Developmental changes in endogenous retinoids during pregnancy and embryogenesis in the mouse

Area of Science:

• Developmental Biology
• Maternal-Fetal Medicine
• Nutritional Biochemistry

Background:

• Vitamin A, particularly retinoic acid (RA), is crucial for embryonic development, acting as an endogenous morphogen.
• Mammalian embryos rely on maternal supply of RA or its precursors due to limited de novo synthesis.
• Understanding maternal-embryonic retinoid dynamics is key, especially during critical organogenesis periods.

Purpose of the Study:

• To investigate the relationship between maternal and embryonic levels of retinoic acid (RA), retinol, and retinyl esters during mouse pregnancy.
• To determine how maternal vitamin A homeostasis is altered during embryonic organogenesis.
• To elucidate the acquisition and distribution of retinoids by the developing embryo and placenta.

Main Methods:

• Quantification of RA, retinol, and retinyl esters in maternal plasma, embryonic tissues, and placenta across different gestational stages in mice.
• Analysis of retinoid levels specifically during the period of organogenesis (gestational Days 9-14).
• Assessment of retinoid accumulation patterns in the embryonic liver and comparative analysis between embryo and placenta.

Main Results:

• Maternal plasma retinol levels decreased significantly during organogenesis, suggesting mobilization from hepatic stores to the conceptus.
• Embryonic retinol levels increased steadily during organogenesis, with minimal changes in RA and retinyl esters; embryonic liver storage began by mid-organogenesis.
• Placental retinoid levels remained constant, while the conceptus showed a shift in retinoid majority from placenta to embryo by mid-organogenesis.

Conclusions:

• Pregnancy in mice involves significant alterations in maternal retinoid homeostasis, coinciding with embryonic organogenesis.
• The developing embryo actively acquires retinol from maternal circulation, with functional hepatic storage commencing mid-organogenesis.
• These maternal-fetal retinoid dynamics are critical during periods of high embryonic sensitivity to exogenous retinoids.