Epithelial cell protein milk fat globule epidermal growth factor 8 and human chorionic gonadotropin regulate stromal cell apoptosis in the human endometrium

Capsule:
Milk fat globule–epidermal growth factor 8, a multifunctional epithelial protein in the human endometrium, and hCG modulate apoptosis of stromal cells.

Authors:
Ryan M. Riggs, M.D., Silvina Bocca, M.D., Ph.D., Sandra Anderson, B.S., Anahi Franchi, Ph.D., Bhaskara S. Rhavi, M.Sc., Sergio Oehninger, M.D., Ph.D.

Volume 98, Issue 6, Pages 1549-1556.e3, December 2012

Abstract:

Objective:
To study the regulation of apoptosis in human endometrial cells. The specific aims were: 1) to determine if MFG-E8, a novel endometrial epithelial protein, modulates caspase activation and DNA fragmentation; and 2) to examine if hCG, an early embryonic product, regulates Bax and Bcl-2 equilibrium, as well as MFG-E8 expression.

Design:
Primary cultures of human endometrial epithelial (EEC) and stromal (ESC) cells.

Setting:
Academic center.

Subjects:
Ovulatory women aged 21-30 years.

Interventions:
Treatment with MFG-E8 and hCG.

Main Outcome Measure(s):
Apoptotic activity was quantified using a luciferase assay. DNA fragmentation was detected by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-fluorescein nick-end labeling assay (TUNEL). Bax, Bcl-2 and MFG-E8 mRNA expression levels were determined by qRT-PCR. Immunocytochemistry was used to establish cell purity and presence of MFG-E8 and hCG-R (receptor) proteins.

Results:
EEC were cytokeratin+, vimentin-, MFG-E8+, and hCG-R+ whereas ESC were vimentin+, cytokeratin-, MFG-E8- and hCG-R+. MFG-E8 treatment of ESC resulted in a 13-fold increase in caspase activity and a 30-fold increase in TUNEL. On the other hand, hCG decreased mRNA expression of Bax in ESC.

Conclusion(s):
Milk fat globule–epidermal growth factor 8 has proapoptotic activity, suggesting participation in endometrial remodeling via an epithelial–stromal cell paracrine effect. Conversely, pregnancy levels of hCG has opposite effects on stromal cells.

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