in the human system.
