Relaxin regulates endometrial structure and function in the rhesus monkey

Area of Science:

• Reproductive biology
• Endocrinology
• Pregnancy research

Background:

• The function of relaxin in human endometrial processes during early pregnancy remains unclear due to limited in vivo data.
• Species-specific actions of relaxin necessitate the use of appropriate animal models for studying its effects.

Purpose of the Study:

• To investigate the in vivo effects of relaxin on the primate endometrium in a model of early human pregnancy.
• To elucidate the mechanisms by which relaxin influences endometrial tissue remodeling and hormone receptor expression.

Main Methods:

• Established a model of early human pregnancy using ovariectomized, steroid-primed rhesus monkeys.
• Administered relaxin and assessed its impact on uterine weight, endometrial angiogenesis, matrix metalloproteinase (MMP) expression, collagen content, and hormone receptor levels.

Main Results:

• Relaxin significantly increased uterine weight and stimulated endometrial angiogenesis (new blood vessel formation).
• Relaxin downregulated endometrial matrix metalloproteinases (MMP-1, MMP-3) and upregulated their inhibitor (TIMP-1), preserving collagen content.
• Relaxin inhibited endometrial estrogen receptor alpha and progesterone receptor isoforms (B and A).

Conclusions:

• Relaxin plays a crucial role in establishing and maintaining early pregnancy by promoting angiogenesis and endometrial connective tissue integrity.
• The distinct effects of relaxin on endometrial MMPs, contrasting with other tissues, highlight its specialized role in pregnancy.
• Modulation of key hormone receptors by relaxin suggests a complex interplay in endometrial receptivity.