The Role of Biglycan on Properties of Murine Cementum

Introduction: Matrix proteoglycans (PGs) play a significant role in mineralization, structure, and resulting biomechanics of soft and hard tissues. Objective: In this study the role of nanoscale small leucine rich PGs (SLRPs), biglycan (BGN) on microscale structure, chemical and mechanical properties on murine cementum and its interface: the cementum-dentin junction (CDJ), were determined. Materials and Methods: Mandibular jaws from 7-10 month old male C3H mice from 2 groups (5 jaws per group); wild type ‘WT' and Biglycan-knockouts ‘BGN KO' were mounted on AFM stubs and ultrasectioned using a diamond knife and an ultramicrotome. The microscale-cementum and -CDJ structure of the ultrasectioned block surfaces were characterized using an atomic force microscope (AFM). The elastic modulus values for respective groups under dry and wet conditions were determined using a nanoindenter. Results: No microscale-structural changes were observed between control and BGN KO cementums. In both groups, radially oriented periodontal ligament fibers within bulk cementum with no discernable hygroscopic CDJ as seen in humans were observed. However, in both groups a porous region along the perimeter of root dentin was observed. Student's t-test with 95% confidence interval illustrated a significant difference in elastic moduli of cementums between BGN KO and WT. Additionally a significant difference between dry (E_WT = 23.7 ± 3.5 GPa, E_{BGN KO} = 21.2 ± 4.4 GPa) and wet (E_WT = 13.4 ± 4.2 GPa, E_{BGN KO} = 16.0 ± 3.4 GPa) cementum within respective groups was observed. On-going work is being performed to determine the mineral density variations between BGN KO cementum in comparison to wildtype. Conclusion: Based on current results, the nanoscale BGN matrix molecule could cause a change in mineral content and mineral-collagen interactions suggesting a significant role of BGN toward cementum mineralization. Supported by NIH/NIDCR P01DE09859.