The Onset of In-Vivo Dehydration in Gas -Based Intraperitoneal Hyperthermia and Its Cytotoxic Effects on Colon Cancer Cells

Abstract

Background: Peritoneal metastasis (PM) is an ongoing challenge in surgical oncology. Current therapeutic options, including intravenous and intraperitoneal (i.p.) chemotherapies display limited clinical efficacy, resulting in an overall poor prognosis in affected patients. Combined hyperthermia and dehydration induced by a high-flow, gas-based i.p. hyperthermic procedure could be a novel approach in PM treatment. Our study is the first to evaluate the therapeutic potential of i.p. dehydration, hyperthermia, as well as the combination of both mechanisms in an in-vivo setting.

Methods: For this study, three swine were subjected to diagnostic laparoscopy under a high-flow air stream at 48°, 49° and 50°Celsius (C). Hygrometry of the in- and outflow airstream was measured to calculate surface evaporation and i.p. dehydration. To analyze the effects of this concept, in vitro colon cancer cells (HT-29) were treated with hyperthermia and dehydration. Cytotoxicity and cell viability were measured at different time intervals. Additionally, structural changes of dehydrated cells were analyzed using scanning electron microscopy.

Results: According to our results, both dehydration and hyperthermia were cytotoxic to HT-29 cells. However, while dehydration reduced cell viability, hyperthermia did not. However, dehydration effects on cell viability were significantly increased when combined with hyperthermia (p<0.01).

Conclusions: Changes to the physiological milieu of the peritoneal cavity could significantly reduce PM. Therefore, limited dehydration of the abdominal cavity might be a feasible, additional tool in PM treatment. Further studies are required to investigate dehydration effects and their applicability in PM management.

Keywords: colorectal cancer; dehydration; electron microscopy; hyperthermia; peritoneal metastasis (PM).

Figure 1

(A) In-vivo high-flow laparoscopy model to evaluate dehydration and hyperthermic airflow effects. (B) Model of the laparoscopic setting. Two trocars are used as in- and outflow while other trocars are placed for optics and temperature sensors.

Figure 2

Laparoscopic view of the intraabdominal cavity during high-flow air-based hyperthermia. (A) Start of the laparoscopy. The figure displays normal small intestinal tissue as is expected during laparoscopy. (B) Laparoscopic view of the intraabdominal cavity after 30 minutes into the procedure. Peritoneal dehydration “drying” is visible in the exposed area. The peritoneal surface appears to “peel-off” and light reflection on the peritoneal surface increases.

Figure 3

(A) Mathematical model for the removal of fluid/water from the abdominal cavity at 15 liter/minute flow rate assuming an inflow air humidity of 50%. The correlation is linear. (B) Mathematical model of dehydration at 15 liter/minute flow rate assuming an inflow air humidity of 50%. At the marked red points, dehydration of tissue is visible during laparoscopy. The estimated amount of removed water per time is indicated at each time point.

Figure 4

(A) In vitro cytotoxicity on colon cancer cells after 30 minutes of hyperthermia exposure (without dehydration) at 45°C and 48°C. Control cells were only exposed to the physiological temperature of 37°C. (B) In vitro cytotoxicity on colon cancer cells after 30 minutes of hyperthermia exposure and dehydration at 37°, 45°C and 48°C. (C) Cytotoxicity compared to control cells. Levels of cytotoxicity were measured at different exposure times to dehydration and hyperthermia (5, 10, 20, 25 and 30 minutes). Significance levels: #=p>0.05, *=p<0.05, **= p<0.001.

Figure 5

(A) In vitro cell-viability of colon cancer cells after 30 minutes of hyperthermia (without dehydration) at 45°C and 48°C. Control cells were only exposed to the physiological temperature of 37°C. (B) In vitro cell-viability of colon cancer cells after 30 minutes of hyperthermia and dehydration at 37°, 45°C and 48°C. (C) Course of cell viability following different exposure times of dehydration and hyperthermia 0 (Control), 5, 10, 20, 25 and 30 minutes. Significance levels: #=p>0.05,**= p<0.01.

Figure 6

Electron microscopy (EM) of HT-29 cells. (A) Untreated HT-29 Cells in EM (control/magnification level 1000X). (B) HT-29 Cells in EM following dehydration and hyperthermia for 20 minutes (magnification level 1000X).