TRPM3/TRPV4 regulates Ca2+-mediated RANKL/NFATc1 expression in osteoblasts

Area of Science:

• Cell Biology
• Biochemistry
• Orthopedics

Background:

• Mechanical stress is a key regulator of bone turnover.
• The cellular mechanisms of hypo-osmotic stress in osteoblasts are not well understood.
• Osteoblasts are critical cells involved in bone remodeling.

Purpose of the Study:

• To investigate the effect of hypo-osmotic stress on bone remodeling factors in osteoblasts.
• To elucidate the role of transient receptor potential (TRP) channels in mediating these responses.

Main Methods:

• Primary mouse osteoblasts and MC3T3-E1 cells were subjected to hypo-osmotic stress.
• Expression of receptor activator of nuclear factor-kappa B ligand (RANKL) and nuclear factor of activated T cells type c1 (NFATc1) was analyzed.
• Intracellular calcium concentration ([Ca2+]i) was measured.
• TRP channel (TRPM3 and TRPV4) agonists and antagonists were used, along with genetic suppression of TRP channels.

Main Results:

• Hypo-osmotic stress significantly increased RANKL mRNA and NFATc1 protein expression, along with intracellular calcium levels.
• TRPM3 and TRPV4 antagonists reduced these effects, while agonists mimicked them.
• Genetic suppression of Trpm3 and Trpv4 attenuated the hypo-osmotic stress-induced responses.

Conclusions:

• Hypo-osmotic stress elevates intracellular calcium via TRPM3 and TRPV4 channels in osteoblasts.
• These channels regulate the expression of RANKL and NFATc1, key factors in bone remodeling.
• Mechanical stress-activated TRP channels are critical for bone turnover.