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2013|14 Annual Report Fraunhofer IGB

68 100 μm 1 A MEDICINE IN-VITRO TEST SYSTEMS FOR THE EVALUATION OF NOVEL BONE IMPLANTS Dipl.-Biol. Claudia Kleinhans, Prof. Dr. rer. nat. Petra J. Kluger Overview Treatments for the diseases and injuries of the musculoskel- etal system are currently focused on the development of new composite materials. Many of these material developments are aimed at improving the biodegradability and mechani- cal properties of the load-bearing areas of the implants. To ensure the utility of the new material, the establishment of biological test systems for the analysis of ingrowth into the bone and the degradation behavior of implant materials are of particular relevance. Although certain animal tests of im- plant materials are still essential, there is a clear directive to develop new human-based in vitro test systems due to ethi- cal considerations, a better correlation to the human system and increasing regulatory restrictions on animal experiments. However, there are no standardized systems for the appropri- ate analysis of material resorption and osteoinduction, which is the material’s ability to stimulate the formation of new bone, analyzing both osteoblast and osteoclast function. The establishment of such systems is part of the Fraunhofer joint project “DegraLast” as an alternative or supplement to animal experiments. Standardized in vitro test systems with bone-forming and bone-degrading cells The standardization of cell-based test systems using osteo- blasts and their precursor cells to simulate bone formation, as well as bone-resorbing cells, the osteoclasts, to mimic bone loss, is the goal of the subproject at the Fraunhofer IGB. To mimic the in vivo situation, a co-culture of primary osteoblast precursor cells and osteoclasts is to be established. Ingrowth and osteoinductive properties To assess the ingrowth and the osteoinductive properties of a material, we investigate the differentiation of human mesen- chymal stem cells (hMSCs) into osteoblasts by analyzing spe- cific differentiation markers on standard materials, as well as newly developed materials and coatings. Cell adhesion, prolif- eration and differentiation are characterized by the qualitative analysis of type I collagen as well as the quantitative examina- tion of alkaline phosphatase and calcium, which showed a sig- nificant increase in differentiated cells relative to control cells. Loss of bone substance Osteoclasts are largely responsible for the resorption of bone. For the osteodegradation test system, monocytes were iso- lated from human peripheral blood and successfully differenti- ated into osteoclasts. The characterization of differentiated osteoclasts was demonstrated by polynuclear size, the re- structuring of the cytoskeleton and the expression of specific marker proteins (Fig. 1). Furthermore, the activity of the cells was determined by the absorption of a bovine bone substitute material (Fig. 2). 100 μm 1 B

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