Syndecan-3 enhances anabolic bone formation through WNT signaling

Area of Science:

• Bone biology
• Metabolic bone disorders
• Signaling pathways

Background:

• Osteoporosis is a prevalent age-related metabolic bone disorder characterized by low bone mass and architectural deterioration, leading to fragility fractures.
• Current anabolic osteoporosis treatments are limited and have restricted usage durations.
• Stimulating osteoblasts to form new bone is crucial for restoring bone structure.

Purpose of the Study:

• To investigate the role of Syndecan-3 (Sdc3) in bone formation and its potential as a therapeutic target for osteoporosis.
• To elucidate the molecular mechanisms by which Sdc3 influences osteoblast function and WNT signaling.

Main Methods:

• Analysis of Sdc3 knockout (Sdc3^-/-) mice to assess bone phenotypes and responses to mechanical loading.
• Overexpression of Sdc3 in osteoblasts using the Col1a1 promoter in both knockout and wild-type (WT) mice.
• Investigation of WNT signaling pathway components, including Frizzled 1 stabilization.

Main Results:

• Sdc3^-/- mice exhibited reduced bone volume, impaired bone formation, increased marrow adipose tissue, heightened bone fragility, and a blunted response to mechanical loading.
• These phenotypes in Sdc3^-/- mice were attributed to delayed osteoblast maturation, impaired osteoblast function, and increased osteoclast-mediated bone resorption.
• Overexpression of Sdc3 rescued the low bone volume phenotype in Sdc3^-/- mice and increased bone volume in WT mice.

Conclusions:

• Syndecan-3 plays a critical role in regulating bone formation and maintaining bone mass.
• SDC3 enhances canonical WNT signaling in osteoblasts by stabilizing Frizzled 1.
• SDC3 represents a promising therapeutic target for developing novel bone anabolic drugs to treat osteoporosis.