Aberrant gene expression profile in a mouse model of endometriosis mirrors that observed in women

Abstract

Objective: To define the altered gene expression profile of endometriotic lesions in a mouse model of surgically induced endometriosis.

Design: Autologous experimental mouse model.

Setting: Medical school department.

Animal(s): Adult C57Bl6 mice.

Intervention(s): Endometriosis was surgically induced by autotransplantation of uterine tissue to the intestinal mesentery. Endometriotic lesions and eutopic uteri were recovered at 3 or 29 days after induction.

Main outcome measure(s): Altered gene expression was measured in the endometriotic lesion relative to the eutopic uterus by genome-wide complementary DNA microarray analysis and was confirmed by real-time reverse transcriptase-polymerase chain reaction for six genes. Relevant categories of altered genes were identified using gene ontology analysis to determine groups of genes enriched for altered expression.

Result(s): The expression of 479 and 114 genes was altered in the endometriotic lesion compared with the eutopic uterus at 3 or 29 days after induction, respectively. Gene ontology enrichment analysis revealed that genes associated with the extracellular matrix, cell adhesions, immune function, cell growth, and angiogenesis were altered in the endometriotic lesion compared with the eutopic uterus.

Conclusion(s): According to gene expression analysis, the mouse model of surgically induced endometriosis is a good model for studying the pathophysiology and treatment of endometriosis.

Figure 1. Surgical induction and collection of endometriosis in the mouse

Endometriotic lesions were collected 3 or 29 days post-induction from mice surgically-induced to have endometriosis. (A) Three uterine biopsies prior to surgical induction. (B) Three implants sutured to alternating arteries of the intestinal mesentery. (C) An endometriotic lesion 29 days post-induction. (D) Two endometriotic lesions that are surrounded by numerous adhesions 29 days post-induction of endometriosis.

Figure 2. Histology of mouse endometriotic lesion and eutopic uterus

Mice underwent surgical-induction of endometriosis and eutopic uteri (A, C) and endometriotic lesions (B, D) were excised 3 (A, B) or 29 (C, D) days later. Representative hematoxylin and eosin stained sections at 400× magnification are shown.

Figure 3. Immunohistochemistry of mouse endometriotic lesion and eutopic uterus

Mice underwent surgical induction of endometriosis and eutopic uteri (A, C) and endometriotic lesions (B, D) were excised 3 (A, B) or 29 (C, D) days later. Representative Ki67 stained sections at 400× magnification are shown. Inset is negative staining control. Pictures are sister sections to those in Fig. 2.

Figure 4. Ki67 quantification

Tissue sections were immunohistochemically stained with Ki67. Positively stained cells in the stroma were identified and quantified in each section with the aid of the computer program Metamorph. Results shown are average ± standard deviation Ki67 positive cells/field in the eutopic uterus and endometriotic lesion stroma at 3 days post-induction of endometriosis. *Paired t-test, P < 0.05.

Figure 5. RT-PCR confirmation of microarray results for selected genes

Endometriotic lesions and eutopic uteri were excised from mice surgically-induced to have endometriosis after 3 or 29 days. RNA was isolated, cDNA generated, and RT-PCR performed and analyzed using the ΔΔCt method (35). Scatter plots show representative fold changes for each animal collected at 3 or 29 days post-induction. Fold change is relative to the eutopic uterus at each time point, and a fold change of 1 indicates there is no difference between gene expression levels in the endometriotic lesion and eutopic uterus. The gray bar represents the average fold change in the endometriotic lesion at each time point. *P<0.05 for average gene expression in endometriotic lesion versus eutopic uterus.