Die Expression der G-Protein gekoppelten Rezeptoren LGR 4, LGR 5, LGR 7 und LGR 8 im humanen nicht-graviden und graviden Uterus sowie in Karzinomzelllinien des Reproduktionstraktes und der Mamma

摘要

Up today, the complex hormonal regulation in the human endometrium and decidua during pregnancy is not completely understood. Since recently, we know that a particular class of G Protein-coupled receptors, the leucin-rich repeat-containing G protein-coupled receptors (LGRs), is expressed in human physiological and pathological uterine tissues. The LGR 7 binds the hormone Relaxin, the ligand of the LGR 8 is the Relaxin-related hormone INSL3. The receptors LGR 4 and LGR 5 are still orphan. So far, the expression of these receptors is not explored in detail or in case of the LGR 7 there is contradictive data. In this work the LGR-mRNA expression was investigated in human endometrium (complete cycle) and decidua (first and second trimester) via semiquantitative and Real-time RT-PCR. Northern Hybridization was used to detect the size of the mRNAs. Additionally, semiquantitative RT-PCR experiments were performed with human placenta and myometrium as well as with different carcinoma cell lines. Protein expression was localized using immunohistochemistry. The human endometrium constitutively expresses the LGR 4-, LGR 5- and LGR 7 mRNA during the whole cycle. Besides, the mRNAs were detectable in the first and second trimester decidua. The LGR 4- and LGR 7-mRNA expression is significantly increased between these two periods of human pregnancy. Due to an unreliable LGR 4 antibody the LGR 4 protein expression was not characterized in the human uterus. The LGR 5 protein was found in the basal glands of the decidua. During the late proliferative and the secretory phase the human endometrium showed a clear LGR 7 staining of the surface epithelial cells and the functional glands. In the Decidua, the glandular epithelial cells, several leukocytes and individual cells of the extravillous trophoblast were positive for LGR 7 immunostaining. A specific LGR 8 mRNA expression was detected in myometrium, decidua and placenta. LGR 4 -/- knock-out mice suffer from infertility, indicating that this receptor system plays a role in reproduction. Recently, the LGR 5 was described as a marker for stem cells in the human colon. Future studies will determine if the LGR 5 highlights the stem cell compartment in the human uterus. Concerning the LGR 7, the data about hormonal regulation and localization of expression is contradictive. The results of this work clarify the protein localization and clearly demonstrate that the expression of the relaxin receptor LGR 7 is not influenced by the hormones oestradiol and progesterone. INSL 3, the ligand of the LGR 8, is produced by the receptor negative endometrium. Potentially, the INSL3-LGR 8 system is involved in the endometrial-myometrial dialogue. The chorioncarcinoma cell lines Jeg-3 and Jar as well as the endometrial carcinoma cell line Hec 1a express the LGR 4-, LGR 5- and LGR 7-mRNA, whereas BeWo-cells additionally express the LGR 7-mRNA. In the breast carcinoma cell lines T47D and MCF7 only the mRNAs of LGR 4 and LGR 5 were detectable. According to the literature, the LGRs increase invasiveness and the tendency towards metastasis in several tumor cells. Thus, these receptors are potential therapeutical targets for the treatment of gynaecological tumors in the future. In conclusion, the LGRs are expected to become a promising target in reproductive and oncological research.