Suture Cells in a Mechanical Stretching Niche: Critical Contributors to Trans-sutural Distraction Osteogenesis

RhoA/ROCK-TAZ Axis regulates bone formation within calvarial trans-sutural distraction osteogenesis

BACKGROUND

Craniofacial skeletal deformities can be addressed by applying tensile force to sutures to prompt sutural bone formation. The intricate process of mechanical modulation in craniofacial sutures involves complex biomechanical signal transduction. The small GTPase Ras homolog gene family member A (RhoA) functions as a key mechanotransduction protein, orchestrating the dynamic assembly of the cytoskeleton by activating the Rho-associated coiled-coil containing protein kinase (ROCK). Transcriptional coactivator with PDZ-binding motif (TAZ) serves as a crucial mediator in the regulation of genes and the orchestration of biological functions within the mechanotransduction signaling pathway. However, the role of RhoA/ROCK-TAZ in trans-sutural distraction osteogenesis has not been reported.

METHODS

We utilized pre-osteoblast-specific RhoA deletion mice to establish an in vivo calvarial trans-sutural distraction model and an in vitro mechanical stretch model for pre-osteoblasts isolated from neonatal mice. Micro-CT and histological staining were utilized to detect the formation of new bone in the sagittal suture of the skull as well as the activation of RhoA, Osterix and TAZ. The activation of ROCK-limk-cofilin and the nuclear translocation of TAZ in pre-osteoblasts under mechanical tension were detected through Western blot, qRT-PCR, and immunofluorescence.

RESULTS

The osteogenic differentiation of pre-osteoblasts was facilitated by mechanical tension through the activation of RhoA and Rho-associated kinase (ROCK), while ablation of RhoA impaired osteogenesis by inhibiting pre-osteoblast differentiation after suture expansion. Furthermore, inhibiting RhoA expression could block tensile-stimulated nuclear translocation of TAZ by preventing F-actin assembly through ROCK-LIM-domain kinase (LIMK)-cofilin pathway. In addition, the TAZ agonist TM-25659 could attenuate impaired osteogenesis caused by ablation of RhoA in pre-osteoblasts by increasing TAZ nuclear accumulation.

CONCLUSIONS

This study demonstrates that mechanical stretching promotes the osteogenic differentiation of pre-osteoblasts in trans-sutural distraction osteogenesis, and this process is mediated by the RhoA/ROCK-TAZ signaling axis. Overall, our results may provide an insight for potential treatment strategies for craniosynostosis patients through trans-sutural distraction osteogenesis.

Extracellular vesicles derived from M1 macrophages enhance rat midpalatal suture expansion by promoting initial bone turnover and inflammation

BACKGROUND

Midpalatal suture (MPS) expansion can be affected by many factors, and researchers have attempted to regulate the initial inflammatory stage of expansion to optimize clinical outcomes and their underlying mechanisms. This study aimed to investigate the potential effects and mechanisms of M1 macrophage small extracellular vesicles during rat MPS expansion.

MATERIALS AND METHODS

RAW264.7 cells were induced to M1 or M2 polarization and, small extracellular vesicles were isolated from the polarized macrophages. Male Sprague-Dawley rats (6-7 weeks) were administered 70 ± 5 g expansion force devices for 7 days. Rats with expanders without force served as controls. M1/M2 small extracellular vesicles were injected into the MPS region (50 µg/day) in the M1 and M2 small extracellular vesicle-assisted groups, while 0.9% saline was injected into the expansion-only group. Suture width, bone mass, and morphological changes in the region of interest (ROI) were examined.

RESULTS

The M1 small extracellular vesicle-assisted group showed a significantly increased MPS suture width in vivo (P < 0.001), and less bone mass was observed in the ROI (P < 0.05). Histological examination showed that the M1 small extracellular vesicle-assisted group exhibited a wider palatal area and obvious fibrous tissue rearrangement. The expression of RANKL and the number of osteoclasts were increased (P < 0.01) in the bony edges, and the p65 protein expression was significantly higher (P < 0.001).

CONCLUSIONS

M1 macrophage-derived small extracellular vesicles have a positive effect in MPS expansion and increase p65 protein content and RANKL expression, thus promoting bone turnover. This study may contribute to the clinical application of small extracellular vesicles in the expansion of the palatal suture.

A bibliometric analysis of research on craniomaxillofacial distraction osteogenesis from 2000 to 2021

Objective

This study collected and summarized publications related to craniomaxillofacial distraction osteogenesis(DO) from 2000 to 2021, investigated trends in related research, and compared publications from different countries, institutions and journals. The aim is showcasing hotspots and frontiers in the field and providing a reference for future research.

Background

Craniomaxillofacial DO serves to treat different types of craniomaxillofacial dysplasia and bone defects and deformities. DO can significantly reduce surgical trauma, complications, and recurrence rate compared to conventional surgery. However, there is a lack of bibliometric analyses regarding Craniomaxillofacial DO.

Methods

CiteSpace and VOSviewer were used to analyze and visualize 3,141 articles and reviews searching through the Web of Science Core Collection(WOSCC) to obtain publications on craniomaxillofacial DO from 1 January 2000 to 31 December 2021.

Results

In the last 21 years, there has been a significant increase in the number of publications. The United States, the People's Republic of China, and Italy produce the vast majority of publications. University of Milan and University of Bologna are the most influential in this field. McCarthy JG is the most influential author. Obstructive sleep apnea, TMJ ankylosis and cleft lip and palate are potential research direction in this field.

Conclusion

Future research should focus on the precise indications and optimal timing of craniomaxillofacial DO and the evaluation of the long-term outcomes of various modified procedures. This study provides a relatively objective reference for related researchers, medical practitioners, and global health systems.