Different Effects of Fluoride Exposure on the Three Major Bone Cell Types

Area of Science:

• Biochemistry
• Cell Biology
• Toxicology

Background:

• Fluoride accumulation in bones causes skeletal fluorosis, a condition with phased bone lesions.
• Previous studies often overlooked the simultaneous roles of osteocytes, osteoclasts, and osteoblasts in fluorosis.
• Understanding differential cell responses is crucial for managing fluoride toxicity.

Purpose of the Study:

• To investigate the distinct responses of osteocytes, osteoclasts, and osteoblasts to fluoride exposure.
• To examine how fluoride affects cell viability and apoptosis in these bone cell types.
• To assess fluoride's impact on apoptosis induced by parathyroid hormone (PTH) and transforming growth factor-beta (TGF-β).

Main Methods:

• Osteocyte-like cells were identified by sclerostin (SOST) expression.
• Osteoclast-like cells were characterized by tartrate-resistant acid phosphatase (TRACP) staining.
• Bone mesenchymal stem cells (BMSCs) were purified, and cell viability/apoptosis were assessed using MTT and Annexin V FITC assays.

Main Results:

• Osteocytes exhibited high tolerance to fluoride, whereas osteoclasts showed sensitivity to fluoride dose variations.
• Osteoblasts displayed a narrow concentration range for anabolic fluoride action.
• Fluoride exposure exacerbated PTH-induced osteocyte apoptosis and TGF-β-induced osteoclast apoptosis.

Conclusions:

• Bone cells (osteocytes, osteoclasts, osteoblasts) have varied sensitivities to fluoride.
• Fluoride differentially impacts cell viability and apoptosis, particularly when combined with other signaling molecules.
• These findings provide insights into the cellular mechanisms of skeletal fluorosis.