NFAT and Osterix cooperatively regulate bone formation.

Area of Science:

• Immunology
• Bone Biology
• Pharmacology

Background:

• Immunosuppressants like FK506 are vital post-transplantation but cause skeletal side effects.
• Calcineurin inhibitors block nuclear factor of activated T cells (NFAT) signaling.
• NFATc1 is known to be critical for osteoclast differentiation.

Purpose of the Study:

• To investigate the impact of FK506 on bone mass and formation.
• To determine the role of NFAT transcription factors in osteoblast biology.
• To elucidate the mechanism by which FK506 affects bone metabolism.

Main Methods:

• Administration of FK506 to mice and osteoblasts.
• Analysis of bone mass and osteoblast differentiation markers.
• Investigation of NFATc1 and NFATc2 deficient cells.
• Examination of NFAT and Osterix interaction using co-immunoprecipitation and reporter assays.

Main Results:

• FK506 treatment reduced bone mass by impairing bone formation, not by affecting osteoclast differentiation.
• Bone formation was inhibited in NFATc1/c2 deficient cells and FK506-treated osteoblasts.
• NFATc1 overexpression enhanced Osterix-dependent Col1a1 promoter activity.
• NFAT and Osterix form a complex crucial for Osterix transcriptional activity.

Conclusions:

• NFAT transcription factors play a significant role in osteoblast differentiation and bone formation.
• NFAT and Osterix act cooperatively to control osteoblastic bone formation.
• Findings offer insights into managing post-transplantation osteoporosis and promoting bone regeneration.