Induction of endometriosis in the mouse inhibits spleen leukocyte function

BACKGROUND

It is still unclear whether the immunologic perturbation observed in women with endometriosis represents an intrinsic defect of the immune system or it is consequent to the presence of endometrium in ectopic sites. The present study was aimed to evaluate the immunoregulatory properties of ectopic endometrial implants in a model of experimental endometriosis in mice.

METHODS

Endometriosis was induced in n=10 mice by inoculating endometrial fragments obtained from syngenic donor mice into the peritoneal space. Twelve mice were similarly treated but were not inoculated with endometrium and were used as control mice. At an explorative laparotomy performed in all the animals after three weeks, the extent of peritoneal lesions, when present, was evaluated by weight assessment and surface area measurement. In both mice that were inoculated with endometrium and control animals, spleens were removed. The effect of endometriosis induction on concanavalin A-induced spleenocyte proliferation was investigated.

RESULTS

A significant inhibition of spleenocyte growth was demonstrated in mice in which endometriosis was induced (36156+/-3061 cpm) compared to control animals (47172+/-3210 cpm; p<0.05). Moreover, a significant inverse correlation was found between spleenocyte proliferation and weight and surface area of the peritoneal endometriotic lesions (r=0.76; p<0.02 and r=0.75; p<0.02, respectively).

CONCLUSION

These findings suggest that the presence of ectopic endometrial implants within the peritoneal cavity leads to substantial changes of the immune response in vivo. These changes may have significant implications for the understanding of the etiopathogenesis of endometriosis.

Use of knockout transgenic mice in the study of endometriosis: insights from mice lacking beta(2)-microglobulin and interleukin-12p40

OBJECTIVE

To test the possibility of using transgenic knockout mice in the study of endometriosis and to investigate specific immunologic aspects of the disease.

DESIGN

Experimental blinded study.

SETTING

Academic research center.

ANIMAL(S)

Thirty-two mice with experimentally induced endometriosis.

INTERVENTION(S)

Endometriosis was induced in 8 beta(2)-microglobulin-deficient BALB/c mice and 7 wild-type BALB/c controls. Similarly, endometriosis was induced in 8 interleukin-12-deficient C57BL/6 mice and in 9 wild-type C57BL/6 controls.

MAIN OUTCOME MEASURE(S)

Weight and surface area of endometriotic lesions.

RESULT(S)

Total weight and surface area of endometriotic lesions was markedly lower in beta(2)-microglobulin-deficient BALB/c mice than in wild-type BALB/c controls. A slight but statistically insignificant increase in total weight and surface area of lesions was observed in interleukin-12-deficient C57BL/6 mice compared to wild-type C57BL/6 controls.

CONCLUSION(S)

Knockout transgenic mice can be used successfully for the study of endometriosis; however, in these animals, the redundancy of the immunologic cytokine-mediated regulatory mechanisms may lead to compensation from the remaining genome. Results from beta(2)-microglobulin-deficient mice support the critical role of the immune system in the pathogenesis of the disease.

Dynamic aspects of endometriosis in a mouse model through analysis of implantation and progression

The aim of this study was to use normal immunocompetent mice to set up a model for endometriosis which allowed to study the dynamic aspects involved in initiation and progression of the disease. Thirty mice were surgically transplanted with autologous endometrium and at 3 weeks showed evidence of endometriosis. Diagnosis of endometriotic lesions was histologically confirmed. Visual inspection using a caliper revealed that, after an initial decrease in size (from 33.44+/-2.33 mm2 to 24.24+/-2.37 mm2 (p<0.01)) detected at 3 weeks after transplantation, there was a significant increase of lesion area from 21.30+/-3.15 mm2 to 43.93+/-6.29 mm2 (p<0.05) in the following 4 weeks. When we compared these results to those obtained in mice which underwent bilateral annessiectomy, we observed that, when bilateral annessiectomy was performed simultaneously to endometrial transplantation, lesion surfaces were similar between mice which were or were not subjected to bilateral ovariectomy. On the other hand, when bilateral annessiectomy was performed at second laparotomy and then evaluated after 4 weeks, differently from what observed in control mice, surface values decreased from 21.24+/-2.29 mm2 to 10.58+/-3.40 mm2 (p<0.01). Finally, progression of lesions in estrogen supplemented mice seems less evident than in control mice since only a slight but not significant increase in size (from 21.32+/-3.32 mm2 to 26.18+/-6.98 mm2, p=0.32) was detected. The results presented herein demonstrate that surgically induced endometrial implants in mice are dynamic lesions and that implantation and progression of endometriosis represent different stages in the ethiopathogenesis of the disease. Moreover, we showed that progression, but not implantation, of ectopic endometrium is dependent upon the functionally and structurally integrity of the ovaries. This is a model of endometriosis established in normal immunocompetent mice, and, consequently, may represent a reliable tool for testing new immunological therapeutical approaches and studying the role of different genes using transgenic mice.