In Vitro Modeling of Diurnal Changes in Bone Metabolism

Area of Science:

• Bone Biology
• Circadian Rhythms
• Cell Culture Models

Background:

• Bone health is intrinsically linked to circadian rhythm function.
• Existing research predominantly uses mouse models, which may not fully translate to human physiology due to species-specific differences.
• A human-based in vitro model is needed to accurately study diurnal bone metabolism.

Purpose of the Study:

• To develop an in vitro model system that mimics diurnal variations in human bone metabolism.
• To investigate the impact of time-of-day serum collection on bone cell precursors.
• To establish a platform for studying bone function under circadian influence.

Main Methods:

• Co-culture of SCP-1 (osteoblast precursors) and THP-1 (osteoclast precursors) cells.
• Induction of diurnal effects by substituting fetal calf serum (FCS) with human serum pools (HSPs) collected at different times of day (morning, noon, evening).
• Assessment of cell viability, gene expression (circadian clock genes), and osteoblast/osteoclast function, including 3D co-culture mineral density and stiffness.

Main Results:

• Human serum pools (HSPs) enhanced cell viability and altered circadian clock gene expression compared to FCS.
• Osteoblast and osteoclast functions were modulated by the time of day the HSPs were collected.
• 3D co-cultures showed increased mineral density and stiffness when differentiated with morning, noon, or evening HSPs, respectively.

Conclusions:

• A novel in vitro model system accurately represents diurnal changes in human bone metabolism.
• The use of time-specific human serum pools (HSPs) is effective in simulating daily fluctuations in bone cell activity.
• This model serves as a valuable platform for investigating bone function and circadian rhythm interactions in various contexts.