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The adipose tissue is the site of expression and secretion of a range of biologically active proteins, called adipokines, for example, leptin, adiponectin, and resistin. Leptin has previously been shown to be expressed in osteoblasts and to promote bone mineralization, whereas adiponectin expression is enhanced during osteoblast differentiation. In the present study we explored the possible role of resistin in bone metabolism. We found that resistin is expressed in murine preosteoclasts and preosteoblasts (RAW 264.7, MC3T3-E1), in primary human bone marrow stem cells and in mature human osteoblasts. The expression of resistin mRNA in RAW 264.7 was increased during differentiation and seemed to be regulated through PKC- and PKA-dependent mechanisms. Recombinant resistin increased the number of differentiated osteoclasts and stimulated NFkappaB promoter activity, indicating a role in osteoclastogenesis. Resistin also enhanced the proliferation of MC3T3-E1 cells in a PKA and PKC-dependent manner, but only weakly interfered with genes known to be upregulated during differentiation of MC3T3-E1 into osteoblasts. All together, our results indicate that resistin may play a role in bone remodeling.

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Etching is used for the surface modification of titanium to improve the implant performance in bone. In this study, pure titanium implants were surface modified by a cathodic reduction process by using hydrofluoric acid (HF) at various concentrations (0.001, 0.01, and 0.1 vol %) and a constant current of 1 mA/cm(2). The resulting surface microtopographies were analyzed by atomic force microscopy, scanning electron microscopy, and profilometry, while the surface chemical contents were evaluated by time of flight secondary ion mass spectrometry. The competitive forces between ionic surface implementation induced by the current direction and the HF etching effect on titanium were highlighted. The implant performance was evaluated in an in vivo rabbit model by using a pull-out test method. The group of implants modified with 0.01% HF showed the highest retention in bone. Fluoride and hydride amounts measured in the surfaces, as well as surface skewness (S(sk)), kurtosis (S(ku)), and core fluid retention (S(ci)) were positively correlated to the implant's retention in bone in vivo. Frequently used parameters for characterizing the implant, such as oxide content and the average height deviation from the mean plane (S(a)), were not correlated to implant performance, suggesting that these parameters are not the most important in predicting the implant performance.