While high-performance ceramics like alumina and zirconia exhibit excellent wear resistance, they provide poor osseointegration capacity. As osseointegration is crucial for non-cemented joint prostheses, new techniques have been successfully developed for biofunctionalizing high-performance ceramic surfaces. Stable cell adhesion can be achieved by covalently bound specific peptides. In this study we investigate the effect of sterilization processes on organo-chemically functionalized surfaces. To enhance the performance of alumina-toughened zirconia ceramics (ATZ), a 3-aminopropyldiisopropylethoxysilane (APDS) monolayer was applied and coupled with cyclo-RGD peptides (cRGD) by using bifunctional crosslinker bis(sulfosuccinimidyl)suberat (BS³). The samples were sterilized using e-beam or gamma-sterilization at 25 kGy, either before or after biofunctionalization with cRGD. Functionalization stability was investigated by contact angle measurements. The functionality of cRGD after sterilization was demonstrated using proliferation tests and cytotoxicity assays. Immunofluorescence staining (pFAK, Actin, DAPI) was conducted to evaluate the adhesion potential between the samples and human mesenchymal stem cells (hMSCs). Functionalized samples before and after sterilization showed no significant difference regarding their contact angles. A proliferation test demonstrated that the cells on functionalized samples proliferate significantly more than on untreated samples before and after sterilization. hMSCs showed a significant higher proliferation on gamma sterilized samples compared to all other groups after 14 days. It was confirmed that the samples did not exhibit cytotoxic behavior before or after sterilization. Fluorescence microscopy demonstrated that both, cells on sterilized and on non-sterilized samples, expressed high levels of pFAK-Y397. The investigated functionalization enables improved adhesion and proliferation of hMSCs and is stable against the investigated sterilization processes. This is of importance as the option of having a sterile product enables the start of the translation of this biofunctional coating towards preclinical and subsequently first-in-man applications.
Aim of the study was to evaluate if abrasion-arthroplasty (AAP) and abrasion-chondroplasty (ACP) leads to a release of mesenchymal stem cell (MSC) like cells from the bone marrow to the joint cavity where they probably differentiate into a chondrogenic phenotype. Cartilage demage is a sever problem in our aging society. About 5 million people only in Germany are affected. Osteoathritis is a degeneration of cartilage caused by aging or traumata 50 % of the people over 40 have signs of osteoarthritis. But the ability of self-regeneration of cartilage is strongly limited. There are different approaches to therapy osteoathritic lesions. Arthroscopic treatment of OA includes bone marrow stimulation technique such as abrasion arthroplasty (AAP) and microfracturing (MF). Beside the support of chondrocyte progenitor cells the environment is also important for the commitment to chondrocytes. Therefore insulin-like growth factor-1 (IGF-1) and transforming growth factor beta-1 (TGF-β1) are important factors during the regeneration process. In the present study we characterised the heamarthrosis and the released cells after AAP and its ability to differentiate into the chondrocyte lineage. Postoperative haemarthrosis was taken 5, 22 or 44 hours after surgery. 7.5 mg Dexamethasone (Corticosteroid) was administered into the knee joint to prevent postoperative inflammation. Mononuclear cells were isolated from haemarthrosis from the drainage bottle by ficoll density gradient centrifugation. The isolated cells were characterised using fluorescence-activated cell-sorting (FACS) analysis for characteristic markers of MSC such as CD 44, 73, 90, 105. After expanding cells were cultured in a pellet culture. After 3 weeks, histochemistry and immunohistochemistry against Sox9, collagen II and proteoglycan were performed. The release of IGF1, BMP4 and BMP7 was analysed in haemarthrosis serum by ELISA and Luminex technology.Introduction
Material and Methods
