A Study Of Effects Of CO₂ Pneumoperitoneum On Living Cell Labeled With GFP Migrating To Liver Through Blood Route In A Rat Laparoscopy Model

Backgroud: Even since the French doctor Mouret carried out the first laparoscopic cholecystectomy in 1987,the concept of minimally invasive surgery has been generally accepted gradually. Meanwhile, the applications of laparoscopic tumour-reductive surgery have been developed increasingly as well, which becomes one of the hot spots of oncosurgery.However, a high incidence rate of Port-site metastasis(PSM) has been reported recently in clinic,Which brings some disputions on the new technique.Previously, many reseaches were concentrated on the effect of CO2 pneumoperitoneum on tumor cell growth .Some findings show that gas insufflation as well as regional subacidity environment caused by CO2 pneumoperitoneum may result in Port-site metastasis(PSM).As we known, some investigations show that there are many free tumor cells in blood while operating on malignant tumor , which must have something to do with metastasis.Undoubtedly, in the laparoscopic operation CO2 pneumoperitoneum must make a pressure on intraperitoneal blood vessels ,which can cause blood flow changing. For this reason, we ought to pay close attention to the change that maybe have effect on tumor cell transferring through blood route. But there are no reports on such studys in domestic at present. In this experiment, we established a rat pneumoperitoneum model in vivo and all rats inoculated intraportally with high dose liver cells from transgenic C57BL/6 mice labeled with green flouresent protein (GFP) before suffered different pressure gas insufflation .After our experiment, we made comparisons and analyzed on the situations of accumulation and expression of living cells labeled with GFP in rat livers between different pressure groups in order to illuminate the effect of CO2 pneumoperitoneum on living cells migrating through blood route and discuss the possible mechanisms. Above of all, we hope to provide experiment and theory basement on prevention of liver metastasis in laparoscopic tumour-reductive surgery. Objective: The effect of CO2 pneumoperitoneum on cells migrating through blood route was investigated in a rat model. The possible mechanisms involved in the pressure-related enhancement of cells migrating through blood route were also discussed. Methods: Rats inoculated intraportally with high dose liver cells from transgenic C57BL/6 mice labeled with GFP (5×106 cells) after cutting belly open.Pneumoperitoneum was created immediately after closing the abdominal wall. Rats were randomized to receive CO2 pneumoperitoneum at 5, 10, or15mmHg or no treatment other than cells inoculation. The duration of pneumoperitoneum is 30mins.After that, all rats were euthanized by cervical dislocation, and each liver was removed. A sample obtained from each rat liver underwent fast frozen section biopsy. The situations of accumulation and expression of living cells labeled with GFP in rat livers were compared between groups.Results: The numbers of fluorescent cells in the three pneumoperitoneum groups were higher than the non-pneumoperitoneum group. What's more, The numbers of fluorescent cells in the high pressure groups (15mmHg and 10mmHg) were significantly different higher than those in the low pressure group (5mmHg) and the non-pneumoperitoneum group(13.89±4.37,15.50±6.29 vs 7.67±2.83,6.63±2.45, P<0.01). However, there had no statistically significant difference between the 15mmHg and 10mmHg groups, as well as between the 5mmHg and non-pneumoperitoneum groups.Conclusion: 1. CO2 pneumoperitoneum can enhance cells migrating to liver through blood route. And more higher the pressure, more effect of the pneumoperitoneum will form. One of most possible mechanisms is that impaired portal blood flow caused by high abdominal insufflation may inhabit the flushing of GFP cells from the intrahepatic portal system, forming favorable conditions for cells lodged in the liver. 2. Therefor , CO2 pneumoperitoneum may enhance liver metastasis by damaging portal blood flow, which can form favorable conditions for cancer cells lodged in the liver. Accordingly,we can carry on laparoscopic tumour-reductive operation with a low pressure artifical CO2 pneumoperitoneum to avoid the risk of liver metastasis.