Calcium mobilization is required for spreading in human osteoblasts.

Area of Science:

• Cell Biology
• Biochemistry
• Biophysics

Background:

• Osteoblast adhesion to the bone matrix is crucial for bone remodeling.
• Integrin-mediated signaling plays a key role in cell adhesion and spreading.
• Calcium ions are vital second messengers in cellular processes.

Purpose of the Study:

• To investigate the role of intracellular calcium concentration ([Ca2+]i) changes during human osteoblast adhesion.
• To determine the mechanisms and requirements of calcium mobilization during osteoblast spreading on bone matrix proteins.

Main Methods:

• Measurement of intracellular calcium concentration in human osteoblasts using fluorescent indicators.
• Adhesion and spreading assays on collagen type I, fibronectin, and laminin.
• Inhibition studies using calcium channel blockers (Carboxyamido triazole) and calcium chelators (BAPTA-AM).

Main Results:

• Osteoblast adhesion to collagen I, fibronectin, and laminin induced a rapid, approximately 2-fold increase in [Ca2+]i, followed by a decline within 1 hour.
• Calcium mobilization resulted from influx across the plasma membrane and was dependent on integrin-ligand interactions.
• Inhibitors of non-voltage-dependent calcium channels and intracellular calcium chelators dose-dependently inhibited osteoblast adhesion and spreading.

Conclusions:

• Calcium mobilization is an early event triggered by integrin-ligand contact during osteoblast adhesion.
• Calcium influx is a necessary component for successful osteoblast adhesion and spreading on bone matrix proteins.
• These findings underscore the importance of calcium signaling in osteoblast mechanotransduction and bone matrix interaction.