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ABSTRACT
Purpose: Biglycan is a proteoglycan of the small leucine-rich repeat family. It is present in all connective tissues and plays key structural and signaling roles. This review aimed to compile available evidence in the characteristics and distribution of biglycan and its glycosylated and non-glycosylated forms in connective tissues with a specific focus on the contribution to homeostasis of bone and changes of biglycan structure with aging.
Methods: The Pubmed database was searched and included the terms “biglycan”, “proteoglycans”, “glycosaminoglycans”, “bone”, “osteoblast”, “osteocyte”, “osteoclast”, “aging”, “inflammation”, “cartilage”. Abstracts were appraised and a series of original articles and reviews studied to generate this narrative review.
Results: Based on the search, biglycan significantly affects bone development and homeostasis and can be significantly changed by the aging process in several connective tissues, which in turn affects the behavior of tissue and cell responses in aged networks. Further, as the understanding of the various forms of biglycan in vivo is expanded and the function of its components in vitro is dissected, this proteoglycan can potentially serve as a therapeutic or biomarker molecule to detect tissue destruction.
Conclusions: Biglycan is a key player in skeletal bone homeostasis, and overall, there is more evidence on the role of biglycan in development and less in the adult physiological or diseased young and aged systems. Further understanding of its conformation, degradation peptides and post-translational modifications will be required to understand the role of biglycan in bone maintenance and to support the development of treatments for age-related bone dysfunctions.
Glossary of terms
| ALK | = | Activin receptor-like kinase |
| BGN | = | Biglycan |
| BMP | = | Bone morphogenetic protein |
| BMPR | = | Bone morphogenetic protein receptor |
| BSP | = | Bone sialoprotein |
| CBFA-1 | = | Core binding factor α1 |
| Chsy | = | Chondroitin synthase |
| CS | = | Chondroitin sulfate |
| Cys | = | Cysteine |
| C2C12 | = | Muscle derived cell line |
| DCN | = | Decorin |
| DS | = | Dermatan sulfate |
| ECM | = | Extracellular matrix |
| FGF | = | Fibroblast growth factor |
| GAG | = | Glycosaminoglycan |
| GalN | = | Galactosamine |
| GalNAc | = | N-acetyl galactosamine |
| Galt | = | Galactosyltransferase |
| Gat | = | Glucuronosyltransferase |
| GlcA | = | Glucuronic acid |
| GlcN | = | Glucosamine |
| GST | = | Glutathione-S-transferase |
| HAP | = | Hydroxyapatite |
| HS | = | Heparan sulfate |
| IdoA | = | Iduronic acid |
| IL | = | Interleukin |
| IP | = | Immunoprecipitation |
| kDa | = | Kilodalton |
| LPS | = | Lipopolysaccharide |
| LRR | = | Leucine rich repeat |
| MAPK | = | Mitogen activated protein kinase |
| MC | = | MC3T3-E1 osteoblastic cell line from calvaria |
| OCN | = | Osteocalcin |
| OPG | = | Osteoprotegerin |
| OSX | = | Osterix |
| RANKL | = | Receptor activator of nuclear factor kappa-B ligand |
| Runx-2 | = | Runt-related transcription factor 2 |
| Smad | = | Mothers against decapentaplegic |
| SLRPs | = | Small leucine rich proteoglycans |
| Ser | = | Serine |
| TGF | = | Transforming growth factor |
| TLR | = | Toll like receptor |
| TNF | = | Tumor necrosis factor |
| Tsg | = | Twisted gastrulation |
| UV | = | Ultra-violet light |
| WB | = | Western blotting |
| WISP1 | = | wnt-induced protein 1 |
| Wnt | = | Wnt signaling |
| Xyl | = | Xylose |
| Xylt | = | Xylosyl transferase |
Disclosure statement
No potential conflict of interest was reported by the author.