FGF23 and Cell Stress in SaOS-2 Cells-A Model Reflecting X-Linked Hypophosphatemia Dynamics

Area of Science:

• Cell Biology
• Skeletal Pathophysiology
• Biochemistry

Background:

• Fibroblast Growth Factor 23 (FGF23) is a key regulator of phosphate and vitamin D metabolism, crucial for bone health.
• Dysregulation of FGF23 signaling is implicated in skeletal disorders such as X-linked hypophosphatemia (XLH).
• Understanding FGF23's cellular effects is vital for elucidating disease mechanisms.

Purpose of the Study:

• To investigate the impact of FGF23 overexpression on SaOS-2 cell morphology and stress responses.
• To elucidate the role of the endoplasmic reticulum (ER) and mitochondria in FGF23-induced cellular changes.
• To explore the activation of unfolded protein response (UPR) and apoptotic pathways.

Main Methods:

• SaOS-2 cells were engineered to overexpress FGF23.
• Transmission electron microscopy (TEM) was used to analyze cellular ultrastructure, focusing on the rough endoplasmic reticulum (rER) and mitochondria.
• Western blot analysis was performed to quantify protein expression related to ER stress and apoptosis.

Main Results:

• FGF23 overexpression led to significant morphological alterations, including enlarged and elongated rER and mitochondria with increased contact zones.
• Elevated expression of ER stress markers (CHOP, XBP1, GRP94, eIF2α) and apoptotic markers (BAX) was observed.
• Increased apoptosis rates were detected in FGF23-overexpressing cells after 24-72 hours in vitro.

Conclusions:

• FGF23 overexpression robustly activates the UPR and apoptotic pathways in SaOS-2 cells.
• Enhanced interaction between rER and mitochondria suggests adaptive responses to increased protein synthesis demands.
• These findings provide mechanistic insights into FGF23's role in cellular homeostasis and skeletal pathologies like XLH.