Absence of complement factor H alters bone architecture and dynamics.

Area of Science:

• Immunology
• Bone Biology
• Genetics

Background:

• The complement system, particularly Factor H (FH), regulates immune responses.
• Emerging evidence suggests the complement system influences bone development and homeostasis.
• FH deficiency is linked to pathologies in various organs, but its role in bone is less understood.

Purpose of the Study:

• To investigate the role of Complement Factor H (FH) in maintaining bone architecture and function.
• To analyze bone changes in FH knockout (fh-/-) mice.
• To examine the effects of FH absence on osteoblast and osteoclast activity.

Main Methods:

• Utilized 3D micro-computed tomography for femur analysis in fh-/- mice and wild-type (WT) controls.
• Assessed kidney function and histology to differentiate bone-specific effects.
• Cultured and analyzed osteoblasts and osteoclasts from bone marrow to evaluate cellular changes and function.

Main Results:

• FH knockout mice exhibited significantly reduced bone volume/total volume, trabecular number, and tissue mineral density, with increased marrow area.
• Bone changes in fh-/- mice occurred before kidney dysfunction.
• Absence of FH led to increased osteoblast and osteoclast numbers, elevated cathepsin K expression, enhanced osteoclast function, and altered actin organization in bone cells.

Conclusions:

• Complement Factor H plays a direct and critical role in maintaining bone structure and cellular function.
• FH deficiency leads to significant skeletal abnormalities.
• FH emerges as a promising therapeutic target for treating bone diseases associated with complement dysregulation.