Related Experiment Videos
Biglycan knockout mice: new models for musculoskeletal diseases
Marian F Young1, Yanming Bi, Laurent Ameye
1Craniofacial and Skeletal Diseases Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Department of Health and Human Services. myoung@dir.nidcr.nih.gov
Glycoconjugate Journal
|September 17, 2003
Summary
Biglycan deficiency in mice leads to osteoporosis due to impaired bone cell formation and function. Compensatory mechanisms with other Small Leucine Rich Proteoglycans (SLRPs) are insufficient, highlighting SLRPs
Area of Science:
- Biochemistry
- Genetics
- Orthopedics
Background:
- Biglycan, a Class I Small Leucine Rich Proteoglycan (SLRP), is located on human chromosome Xq28.
- Its structure suggests a possible gene duplication origin with decorin, another Class I SLRP.
- Biglycan possesses two chondroitin sulfate glycosaminoglycan (GAG) chains, differing from decorin's single GAG chain.
Purpose of the Study:
- To investigate the in vivo function of biglycan using knockout mouse models.
- To determine the cellular and molecular mechanisms underlying biglycan deficiency-related phenotypes.
- To explore functional compensation between different SLRPs in bone and connective tissue integrity.
Main Methods:
- Generation and analysis of biglycan-deficient (knockout) mice.
- Double tetracycline-calcein labeling to assess bone formation capacity.
- Isolation and characterization of marrow stromal cells and calvaria cells.
- Assessment of cellular responses to TGF-beta, collagen synthesis, apoptosis, and differentiation markers.
- Generation of double knockout mice (biglycan/decorin and biglycan/fibromodulin).
- Transmission electron microscopy and biomechanical analysis of collagen structures and tendon strength.
Main Results:
- Biglycan knockout mice exhibit progressive diminished bone mass and defective bone formation with age.
- Deficiencies in marrow stromal cell production, reduced TGF-beta response, impaired collagen synthesis, and increased apoptosis were observed.
- Calvaria cells showed reduced expression of late differentiation markers and diminished calcium accumulation.
- Double knockout mice (biglycan/decorin) showed more severe osteopenia, indicating SLRP redundancy.
- Double knockout mice (biglycan/fibromodulin) displayed impaired gait, ectopic calcification, osteoarthritis, and disturbed collagen structures.
- Biomechanical analysis revealed weaker tendons in fibromodulin/biglycan knockout mice, suggesting joint instability.
Conclusions:
- Biglycan plays a critical role in maintaining bone mass and osteogenic cell function.
- Defects in osteogenic cells, including reduced proliferation and differentiation, contribute to the osteoporosis-like phenotype.
- Functional redundancy exists among SLRPs, but combined deficiencies lead to severe connective tissue abnormalities and musculoskeletal diseases.