Alterations to maternal cortical and trabecular bone in multiparous middle-aged mice

Area of Science:

• Reproductive Biology
• Bone Physiology
• Mammalian Endocrinology

Background:

• Reproductive cycles alter calcium homeostasis, increasing bone resorption during pregnancy and lactation.
• Lactation can lead to significant bone mineral density loss (1-3% per month), comparable to annual post-menopausal loss.
• Understanding parity's long-term effects on bone is crucial for women's health.

Purpose of the Study:

• To investigate the impact of parity (number of pregnancies) on bone formation in middle-aged mice.
• To assess changes in trabecular and cortical bone density in relation to parity.
• To evaluate associated changes in key bone metabolism markers.

Main Methods:

• Mice were grouped by parity number and compared to age-matched nulliparous controls.
• Femoral trabecular and cortical bone mineral density were measured.
• Serum calcium, protein, and alkaline phosphatase levels were analyzed.

Main Results:

• A single parity event increased trabecular bone mineral density compared to nulliparous controls.
• Increasing parity from one to five pregnancies resulted in a decrease in trabecular bone mineral density.
• Cortical bone formation and serum biochemical markers showed no significant alterations related to parity.

Conclusions:

• Parity significantly influences trabecular bone formation in middle-aged mice.
• The number of pregnancies affects bone density, with notable changes observed in parous groups.
• These findings highlight the complex relationship between reproductive history and skeletal health.