Detection of Cannabinoid Receptor Expression by Endometriotic Lesions in Women with Endometriosis as an Alternative to Opioid-Based Pain Medication

Figure 5

Expression of cannabinoid receptor 2 (CB2) by the epithelial cells or stromal cells in ovaries with or without endometriosis. (a) Section of a normal ovary showing occasional staining by a few epithelial cells of the ovarian surface. (b) Section of a normal ovary showing CB2 staining by a few immune cell-like cells in the stroma (S). (c) Section of an ovary with endometriosis showing CB2 expression by the cell membrane and nuclei of the epithelial cells in endometriotic lesions (EL). Interlesion stromal cells also showed staining for CB2. (d) Section of an ovary with endometriosis showing CB2 expression by many immune cell-like cells in the stroma. (e) Intensity of the CB2 expression was significantly higher in the epithelial layers in endometriotic lesions than the stroma in ovaries with endometriosis (). (f) CB2 protein expression: immunoblotting detected CB2 protein of approximately 40 kDa in tissue extracts from ovaries with endometriosis, normal endometrial, and myometrial tissue extracts. Extracts from normal ovaries showed no or very weak expression for CB2. In contrast, ovaries with endometriosis showed strong signal for CB2. (g) Gene expression studies detected strong expression for CNR2 gene in ovaries with endometriosis, while it was almost undetectable in normal ovarian tissues. EL = endometriotic lesions; OSE = ovarian surface epithelial cells; Normal En = normal endometrium; Normal My = normal myometrium; S = stroma; 40x = magnification. Arrows indicate examples of immunopositive CB2 cells in the normal OSE cells and immune cell-like stromal cells (blue arrows) and nuclei (red arrows) of the endometriotic cells. Bars with different letters denote significant difference between them.

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