IADR Abstract Archives
RELAXIN Enhances Bone Remodeling During Murine Calvarial Sagittal Suture Expansion
Objectives: As we have previously reported, RELAXIN (RLN) is an insulin-like hormone associated with extracellular matrix degradation, osteoclastogenesis, and osteoblast differentiation. We believe RLN could affect bone remodeling during calvarial suture expansion and, therefore, assessed the effect of RLN-treatment during expansion of the murine sagittal suture in vivo.
Methods: An RLN-liposome complex (20 ng/mL) was constructed and injected into the sagittal suture of 8-10 week old C57BL/6J mice. The sagittal sutures were then expanded laterally with wire springs (0.014 Elgiroy) inserted on both parietal bones. Four groups (N= 6) were examined which included negative control, expansion control, expansion with vehicle control and experimental (RLN) groups. After 48 hours or one week, the expansion range was measured using a caliper, bone mineral density and volume were analyzed using micro computed tomography and morphological observations, collagen deposition and osteoclast differentiation, were assessed using hematolxylin-eosin, Verhoeff van-Geison and tartrate resistant acid phosphatase (TRAP) staining, respectively.
Results: The expansion range was not significantly different between the RLN-treated and RLN-untreated expansion samples after 48 hours; however, less collagen was detected in the RLN- treated samples. Significantly higher bone mineral density and volume and thicker, well-organized calluses with multinucleated TRAP positive cells were observed only in the RLN-treated samples after one week of expansion. Fibroblast dendrites in the RLN-treated samples were spindle-like whereas they were nodular in control samples, suggesting that the RLN-treated samples were no longer subject to stress forces after one week of expansion.
Conclusions: Our in vivo results show that RLN can promote effective suture expansion by stimulating rapid bone turnover in the expansion area, and that it could contribute to prompt callus formation after suture expansion.
Methods: An RLN-liposome complex (20 ng/mL) was constructed and injected into the sagittal suture of 8-10 week old C57BL/6J mice. The sagittal sutures were then expanded laterally with wire springs (0.014 Elgiroy) inserted on both parietal bones. Four groups (N= 6) were examined which included negative control, expansion control, expansion with vehicle control and experimental (RLN) groups. After 48 hours or one week, the expansion range was measured using a caliper, bone mineral density and volume were analyzed using micro computed tomography and morphological observations, collagen deposition and osteoclast differentiation, were assessed using hematolxylin-eosin, Verhoeff van-Geison and tartrate resistant acid phosphatase (TRAP) staining, respectively.
Results: The expansion range was not significantly different between the RLN-treated and RLN-untreated expansion samples after 48 hours; however, less collagen was detected in the RLN- treated samples. Significantly higher bone mineral density and volume and thicker, well-organized calluses with multinucleated TRAP positive cells were observed only in the RLN-treated samples after one week of expansion. Fibroblast dendrites in the RLN-treated samples were spindle-like whereas they were nodular in control samples, suggesting that the RLN-treated samples were no longer subject to stress forces after one week of expansion.
Conclusions: Our in vivo results show that RLN can promote effective suture expansion by stimulating rapid bone turnover in the expansion area, and that it could contribute to prompt callus formation after suture expansion.