Stress exacerbates endometriosis manifestations and inflammatory parameters in an animal model

Abstract

Women with endometriosis have significant emotional distress; however, the contribution of stress to the pathophysiology of this disease is unclear. We used a rat model of endometriosis to examine the effects of stress on the development of this condition and its influence on inflammatory parameters. Female Sprague-Dawley rats were subjected to swim stress for 10 consecutive days prior to the surgical induction of endometriosis by suturing uterine horn implants next to the intestinal mesentery (endo-stress). Sham-stress animals had sutures only, and an endo-no stress group was not subjected to the stress protocol. At the time of sacrifice on day 60, endometriotic vesicles were measured and colons assessed for macroscopic and microscopic damage. Colonic tissue and peritoneal fluid were collected for inflammatory cell analysis. Endometriosis, regardless of stress, produced a decrease in central corticotropin-releasing factor immunoreactivity, specifically in the CA3 subregion of the hippocampus. Prior exposure to stress increased both the number and severity of vesicles found in animals with endometriosis. Stress also increased colonic inflammation, motility, myeloperoxidase levels, and numbers of mast cells. In summary, prior stress may contribute to the development and severity of endometriosis in this animal model through mechanisms involving cell recruitment (eg, mast cells), release of inflammatory mediators, and deregulation of hypothalamic-pituitary axis responses in the hippocampus.

Figure 1.

Experimental design. Animals were subjected to swim stress for 10 consecutive days prior to the surgical induction of endometriosis. All animals were checked for regular cycling by analysis of smears during the protocol and sacrificed 60 days after surgery. FPC indicates fecal pellet count.

Figure 2.

Stress increases anxiety levels. Both the sham-stress and endo-stress groups had increased fecal pellet counts compared to endo-no stress, indicating increased anxiety levels *P < .05,**P < .01,***P < .001 versus endo-no stress (9-10 animals/group).

Figure 3.

Prior stress increases implant frequency and severity. None of the sham-stress animals developed vesicles. The endo-no stress group developed a vesicle in 50% of their sutures (grades 2, 3, or 4). Prior exposure to stress increased both, (A) the number of vehicles developed and (B) the average vesicle grade (9-10 animals/group; *P < .05 vs endo-no stress).

Figure 4

Effect of prior stress on myeloperoxidase (MPO) activity and mast cell numbers. A, The endo-stress animals had the highest MPO levels in colonic tissue (9-10 animals/group), but this difference did not reach statistical significance. B, Representative tissue sections of colon; ×400; C, Average mast cell numbers per field of view in the colon (5-6 animals/group).

Figure 5.

Corticosterone levels in serum. Endo-no stress rats have the highest corticosterone levels. Endo-stress and sham-stress animals have a similar pattern of corticosterone levels (4-6 animals per group).

Figure 6.

Hypothalamic CRF immunoreactivity. A, Representative tissue section of the parvocellular and magnocellular subdivisions of the paraventricular nucleus of the hypothalamus. B, Quantitative light densitometry analysis showed no significant differences in CRF immunoreactivity between endo-no stress, sham-stress and endo-stress groups. CRF indicates corticotropin releasing factor.

Figure 7.

Hippocampal CRF immunoreactivity. A, Representative tissue section of the CA3 regions of the hippocampus from a sham-stress animal. B, Quantitative light densitometry analysis revealed higher levels of CRF in CA3 regions of sham-stress animals compared to both the endo-stress and endo-no stress. *represents P < .05 compared to the other 2 groups; ^represents P < .05 from endo-no-stress group only.