Translocator protein expression and localization in human endometrium and endometriosis: A potential target for a noninvasive diagnosis?

The limitations of current imaging methods to detect small or superficial endometriotic lesions prompt the search for new molecular targets. TSPO is an 18 KDa protein located in the outer mitochondrial membrane, which can be traced by positron emission tomography (PET) using specific ligands. TSPO is located mostly in neurons and inflammatory sites outside the brain. We hypothesized that it might also be expressed in the human endometrium and endometrial-like tissue, being a target for molecular imaging of endometriosis. This prospective cross-sectional study included 28 women with endometriosis and 11 endometriosis-free controls. Endometriotic lesions (n = 49) and normal peritoneum (n = 13) from endometriosis patients were obtained during laparoscopy, while samples of eutopic endometrium from patients with endometriosis (n = 28) and from control women (n = 11) were collected in the operating room using a flexible device. TSPO mRNA expression was evaluated by quantitative reverse-transcription real-time PCR while protein expression was evaluated by immunohistochemistry with a monoclonal antibody antihuman TSPO. TSPO mRNA expression was detected in an invariable fashion in all tissue types evaluated; however, TSPO protein was found to be more abundant in the glandular epithelium than in the stroma, both in the endometrium and in the endometriotic lesions. Interestingly, hormone therapies did not alter the expression of TSPO, and its presence was mostly negative in tissues adjacent to endometriotic implants. As a proof of concept, the protein expression pattern of TSPO in endometriotic tissue and along the adjacent areas suggests that TSPO-based molecular imaging might be used for noninvasive endometriosis detection.

IL-1ß Stimulates Brain-Derived Neurotrophic Factor Production in Eutopic Endometriosis Stromal Cell Cultures: A Model for Cytokine Regulation of Neuroangiogenesis.

Endometriosis implants are comprised of glandular and stromal elements, macrophages, nerves, and blood vessels and are commonly accompanied by pelvic pain. We propose that activated macrophages are recruited to and infiltrate nascent lesions, where they secrete proinflammatory cytokines, promoting the production of chemokines, neurotrophins, and angiogenic growth factors that sustain an inflammatory microenvironment. Immunohistochemical evaluation of endometriosis lesions reveals in situ colocalization of concentrated macrophages, brain-derived neurotrophic factor (BDNF), and nerve fibers. These observations were coupled with biochemical analyses of primary eutopic endometriosis stromal cell (EESC) cultures, which allowed defining potential pathways leading to the neuroangiogenic phenotype of these lesions. Our findings indicate that IL-1ß potently (EC50 = 7 ± 2 ng/mL) stimulates production of EESC BDNF at the mRNA and protein levels in an IL-1 receptor-dependent fashion. Selective kinase inhibitors demonstrate that this IL-1ß effect is mediated by c-Jun N-terminal kinase (JNK), NF-κB, and mechanistic target of rapamycin signal transduction pathways. IL-1ß regulation of regulated on activation normal T cell expressed and secreted (RANTES), a prominent EESC chemokine, also relies on JNK and NF-κB. An important clinical implication of the study is that interference with BDNF and RANTES production, by selectively targeting the JNK and NF-κB cascades, may offer a tractable therapeutic strategy to mitigate the pain and inflammation associated with endometriosis.

Type 2 Endometrial Cancer is Associated With a High Density of Tumor-Associated Macrophages in the Stromal Compartment.

INTRODUCTION: Tumor-associated macrophages (TAMs) play a pivotal role in orchestrating the microenvironment. The TAMs differentially polarize into M1 or M2 macrophages with distinct actions. The aim of our work is to characterize density, subtype, and location of TAMs in endometrial hyperplasia and cancer. METHODS: Formalin-fixed, paraffin-embedded sections of hyperplasia (n = 5), type 1 (n = 5), and type 2 (n = 5) endometrial cancer were stained with anti-CD68 and anti-CD163 monoclonal antibodies as markers for total TAMs and M2 TAMs, respectively. Macrophages were counted at 40× magnification in 10 high-power fields (HPFs) per slide by 4 observers. Repeated measures models were constructed to determine the relationships between macrophages and lesion categories. RESULTS: Most CD68+ TAMs were located in the stromal (mean = 41.0/HPF) compared to epithelial (mean = 11.0/HPF) or luminal (mean = 11.6/HPF) compartments. Similar but reduced findings were observed for CD163+ (M2 subtype) TAMs. The CD68+ stromal TAM density was highest in patients with type 2 cancers (mean = 54.0/HPF) compared to those with type 1 cancers (mean = 35.5/HPF) and hyperplasia (mean = 29.0/HPF). Women with hyperplasia had more CD163+ (M2 subtype) TAMs (26.7/HPF) than patients with either type of cancer (type 1 = 12.5/HPF and type 2 = 11.5/HPF). Based on the repeated measures models, type 2 cancers had 38.6/HPF more CD68+ TAMs than type 1 cancers (P < .0001) and type 1 and type 2 cancers had similar numbers of CD163+ TAMs (P = .27). CONCLUSIONS: Type 2 cancers have nearly twice the TAM density of type 1 cancers. This difference may be due to M1 macrophage predominance in the stroma of type 2 cancers.

Proteomic identification of neurotrophins in the eutopic endometrium of women with endometriosis.

OBJECTIVE: To evaluate neurotrophin (NT) expression in the endometrium of women with and without endometriosis. DESIGN: Prospective, cross-sectional, translational study. SETTING: Academic hospital. PATIENT(S): Thirty-three reproductive-age women undergoing laparoscopy for infertility, pelvic pain, intramural fibroids, or tubal ligation. INTERVENTION(S): Endometrial biopsies, protein microarrays, reverse transcriptase-polymerase chain reaction, ELISAs, and Western blotting. MAIN OUTCOME MEASURE(S): Neurotrophin proteins and mRNAs in eutopic endometrial biopsies. RESULT(S): Among seven neurotrophic proteins detected on the antibody microarrays, reverse transcriptase-polymerase chain reaction analysis confirmed nerve growth factor, NT-4/5, and brain-derived neurotrophic factor mRNAs in endometrial tissue. Quantitative ELISAs revealed that NT-4/5 (806 ± 701 vs. 256 ± 190 pg/100 mg protein) and brain-derived neurotrophic factor (121 ± 97 vs. 14 ± 11 ng/100 mg protein) concentrations were significantly higher in women with endometriosis. Nerve growth factor (100 ± 74 vs. 93 ± 83 pg/100 mg protein) levels did not differ between cases and controls. CONCLUSION(S): Neurotrophins are synthesized in situ within the endometrium. NT-4/5 and brain-derived neurotrophic factor proteins were more concentrated in biopsies from endometriosis cases than controls, whereas nerve growth factor levels were similar. We hypothesize that the local production of NTs induces sensory innervation of endometrium of women with endometriosis. These NTs represent novel targets for the diagnosis and treatment of endometriosis.