https://orcid.org/0000-0002-2721-6667
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Abstract
Background
The potential of relapse of craniofacial disharmony after trans-sutural distraction osteogenesis is high due to the failure to produce a stable bone bridge in the suture gap. The aim of this study is to evaluate whether hydroxyapatite nanoparticles (nHAP) have the effect of promoting osteoblast differentiation of suture-derived stem cells (SuSCs) and bone formation in sagittal suture during expansion.
Methods
SuSCs were isolated from sagittal sutures and exposed to various concentrations of nHAP (0, 25, 50, and 100 μg mL−1) to determine the optimal concentration of nHAP in osteoblast differentiation via performing Western Blotting and RT-qPCR. Twenty 4-week-old male Sprague–Dawley rats were randomly assigned into 4 groups: SHAM (sham-surgery), distraction, ACS (absorbable collagen sponge) and ACS+nHAP groups. In the ACS and ACS+nHAP groups, saline solution and nHAP suspended in a saline solution were delivered by ACS placed across the sagittal suture, respectively. In the latter three groups, the suture was expanded for 14 days by 50 g of constant force via a W shape expansion device. Suture gap area, bone volume fraction (BV/TV) and bone mineral density (BMD) of sagittal sutures were assessed via micro-CT, while the mechanical properties of sagittal sutures were evaluated via nanoindentation test. The efficacy of nHAP on bone formation in sagittal suture was also evaluated via BMP-2 immunohistochemistry staining.
Results
The expression of osteoblast related genes and proteins induced by 25μg mL−1 nHAP were significantly higher than the other groups in vitro (p<0.05). Furthermore, treating with 25μg mL−1 nHAP in vivo, the suture gap area was significantly reduced when compared with the distraction group. Correspondingly, the BV/TV, BMD, hardness and modulus of sagittal sutures were significantly increased in the ACS+nHAP group (p<0.05).
Conclusion
The 25μg mL−1 dose of nHAP delivered by ACS can facilitate bone formation into the sagittal suture during expansion via inducing osteoblast differentiation of SuSCs.
Acknowledgments
This project was supported by the National Natural Science Funder of China (No. 81571925). We are thankful for the technical support provided by the Animal Experiment Center of Peking University Health Science Center. We thank Professor YI Weining from the Department of Public Health, Peking University Health Science Center, who provided guidance on the statistical methods used, and Hung Kanlin, who helped edit and polish our manuscript carefully.
Abbreviations
TSDO, trans-sutural distraction osteogenesis; SuSCs, calvarial suture-derived stem cells; BMD, bone mineral density; EDTA, ethylene diaminetetra acetic acid; H&E, hematoxylin and eosin; MSCs, mesenchymal stem cells; ALP, Alkaline phosphatase; Runx2, RUNX family transcription factor 2; COL1, Collagen type I; nHAP, hydroxyapatite nanoparticle; SHAM, sham-surgery; ACS, absorbable collagen sponge; BV/TV, bone volume fraction; BMP-2, bone morphogenetic protein-2; CTAB, Hexadecyl (cetyl) trimethyl ammonium bromide; DLS, dynamic light scattering; XRD, X-ray diffraction; FACS, fluorescent-activated cell sorting; CLSM, confocal laser scanning microscope; PI, propidium iodide.
Author Contributions
All authors made substantial contributions to conception and design, acquisition of data, or analysis and interpretation of data; took part in drafting the article or revising it critically for important intellectual content; agreed to submit to the current journal; gave final approval of the version to be published; and agree to be accountable for all aspects of the work.
Disclosure
The authors report no conflicts of interest for this work and declare no competing financial interests.