Regulation of osteoclastogenesis by gap junction communication

Area of Science:

• Cell Biology
• Bone Biology
• Signaling Pathways

Background:

• Receptor activator of NF-kappaB ligand (RANKL) is key to osteoclastogenesis, but its signaling is not fully understood.
• Gap junction intercellular communication allows cell-to-cell exchange of signaling molecules.
• Connexin 43 (Cx43) is a protein forming gap junctions.

Purpose of the Study:

• To investigate the role of gap junction communication in osteoclastogenesis.
• To determine if Cx43 is present in osteoclast precursors and mature osteoclasts.
• To assess the effect of blocking gap junction communication on osteoclast differentiation.

Main Methods:

• Mouse bone marrow cultures were used to study osteoclastogenesis.
• Carbenoxolone (CBX) was used to inhibit gap junction communication.
• Gap junction function was assessed using dye transfer techniques.
• Osteoclast formation was quantified by counting tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells.
• Quantitative real-time PCR was used to analyze gene expression.

Main Results:

• Immunoreactive Cx43 was detected in marrow stromal cells and mature osteoclasts.
• CBX significantly inhibited osteoclast formation stimulated by parathyroid hormone (PTH), forskolin (FSK), prostaglandin E2 (PGE2), and 1,25(OH)2-vitamin D3.
• CBX inhibited RANKL-stimulated osteoclastogenesis.
• CBX downregulated osteoclast phenotypic markers but did not affect RANK, RANKL, or OPG mRNA levels.

Conclusions:

• Gap junction communication is involved in osteoclast differentiation.
• The results suggest that gap junctional diffusion of messenger molecules interacts with signaling pathways downstream of RANKL.
• Further research is needed to elucidate the precise mechanisms and molecular targets involved.