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Localization of the expression of complement component 3 in the human endometrium by in situ hybridization
R A Sayegh1, X J Tao, J T Awwad
1Vincent Memorial Obstetrics and Gynecology Service, Massachusetts General Hospital, Boston, USA.
Insights
The human endometrium expresses the third component of complement (C3) gene in both glands and stroma. C3 expression is significantly higher in the secretory phase, particularly in the basalis layer, suggesting roles in implantation and immune response.
Area of Science:
- Reproductive Immunology
- Complement System Biology
Background:
- The third component of complement (C3) is a key protein in the complement system.
- Previous studies indicated C3 production in the human endometrium.
Purpose of the Study:
- To determine the specific location and regulation of C3 gene expression within the human endometrium.
- To investigate the spatial and temporal patterns of C3 expression during the menstrual cycle.
Main Methods:
- In situ hybridization using a radiolabeled riboprobe for human C3 cDNA.
- Analysis of archival endometrial samples from proliferative and secretory phases.
- Qualitative assessment of autoradiograms via light and darkfield microscopy.
Main Results:
- C3 gene expression was minimal in proliferative endometrium, localized to scattered stromal and glandular cells.
- Prominent C3 expression was observed in both endometrial glands and stroma of the basalis layer during the secretory phase.
- Endometrial lymphocytes did not express C3, though other lymphoid elements might.
Conclusions:
- Endometrial stromal and glandular cells are the primary sites of C3 gene expression.
- The increased C3 expression in the secretory phase suggests a role in endometrial receptivity and immune modulation during early pregnancy.
- The spatial and temporal expression pattern of C3 may influence endometrial physiology and the maternal immune response to the trophoblast.
Abstract:
C3 production by the human endometrium has been previously described. The objective of the current study was to localize the site of expression and regulation of the third component of complement, C3, in the endometrium. Eight secretory and eight proliferative archival endometrial samples from hysterectomy and endometrial biopsy specimens were used for in situ hybridization analysis. This analysis was performed with a radiolabeled riboprobe synthesized from a 736-bp template representing sequence 1944-2680 of the human C3 complementary DNA. Duplicate sections were hybridized with sense and antisense riboprobes. Resultant autoradiograms were analyzed qualitatively by light- and darkfield microscopy. In proliferative endometrium, minimal expression of C3 was observed and was limited to a few stromal patches and glands throughout the section. In the secretory samples, prominent C3 expression was observed in both the glands and stroma of the basalis layer. Endometrial lymphocytes did not express C3. Endometrial stromal and glandular cells express the C3 gene. Endometrial lymphocytes did not express C3, but other nondistinct lymphoid elements scattered in the stroma may be expressing C3. There was a visibly more intense expression of C3 in the basalis layer of the secretory endometrium than in proliferative endometrium. The spatial and temporal pattern of C3 expression may have implications in normal menstrual physiology and in the immunological response of the endometrium to the invading trophoblast during placentation.