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Expression of two isoforms of CD44 in human endometrium
F Behzad1, M W Seif, S Campbell
1Department of Obstetrics and Gynaecology, University of Manchester, United Kingdom.
Insights
This study reveals that the CD44 glycoprotein is present in human endometrium and decidua throughout the menstrual cycle and pregnancy. Different CD44 isoforms are associated with specific tissue compartments, suggesting distinct functional roles.
Area of Science:
- Reproductive Biology
- Cell Biology
- Molecular Biology
Background:
- The cell-surface adhesion glycoprotein CD44 plays crucial roles in cell adhesion and signaling.
- Understanding CD44 distribution and isoforms in the human endometrium is essential for elucidating its function in reproductive processes.
Purpose of the Study:
- To investigate the distribution and molecular characteristics of CD44 isoforms in the human endometrium during the menstrual cycle and early pregnancy.
- To determine the association of specific CD44 variants with different endometrial tissue compartments.
Main Methods:
- Immunofluorescence staining using monoclonal antibodies against CD44.
- Reverse transcription-polymerase chain reaction (RT-PCR) to analyze CD44 mRNA transcripts.
- Immunoprecipitation to determine the molecular mass of the epithelial CD44 isoform.
Main Results:
- CD44 immunoreactivity was detected in endometrial stroma, vessels, and glandular/luminal epithelium throughout the menstrual cycle.
- A dominant CD44E species (~130 kDa) was identified on the surface of glandular epithelial cells.
- RT-PCR revealed the presence of CD44H and larger isoforms in endometrial tissue, with CD44H being scarce in purified glands but abundant in Ishikawa cells.
Conclusions:
- CD44 is expressed in human endometrium and decidua, with distinct isoforms localized to specific tissue compartments.
- The differential expression of CD44 isoforms suggests compartment-specific functional roles in the endometrium.
- Further research into CD44 isoform function can provide insights into endometrial physiology and pathology.
Abstract:
The distribution of the cell-surface adhesion glycoprotein CD44 in human endometrium was examined by immunofluorescence using six monoclonal antibodies to epitopes common to all forms of the molecule, and by reverse transcription-polymerase chain reaction (RT-PCR). Immunoreactivity was observed throughout the menstrual cycle in stroma, vessels, glandular, and luminal epithelium. Variations in staining intensity were observed, especially in the epithelial compartment. CD44 was also expressed strongly by decidualized stromal cells of first-trimester pregnancy. No systematic variation of immunoreactivity was observed with stages of the normal cycle, but a fraction (25%) of the specimens lacked reactivity in the epithelium. To determine the molecular size of the epithelial isoform, an immunoprecipitation technique was developed using surface-radioiodinated, detergent-extracted glands. This indicated the presence at the cell surface of a single dominant CD44E species with an approximate molecular mass of 130 kDa. RT-PCR was used to investigate the isoforms present in whole endometrial tissue, isolated gland fragments, and Ishikawa endometrial carcinoma cells. Complementary DNA produced from total endometrial mRNA was PCR-amplified across the splice junction between exons 5 and 15. Transcripts corresponding to the hyaluronate receptor CD44H as well as a larger isoform were identified. CD44H was absent, or very scarce, in cDNA from purified gland epithelium. In contrast, Ishikawa cells expressed this form abundantly. The glands and Ishikawa cells also expressed CD44E containing sequences encoded by exons 12, 13, and 14. These data demonstrate the presence of CD44 in human endometrium and decidua, and show that different isoforms of CD44 are associated with tissue compartments in which different functional roles can be anticipated.