Defining the Antagonistic Role of Omega-3 Polyunsaturated Fatty Acid in the Establishment and Early Maintenance of Endometriosis-Like Lesions in a Murine Model.

Several inflammatory cytokines and chemokines have been implicated in the pathogenesis of endometriosis. It has also been argued that polyunsaturated fatty acids (PUFA) may attenuate the inflammatory response in a myriad of human diseases. We hypothesize that high levels of omega-3 PUFA have an antagonistic effect on the establishment of the endometriosis. Unfortunately there is no ideal animal model to demonstrate cause and/or effect relationships between PUFA and inflammatory cytokines and chemokines in the context of endometriosis. Therefore, our objective was to utilize a novel in vivo model to demonstrate the potential relationship between PUFA and inflammatory cytokines/chemokines in a murine model for endometriosis. To accomplish this, we employed a tissue transplant model with syngeneic immunocompetent WT C57BL/6 and transgenic fat-1 mice. Fat-1 mice are genetically engineered to carry an n-3 fatty acid desaturase gene which is capable of endogenously converting n-6 PUFA to n-3 PUFA. Fat-1 mice require high n-6 PUFA in order to facilitate endogenous production of n-3 PUFA. All recipient mice were ovariectomized and an estradiol (E2) implant was placed 14 days prior to transplantation. Endometrium of donor mice were primed with an E2 injection 4 days prior to harvesting uteri. Intraperitoneal tissue transplantation into the host mouse occurred at 8-10 weeks of age. Experimental groups included were: A) transplantation of endometrium from WT mice maintained on regular rodent diet into peritoneum of WT mice on the same diet, B) transplantation of WT endometrium of mice maintained on regular rodent diet into a fat-1 mouse maintained on a diet composed of 10% corn oil (high n-6 PUFA), and C) transplantation of endometrium from fat-1 mice maintained on a 10% corn oil diet into a fat-1 host on the same diet. Mice were sacrificed 7 days after tissue transfer and endometriosis-like lesions collected. Each lesion was divided and placed in PFA or flash frozen in liquid nitrogen and placed in -80 C. PFA fixed samples were sectioned at 6 ìm and stained with H&E to confirm the presence of endometrial glands. Protein lysates were obtained from frozen samples and utilized for flow cytometric analysis of IL-1 beta, IL-6, TNF-alpha, MCP-1 and RANTES. Mann Whitney U and t-tests were utilized for analyses. There was evidence of viable glands in all lesions in all groups, but the size of the lesions varied considerably. There was an overall reduction in the number of mice that had elevated levels of IL-6 in groups B and C compared to group A. Interestingly, there was high degree of variation of the other cytokines (IL-1 beta, TNF-alpha, MCP-1 and RANTES) within group C which was observed in tandem with either the presence or absence of necrosis. In conclusion, our results provide evidence to suggest that high levels of host systemic n-3 PUFA impair an increase and or the type of response of requisite inflammatory cytokines, such as IL-6, implicated in lesion establishment. The variation in cytokine levels observed in the group C model may be the result of a switch from innate to adaptive immunity with an increase in necrosis evident in the fat-1 host. (poster)