Stress management affects outcomes in the pathophysiology of an endometriosis model

Abstract

We have previously shown detrimental effects of stress in an animal model of endometriosis. We now investigated whether the ability to control stress can affect disease parameters. Endometriosis was surgically induced in female Sprague-Dawley rats before exposing animals to a controllable (submerged platform) or uncontrollable (no platform) swim stress protocol. Corticosterone levels and fecal pellet numbers were measured as an indicator of stress. Uncontrollable stress increased the number and size of the endometriotic cysts. Rats receiving uncontrollable stress had higher anxiety than those exposed to controllable stress or no stress and higher corticosterone levels. Uncontrollable stressed rats had more colonic damage and uterine cell infiltration compared to no stress, while controllable stress rats showed less of an effect. Uncontrollable stress also increased both colonic and uterine motility. In summary, the level of stress controllability appears to modulate the behavior and pathophysiology of endometriosis and offers evidence for evaluating therapeutic interventions.

Keywords: animal model; controllable; corticosterone; corticotrophin releasing factor; endometriosis; rat; stress.

Figure 1.

Stress increases anxiety levels. A, Animals were subjected to “controllable” (platform) or “uncontrollable” (no platform) swim stress for 10 consecutive days following the surgical induction of endometriosis. Endo-stress uncontrollable and endo-stress controllable groups had increased fecal pellet counts (B) and corticosterone levels (C), compared to the no stress groups, indicating increased anxiety levels (n = 12-14 ± SEM; *P < .05, **P < .01, ***P < .001 vs sham-no stress, ^# P < .05, ^## P < .01, ^### P < .001 vs endo-no stress, ^$ P < .05 vs uncontrollable). SEM indicates standard error of the mean.

Figure 2.

The type of stress affects learning parameters. A, Animals exposed to uncontrollable stress were allowed to swim freely whereas those exposed to controllable stress learnt to find a hidden platform. B, The endo-stress uncontrollable animals had more thigmotaxis activity than the endo-stress controllable group indicating increased anxiety (**P < .01, ***P < .001). C, There were no differences in the latency period (the time taken to find the platform) since animals were pair matched, and the animals learned to find the platform as demonstrated by significantly shorter latency periods compared to day 1 (n = 14 ± SEM; **P < .01 vs day 1). SEM indicates standard error of the mean.

Figure 3.

Controllable stress decreases implant size. None of the sham-no stress animals developed vesicles. The endo-no stress group (n = 12) developed a vesicle in 77% of their sutures (grades 2, 3 or 4). A, Exposure to uncontrollable stress increased the number of vehicles developed and their average grade; (B) animals exposed to uncontrollable stress (n = 14) had vesicles of a larger size than those found in the controllable group (n = 14); *P < .05 vs endo-stress controllable). SEM indicates standard error of the mean.

Figure 4.

Effect of stress on colonic damage. Endometriosis animals receiving uncontrollable stress had (A) increased macroscopic damage (presence of adhesions, presence of diarrhea, thickness of the colon wall, and severity of ulceration) and (B) increased microscopic damage (loss of mucosal architecture, muscle thickness, neutrophil infiltration, crypt abscess formation, and goblet cell depletion) compared to animals receiving no stress. In contrast, damage in the endo-stress controllable group was no worse than that found in the no stress groups (n = 12-14 ± SEM; **P < .01, ***P <.001 vs sham-no stress, ^# P < .05 vs endo-no stress). SEM indicates standard error of the mean.

Figure 5.

Effect of stress controllability on mast cells in the colon. A, Increased numbers of mast cells were found in colonic tissue from endo-stress rats (n = 10-14 ± SEM). Representative photos of Toluidine blue staining from colon in (B) sham-no stress, (C) endo-no stress, (D) endo-stress uncontrollable, and (E) endo-stress controllable. F, The uncontrollable stress group had significantly more chymase-positive mast cells compared to no stress groups and endo-stress controllable stress (**P < .01 vs sham, ^# P < .05 vs endo no stress, ^$ P < .05 vs controllable stress group). Representative photos of (G) sham-no stress, (H) endo-no stress, (I) endo-stress uncontrollable, and (J) endo-stress controllable (40× magnification). SEM indicates standard error of the mean.

Figure 6.

Effect of stress controllability on mast cells in the vesicles. A, Endometriosis animals exposed to uncontrollable stress had an increased number of mast cells as stained with Toluidine blue (n = 10-14 ± SEM; ^# P < .05 vs endo-stress controllable); (B) this pattern was echoed by chymase expression. Representative photos of Toluidine blue/chymase staining from vesicles in (C/F) endo-no stress, (D/G) endo-stress uncontrollable, and (E/H) endo-stress controllable animals (40× magnification). SEM indicates standard error of the mean.

Figure 7.

Stress affects muscle contractility in the colon and uterus. Both longitudinal and circular muscles from colon and uterus responded to carbachol in a concentration-dependent manner. A, The colonic longitudinal muscle of the endo-stress animals exhibited a significantly greater response to carbachol at 10⁻⁷ and 10⁻³ mol/L; (B) no differences in colonic circular muscle contractility were found between endo-stress and endo-no stress animals. C, The uterine longitudinal muscle of the endo-stress animals exhibited a significantly greater response to carbachol than did tissue from endo-no stress; (D) the circular muscle contractility of uterus from the endo-stress animals exhibited a significantly higher response at 10⁻⁷ and 10⁻⁶ mol/L carbachol (*P < .05, **P < .01 vs endo-no stress; n = 12-14 ± SEM). SEM indicates standard error of the mean.