| Background and ObjectiveMidfacial hypoplasia seriously affects the physical and mental health of patients.Orthognatic surgical treatment,orthodontic treatment,distraction Osteogenesis and Trans-sutural Distraction Osteogenesis(TSDO)have been used to treat this disease in clinic currently.But due to its unclear pathogenesis,no better treatment has been found.TSDO promotes osteogenesis by loading a continuously distraction force on the patient’s facial sutures,and has less invasion.It might be a better choice for the growing patients.Suture is a growing center of the cranial-facial bone including undifferentiated mesechymal cells.The current academia are more concerned about the cranial sutures but not the facial sutures.The model and the conclusion of the facial suture study always refer to those of the cranial suture studies.While,different sutures of diverse position have multiple biological characteristics.Facial bones do not have the dura mater which belongs to the cranial vault.Meanwhile,facial bones and sutures are exposed to the external mechanical environment at all time during the lifetime,such as the impact generated by chewing.In summary,what are the characteristics of facial sutures that are different from cranial sutures,and how to construct a mechanical model of TSDO facial suture cells in vitro all need to be clarified.Therefore,the purpose of this study is to prove for the first time that TSDO could promote osteogenesis of the facial bones(zygomatic bone)from the aspect of volume change,and then identify mesenchymal stem cells,residing in the facial suture(zygomaticomaxillary suture)of rats,as well as their surface markers.And finally use the Flexcell-5000T system to perform both static and cyclic stretching on those cells to find a suitable method applying short-term stretching on zygomaticomaxillary suture mesenchymal stem cell of rat(rZSMSCs)in vitro,so as to build a new cell model and supply a new research strategy for the TSDO used in treating midfacial hypoplasia.Methods1.We collected all original data of head-face-computed-tomography-scan belonging to whom were treated with TSDO during January 2018 to March 2018 because of "maxillary retrusion" or "midfacial hypoplasia" in Peking University Third Hospital.There are 10 patients met the inclusion criteria.Their data was imported in Mimics 20.0 and 3-Matic Research 13.0.After superimposing and cutting their reconstructed skull image,we analyzed the preoperative and postoperative volume change in their zygomatic bone.The SPSS 25 and Graphpad Prism 9.0.0 were used with paired t test.The difference has statistically significant if the p value<0.05.2.The rZSMSCs were extracted for expansion and culturing in vitro.The cells of the 2nd to 8th passages were used for flow cytometry to identify cell surface markers,and induced for three-line-differentiation.rZSMSCs were cultured in osteogenic,adipogenic,and chondrogenic differentiation medium.Alizarin red,oil red O,alcian blue staining were used to detect the ability of osteogenic,adipogenic,and chondrogenic differentiation.3.10%static continuous tensile stretch and 1Hz,10%cyclic continuous stretch were respectively applied on rZSMSCs by Flexcell-5000T stress loading system for 24h,and the osteogenic specific genes expression of Runx-2,Opn and Col-1 were detected by Quantitative-Real-time PCR to determine a suitable mechanical parameter for establishing an ideal short-term continuous force-loading cell model of TSDO in vitro.Before detecting,rZSMSCs were observed under the inverted microscope to compare their changing in shape.The Graphpad Prism 9.0.0 was used with unpaired t test.The result was shown in the form of mean ± standard deviation.The difference has statistically significant if the p value<0.05.Results1.The course of the TSDO treatment is 5.2±2.33 months.The volume of the preoperative zygomatic bone is 5423.52±2154.06 mm3,and the volume of the postoperative volume change in their zygomatic bone is 6387.92±2317.79 mm3.The volume of the postoperative zygomatic bone increased 964.4 mm3,and the 95%confidence intervals are 532.3～1396 mm3(p<0.05).The difference has statistically significant.2.The results of flow cytometry and osteogenic,adipogenesis,and chondrogenic differentiation showed that rZSMSCs have the characteristics of stem cells and the potential for multi-differentiation.The surface marker of the rZSMSCs are different from those of the rat cranial sagittal suture mesenchymal cells.3.After loading static stretch on rZSMSCs for 24 hours,the mRNA level of Runx2 was significantly increased(p<0.05).The mRNA level of Opn as well as Col-1 are both increased by it,but the difference of these results have no statistically significant.Continuous application of 1Hz,10%cyclic stretch for 24h could significantly increase all mRNA levels of the osteogenic gene(p<0.05).Both of the two stretch could change the shape of the rZSMSCs.Conclusions1.TSDO could reconstruct the facial bones,and increase the volume of the postoperative zygomatic bone.2.The rZSMSCs have the properties of stem cells,and these surface markers are different from those from the rat cranial sagittal suture mesenchymal cells.3.Using 1Hz,10%cyclic continuously tensile stress is an optimal mechanical parameter from the perspective of mRNA level,which could establish a satisfied 24 hour TSDO facial sutural cell stretching model in vitro. |
PDF Full Text Request