The Study Of Reconstruction Mesenchymal Stem Cells-implant And Insertion In The Irradiated Bone

Until now the endosseos implants has been used for the retention of ear prosthetics, orbit prosthetics, nose prosthetics and midface prosthetics. In recent years, an increasing number of cancer patients, particularly malignant tumor patients, which urgently needed the implant-supported prosthestics after surgery. But radiotherapy, which harmed bone around implants, decreased the success rate of endosseous implant significantly and limited the application of implants. Implant failures were higher after radiotherapy, which limited the use of endosseous implant supported maxillofacial prosthetics. How to resolve this "bottleneck" problem directly related to the retension effect of maxillofacial prosthetics. The therapeutic effect of HBO is related to an elevated partial pressure of oxygen in the tissue. The pressure itself enhances oxygen solubility in the tissue fluids. HBO only plays an adjunctive roles as only stationary results are achieved local reatement. Whether HBO improve the osseointegration is still controversy.In resent years, however, the devolpment of tissue engineering technology may provide a new way to solve the osseointegration problem. Bone marrow stem cells (MSCs) with strong proliferation and tissue repair are the most commonly used in tissue engineering as seed cells. The MSC-implant composed by MSC cell sheet with implants in vitro forms the osseointegration not only by bone tissue around implant, but also by MSCs aound implant. Then we hypothesize that MSC-implant have the ability to accelerate the implant ossintegration in irradiated bone. Therefore, this study was to construct MSC-implant in vitro, to test its biology and explore the feasibility to use in irradiated bone, in order to provide a new way to resolve the implant failure problem.The major findings are as follows:Part I. Confirmed feasibility of construction Msc-implant in vitro with tissue engineering technologyIn this study, we isolated and cultured bone marrow-derived mesenchymal stem cells (MSCs) and formed the cell sheet, then constructed the MSC-implant with two kinds of implant in vitro. The biological properties of MSC-implant were analyzied in gross, histological, and molecular level. After thransplanted in nude mouse, the MSC-implant can regenerate bone-like tissue and vascular-like tissue. The results showed that bone marrow mesenchymal stem cells formed cell sheet easily which could composed with implant tightly in vitro. The MSCs in cell sheet still kept secreting extracellular matrix. The novel MSC-implant had the ability to form new bone and blood vessels, and expressed the osteogenesis and vascular gene. The Ti implant had higher capability to accelerate the bone forming than Zr implant. But it was lower in accelerating the vascular forming.The results suggest that it is feasibility to construct the MSC-implant in vitro, which has the ability to accelerate the tissue healing. The different materials of implants have the different impact on cell sheet.Part II: the study of different implants inserting the irradiated bone in different timeIn order to compare different materials implants insertion before and after radiotherapy had the impact on osseointegration. Two kinds of zirconia ceramic and titanium implant were selected. The study compared the different osseointegration before and after 3 months irradiation. The results showed that: bone-implant contact (BIC) was higher before irradiation insertion implants than after irradiation. The osseointegrated strength of titanium implants was higher than zirconia implants, while in vascular forming it was lower.The results suggest that the ossointegration insertion before irradiation, less than 50Gy radiation dose, was significantly better than after irradiation insertion. There was no obvious difference between titanium and zirconia implants used in irradiated bone.Part III: the study about MSC-implants used in irradiated boneTo assess the effect of MSC-implant, which was constructed in vitro,, inserted in irradiated bone. The MSCs of dogs were isolated and cultured, formed the cell sheet and constructed the MSC-implant. Then it was inserted in irradiated bone compared with normal implants. The results showed that the MSC-implant had higher capability to accelerate bone healing than normal implants. There were no obvious different between MSC-Ti implant and MSC-Zr implant when they inserted in irradiated bone.The results suggests that contructing MSC-implant in vitro inserts in irradiated bone may be a novel implant surface modifying method, which could improve the success rate of implants in irradiated bone.